shmem.c 89.7 KB
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/*
 * Resizable virtual memory filesystem for Linux.
 *
 * Copyright (C) 2000 Linus Torvalds.
 *		 2000 Transmeta Corp.
 *		 2000-2001 Christoph Rohland
 *		 2000-2001 SAP AG
 *		 2002 Red Hat Inc.
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 * Copyright (C) 2002-2011 Hugh Dickins.
 * Copyright (C) 2011 Google Inc.
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 * Copyright (C) 2002-2005 VERITAS Software Corporation.
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 * Copyright (C) 2004 Andi Kleen, SuSE Labs
 *
 * Extended attribute support for tmpfs:
 * Copyright (c) 2004, Luke Kenneth Casson Leighton <lkcl@lkcl.net>
 * Copyright (c) 2004 Red Hat, Inc., James Morris <jmorris@redhat.com>
 *
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 * tiny-shmem:
 * Copyright (c) 2004, 2008 Matt Mackall <mpm@selenic.com>
 *
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 * This file is released under the GPL.
 */

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#include <linux/fs.h>
#include <linux/init.h>
#include <linux/vfs.h>
#include <linux/mount.h>
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#include <linux/ramfs.h>
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#include <linux/pagemap.h>
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#include <linux/file.h>
#include <linux/mm.h>
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#include <linux/export.h>
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#include <linux/swap.h>
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#include <linux/uio.h>
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static struct vfsmount *shm_mnt;

#ifdef CONFIG_SHMEM
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/*
 * This virtual memory filesystem is heavily based on the ramfs. It
 * extends ramfs by the ability to use swap and honor resource limits
 * which makes it a completely usable filesystem.
 */

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#include <linux/xattr.h>
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#include <linux/exportfs.h>
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#include <linux/posix_acl.h>
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#include <linux/posix_acl_xattr.h>
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#include <linux/mman.h>
#include <linux/string.h>
#include <linux/slab.h>
#include <linux/backing-dev.h>
#include <linux/shmem_fs.h>
#include <linux/writeback.h>
#include <linux/blkdev.h>
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#include <linux/pagevec.h>
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#include <linux/percpu_counter.h>
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#include <linux/falloc.h>
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#include <linux/splice.h>
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#include <linux/security.h>
#include <linux/swapops.h>
#include <linux/mempolicy.h>
#include <linux/namei.h>
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#include <linux/ctype.h>
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#include <linux/migrate.h>
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#include <linux/highmem.h>
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#include <linux/seq_file.h>
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#include <linux/magic.h>
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#include <linux/syscalls.h>
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#include <linux/fcntl.h>
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#include <uapi/linux/memfd.h>
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#include <asm/uaccess.h>
#include <asm/pgtable.h>

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#include "internal.h"

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#define BLOCKS_PER_PAGE  (PAGE_CACHE_SIZE/512)
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#define VM_ACCT(size)    (PAGE_CACHE_ALIGN(size) >> PAGE_SHIFT)

/* Pretend that each entry is of this size in directory's i_size */
#define BOGO_DIRENT_SIZE 20

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/* Symlink up to this size is kmalloc'ed instead of using a swappable page */
#define SHORT_SYMLINK_LEN 128

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/*
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 * shmem_fallocate communicates with shmem_fault or shmem_writepage via
 * inode->i_private (with i_mutex making sure that it has only one user at
 * a time): we would prefer not to enlarge the shmem inode just for that.
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 */
struct shmem_falloc {
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	wait_queue_head_t *waitq; /* faults into hole wait for punch to end */
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	pgoff_t start;		/* start of range currently being fallocated */
	pgoff_t next;		/* the next page offset to be fallocated */
	pgoff_t nr_falloced;	/* how many new pages have been fallocated */
	pgoff_t nr_unswapped;	/* how often writepage refused to swap out */
};

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/* Flag allocation requirements to shmem_getpage */
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enum sgp_type {
	SGP_READ,	/* don't exceed i_size, don't allocate page */
	SGP_CACHE,	/* don't exceed i_size, may allocate page */
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	SGP_DIRTY,	/* like SGP_CACHE, but set new page dirty */
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	SGP_WRITE,	/* may exceed i_size, may allocate !Uptodate page */
	SGP_FALLOC,	/* like SGP_WRITE, but make existing page Uptodate */
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};

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#ifdef CONFIG_TMPFS
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static unsigned long shmem_default_max_blocks(void)
{
	return totalram_pages / 2;
}

static unsigned long shmem_default_max_inodes(void)
{
	return min(totalram_pages - totalhigh_pages, totalram_pages / 2);
}
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#endif
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static bool shmem_should_replace_page(struct page *page, gfp_t gfp);
static int shmem_replace_page(struct page **pagep, gfp_t gfp,
				struct shmem_inode_info *info, pgoff_t index);
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static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
	struct page **pagep, enum sgp_type sgp, gfp_t gfp, int *fault_type);

static inline int shmem_getpage(struct inode *inode, pgoff_t index,
	struct page **pagep, enum sgp_type sgp, int *fault_type)
{
	return shmem_getpage_gfp(inode, index, pagep, sgp,
			mapping_gfp_mask(inode->i_mapping), fault_type);
}
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static inline struct shmem_sb_info *SHMEM_SB(struct super_block *sb)
{
	return sb->s_fs_info;
}

/*
 * shmem_file_setup pre-accounts the whole fixed size of a VM object,
 * for shared memory and for shared anonymous (/dev/zero) mappings
 * (unless MAP_NORESERVE and sysctl_overcommit_memory <= 1),
 * consistent with the pre-accounting of private mappings ...
 */
static inline int shmem_acct_size(unsigned long flags, loff_t size)
{
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	return (flags & VM_NORESERVE) ?
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		0 : security_vm_enough_memory_mm(current->mm, VM_ACCT(size));
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}

static inline void shmem_unacct_size(unsigned long flags, loff_t size)
{
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	if (!(flags & VM_NORESERVE))
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		vm_unacct_memory(VM_ACCT(size));
}

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static inline int shmem_reacct_size(unsigned long flags,
		loff_t oldsize, loff_t newsize)
{
	if (!(flags & VM_NORESERVE)) {
		if (VM_ACCT(newsize) > VM_ACCT(oldsize))
			return security_vm_enough_memory_mm(current->mm,
					VM_ACCT(newsize) - VM_ACCT(oldsize));
		else if (VM_ACCT(newsize) < VM_ACCT(oldsize))
			vm_unacct_memory(VM_ACCT(oldsize) - VM_ACCT(newsize));
	}
	return 0;
}

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/*
 * ... whereas tmpfs objects are accounted incrementally as
 * pages are allocated, in order to allow huge sparse files.
 * shmem_getpage reports shmem_acct_block failure as -ENOSPC not -ENOMEM,
 * so that a failure on a sparse tmpfs mapping will give SIGBUS not OOM.
 */
static inline int shmem_acct_block(unsigned long flags)
{
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	return (flags & VM_NORESERVE) ?
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		security_vm_enough_memory_mm(current->mm, VM_ACCT(PAGE_CACHE_SIZE)) : 0;
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}

static inline void shmem_unacct_blocks(unsigned long flags, long pages)
{
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	if (flags & VM_NORESERVE)
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		vm_unacct_memory(pages * VM_ACCT(PAGE_CACHE_SIZE));
}

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static const struct super_operations shmem_ops;
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static const struct address_space_operations shmem_aops;
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static const struct file_operations shmem_file_operations;
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static const struct inode_operations shmem_inode_operations;
static const struct inode_operations shmem_dir_inode_operations;
static const struct inode_operations shmem_special_inode_operations;
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static const struct vm_operations_struct shmem_vm_ops;
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static LIST_HEAD(shmem_swaplist);
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static DEFINE_MUTEX(shmem_swaplist_mutex);
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static int shmem_reserve_inode(struct super_block *sb)
{
	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
	if (sbinfo->max_inodes) {
		spin_lock(&sbinfo->stat_lock);
		if (!sbinfo->free_inodes) {
			spin_unlock(&sbinfo->stat_lock);
			return -ENOSPC;
		}
		sbinfo->free_inodes--;
		spin_unlock(&sbinfo->stat_lock);
	}
	return 0;
}

static void shmem_free_inode(struct super_block *sb)
{
	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
	if (sbinfo->max_inodes) {
		spin_lock(&sbinfo->stat_lock);
		sbinfo->free_inodes++;
		spin_unlock(&sbinfo->stat_lock);
	}
}

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/**
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 * shmem_recalc_inode - recalculate the block usage of an inode
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 * @inode: inode to recalc
 *
 * We have to calculate the free blocks since the mm can drop
 * undirtied hole pages behind our back.
 *
 * But normally   info->alloced == inode->i_mapping->nrpages + info->swapped
 * So mm freed is info->alloced - (inode->i_mapping->nrpages + info->swapped)
 *
 * It has to be called with the spinlock held.
 */
static void shmem_recalc_inode(struct inode *inode)
{
	struct shmem_inode_info *info = SHMEM_I(inode);
	long freed;

	freed = info->alloced - info->swapped - inode->i_mapping->nrpages;
	if (freed > 0) {
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		struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
		if (sbinfo->max_blocks)
			percpu_counter_add(&sbinfo->used_blocks, -freed);
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		info->alloced -= freed;
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		inode->i_blocks -= freed * BLOCKS_PER_PAGE;
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		shmem_unacct_blocks(info->flags, freed);
	}
}

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/*
 * Replace item expected in radix tree by a new item, while holding tree lock.
 */
static int shmem_radix_tree_replace(struct address_space *mapping,
			pgoff_t index, void *expected, void *replacement)
{
	void **pslot;
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	void *item;
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	VM_BUG_ON(!expected);
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	VM_BUG_ON(!replacement);
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	pslot = radix_tree_lookup_slot(&mapping->page_tree, index);
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	if (!pslot)
		return -ENOENT;
	item = radix_tree_deref_slot_protected(pslot, &mapping->tree_lock);
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	if (item != expected)
		return -ENOENT;
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	radix_tree_replace_slot(pslot, replacement);
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	return 0;
}

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/*
 * Sometimes, before we decide whether to proceed or to fail, we must check
 * that an entry was not already brought back from swap by a racing thread.
 *
 * Checking page is not enough: by the time a SwapCache page is locked, it
 * might be reused, and again be SwapCache, using the same swap as before.
 */
static bool shmem_confirm_swap(struct address_space *mapping,
			       pgoff_t index, swp_entry_t swap)
{
	void *item;

	rcu_read_lock();
	item = radix_tree_lookup(&mapping->page_tree, index);
	rcu_read_unlock();
	return item == swp_to_radix_entry(swap);
}

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/*
 * Like add_to_page_cache_locked, but error if expected item has gone.
 */
static int shmem_add_to_page_cache(struct page *page,
				   struct address_space *mapping,
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				   pgoff_t index, void *expected)
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{
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	int error;
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	VM_BUG_ON_PAGE(!PageLocked(page), page);
	VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
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	page_cache_get(page);
	page->mapping = mapping;
	page->index = index;

	spin_lock_irq(&mapping->tree_lock);
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	if (!expected)
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		error = radix_tree_insert(&mapping->page_tree, index, page);
	else
		error = shmem_radix_tree_replace(mapping, index, expected,
								 page);
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	if (!error) {
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		mapping->nrpages++;
		__inc_zone_page_state(page, NR_FILE_PAGES);
		__inc_zone_page_state(page, NR_SHMEM);
		spin_unlock_irq(&mapping->tree_lock);
	} else {
		page->mapping = NULL;
		spin_unlock_irq(&mapping->tree_lock);
		page_cache_release(page);
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	}
	return error;
}

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/*
 * Like delete_from_page_cache, but substitutes swap for page.
 */
static void shmem_delete_from_page_cache(struct page *page, void *radswap)
{
	struct address_space *mapping = page->mapping;
	int error;

	spin_lock_irq(&mapping->tree_lock);
	error = shmem_radix_tree_replace(mapping, page->index, page, radswap);
	page->mapping = NULL;
	mapping->nrpages--;
	__dec_zone_page_state(page, NR_FILE_PAGES);
	__dec_zone_page_state(page, NR_SHMEM);
	spin_unlock_irq(&mapping->tree_lock);
	page_cache_release(page);
	BUG_ON(error);
}

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/*
 * Remove swap entry from radix tree, free the swap and its page cache.
 */
static int shmem_free_swap(struct address_space *mapping,
			   pgoff_t index, void *radswap)
{
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	void *old;
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	spin_lock_irq(&mapping->tree_lock);
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	old = radix_tree_delete_item(&mapping->page_tree, index, radswap);
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	spin_unlock_irq(&mapping->tree_lock);
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	if (old != radswap)
		return -ENOENT;
	free_swap_and_cache(radix_to_swp_entry(radswap));
	return 0;
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}

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/*
 * SysV IPC SHM_UNLOCK restore Unevictable pages to their evictable lists.
 */
void shmem_unlock_mapping(struct address_space *mapping)
{
	struct pagevec pvec;
	pgoff_t indices[PAGEVEC_SIZE];
	pgoff_t index = 0;

	pagevec_init(&pvec, 0);
	/*
	 * Minor point, but we might as well stop if someone else SHM_LOCKs it.
	 */
	while (!mapping_unevictable(mapping)) {
		/*
		 * Avoid pagevec_lookup(): find_get_pages() returns 0 as if it
		 * has finished, if it hits a row of PAGEVEC_SIZE swap entries.
		 */
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		pvec.nr = find_get_entries(mapping, index,
					   PAGEVEC_SIZE, pvec.pages, indices);
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		if (!pvec.nr)
			break;
		index = indices[pvec.nr - 1] + 1;
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		pagevec_remove_exceptionals(&pvec);
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		check_move_unevictable_pages(pvec.pages, pvec.nr);
		pagevec_release(&pvec);
		cond_resched();
	}
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}

/*
 * Remove range of pages and swap entries from radix tree, and free them.
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 * If !unfalloc, truncate or punch hole; if unfalloc, undo failed fallocate.
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 */
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static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend,
								 bool unfalloc)
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{
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	struct address_space *mapping = inode->i_mapping;
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	struct shmem_inode_info *info = SHMEM_I(inode);
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	pgoff_t start = (lstart + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
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	pgoff_t end = (lend + 1) >> PAGE_CACHE_SHIFT;
	unsigned int partial_start = lstart & (PAGE_CACHE_SIZE - 1);
	unsigned int partial_end = (lend + 1) & (PAGE_CACHE_SIZE - 1);
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	struct pagevec pvec;
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	pgoff_t indices[PAGEVEC_SIZE];
	long nr_swaps_freed = 0;
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	pgoff_t index;
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	int i;

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	if (lend == -1)
		end = -1;	/* unsigned, so actually very big */
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	pagevec_init(&pvec, 0);
	index = start;
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	while (index < end) {
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		pvec.nr = find_get_entries(mapping, index,
			min(end - index, (pgoff_t)PAGEVEC_SIZE),
			pvec.pages, indices);
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		if (!pvec.nr)
			break;
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		for (i = 0; i < pagevec_count(&pvec); i++) {
			struct page *page = pvec.pages[i];

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			index = indices[i];
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			if (index >= end)
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				break;

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			if (radix_tree_exceptional_entry(page)) {
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				if (unfalloc)
					continue;
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				nr_swaps_freed += !shmem_free_swap(mapping,
								index, page);
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				continue;
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			}

			if (!trylock_page(page))
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				continue;
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			if (!unfalloc || !PageUptodate(page)) {
				if (page->mapping == mapping) {
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					VM_BUG_ON_PAGE(PageWriteback(page), page);
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					truncate_inode_page(mapping, page);
				}
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			}
			unlock_page(page);
		}
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		pagevec_remove_exceptionals(&pvec);
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		pagevec_release(&pvec);
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		cond_resched();
		index++;
	}
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	if (partial_start) {
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		struct page *page = NULL;
		shmem_getpage(inode, start - 1, &page, SGP_READ, NULL);
		if (page) {
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			unsigned int top = PAGE_CACHE_SIZE;
			if (start > end) {
				top = partial_end;
				partial_end = 0;
			}
			zero_user_segment(page, partial_start, top);
			set_page_dirty(page);
			unlock_page(page);
			page_cache_release(page);
		}
	}
	if (partial_end) {
		struct page *page = NULL;
		shmem_getpage(inode, end, &page, SGP_READ, NULL);
		if (page) {
			zero_user_segment(page, 0, partial_end);
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			set_page_dirty(page);
			unlock_page(page);
			page_cache_release(page);
		}
	}
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	if (start >= end)
		return;
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	index = start;
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	while (index < end) {
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		cond_resched();
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		pvec.nr = find_get_entries(mapping, index,
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				min(end - index, (pgoff_t)PAGEVEC_SIZE),
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				pvec.pages, indices);
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		if (!pvec.nr) {
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			/* If all gone or hole-punch or unfalloc, we're done */
			if (index == start || end != -1)
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				break;
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			/* But if truncating, restart to make sure all gone */
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			index = start;
			continue;
		}
		for (i = 0; i < pagevec_count(&pvec); i++) {
			struct page *page = pvec.pages[i];

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			index = indices[i];
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			if (index >= end)
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				break;

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			if (radix_tree_exceptional_entry(page)) {
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				if (unfalloc)
					continue;
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				if (shmem_free_swap(mapping, index, page)) {
					/* Swap was replaced by page: retry */
					index--;
					break;
				}
				nr_swaps_freed++;
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				continue;
			}

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			lock_page(page);
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			if (!unfalloc || !PageUptodate(page)) {
				if (page->mapping == mapping) {
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					VM_BUG_ON_PAGE(PageWriteback(page), page);
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					truncate_inode_page(mapping, page);
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				} else {
					/* Page was replaced by swap: retry */
					unlock_page(page);
					index--;
					break;
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				}
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			}
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			unlock_page(page);
		}
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		pagevec_remove_exceptionals(&pvec);
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		pagevec_release(&pvec);
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		index++;
	}
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	spin_lock(&info->lock);
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	info->swapped -= nr_swaps_freed;
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	shmem_recalc_inode(inode);
	spin_unlock(&info->lock);
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}
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void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
{
	shmem_undo_range(inode, lstart, lend, false);
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	inode->i_ctime = inode->i_mtime = CURRENT_TIME;
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}
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EXPORT_SYMBOL_GPL(shmem_truncate_range);
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static int shmem_getattr(struct vfsmount *mnt, struct dentry *dentry,
			 struct kstat *stat)
{
	struct inode *inode = dentry->d_inode;
	struct shmem_inode_info *info = SHMEM_I(inode);

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	if (info->alloced - info->swapped != inode->i_mapping->nrpages) {
		spin_lock(&info->lock);
		shmem_recalc_inode(inode);
		spin_unlock(&info->lock);
	}
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	generic_fillattr(inode, stat);
	return 0;
}

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static int shmem_setattr(struct dentry *dentry, struct iattr *attr)
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{
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	struct inode *inode = d_inode(dentry);
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	struct shmem_inode_info *info = SHMEM_I(inode);
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	int error;

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	error = inode_change_ok(inode, attr);
	if (error)
		return error;

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	if (S_ISREG(inode->i_mode) && (attr->ia_valid & ATTR_SIZE)) {
		loff_t oldsize = inode->i_size;
		loff_t newsize = attr->ia_size;
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		/* protected by i_mutex */
		if ((newsize < oldsize && (info->seals & F_SEAL_SHRINK)) ||
		    (newsize > oldsize && (info->seals & F_SEAL_GROW)))
			return -EPERM;

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		if (newsize != oldsize) {
582 583 584 585
			error = shmem_reacct_size(SHMEM_I(inode)->flags,
					oldsize, newsize);
			if (error)
				return error;
586 587 588
			i_size_write(inode, newsize);
			inode->i_ctime = inode->i_mtime = CURRENT_TIME;
		}
589
		if (newsize <= oldsize) {
590
			loff_t holebegin = round_up(newsize, PAGE_SIZE);
591 592 593 594 595 596
			if (oldsize > holebegin)
				unmap_mapping_range(inode->i_mapping,
							holebegin, 0, 1);
			if (info->alloced)
				shmem_truncate_range(inode,
							newsize, (loff_t)-1);
597
			/* unmap again to remove racily COWed private pages */
598 599 600
			if (oldsize > holebegin)
				unmap_mapping_range(inode->i_mapping,
							holebegin, 0, 1);
601
		}
L
Linus Torvalds 已提交
602 603
	}

604 605
	setattr_copy(inode, attr);
	if (attr->ia_valid & ATTR_MODE)
C
Christoph Hellwig 已提交
606
		error = posix_acl_chmod(inode, inode->i_mode);
L
Linus Torvalds 已提交
607 608 609
	return error;
}

A
Al Viro 已提交
610
static void shmem_evict_inode(struct inode *inode)
L
Linus Torvalds 已提交
611 612 613
{
	struct shmem_inode_info *info = SHMEM_I(inode);

614
	if (inode->i_mapping->a_ops == &shmem_aops) {
L
Linus Torvalds 已提交
615 616
		shmem_unacct_size(info->flags, inode->i_size);
		inode->i_size = 0;
617
		shmem_truncate_range(inode, 0, (loff_t)-1);
L
Linus Torvalds 已提交
618
		if (!list_empty(&info->swaplist)) {
619
			mutex_lock(&shmem_swaplist_mutex);
L
Linus Torvalds 已提交
620
			list_del_init(&info->swaplist);
621
			mutex_unlock(&shmem_swaplist_mutex);
L
Linus Torvalds 已提交
622
		}
623 624
	} else
		kfree(info->symlink);
625

626
	simple_xattrs_free(&info->xattrs);
627
	WARN_ON(inode->i_blocks);
628
	shmem_free_inode(inode->i_sb);
629
	clear_inode(inode);
L
Linus Torvalds 已提交
630 631
}

632 633 634
/*
 * If swap found in inode, free it and move page from swapcache to filecache.
 */
635
static int shmem_unuse_inode(struct shmem_inode_info *info,
636
			     swp_entry_t swap, struct page **pagep)
L
Linus Torvalds 已提交
637
{
638
	struct address_space *mapping = info->vfs_inode.i_mapping;
639
	void *radswap;
640
	pgoff_t index;
641 642
	gfp_t gfp;
	int error = 0;
L
Linus Torvalds 已提交
643

644
	radswap = swp_to_radix_entry(swap);
645
	index = radix_tree_locate_item(&mapping->page_tree, radswap);
646
	if (index == -1)
647
		return -EAGAIN;	/* tell shmem_unuse we found nothing */
648

H
Hugh Dickins 已提交
649 650
	/*
	 * Move _head_ to start search for next from here.
A
Al Viro 已提交
651
	 * But be careful: shmem_evict_inode checks list_empty without taking
H
Hugh Dickins 已提交
652
	 * mutex, and there's an instant in list_move_tail when info->swaplist
653
	 * would appear empty, if it were the only one on shmem_swaplist.
H
Hugh Dickins 已提交
654 655 656
	 */
	if (shmem_swaplist.next != &info->swaplist)
		list_move_tail(&shmem_swaplist, &info->swaplist);
657

658 659 660 661 662 663 664
	gfp = mapping_gfp_mask(mapping);
	if (shmem_should_replace_page(*pagep, gfp)) {
		mutex_unlock(&shmem_swaplist_mutex);
		error = shmem_replace_page(pagep, gfp, info, index);
		mutex_lock(&shmem_swaplist_mutex);
		/*
		 * We needed to drop mutex to make that restrictive page
665 666 667 668 669 670 671 672 673 674 675 676 677 678 679
		 * allocation, but the inode might have been freed while we
		 * dropped it: although a racing shmem_evict_inode() cannot
		 * complete without emptying the radix_tree, our page lock
		 * on this swapcache page is not enough to prevent that -
		 * free_swap_and_cache() of our swap entry will only
		 * trylock_page(), removing swap from radix_tree whatever.
		 *
		 * We must not proceed to shmem_add_to_page_cache() if the
		 * inode has been freed, but of course we cannot rely on
		 * inode or mapping or info to check that.  However, we can
		 * safely check if our swap entry is still in use (and here
		 * it can't have got reused for another page): if it's still
		 * in use, then the inode cannot have been freed yet, and we
		 * can safely proceed (if it's no longer in use, that tells
		 * nothing about the inode, but we don't need to unuse swap).
680 681 682 683 684
		 */
		if (!page_swapcount(*pagep))
			error = -ENOENT;
	}

K
KAMEZAWA Hiroyuki 已提交
685
	/*
686 687 688
	 * We rely on shmem_swaplist_mutex, not only to protect the swaplist,
	 * but also to hold up shmem_evict_inode(): so inode cannot be freed
	 * beneath us (pagelock doesn't help until the page is in pagecache).
K
KAMEZAWA Hiroyuki 已提交
689
	 */
690 691
	if (!error)
		error = shmem_add_to_page_cache(*pagep, mapping, index,
692
						radswap);
693
	if (error != -ENOMEM) {
694 695 696 697
		/*
		 * Truncation and eviction use free_swap_and_cache(), which
		 * only does trylock page: if we raced, best clean up here.
		 */
698 699
		delete_from_swap_cache(*pagep);
		set_page_dirty(*pagep);
700 701 702 703 704 705
		if (!error) {
			spin_lock(&info->lock);
			info->swapped--;
			spin_unlock(&info->lock);
			swap_free(swap);
		}
L
Linus Torvalds 已提交
706
	}
707
	return error;
L
Linus Torvalds 已提交
708 709 710
}

/*
711
 * Search through swapped inodes to find and replace swap by page.
L
Linus Torvalds 已提交
712
 */
713
int shmem_unuse(swp_entry_t swap, struct page *page)
L
Linus Torvalds 已提交
714
{
715
	struct list_head *this, *next;
L
Linus Torvalds 已提交
716
	struct shmem_inode_info *info;
717
	struct mem_cgroup *memcg;
718 719 720 721
	int error = 0;

	/*
	 * There's a faint possibility that swap page was replaced before
722
	 * caller locked it: caller will come back later with the right page.
723
	 */
724
	if (unlikely(!PageSwapCache(page) || page_private(page) != swap.val))
725
		goto out;
726 727 728 729 730 731

	/*
	 * Charge page using GFP_KERNEL while we can wait, before taking
	 * the shmem_swaplist_mutex which might hold up shmem_writepage().
	 * Charged back to the user (not to caller) when swap account is used.
	 */
732
	error = mem_cgroup_try_charge(page, current->mm, GFP_KERNEL, &memcg);
733 734
	if (error)
		goto out;
735
	/* No radix_tree_preload: swap entry keeps a place for page in tree */
736
	error = -EAGAIN;
L
Linus Torvalds 已提交
737

738
	mutex_lock(&shmem_swaplist_mutex);
739 740
	list_for_each_safe(this, next, &shmem_swaplist) {
		info = list_entry(this, struct shmem_inode_info, swaplist);
741
		if (info->swapped)
742
			error = shmem_unuse_inode(info, swap, &page);
743 744
		else
			list_del_init(&info->swaplist);
745
		cond_resched();
746
		if (error != -EAGAIN)
747
			break;
748
		/* found nothing in this: move on to search the next */
L
Linus Torvalds 已提交
749
	}
750
	mutex_unlock(&shmem_swaplist_mutex);
751

752 753 754 755 756 757
	if (error) {
		if (error != -ENOMEM)
			error = 0;
		mem_cgroup_cancel_charge(page, memcg);
	} else
		mem_cgroup_commit_charge(page, memcg, true);
758
out:
H
Hugh Dickins 已提交
759 760
	unlock_page(page);
	page_cache_release(page);
761
	return error;
L
Linus Torvalds 已提交
762 763 764 765 766 767 768 769 770 771
}

/*
 * Move the page from the page cache to the swap cache.
 */
static int shmem_writepage(struct page *page, struct writeback_control *wbc)
{
	struct shmem_inode_info *info;
	struct address_space *mapping;
	struct inode *inode;
772 773
	swp_entry_t swap;
	pgoff_t index;
L
Linus Torvalds 已提交
774 775 776 777 778 779 780 781

	BUG_ON(!PageLocked(page));
	mapping = page->mapping;
	index = page->index;
	inode = mapping->host;
	info = SHMEM_I(inode);
	if (info->flags & VM_LOCKED)
		goto redirty;
782
	if (!total_swap_pages)
L
Linus Torvalds 已提交
783 784
		goto redirty;

785
	/*
C
Christoph Hellwig 已提交
786 787 788 789 790
	 * Our capabilities prevent regular writeback or sync from ever calling
	 * shmem_writepage; but a stacking filesystem might use ->writepage of
	 * its underlying filesystem, in which case tmpfs should write out to
	 * swap only in response to memory pressure, and not for the writeback
	 * threads or sync.
791
	 */
792 793 794 795
	if (!wbc->for_reclaim) {
		WARN_ON_ONCE(1);	/* Still happens? Tell us about it! */
		goto redirty;
	}
796 797 798 799 800

	/*
	 * This is somewhat ridiculous, but without plumbing a SWAP_MAP_FALLOC
	 * value into swapfile.c, the only way we can correctly account for a
	 * fallocated page arriving here is now to initialize it and write it.
801 802 803 804 805 806
	 *
	 * That's okay for a page already fallocated earlier, but if we have
	 * not yet completed the fallocation, then (a) we want to keep track
	 * of this page in case we have to undo it, and (b) it may not be a
	 * good idea to continue anyway, once we're pushing into swap.  So
	 * reactivate the page, and let shmem_fallocate() quit when too many.
807 808
	 */
	if (!PageUptodate(page)) {
809 810 811 812 813
		if (inode->i_private) {
			struct shmem_falloc *shmem_falloc;
			spin_lock(&inode->i_lock);
			shmem_falloc = inode->i_private;
			if (shmem_falloc &&
814
			    !shmem_falloc->waitq &&
815 816 817 818 819 820 821 822 823
			    index >= shmem_falloc->start &&
			    index < shmem_falloc->next)
				shmem_falloc->nr_unswapped++;
			else
				shmem_falloc = NULL;
			spin_unlock(&inode->i_lock);
			if (shmem_falloc)
				goto redirty;
		}
824 825 826 827 828
		clear_highpage(page);
		flush_dcache_page(page);
		SetPageUptodate(page);
	}

829 830 831
	swap = get_swap_page();
	if (!swap.val)
		goto redirty;
832

833 834
	/*
	 * Add inode to shmem_unuse()'s list of swapped-out inodes,
835 836
	 * if it's not already there.  Do it now before the page is
	 * moved to swap cache, when its pagelock no longer protects
837
	 * the inode from eviction.  But don't unlock the mutex until
838 839
	 * we've incremented swapped, because shmem_unuse_inode() will
	 * prune a !swapped inode from the swaplist under this mutex.
840
	 */
841 842 843
	mutex_lock(&shmem_swaplist_mutex);
	if (list_empty(&info->swaplist))
		list_add_tail(&info->swaplist, &shmem_swaplist);
844

845
	if (add_to_swap_cache(page, swap, GFP_ATOMIC) == 0) {
846 847
		spin_lock(&info->lock);
		shmem_recalc_inode(inode);
848
		info->swapped++;
849
		spin_unlock(&info->lock);
850

851 852 853
		swap_shmem_alloc(swap);
		shmem_delete_from_page_cache(page, swp_to_radix_entry(swap));

854
		mutex_unlock(&shmem_swaplist_mutex);
855
		BUG_ON(page_mapped(page));
H
Hugh Dickins 已提交
856
		swap_writepage(page, wbc);
L
Linus Torvalds 已提交
857 858 859
		return 0;
	}

860
	mutex_unlock(&shmem_swaplist_mutex);
861
	swapcache_free(swap);
L
Linus Torvalds 已提交
862 863
redirty:
	set_page_dirty(page);
864 865 866 867
	if (wbc->for_reclaim)
		return AOP_WRITEPAGE_ACTIVATE;	/* Return with page locked */
	unlock_page(page);
	return 0;
L
Linus Torvalds 已提交
868 869 870
}

#ifdef CONFIG_NUMA
871
#ifdef CONFIG_TMPFS
872
static void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
873
{
874
	char buffer[64];
875

876
	if (!mpol || mpol->mode == MPOL_DEFAULT)
877
		return;		/* show nothing */
878

879
	mpol_to_str(buffer, sizeof(buffer), mpol);
880 881

	seq_printf(seq, ",mpol=%s", buffer);
882
}
883 884 885 886 887 888 889 890 891 892 893 894

static struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
{
	struct mempolicy *mpol = NULL;
	if (sbinfo->mpol) {
		spin_lock(&sbinfo->stat_lock);	/* prevent replace/use races */
		mpol = sbinfo->mpol;
		mpol_get(mpol);
		spin_unlock(&sbinfo->stat_lock);
	}
	return mpol;
}
895 896
#endif /* CONFIG_TMPFS */

897 898
static struct page *shmem_swapin(swp_entry_t swap, gfp_t gfp,
			struct shmem_inode_info *info, pgoff_t index)
L
Linus Torvalds 已提交
899 900
{
	struct vm_area_struct pvma;
M
Mel Gorman 已提交
901
	struct page *page;
902

L
Linus Torvalds 已提交
903
	/* Create a pseudo vma that just contains the policy */
904
	pvma.vm_start = 0;
905 906
	/* Bias interleave by inode number to distribute better across nodes */
	pvma.vm_pgoff = index + info->vfs_inode.i_ino;
907
	pvma.vm_ops = NULL;
M
Mel Gorman 已提交
908 909 910 911 912 913 914 915
	pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, index);

	page = swapin_readahead(swap, gfp, &pvma, 0);

	/* Drop reference taken by mpol_shared_policy_lookup() */
	mpol_cond_put(pvma.vm_policy);

	return page;
L
Linus Torvalds 已提交
916 917
}

918
static struct page *shmem_alloc_page(gfp_t gfp,
919
			struct shmem_inode_info *info, pgoff_t index)
L
Linus Torvalds 已提交
920 921
{
	struct vm_area_struct pvma;
M
Mel Gorman 已提交
922
	struct page *page;
L
Linus Torvalds 已提交
923

924 925
	/* Create a pseudo vma that just contains the policy */
	pvma.vm_start = 0;
926 927
	/* Bias interleave by inode number to distribute better across nodes */
	pvma.vm_pgoff = index + info->vfs_inode.i_ino;
928
	pvma.vm_ops = NULL;
929
	pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, index);
930

M
Mel Gorman 已提交
931 932 933 934 935 936
	page = alloc_page_vma(gfp, &pvma, 0);

	/* Drop reference taken by mpol_shared_policy_lookup() */
	mpol_cond_put(pvma.vm_policy);

	return page;
L
Linus Torvalds 已提交
937
}
938 939
#else /* !CONFIG_NUMA */
#ifdef CONFIG_TMPFS
940
static inline void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
941 942 943 944
{
}
#endif /* CONFIG_TMPFS */

945 946
static inline struct page *shmem_swapin(swp_entry_t swap, gfp_t gfp,
			struct shmem_inode_info *info, pgoff_t index)
L
Linus Torvalds 已提交
947
{
948
	return swapin_readahead(swap, gfp, NULL, 0);
L
Linus Torvalds 已提交
949 950
}

951
static inline struct page *shmem_alloc_page(gfp_t gfp,
952
			struct shmem_inode_info *info, pgoff_t index)
L
Linus Torvalds 已提交
953
{
954
	return alloc_page(gfp);
L
Linus Torvalds 已提交
955
}
956
#endif /* CONFIG_NUMA */
L
Linus Torvalds 已提交
957

958 959 960 961 962 963 964
#if !defined(CONFIG_NUMA) || !defined(CONFIG_TMPFS)
static inline struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
{
	return NULL;
}
#endif

965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004
/*
 * When a page is moved from swapcache to shmem filecache (either by the
 * usual swapin of shmem_getpage_gfp(), or by the less common swapoff of
 * shmem_unuse_inode()), it may have been read in earlier from swap, in
 * ignorance of the mapping it belongs to.  If that mapping has special
 * constraints (like the gma500 GEM driver, which requires RAM below 4GB),
 * we may need to copy to a suitable page before moving to filecache.
 *
 * In a future release, this may well be extended to respect cpuset and
 * NUMA mempolicy, and applied also to anonymous pages in do_swap_page();
 * but for now it is a simple matter of zone.
 */
static bool shmem_should_replace_page(struct page *page, gfp_t gfp)
{
	return page_zonenum(page) > gfp_zone(gfp);
}

static int shmem_replace_page(struct page **pagep, gfp_t gfp,
				struct shmem_inode_info *info, pgoff_t index)
{
	struct page *oldpage, *newpage;
	struct address_space *swap_mapping;
	pgoff_t swap_index;
	int error;

	oldpage = *pagep;
	swap_index = page_private(oldpage);
	swap_mapping = page_mapping(oldpage);

	/*
	 * We have arrived here because our zones are constrained, so don't
	 * limit chance of success by further cpuset and node constraints.
	 */
	gfp &= ~GFP_CONSTRAINT_MASK;
	newpage = shmem_alloc_page(gfp, info, index);
	if (!newpage)
		return -ENOMEM;

	page_cache_get(newpage);
	copy_highpage(newpage, oldpage);
1005
	flush_dcache_page(newpage);
1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019

	__set_page_locked(newpage);
	SetPageUptodate(newpage);
	SetPageSwapBacked(newpage);
	set_page_private(newpage, swap_index);
	SetPageSwapCache(newpage);

	/*
	 * Our caller will very soon move newpage out of swapcache, but it's
	 * a nice clean interface for us to replace oldpage by newpage there.
	 */
	spin_lock_irq(&swap_mapping->tree_lock);
	error = shmem_radix_tree_replace(swap_mapping, swap_index, oldpage,
								   newpage);
1020 1021 1022 1023
	if (!error) {
		__inc_zone_page_state(newpage, NR_FILE_PAGES);
		__dec_zone_page_state(oldpage, NR_FILE_PAGES);
	}
1024 1025
	spin_unlock_irq(&swap_mapping->tree_lock);

1026 1027 1028 1029 1030 1031 1032 1033
	if (unlikely(error)) {
		/*
		 * Is this possible?  I think not, now that our callers check
		 * both PageSwapCache and page_private after getting page lock;
		 * but be defensive.  Reverse old to newpage for clear and free.
		 */
		oldpage = newpage;
	} else {
1034
		mem_cgroup_replace_page(oldpage, newpage);
1035 1036 1037
		lru_cache_add_anon(newpage);
		*pagep = newpage;
	}
1038 1039 1040 1041 1042 1043 1044

	ClearPageSwapCache(oldpage);
	set_page_private(oldpage, 0);

	unlock_page(oldpage);
	page_cache_release(oldpage);
	page_cache_release(oldpage);
1045
	return error;
1046 1047
}

L
Linus Torvalds 已提交
1048
/*
1049
 * shmem_getpage_gfp - find page in cache, or get from swap, or allocate
L
Linus Torvalds 已提交
1050 1051 1052 1053 1054
 *
 * If we allocate a new one we do not mark it dirty. That's up to the
 * vm. If we swap it in we mark it dirty since we also free the swap
 * entry since a page cannot live in both the swap and page cache
 */
1055
static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
1056
	struct page **pagep, enum sgp_type sgp, gfp_t gfp, int *fault_type)
L
Linus Torvalds 已提交
1057 1058
{
	struct address_space *mapping = inode->i_mapping;
1059
	struct shmem_inode_info *info;
L
Linus Torvalds 已提交
1060
	struct shmem_sb_info *sbinfo;
1061
	struct mem_cgroup *memcg;
H
Hugh Dickins 已提交
1062
	struct page *page;
L
Linus Torvalds 已提交
1063 1064
	swp_entry_t swap;
	int error;
1065
	int once = 0;
1066
	int alloced = 0;
L
Linus Torvalds 已提交
1067

1068
	if (index > (MAX_LFS_FILESIZE >> PAGE_CACHE_SHIFT))
L
Linus Torvalds 已提交
1069 1070
		return -EFBIG;
repeat:
1071
	swap.val = 0;
1072
	page = find_lock_entry(mapping, index);
1073 1074 1075 1076 1077
	if (radix_tree_exceptional_entry(page)) {
		swap = radix_to_swp_entry(page);
		page = NULL;
	}

1078
	if (sgp != SGP_WRITE && sgp != SGP_FALLOC &&
1079 1080
	    ((loff_t)index << PAGE_CACHE_SHIFT) >= i_size_read(inode)) {
		error = -EINVAL;
1081
		goto unlock;
1082 1083
	}

1084 1085 1086
	if (page && sgp == SGP_WRITE)
		mark_page_accessed(page);

1087 1088 1089 1090 1091 1092 1093 1094
	/* fallocated page? */
	if (page && !PageUptodate(page)) {
		if (sgp != SGP_READ)
			goto clear;
		unlock_page(page);
		page_cache_release(page);
		page = NULL;
	}
1095 1096 1097
	if (page || (sgp == SGP_READ && !swap.val)) {
		*pagep = page;
		return 0;
H
Hugh Dickins 已提交
1098 1099 1100
	}

	/*
1101 1102
	 * Fast cache lookup did not find it:
	 * bring it back from swap or allocate.
H
Hugh Dickins 已提交
1103
	 */
1104 1105
	info = SHMEM_I(inode);
	sbinfo = SHMEM_SB(inode->i_sb);
L
Linus Torvalds 已提交
1106 1107 1108

	if (swap.val) {
		/* Look it up and read it in.. */
H
Hugh Dickins 已提交
1109 1110
		page = lookup_swap_cache(swap);
		if (!page) {
L
Linus Torvalds 已提交
1111
			/* here we actually do the io */
1112 1113
			if (fault_type)
				*fault_type |= VM_FAULT_MAJOR;
1114
			page = shmem_swapin(swap, gfp, info, index);
H
Hugh Dickins 已提交
1115
			if (!page) {
1116 1117
				error = -ENOMEM;
				goto failed;
L
Linus Torvalds 已提交
1118 1119 1120 1121
			}
		}

		/* We have to do this with page locked to prevent races */
1122
		lock_page(page);
1123
		if (!PageSwapCache(page) || page_private(page) != swap.val ||
1124
		    !shmem_confirm_swap(mapping, index, swap)) {
1125
			error = -EEXIST;	/* try again */
1126
			goto unlock;
1127
		}
H
Hugh Dickins 已提交
1128
		if (!PageUptodate(page)) {
L
Linus Torvalds 已提交
1129
			error = -EIO;
1130
			goto failed;
L
Linus Torvalds 已提交
1131
		}
1132 1133
		wait_on_page_writeback(page);

1134 1135 1136 1137
		if (shmem_should_replace_page(page, gfp)) {
			error = shmem_replace_page(&page, gfp, info, index);
			if (error)
				goto failed;
L
Linus Torvalds 已提交
1138
		}
H
Hugh Dickins 已提交
1139

1140
		error = mem_cgroup_try_charge(page, current->mm, gfp, &memcg);
1141
		if (!error) {
1142
			error = shmem_add_to_page_cache(page, mapping, index,
1143
						swp_to_radix_entry(swap));
1144 1145 1146 1147 1148 1149 1150 1151
			/*
			 * We already confirmed swap under page lock, and make
			 * no memory allocation here, so usually no possibility
			 * of error; but free_swap_and_cache() only trylocks a
			 * page, so it is just possible that the entry has been
			 * truncated or holepunched since swap was confirmed.
			 * shmem_undo_range() will have done some of the
			 * unaccounting, now delete_from_swap_cache() will do
1152
			 * the rest.
1153 1154 1155
			 * Reset swap.val? No, leave it so "failed" goes back to
			 * "repeat": reading a hole and writing should succeed.
			 */
1156 1157
			if (error) {
				mem_cgroup_cancel_charge(page, memcg);
1158
				delete_from_swap_cache(page);
1159
			}
1160
		}
1161 1162 1163
		if (error)
			goto failed;

1164 1165
		mem_cgroup_commit_charge(page, memcg, true);

1166
		spin_lock(&info->lock);
1167
		info->swapped--;
1168
		shmem_recalc_inode(inode);
H
Hugh Dickins 已提交
1169
		spin_unlock(&info->lock);
1170

1171 1172 1173
		if (sgp == SGP_WRITE)
			mark_page_accessed(page);

1174
		delete_from_swap_cache(page);
H
Hugh Dickins 已提交
1175 1176 1177
		set_page_dirty(page);
		swap_free(swap);

1178 1179 1180 1181
	} else {
		if (shmem_acct_block(info->flags)) {
			error = -ENOSPC;
			goto failed;
L
Linus Torvalds 已提交
1182
		}
1183
		if (sbinfo->max_blocks) {
1184
			if (percpu_counter_compare(&sbinfo->used_blocks,
1185 1186 1187 1188
						sbinfo->max_blocks) >= 0) {
				error = -ENOSPC;
				goto unacct;
			}
1189
			percpu_counter_inc(&sbinfo->used_blocks);
1190
		}
L
Linus Torvalds 已提交
1191

1192 1193 1194 1195
		page = shmem_alloc_page(gfp, info, index);
		if (!page) {
			error = -ENOMEM;
			goto decused;
L
Linus Torvalds 已提交
1196 1197
		}

1198
		__SetPageSwapBacked(page);
1199
		__set_page_locked(page);
1200
		if (sgp == SGP_WRITE)
1201
			__SetPageReferenced(page);
1202

1203
		error = mem_cgroup_try_charge(page, current->mm, gfp, &memcg);
1204 1205
		if (error)
			goto decused;
1206
		error = radix_tree_maybe_preload(gfp & GFP_RECLAIM_MASK);
1207 1208
		if (!error) {
			error = shmem_add_to_page_cache(page, mapping, index,
1209
							NULL);
1210 1211 1212
			radix_tree_preload_end();
		}
		if (error) {
1213
			mem_cgroup_cancel_charge(page, memcg);
1214 1215
			goto decused;
		}
1216
		mem_cgroup_commit_charge(page, memcg, false);
1217 1218 1219
		lru_cache_add_anon(page);

		spin_lock(&info->lock);
L
Linus Torvalds 已提交
1220
		info->alloced++;
1221 1222
		inode->i_blocks += BLOCKS_PER_PAGE;
		shmem_recalc_inode(inode);
L
Linus Torvalds 已提交
1223
		spin_unlock(&info->lock);
1224
		alloced = true;
1225

1226
		/*
1227 1228 1229 1230 1231 1232 1233 1234 1235
		 * Let SGP_FALLOC use the SGP_WRITE optimization on a new page.
		 */
		if (sgp == SGP_FALLOC)
			sgp = SGP_WRITE;
clear:
		/*
		 * Let SGP_WRITE caller clear ends if write does not fill page;
		 * but SGP_FALLOC on a page fallocated earlier must initialize
		 * it now, lest undo on failure cancel our earlier guarantee.
1236 1237 1238 1239 1240 1241
		 */
		if (sgp != SGP_WRITE) {
			clear_highpage(page);
			flush_dcache_page(page);
			SetPageUptodate(page);
		}
1242
		if (sgp == SGP_DIRTY)
H
Hugh Dickins 已提交
1243
			set_page_dirty(page);
L
Linus Torvalds 已提交
1244
	}
1245

1246
	/* Perhaps the file has been truncated since we checked */
1247
	if (sgp != SGP_WRITE && sgp != SGP_FALLOC &&
1248
	    ((loff_t)index << PAGE_CACHE_SHIFT) >= i_size_read(inode)) {
1249 1250 1251 1252 1253 1254 1255
		if (alloced) {
			ClearPageDirty(page);
			delete_from_page_cache(page);
			spin_lock(&info->lock);
			shmem_recalc_inode(inode);
			spin_unlock(&info->lock);
		}
1256
		error = -EINVAL;
1257
		goto unlock;
H
Hugh Dickins 已提交
1258
	}
1259 1260
	*pagep = page;
	return 0;
L
Linus Torvalds 已提交
1261

1262
	/*
1263
	 * Error recovery.
1264
	 */
1265 1266 1267 1268 1269 1270
decused:
	if (sbinfo->max_blocks)
		percpu_counter_add(&sbinfo->used_blocks, -1);
unacct:
	shmem_unacct_blocks(info->flags, 1);
failed:
1271
	if (swap.val && !shmem_confirm_swap(mapping, index, swap))
1272 1273
		error = -EEXIST;
unlock:
H
Hugh Dickins 已提交
1274
	if (page) {
1275
		unlock_page(page);
H
Hugh Dickins 已提交
1276
		page_cache_release(page);
1277 1278 1279 1280 1281 1282
	}
	if (error == -ENOSPC && !once++) {
		info = SHMEM_I(inode);
		spin_lock(&info->lock);
		shmem_recalc_inode(inode);
		spin_unlock(&info->lock);
H
Hugh Dickins 已提交
1283
		goto repeat;
1284
	}
1285
	if (error == -EEXIST)	/* from above or from radix_tree_insert */
1286 1287
		goto repeat;
	return error;
L
Linus Torvalds 已提交
1288 1289
}

N
Nick Piggin 已提交
1290
static int shmem_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
L
Linus Torvalds 已提交
1291
{
A
Al Viro 已提交
1292
	struct inode *inode = file_inode(vma->vm_file);
L
Linus Torvalds 已提交
1293
	int error;
1294
	int ret = VM_FAULT_LOCKED;
L
Linus Torvalds 已提交
1295

1296 1297 1298 1299
	/*
	 * Trinity finds that probing a hole which tmpfs is punching can
	 * prevent the hole-punch from ever completing: which in turn
	 * locks writers out with its hold on i_mutex.  So refrain from
1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311
	 * faulting pages into the hole while it's being punched.  Although
	 * shmem_undo_range() does remove the additions, it may be unable to
	 * keep up, as each new page needs its own unmap_mapping_range() call,
	 * and the i_mmap tree grows ever slower to scan if new vmas are added.
	 *
	 * It does not matter if we sometimes reach this check just before the
	 * hole-punch begins, so that one fault then races with the punch:
	 * we just need to make racing faults a rare case.
	 *
	 * The implementation below would be much simpler if we just used a
	 * standard mutex or completion: but we cannot take i_mutex in fault,
	 * and bloating every shmem inode for this unlikely case would be sad.
1312 1313 1314 1315 1316 1317
	 */
	if (unlikely(inode->i_private)) {
		struct shmem_falloc *shmem_falloc;

		spin_lock(&inode->i_lock);
		shmem_falloc = inode->i_private;
1318 1319 1320 1321 1322 1323 1324 1325
		if (shmem_falloc &&
		    shmem_falloc->waitq &&
		    vmf->pgoff >= shmem_falloc->start &&
		    vmf->pgoff < shmem_falloc->next) {
			wait_queue_head_t *shmem_falloc_waitq;
			DEFINE_WAIT(shmem_fault_wait);

			ret = VM_FAULT_NOPAGE;
1326 1327
			if ((vmf->flags & FAULT_FLAG_ALLOW_RETRY) &&
			   !(vmf->flags & FAULT_FLAG_RETRY_NOWAIT)) {
1328
				/* It's polite to up mmap_sem if we can */
1329
				up_read(&vma->vm_mm->mmap_sem);
1330
				ret = VM_FAULT_RETRY;
1331
			}
1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349

			shmem_falloc_waitq = shmem_falloc->waitq;
			prepare_to_wait(shmem_falloc_waitq, &shmem_fault_wait,
					TASK_UNINTERRUPTIBLE);
			spin_unlock(&inode->i_lock);
			schedule();

			/*
			 * shmem_falloc_waitq points into the shmem_fallocate()
			 * stack of the hole-punching task: shmem_falloc_waitq
			 * is usually invalid by the time we reach here, but
			 * finish_wait() does not dereference it in that case;
			 * though i_lock needed lest racing with wake_up_all().
			 */
			spin_lock(&inode->i_lock);
			finish_wait(shmem_falloc_waitq, &shmem_fault_wait);
			spin_unlock(&inode->i_lock);
			return ret;
1350
		}
1351
		spin_unlock(&inode->i_lock);
1352 1353
	}

1354
	error = shmem_getpage(inode, vmf->pgoff, &vmf->page, SGP_CACHE, &ret);
N
Nick Piggin 已提交
1355 1356
	if (error)
		return ((error == -ENOMEM) ? VM_FAULT_OOM : VM_FAULT_SIGBUS);
1357

1358 1359 1360 1361
	if (ret & VM_FAULT_MAJOR) {
		count_vm_event(PGMAJFAULT);
		mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
	}
1362
	return ret;
L
Linus Torvalds 已提交
1363 1364 1365
}

#ifdef CONFIG_NUMA
1366
static int shmem_set_policy(struct vm_area_struct *vma, struct mempolicy *mpol)
L
Linus Torvalds 已提交
1367
{
A
Al Viro 已提交
1368
	struct inode *inode = file_inode(vma->vm_file);
1369
	return mpol_set_shared_policy(&SHMEM_I(inode)->policy, vma, mpol);
L
Linus Torvalds 已提交
1370 1371
}

A
Adrian Bunk 已提交
1372 1373
static struct mempolicy *shmem_get_policy(struct vm_area_struct *vma,
					  unsigned long addr)
L
Linus Torvalds 已提交
1374
{
A
Al Viro 已提交
1375
	struct inode *inode = file_inode(vma->vm_file);
1376
	pgoff_t index;
L
Linus Torvalds 已提交
1377

1378 1379
	index = ((addr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
	return mpol_shared_policy_lookup(&SHMEM_I(inode)->policy, index);
L
Linus Torvalds 已提交
1380 1381 1382 1383 1384
}
#endif

int shmem_lock(struct file *file, int lock, struct user_struct *user)
{
A
Al Viro 已提交
1385
	struct inode *inode = file_inode(file);
L
Linus Torvalds 已提交
1386 1387 1388 1389 1390 1391 1392 1393
	struct shmem_inode_info *info = SHMEM_I(inode);
	int retval = -ENOMEM;

	spin_lock(&info->lock);
	if (lock && !(info->flags & VM_LOCKED)) {
		if (!user_shm_lock(inode->i_size, user))
			goto out_nomem;
		info->flags |= VM_LOCKED;
1394
		mapping_set_unevictable(file->f_mapping);
L
Linus Torvalds 已提交
1395 1396 1397 1398
	}
	if (!lock && (info->flags & VM_LOCKED) && user) {
		user_shm_unlock(inode->i_size, user);
		info->flags &= ~VM_LOCKED;
1399
		mapping_clear_unevictable(file->f_mapping);
L
Linus Torvalds 已提交
1400 1401
	}
	retval = 0;
1402

L
Linus Torvalds 已提交
1403 1404 1405 1406 1407
out_nomem:
	spin_unlock(&info->lock);
	return retval;
}

1408
static int shmem_mmap(struct file *file, struct vm_area_struct *vma)
L
Linus Torvalds 已提交
1409 1410 1411 1412 1413 1414
{
	file_accessed(file);
	vma->vm_ops = &shmem_vm_ops;
	return 0;
}

1415
static struct inode *shmem_get_inode(struct super_block *sb, const struct inode *dir,
1416
				     umode_t mode, dev_t dev, unsigned long flags)
L
Linus Torvalds 已提交
1417 1418 1419 1420 1421
{
	struct inode *inode;
	struct shmem_inode_info *info;
	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);

1422 1423
	if (shmem_reserve_inode(sb))
		return NULL;
L
Linus Torvalds 已提交
1424 1425 1426

	inode = new_inode(sb);
	if (inode) {
1427
		inode->i_ino = get_next_ino();
1428
		inode_init_owner(inode, dir, mode);
L
Linus Torvalds 已提交
1429 1430
		inode->i_blocks = 0;
		inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
1431
		inode->i_generation = get_seconds();
L
Linus Torvalds 已提交
1432 1433 1434
		info = SHMEM_I(inode);
		memset(info, 0, (char *)inode - (char *)info);
		spin_lock_init(&info->lock);
D
David Herrmann 已提交
1435
		info->seals = F_SEAL_SEAL;
1436
		info->flags = flags & VM_NORESERVE;
L
Linus Torvalds 已提交
1437
		INIT_LIST_HEAD(&info->swaplist);
1438
		simple_xattrs_init(&info->xattrs);
1439
		cache_no_acl(inode);
L
Linus Torvalds 已提交
1440 1441 1442

		switch (mode & S_IFMT) {
		default:
1443
			inode->i_op = &shmem_special_inode_operations;
L
Linus Torvalds 已提交
1444 1445 1446
			init_special_inode(inode, mode, dev);
			break;
		case S_IFREG:
1447
			inode->i_mapping->a_ops = &shmem_aops;
L
Linus Torvalds 已提交
1448 1449
			inode->i_op = &shmem_inode_operations;
			inode->i_fop = &shmem_file_operations;
1450 1451
			mpol_shared_policy_init(&info->policy,
						 shmem_get_sbmpol(sbinfo));
L
Linus Torvalds 已提交
1452 1453
			break;
		case S_IFDIR:
1454
			inc_nlink(inode);
L
Linus Torvalds 已提交
1455 1456 1457 1458 1459 1460 1461 1462 1463 1464
			/* Some things misbehave if size == 0 on a directory */
			inode->i_size = 2 * BOGO_DIRENT_SIZE;
			inode->i_op = &shmem_dir_inode_operations;
			inode->i_fop = &simple_dir_operations;
			break;
		case S_IFLNK:
			/*
			 * Must not load anything in the rbtree,
			 * mpol_free_shared_policy will not be called.
			 */
1465
			mpol_shared_policy_init(&info->policy, NULL);
L
Linus Torvalds 已提交
1466 1467
			break;
		}
1468 1469
	} else
		shmem_free_inode(sb);
L
Linus Torvalds 已提交
1470 1471 1472
	return inode;
}

1473 1474
bool shmem_mapping(struct address_space *mapping)
{
1475 1476 1477
	if (!mapping->host)
		return false;

C
Christoph Hellwig 已提交
1478
	return mapping->host->i_sb->s_op == &shmem_ops;
1479 1480
}

L
Linus Torvalds 已提交
1481
#ifdef CONFIG_TMPFS
1482
static const struct inode_operations shmem_symlink_inode_operations;
1483
static const struct inode_operations shmem_short_symlink_operations;
L
Linus Torvalds 已提交
1484

1485 1486 1487 1488 1489 1490
#ifdef CONFIG_TMPFS_XATTR
static int shmem_initxattrs(struct inode *, const struct xattr *, void *);
#else
#define shmem_initxattrs NULL
#endif

L
Linus Torvalds 已提交
1491
static int
N
Nick Piggin 已提交
1492 1493 1494
shmem_write_begin(struct file *file, struct address_space *mapping,
			loff_t pos, unsigned len, unsigned flags,
			struct page **pagep, void **fsdata)
L
Linus Torvalds 已提交
1495
{
N
Nick Piggin 已提交
1496
	struct inode *inode = mapping->host;
D
David Herrmann 已提交
1497
	struct shmem_inode_info *info = SHMEM_I(inode);
N
Nick Piggin 已提交
1498
	pgoff_t index = pos >> PAGE_CACHE_SHIFT;
D
David Herrmann 已提交
1499 1500 1501 1502 1503 1504 1505 1506 1507

	/* i_mutex is held by caller */
	if (unlikely(info->seals)) {
		if (info->seals & F_SEAL_WRITE)
			return -EPERM;
		if ((info->seals & F_SEAL_GROW) && pos + len > inode->i_size)
			return -EPERM;
	}

1508
	return shmem_getpage(inode, index, pagep, SGP_WRITE, NULL);
N
Nick Piggin 已提交
1509 1510 1511 1512 1513 1514 1515 1516 1517
}

static int
shmem_write_end(struct file *file, struct address_space *mapping,
			loff_t pos, unsigned len, unsigned copied,
			struct page *page, void *fsdata)
{
	struct inode *inode = mapping->host;

H
Hugh Dickins 已提交
1518 1519 1520
	if (pos + copied > inode->i_size)
		i_size_write(inode, pos + copied);

1521 1522 1523 1524 1525 1526 1527 1528
	if (!PageUptodate(page)) {
		if (copied < PAGE_CACHE_SIZE) {
			unsigned from = pos & (PAGE_CACHE_SIZE - 1);
			zero_user_segments(page, 0, from,
					from + copied, PAGE_CACHE_SIZE);
		}
		SetPageUptodate(page);
	}
N
Nick Piggin 已提交
1529
	set_page_dirty(page);
1530
	unlock_page(page);
N
Nick Piggin 已提交
1531 1532 1533
	page_cache_release(page);

	return copied;
L
Linus Torvalds 已提交
1534 1535
}

A
Al Viro 已提交
1536
static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
L
Linus Torvalds 已提交
1537
{
1538 1539
	struct file *file = iocb->ki_filp;
	struct inode *inode = file_inode(file);
L
Linus Torvalds 已提交
1540
	struct address_space *mapping = inode->i_mapping;
1541 1542
	pgoff_t index;
	unsigned long offset;
1543
	enum sgp_type sgp = SGP_READ;
1544
	int error = 0;
A
Al Viro 已提交
1545
	ssize_t retval = 0;
1546
	loff_t *ppos = &iocb->ki_pos;
1547 1548 1549 1550 1551 1552

	/*
	 * Might this read be for a stacking filesystem?  Then when reading
	 * holes of a sparse file, we actually need to allocate those pages,
	 * and even mark them dirty, so it cannot exceed the max_blocks limit.
	 */
A
Al Viro 已提交
1553
	if (!iter_is_iovec(to))
1554
		sgp = SGP_DIRTY;
L
Linus Torvalds 已提交
1555 1556 1557 1558 1559 1560

	index = *ppos >> PAGE_CACHE_SHIFT;
	offset = *ppos & ~PAGE_CACHE_MASK;

	for (;;) {
		struct page *page = NULL;
1561 1562
		pgoff_t end_index;
		unsigned long nr, ret;
L
Linus Torvalds 已提交
1563 1564 1565 1566 1567 1568 1569 1570 1571 1572 1573
		loff_t i_size = i_size_read(inode);

		end_index = i_size >> PAGE_CACHE_SHIFT;
		if (index > end_index)
			break;
		if (index == end_index) {
			nr = i_size & ~PAGE_CACHE_MASK;
			if (nr <= offset)
				break;
		}

1574 1575 1576 1577
		error = shmem_getpage(inode, index, &page, sgp, NULL);
		if (error) {
			if (error == -EINVAL)
				error = 0;
L
Linus Torvalds 已提交
1578 1579
			break;
		}
H
Hugh Dickins 已提交
1580 1581
		if (page)
			unlock_page(page);
L
Linus Torvalds 已提交
1582 1583 1584

		/*
		 * We must evaluate after, since reads (unlike writes)
1585
		 * are called without i_mutex protection against truncate
L
Linus Torvalds 已提交
1586 1587 1588 1589 1590 1591 1592 1593 1594 1595 1596 1597 1598 1599 1600 1601 1602 1603 1604 1605 1606 1607 1608 1609 1610 1611 1612
		 */
		nr = PAGE_CACHE_SIZE;
		i_size = i_size_read(inode);
		end_index = i_size >> PAGE_CACHE_SHIFT;
		if (index == end_index) {
			nr = i_size & ~PAGE_CACHE_MASK;
			if (nr <= offset) {
				if (page)
					page_cache_release(page);
				break;
			}
		}
		nr -= offset;

		if (page) {
			/*
			 * If users can be writing to this page using arbitrary
			 * virtual addresses, take care about potential aliasing
			 * before reading the page on the kernel side.
			 */
			if (mapping_writably_mapped(mapping))
				flush_dcache_page(page);
			/*
			 * Mark the page accessed if we read the beginning.
			 */
			if (!offset)
				mark_page_accessed(page);
N
Nick Piggin 已提交
1613
		} else {
L
Linus Torvalds 已提交
1614
			page = ZERO_PAGE(0);
N
Nick Piggin 已提交
1615 1616
			page_cache_get(page);
		}
L
Linus Torvalds 已提交
1617 1618 1619 1620 1621

		/*
		 * Ok, we have the page, and it's up-to-date, so
		 * now we can copy it to user space...
		 */
A
Al Viro 已提交
1622
		ret = copy_page_to_iter(page, offset, nr, to);
1623
		retval += ret;
L
Linus Torvalds 已提交
1624 1625 1626 1627 1628
		offset += ret;
		index += offset >> PAGE_CACHE_SHIFT;
		offset &= ~PAGE_CACHE_MASK;

		page_cache_release(page);
A
Al Viro 已提交
1629
		if (!iov_iter_count(to))
L
Linus Torvalds 已提交
1630
			break;
1631 1632 1633 1634
		if (ret < nr) {
			error = -EFAULT;
			break;
		}
L
Linus Torvalds 已提交
1635 1636 1637 1638
		cond_resched();
	}

	*ppos = ((loff_t) index << PAGE_CACHE_SHIFT) + offset;
1639 1640
	file_accessed(file);
	return retval ? retval : error;
L
Linus Torvalds 已提交
1641 1642
}

1643 1644 1645 1646 1647
static ssize_t shmem_file_splice_read(struct file *in, loff_t *ppos,
				struct pipe_inode_info *pipe, size_t len,
				unsigned int flags)
{
	struct address_space *mapping = in->f_mapping;
1648
	struct inode *inode = mapping->host;
1649 1650 1651 1652 1653 1654 1655 1656 1657 1658
	unsigned int loff, nr_pages, req_pages;
	struct page *pages[PIPE_DEF_BUFFERS];
	struct partial_page partial[PIPE_DEF_BUFFERS];
	struct page *page;
	pgoff_t index, end_index;
	loff_t isize, left;
	int error, page_nr;
	struct splice_pipe_desc spd = {
		.pages = pages,
		.partial = partial,
1659
		.nr_pages_max = PIPE_DEF_BUFFERS,
1660 1661 1662 1663 1664
		.flags = flags,
		.ops = &page_cache_pipe_buf_ops,
		.spd_release = spd_release_page,
	};

1665
	isize = i_size_read(inode);
1666 1667 1668 1669 1670 1671 1672 1673 1674 1675 1676 1677 1678
	if (unlikely(*ppos >= isize))
		return 0;

	left = isize - *ppos;
	if (unlikely(left < len))
		len = left;

	if (splice_grow_spd(pipe, &spd))
		return -ENOMEM;

	index = *ppos >> PAGE_CACHE_SHIFT;
	loff = *ppos & ~PAGE_CACHE_MASK;
	req_pages = (len + loff + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1679
	nr_pages = min(req_pages, spd.nr_pages_max);
1680 1681 1682 1683 1684 1685

	spd.nr_pages = find_get_pages_contig(mapping, index,
						nr_pages, spd.pages);
	index += spd.nr_pages;
	error = 0;

1686 1687 1688 1689 1690
	while (spd.nr_pages < nr_pages) {
		error = shmem_getpage(inode, index, &page, SGP_CACHE, NULL);
		if (error)
			break;
		unlock_page(page);
1691 1692 1693 1694 1695 1696 1697
		spd.pages[spd.nr_pages++] = page;
		index++;
	}

	index = *ppos >> PAGE_CACHE_SHIFT;
	nr_pages = spd.nr_pages;
	spd.nr_pages = 0;
1698

1699 1700 1701 1702 1703 1704 1705 1706 1707
	for (page_nr = 0; page_nr < nr_pages; page_nr++) {
		unsigned int this_len;

		if (!len)
			break;

		this_len = min_t(unsigned long, len, PAGE_CACHE_SIZE - loff);
		page = spd.pages[page_nr];

1708 1709 1710 1711
		if (!PageUptodate(page) || page->mapping != mapping) {
			error = shmem_getpage(inode, index, &page,
							SGP_CACHE, NULL);
			if (error)
1712
				break;
1713 1714 1715
			unlock_page(page);
			page_cache_release(spd.pages[page_nr]);
			spd.pages[page_nr] = page;
1716
		}
1717 1718

		isize = i_size_read(inode);
1719 1720 1721 1722 1723 1724 1725 1726 1727 1728 1729 1730 1731 1732 1733 1734 1735 1736 1737 1738 1739 1740 1741 1742 1743 1744 1745 1746 1747
		end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
		if (unlikely(!isize || index > end_index))
			break;

		if (end_index == index) {
			unsigned int plen;

			plen = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
			if (plen <= loff)
				break;

			this_len = min(this_len, plen - loff);
			len = this_len;
		}

		spd.partial[page_nr].offset = loff;
		spd.partial[page_nr].len = this_len;
		len -= this_len;
		loff = 0;
		spd.nr_pages++;
		index++;
	}

	while (page_nr < nr_pages)
		page_cache_release(spd.pages[page_nr++]);

	if (spd.nr_pages)
		error = splice_to_pipe(pipe, &spd);

1748
	splice_shrink_spd(&spd);
1749 1750 1751 1752 1753 1754 1755 1756

	if (error > 0) {
		*ppos += error;
		file_accessed(in);
	}
	return error;
}

1757 1758 1759 1760
/*
 * llseek SEEK_DATA or SEEK_HOLE through the radix_tree.
 */
static pgoff_t shmem_seek_hole_data(struct address_space *mapping,
1761
				    pgoff_t index, pgoff_t end, int whence)
1762 1763 1764 1765 1766 1767 1768 1769 1770 1771
{
	struct page *page;
	struct pagevec pvec;
	pgoff_t indices[PAGEVEC_SIZE];
	bool done = false;
	int i;

	pagevec_init(&pvec, 0);
	pvec.nr = 1;		/* start small: we may be there already */
	while (!done) {
1772
		pvec.nr = find_get_entries(mapping, index,
1773 1774
					pvec.nr, pvec.pages, indices);
		if (!pvec.nr) {
1775
			if (whence == SEEK_DATA)
1776 1777 1778 1779 1780
				index = end;
			break;
		}
		for (i = 0; i < pvec.nr; i++, index++) {
			if (index < indices[i]) {
1781
				if (whence == SEEK_HOLE) {
1782 1783 1784 1785 1786 1787 1788 1789 1790 1791 1792
					done = true;
					break;
				}
				index = indices[i];
			}
			page = pvec.pages[i];
			if (page && !radix_tree_exceptional_entry(page)) {
				if (!PageUptodate(page))
					page = NULL;
			}
			if (index >= end ||
1793 1794
			    (page && whence == SEEK_DATA) ||
			    (!page && whence == SEEK_HOLE)) {
1795 1796 1797 1798
				done = true;
				break;
			}
		}
1799
		pagevec_remove_exceptionals(&pvec);
1800 1801 1802 1803 1804 1805 1806
		pagevec_release(&pvec);
		pvec.nr = PAGEVEC_SIZE;
		cond_resched();
	}
	return index;
}

1807
static loff_t shmem_file_llseek(struct file *file, loff_t offset, int whence)
1808 1809 1810 1811 1812 1813
{
	struct address_space *mapping = file->f_mapping;
	struct inode *inode = mapping->host;
	pgoff_t start, end;
	loff_t new_offset;

1814 1815
	if (whence != SEEK_DATA && whence != SEEK_HOLE)
		return generic_file_llseek_size(file, offset, whence,
1816 1817 1818 1819 1820 1821 1822 1823 1824 1825 1826
					MAX_LFS_FILESIZE, i_size_read(inode));
	mutex_lock(&inode->i_mutex);
	/* We're holding i_mutex so we can access i_size directly */

	if (offset < 0)
		offset = -EINVAL;
	else if (offset >= inode->i_size)
		offset = -ENXIO;
	else {
		start = offset >> PAGE_CACHE_SHIFT;
		end = (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1827
		new_offset = shmem_seek_hole_data(mapping, start, end, whence);
1828 1829 1830 1831
		new_offset <<= PAGE_CACHE_SHIFT;
		if (new_offset > offset) {
			if (new_offset < inode->i_size)
				offset = new_offset;
1832
			else if (whence == SEEK_DATA)
1833 1834 1835 1836 1837 1838
				offset = -ENXIO;
			else
				offset = inode->i_size;
		}
	}

1839 1840
	if (offset >= 0)
		offset = vfs_setpos(file, offset, MAX_LFS_FILESIZE);
1841 1842 1843 1844
	mutex_unlock(&inode->i_mutex);
	return offset;
}

1845 1846 1847 1848 1849 1850 1851 1852 1853 1854 1855 1856 1857 1858 1859 1860 1861 1862 1863 1864 1865 1866 1867 1868 1869 1870 1871 1872 1873 1874 1875 1876 1877 1878 1879 1880 1881 1882 1883 1884 1885 1886 1887 1888 1889 1890 1891 1892 1893
/*
 * We need a tag: a new tag would expand every radix_tree_node by 8 bytes,
 * so reuse a tag which we firmly believe is never set or cleared on shmem.
 */
#define SHMEM_TAG_PINNED        PAGECACHE_TAG_TOWRITE
#define LAST_SCAN               4       /* about 150ms max */

static void shmem_tag_pins(struct address_space *mapping)
{
	struct radix_tree_iter iter;
	void **slot;
	pgoff_t start;
	struct page *page;

	lru_add_drain();
	start = 0;
	rcu_read_lock();

restart:
	radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
		page = radix_tree_deref_slot(slot);
		if (!page || radix_tree_exception(page)) {
			if (radix_tree_deref_retry(page))
				goto restart;
		} else if (page_count(page) - page_mapcount(page) > 1) {
			spin_lock_irq(&mapping->tree_lock);
			radix_tree_tag_set(&mapping->page_tree, iter.index,
					   SHMEM_TAG_PINNED);
			spin_unlock_irq(&mapping->tree_lock);
		}

		if (need_resched()) {
			cond_resched_rcu();
			start = iter.index + 1;
			goto restart;
		}
	}
	rcu_read_unlock();
}

/*
 * Setting SEAL_WRITE requires us to verify there's no pending writer. However,
 * via get_user_pages(), drivers might have some pending I/O without any active
 * user-space mappings (eg., direct-IO, AIO). Therefore, we look at all pages
 * and see whether it has an elevated ref-count. If so, we tag them and wait for
 * them to be dropped.
 * The caller must guarantee that no new user will acquire writable references
 * to those pages to avoid races.
 */
D
David Herrmann 已提交
1894 1895
static int shmem_wait_for_pins(struct address_space *mapping)
{
1896 1897 1898 1899 1900 1901 1902 1903 1904 1905 1906 1907 1908 1909 1910 1911 1912 1913 1914 1915 1916 1917 1918 1919 1920 1921 1922 1923 1924 1925 1926 1927 1928 1929 1930 1931 1932 1933 1934 1935 1936 1937 1938 1939 1940 1941 1942 1943 1944 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954 1955
	struct radix_tree_iter iter;
	void **slot;
	pgoff_t start;
	struct page *page;
	int error, scan;

	shmem_tag_pins(mapping);

	error = 0;
	for (scan = 0; scan <= LAST_SCAN; scan++) {
		if (!radix_tree_tagged(&mapping->page_tree, SHMEM_TAG_PINNED))
			break;

		if (!scan)
			lru_add_drain_all();
		else if (schedule_timeout_killable((HZ << scan) / 200))
			scan = LAST_SCAN;

		start = 0;
		rcu_read_lock();
restart:
		radix_tree_for_each_tagged(slot, &mapping->page_tree, &iter,
					   start, SHMEM_TAG_PINNED) {

			page = radix_tree_deref_slot(slot);
			if (radix_tree_exception(page)) {
				if (radix_tree_deref_retry(page))
					goto restart;

				page = NULL;
			}

			if (page &&
			    page_count(page) - page_mapcount(page) != 1) {
				if (scan < LAST_SCAN)
					goto continue_resched;

				/*
				 * On the last scan, we clean up all those tags
				 * we inserted; but make a note that we still
				 * found pages pinned.
				 */
				error = -EBUSY;
			}

			spin_lock_irq(&mapping->tree_lock);
			radix_tree_tag_clear(&mapping->page_tree,
					     iter.index, SHMEM_TAG_PINNED);
			spin_unlock_irq(&mapping->tree_lock);
continue_resched:
			if (need_resched()) {
				cond_resched_rcu();
				start = iter.index + 1;
				goto restart;
			}
		}
		rcu_read_unlock();
	}

	return error;
D
David Herrmann 已提交
1956 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 2046 2047 2048 2049 2050 2051 2052 2053 2054 2055 2056 2057 2058 2059 2060 2061 2062 2063 2064 2065
}

#define F_ALL_SEALS (F_SEAL_SEAL | \
		     F_SEAL_SHRINK | \
		     F_SEAL_GROW | \
		     F_SEAL_WRITE)

int shmem_add_seals(struct file *file, unsigned int seals)
{
	struct inode *inode = file_inode(file);
	struct shmem_inode_info *info = SHMEM_I(inode);
	int error;

	/*
	 * SEALING
	 * Sealing allows multiple parties to share a shmem-file but restrict
	 * access to a specific subset of file operations. Seals can only be
	 * added, but never removed. This way, mutually untrusted parties can
	 * share common memory regions with a well-defined policy. A malicious
	 * peer can thus never perform unwanted operations on a shared object.
	 *
	 * Seals are only supported on special shmem-files and always affect
	 * the whole underlying inode. Once a seal is set, it may prevent some
	 * kinds of access to the file. Currently, the following seals are
	 * defined:
	 *   SEAL_SEAL: Prevent further seals from being set on this file
	 *   SEAL_SHRINK: Prevent the file from shrinking
	 *   SEAL_GROW: Prevent the file from growing
	 *   SEAL_WRITE: Prevent write access to the file
	 *
	 * As we don't require any trust relationship between two parties, we
	 * must prevent seals from being removed. Therefore, sealing a file
	 * only adds a given set of seals to the file, it never touches
	 * existing seals. Furthermore, the "setting seals"-operation can be
	 * sealed itself, which basically prevents any further seal from being
	 * added.
	 *
	 * Semantics of sealing are only defined on volatile files. Only
	 * anonymous shmem files support sealing. More importantly, seals are
	 * never written to disk. Therefore, there's no plan to support it on
	 * other file types.
	 */

	if (file->f_op != &shmem_file_operations)
		return -EINVAL;
	if (!(file->f_mode & FMODE_WRITE))
		return -EPERM;
	if (seals & ~(unsigned int)F_ALL_SEALS)
		return -EINVAL;

	mutex_lock(&inode->i_mutex);

	if (info->seals & F_SEAL_SEAL) {
		error = -EPERM;
		goto unlock;
	}

	if ((seals & F_SEAL_WRITE) && !(info->seals & F_SEAL_WRITE)) {
		error = mapping_deny_writable(file->f_mapping);
		if (error)
			goto unlock;

		error = shmem_wait_for_pins(file->f_mapping);
		if (error) {
			mapping_allow_writable(file->f_mapping);
			goto unlock;
		}
	}

	info->seals |= seals;
	error = 0;

unlock:
	mutex_unlock(&inode->i_mutex);
	return error;
}
EXPORT_SYMBOL_GPL(shmem_add_seals);

int shmem_get_seals(struct file *file)
{
	if (file->f_op != &shmem_file_operations)
		return -EINVAL;

	return SHMEM_I(file_inode(file))->seals;
}
EXPORT_SYMBOL_GPL(shmem_get_seals);

long shmem_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
{
	long error;

	switch (cmd) {
	case F_ADD_SEALS:
		/* disallow upper 32bit */
		if (arg > UINT_MAX)
			return -EINVAL;

		error = shmem_add_seals(file, arg);
		break;
	case F_GET_SEALS:
		error = shmem_get_seals(file);
		break;
	default:
		error = -EINVAL;
		break;
	}

	return error;
}

2066 2067 2068
static long shmem_fallocate(struct file *file, int mode, loff_t offset,
							 loff_t len)
{
A
Al Viro 已提交
2069
	struct inode *inode = file_inode(file);
2070
	struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
D
David Herrmann 已提交
2071
	struct shmem_inode_info *info = SHMEM_I(inode);
2072
	struct shmem_falloc shmem_falloc;
2073 2074
	pgoff_t start, index, end;
	int error;
2075

2076 2077 2078
	if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE))
		return -EOPNOTSUPP;

2079 2080 2081 2082 2083 2084
	mutex_lock(&inode->i_mutex);

	if (mode & FALLOC_FL_PUNCH_HOLE) {
		struct address_space *mapping = file->f_mapping;
		loff_t unmap_start = round_up(offset, PAGE_SIZE);
		loff_t unmap_end = round_down(offset + len, PAGE_SIZE) - 1;
2085
		DECLARE_WAIT_QUEUE_HEAD_ONSTACK(shmem_falloc_waitq);
2086

D
David Herrmann 已提交
2087 2088 2089 2090 2091 2092
		/* protected by i_mutex */
		if (info->seals & F_SEAL_WRITE) {
			error = -EPERM;
			goto out;
		}

2093
		shmem_falloc.waitq = &shmem_falloc_waitq;
2094 2095 2096 2097 2098 2099
		shmem_falloc.start = unmap_start >> PAGE_SHIFT;
		shmem_falloc.next = (unmap_end + 1) >> PAGE_SHIFT;
		spin_lock(&inode->i_lock);
		inode->i_private = &shmem_falloc;
		spin_unlock(&inode->i_lock);

2100 2101 2102 2103 2104
		if ((u64)unmap_end > (u64)unmap_start)
			unmap_mapping_range(mapping, unmap_start,
					    1 + unmap_end - unmap_start, 0);
		shmem_truncate_range(inode, offset, offset + len - 1);
		/* No need to unmap again: hole-punching leaves COWed pages */
2105 2106 2107 2108 2109

		spin_lock(&inode->i_lock);
		inode->i_private = NULL;
		wake_up_all(&shmem_falloc_waitq);
		spin_unlock(&inode->i_lock);
2110
		error = 0;
2111
		goto out;
2112 2113 2114 2115 2116 2117 2118
	}

	/* We need to check rlimit even when FALLOC_FL_KEEP_SIZE */
	error = inode_newsize_ok(inode, offset + len);
	if (error)
		goto out;

D
David Herrmann 已提交
2119 2120 2121 2122 2123
	if ((info->seals & F_SEAL_GROW) && offset + len > inode->i_size) {
		error = -EPERM;
		goto out;
	}

2124 2125 2126 2127 2128 2129
	start = offset >> PAGE_CACHE_SHIFT;
	end = (offset + len + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
	/* Try to avoid a swapstorm if len is impossible to satisfy */
	if (sbinfo->max_blocks && end - start > sbinfo->max_blocks) {
		error = -ENOSPC;
		goto out;
2130 2131
	}

2132
	shmem_falloc.waitq = NULL;
2133 2134 2135 2136 2137 2138 2139 2140
	shmem_falloc.start = start;
	shmem_falloc.next  = start;
	shmem_falloc.nr_falloced = 0;
	shmem_falloc.nr_unswapped = 0;
	spin_lock(&inode->i_lock);
	inode->i_private = &shmem_falloc;
	spin_unlock(&inode->i_lock);

2141 2142 2143 2144 2145 2146 2147 2148 2149
	for (index = start; index < end; index++) {
		struct page *page;

		/*
		 * Good, the fallocate(2) manpage permits EINTR: we may have
		 * been interrupted because we are using up too much memory.
		 */
		if (signal_pending(current))
			error = -EINTR;
2150 2151
		else if (shmem_falloc.nr_unswapped > shmem_falloc.nr_falloced)
			error = -ENOMEM;
2152
		else
2153
			error = shmem_getpage(inode, index, &page, SGP_FALLOC,
2154 2155
									NULL);
		if (error) {
2156 2157 2158 2159
			/* Remove the !PageUptodate pages we added */
			shmem_undo_range(inode,
				(loff_t)start << PAGE_CACHE_SHIFT,
				(loff_t)index << PAGE_CACHE_SHIFT, true);
2160
			goto undone;
2161 2162
		}

2163 2164 2165 2166 2167 2168 2169 2170
		/*
		 * Inform shmem_writepage() how far we have reached.
		 * No need for lock or barrier: we have the page lock.
		 */
		shmem_falloc.next++;
		if (!PageUptodate(page))
			shmem_falloc.nr_falloced++;

2171
		/*
2172 2173 2174
		 * If !PageUptodate, leave it that way so that freeable pages
		 * can be recognized if we need to rollback on error later.
		 * But set_page_dirty so that memory pressure will swap rather
2175 2176 2177 2178 2179 2180 2181 2182 2183 2184 2185 2186
		 * than free the pages we are allocating (and SGP_CACHE pages
		 * might still be clean: we now need to mark those dirty too).
		 */
		set_page_dirty(page);
		unlock_page(page);
		page_cache_release(page);
		cond_resched();
	}

	if (!(mode & FALLOC_FL_KEEP_SIZE) && offset + len > inode->i_size)
		i_size_write(inode, offset + len);
	inode->i_ctime = CURRENT_TIME;
2187 2188 2189 2190
undone:
	spin_lock(&inode->i_lock);
	inode->i_private = NULL;
	spin_unlock(&inode->i_lock);
2191
out:
2192 2193 2194 2195
	mutex_unlock(&inode->i_mutex);
	return error;
}

2196
static int shmem_statfs(struct dentry *dentry, struct kstatfs *buf)
L
Linus Torvalds 已提交
2197
{
2198
	struct shmem_sb_info *sbinfo = SHMEM_SB(dentry->d_sb);
L
Linus Torvalds 已提交
2199 2200 2201 2202

	buf->f_type = TMPFS_MAGIC;
	buf->f_bsize = PAGE_CACHE_SIZE;
	buf->f_namelen = NAME_MAX;
2203
	if (sbinfo->max_blocks) {
L
Linus Torvalds 已提交
2204
		buf->f_blocks = sbinfo->max_blocks;
2205 2206 2207
		buf->f_bavail =
		buf->f_bfree  = sbinfo->max_blocks -
				percpu_counter_sum(&sbinfo->used_blocks);
2208 2209
	}
	if (sbinfo->max_inodes) {
L
Linus Torvalds 已提交
2210 2211 2212 2213 2214 2215 2216 2217 2218 2219 2220
		buf->f_files = sbinfo->max_inodes;
		buf->f_ffree = sbinfo->free_inodes;
	}
	/* else leave those fields 0 like simple_statfs */
	return 0;
}

/*
 * File creation. Allocate an inode, and we're done..
 */
static int
A
Al Viro 已提交
2221
shmem_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
L
Linus Torvalds 已提交
2222
{
2223
	struct inode *inode;
L
Linus Torvalds 已提交
2224 2225
	int error = -ENOSPC;

2226
	inode = shmem_get_inode(dir->i_sb, dir, mode, dev, VM_NORESERVE);
L
Linus Torvalds 已提交
2227
	if (inode) {
C
Christoph Hellwig 已提交
2228 2229 2230
		error = simple_acl_create(dir, inode);
		if (error)
			goto out_iput;
2231
		error = security_inode_init_security(inode, dir,
2232
						     &dentry->d_name,
2233
						     shmem_initxattrs, NULL);
C
Christoph Hellwig 已提交
2234 2235
		if (error && error != -EOPNOTSUPP)
			goto out_iput;
2236

A
Al Viro 已提交
2237
		error = 0;
L
Linus Torvalds 已提交
2238 2239 2240 2241 2242 2243
		dir->i_size += BOGO_DIRENT_SIZE;
		dir->i_ctime = dir->i_mtime = CURRENT_TIME;
		d_instantiate(dentry, inode);
		dget(dentry); /* Extra count - pin the dentry in core */
	}
	return error;
C
Christoph Hellwig 已提交
2244 2245 2246
out_iput:
	iput(inode);
	return error;
L
Linus Torvalds 已提交
2247 2248
}

2249 2250 2251 2252 2253 2254 2255 2256 2257 2258 2259
static int
shmem_tmpfile(struct inode *dir, struct dentry *dentry, umode_t mode)
{
	struct inode *inode;
	int error = -ENOSPC;

	inode = shmem_get_inode(dir->i_sb, dir, mode, 0, VM_NORESERVE);
	if (inode) {
		error = security_inode_init_security(inode, dir,
						     NULL,
						     shmem_initxattrs, NULL);
C
Christoph Hellwig 已提交
2260 2261 2262 2263 2264
		if (error && error != -EOPNOTSUPP)
			goto out_iput;
		error = simple_acl_create(dir, inode);
		if (error)
			goto out_iput;
2265 2266 2267
		d_tmpfile(dentry, inode);
	}
	return error;
C
Christoph Hellwig 已提交
2268 2269 2270
out_iput:
	iput(inode);
	return error;
2271 2272
}

2273
static int shmem_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
L
Linus Torvalds 已提交
2274 2275 2276 2277 2278
{
	int error;

	if ((error = shmem_mknod(dir, dentry, mode | S_IFDIR, 0)))
		return error;
2279
	inc_nlink(dir);
L
Linus Torvalds 已提交
2280 2281 2282
	return 0;
}

A
Al Viro 已提交
2283
static int shmem_create(struct inode *dir, struct dentry *dentry, umode_t mode,
A
Al Viro 已提交
2284
		bool excl)
L
Linus Torvalds 已提交
2285 2286 2287 2288 2289 2290 2291 2292 2293
{
	return shmem_mknod(dir, dentry, mode | S_IFREG, 0);
}

/*
 * Link a file..
 */
static int shmem_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
{
2294
	struct inode *inode = d_inode(old_dentry);
2295
	int ret;
L
Linus Torvalds 已提交
2296 2297 2298 2299 2300 2301

	/*
	 * No ordinary (disk based) filesystem counts links as inodes;
	 * but each new link needs a new dentry, pinning lowmem, and
	 * tmpfs dentries cannot be pruned until they are unlinked.
	 */
2302 2303 2304
	ret = shmem_reserve_inode(inode->i_sb);
	if (ret)
		goto out;
L
Linus Torvalds 已提交
2305 2306 2307

	dir->i_size += BOGO_DIRENT_SIZE;
	inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
2308
	inc_nlink(inode);
A
Al Viro 已提交
2309
	ihold(inode);	/* New dentry reference */
L
Linus Torvalds 已提交
2310 2311
	dget(dentry);		/* Extra pinning count for the created dentry */
	d_instantiate(dentry, inode);
2312 2313
out:
	return ret;
L
Linus Torvalds 已提交
2314 2315 2316 2317
}

static int shmem_unlink(struct inode *dir, struct dentry *dentry)
{
2318
	struct inode *inode = d_inode(dentry);
L
Linus Torvalds 已提交
2319

2320 2321
	if (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode))
		shmem_free_inode(inode->i_sb);
L
Linus Torvalds 已提交
2322 2323 2324

	dir->i_size -= BOGO_DIRENT_SIZE;
	inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
2325
	drop_nlink(inode);
L
Linus Torvalds 已提交
2326 2327 2328 2329 2330 2331 2332 2333 2334
	dput(dentry);	/* Undo the count from "create" - this does all the work */
	return 0;
}

static int shmem_rmdir(struct inode *dir, struct dentry *dentry)
{
	if (!simple_empty(dentry))
		return -ENOTEMPTY;

2335
	drop_nlink(d_inode(dentry));
2336
	drop_nlink(dir);
L
Linus Torvalds 已提交
2337 2338 2339
	return shmem_unlink(dir, dentry);
}

M
Miklos Szeredi 已提交
2340 2341
static int shmem_exchange(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry)
{
2342 2343
	bool old_is_dir = d_is_dir(old_dentry);
	bool new_is_dir = d_is_dir(new_dentry);
M
Miklos Szeredi 已提交
2344 2345 2346 2347 2348 2349 2350 2351 2352 2353 2354 2355

	if (old_dir != new_dir && old_is_dir != new_is_dir) {
		if (old_is_dir) {
			drop_nlink(old_dir);
			inc_nlink(new_dir);
		} else {
			drop_nlink(new_dir);
			inc_nlink(old_dir);
		}
	}
	old_dir->i_ctime = old_dir->i_mtime =
	new_dir->i_ctime = new_dir->i_mtime =
2356 2357
	d_inode(old_dentry)->i_ctime =
	d_inode(new_dentry)->i_ctime = CURRENT_TIME;
M
Miklos Szeredi 已提交
2358 2359 2360 2361

	return 0;
}

M
Miklos Szeredi 已提交
2362 2363 2364 2365 2366 2367 2368 2369 2370 2371 2372 2373 2374 2375 2376 2377 2378 2379 2380 2381 2382 2383 2384 2385 2386 2387
static int shmem_whiteout(struct inode *old_dir, struct dentry *old_dentry)
{
	struct dentry *whiteout;
	int error;

	whiteout = d_alloc(old_dentry->d_parent, &old_dentry->d_name);
	if (!whiteout)
		return -ENOMEM;

	error = shmem_mknod(old_dir, whiteout,
			    S_IFCHR | WHITEOUT_MODE, WHITEOUT_DEV);
	dput(whiteout);
	if (error)
		return error;

	/*
	 * Cheat and hash the whiteout while the old dentry is still in
	 * place, instead of playing games with FS_RENAME_DOES_D_MOVE.
	 *
	 * d_lookup() will consistently find one of them at this point,
	 * not sure which one, but that isn't even important.
	 */
	d_rehash(whiteout);
	return 0;
}

L
Linus Torvalds 已提交
2388 2389 2390 2391 2392 2393
/*
 * The VFS layer already does all the dentry stuff for rename,
 * we just have to decrement the usage count for the target if
 * it exists so that the VFS layer correctly free's it when it
 * gets overwritten.
 */
M
Miklos Szeredi 已提交
2394
static int shmem_rename2(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry, unsigned int flags)
L
Linus Torvalds 已提交
2395
{
2396
	struct inode *inode = d_inode(old_dentry);
L
Linus Torvalds 已提交
2397 2398
	int they_are_dirs = S_ISDIR(inode->i_mode);

M
Miklos Szeredi 已提交
2399
	if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE | RENAME_WHITEOUT))
M
Miklos Szeredi 已提交
2400 2401
		return -EINVAL;

M
Miklos Szeredi 已提交
2402 2403 2404
	if (flags & RENAME_EXCHANGE)
		return shmem_exchange(old_dir, old_dentry, new_dir, new_dentry);

L
Linus Torvalds 已提交
2405 2406 2407
	if (!simple_empty(new_dentry))
		return -ENOTEMPTY;

M
Miklos Szeredi 已提交
2408 2409 2410 2411 2412 2413 2414 2415
	if (flags & RENAME_WHITEOUT) {
		int error;

		error = shmem_whiteout(old_dir, old_dentry);
		if (error)
			return error;
	}

2416
	if (d_really_is_positive(new_dentry)) {
L
Linus Torvalds 已提交
2417
		(void) shmem_unlink(new_dir, new_dentry);
2418
		if (they_are_dirs) {
2419
			drop_nlink(d_inode(new_dentry));
2420
			drop_nlink(old_dir);
2421
		}
L
Linus Torvalds 已提交
2422
	} else if (they_are_dirs) {
2423
		drop_nlink(old_dir);
2424
		inc_nlink(new_dir);
L
Linus Torvalds 已提交
2425 2426 2427 2428 2429 2430 2431 2432 2433 2434 2435 2436 2437 2438 2439
	}

	old_dir->i_size -= BOGO_DIRENT_SIZE;
	new_dir->i_size += BOGO_DIRENT_SIZE;
	old_dir->i_ctime = old_dir->i_mtime =
	new_dir->i_ctime = new_dir->i_mtime =
	inode->i_ctime = CURRENT_TIME;
	return 0;
}

static int shmem_symlink(struct inode *dir, struct dentry *dentry, const char *symname)
{
	int error;
	int len;
	struct inode *inode;
H
Hugh Dickins 已提交
2440
	struct page *page;
L
Linus Torvalds 已提交
2441 2442 2443 2444 2445 2446 2447
	char *kaddr;
	struct shmem_inode_info *info;

	len = strlen(symname) + 1;
	if (len > PAGE_CACHE_SIZE)
		return -ENAMETOOLONG;

2448
	inode = shmem_get_inode(dir->i_sb, dir, S_IFLNK|S_IRWXUGO, 0, VM_NORESERVE);
L
Linus Torvalds 已提交
2449 2450 2451
	if (!inode)
		return -ENOSPC;

2452
	error = security_inode_init_security(inode, dir, &dentry->d_name,
2453
					     shmem_initxattrs, NULL);
2454 2455 2456 2457 2458 2459 2460 2461
	if (error) {
		if (error != -EOPNOTSUPP) {
			iput(inode);
			return error;
		}
		error = 0;
	}

L
Linus Torvalds 已提交
2462 2463
	info = SHMEM_I(inode);
	inode->i_size = len-1;
2464 2465 2466 2467 2468 2469 2470
	if (len <= SHORT_SYMLINK_LEN) {
		info->symlink = kmemdup(symname, len, GFP_KERNEL);
		if (!info->symlink) {
			iput(inode);
			return -ENOMEM;
		}
		inode->i_op = &shmem_short_symlink_operations;
A
Al Viro 已提交
2471
		inode->i_link = info->symlink;
L
Linus Torvalds 已提交
2472 2473 2474 2475 2476 2477
	} else {
		error = shmem_getpage(inode, 0, &page, SGP_WRITE, NULL);
		if (error) {
			iput(inode);
			return error;
		}
2478
		inode->i_mapping->a_ops = &shmem_aops;
L
Linus Torvalds 已提交
2479
		inode->i_op = &shmem_symlink_inode_operations;
2480
		kaddr = kmap_atomic(page);
L
Linus Torvalds 已提交
2481
		memcpy(kaddr, symname, len);
2482
		kunmap_atomic(kaddr);
2483
		SetPageUptodate(page);
L
Linus Torvalds 已提交
2484
		set_page_dirty(page);
2485
		unlock_page(page);
L
Linus Torvalds 已提交
2486 2487 2488 2489 2490 2491 2492 2493 2494
		page_cache_release(page);
	}
	dir->i_size += BOGO_DIRENT_SIZE;
	dir->i_ctime = dir->i_mtime = CURRENT_TIME;
	d_instantiate(dentry, inode);
	dget(dentry);
	return 0;
}

2495
static const char *shmem_follow_link(struct dentry *dentry, void **cookie)
L
Linus Torvalds 已提交
2496 2497
{
	struct page *page = NULL;
2498
	int error = shmem_getpage(d_inode(dentry), 0, &page, SGP_READ, NULL);
2499 2500 2501 2502 2503
	if (error)
		return ERR_PTR(error);
	unlock_page(page);
	*cookie = page;
	return kmap(page);
L
Linus Torvalds 已提交
2504 2505
}

2506
static void shmem_put_link(struct inode *unused, void *cookie)
L
Linus Torvalds 已提交
2507
{
2508 2509 2510 2511
	struct page *page = cookie;
	kunmap(page);
	mark_page_accessed(page);
	page_cache_release(page);
L
Linus Torvalds 已提交
2512 2513
}

2514
#ifdef CONFIG_TMPFS_XATTR
2515
/*
2516 2517
 * Superblocks without xattr inode operations may get some security.* xattr
 * support from the LSM "for free". As soon as we have any other xattrs
2518 2519 2520 2521
 * like ACLs, we also need to implement the security.* handlers at
 * filesystem level, though.
 */

2522 2523 2524 2525 2526 2527 2528 2529 2530
/*
 * Callback for security_inode_init_security() for acquiring xattrs.
 */
static int shmem_initxattrs(struct inode *inode,
			    const struct xattr *xattr_array,
			    void *fs_info)
{
	struct shmem_inode_info *info = SHMEM_I(inode);
	const struct xattr *xattr;
2531
	struct simple_xattr *new_xattr;
2532 2533 2534
	size_t len;

	for (xattr = xattr_array; xattr->name != NULL; xattr++) {
2535
		new_xattr = simple_xattr_alloc(xattr->value, xattr->value_len);
2536 2537 2538 2539 2540 2541 2542 2543 2544 2545 2546 2547 2548 2549 2550 2551
		if (!new_xattr)
			return -ENOMEM;

		len = strlen(xattr->name) + 1;
		new_xattr->name = kmalloc(XATTR_SECURITY_PREFIX_LEN + len,
					  GFP_KERNEL);
		if (!new_xattr->name) {
			kfree(new_xattr);
			return -ENOMEM;
		}

		memcpy(new_xattr->name, XATTR_SECURITY_PREFIX,
		       XATTR_SECURITY_PREFIX_LEN);
		memcpy(new_xattr->name + XATTR_SECURITY_PREFIX_LEN,
		       xattr->name, len);

2552
		simple_xattr_list_add(&info->xattrs, new_xattr);
2553 2554 2555 2556 2557
	}

	return 0;
}

2558
static const struct xattr_handler *shmem_xattr_handlers[] = {
2559
#ifdef CONFIG_TMPFS_POSIX_ACL
C
Christoph Hellwig 已提交
2560 2561
	&posix_acl_access_xattr_handler,
	&posix_acl_default_xattr_handler,
2562
#endif
2563 2564
	NULL
};
2565 2566 2567 2568 2569 2570 2571 2572 2573 2574 2575 2576 2577 2578 2579 2580 2581 2582 2583 2584 2585 2586 2587

static int shmem_xattr_validate(const char *name)
{
	struct { const char *prefix; size_t len; } arr[] = {
		{ XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN },
		{ XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN }
	};
	int i;

	for (i = 0; i < ARRAY_SIZE(arr); i++) {
		size_t preflen = arr[i].len;
		if (strncmp(name, arr[i].prefix, preflen) == 0) {
			if (!name[preflen])
				return -EINVAL;
			return 0;
		}
	}
	return -EOPNOTSUPP;
}

static ssize_t shmem_getxattr(struct dentry *dentry, const char *name,
			      void *buffer, size_t size)
{
2588
	struct shmem_inode_info *info = SHMEM_I(d_inode(dentry));
2589 2590 2591 2592 2593 2594 2595 2596 2597 2598 2599 2600 2601 2602
	int err;

	/*
	 * If this is a request for a synthetic attribute in the system.*
	 * namespace use the generic infrastructure to resolve a handler
	 * for it via sb->s_xattr.
	 */
	if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
		return generic_getxattr(dentry, name, buffer, size);

	err = shmem_xattr_validate(name);
	if (err)
		return err;

2603
	return simple_xattr_get(&info->xattrs, name, buffer, size);
2604 2605 2606 2607 2608
}

static int shmem_setxattr(struct dentry *dentry, const char *name,
			  const void *value, size_t size, int flags)
{
2609
	struct shmem_inode_info *info = SHMEM_I(d_inode(dentry));
2610 2611 2612 2613 2614 2615 2616 2617 2618 2619 2620 2621 2622 2623
	int err;

	/*
	 * If this is a request for a synthetic attribute in the system.*
	 * namespace use the generic infrastructure to resolve a handler
	 * for it via sb->s_xattr.
	 */
	if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
		return generic_setxattr(dentry, name, value, size, flags);

	err = shmem_xattr_validate(name);
	if (err)
		return err;

2624
	return simple_xattr_set(&info->xattrs, name, value, size, flags);
2625 2626 2627 2628
}

static int shmem_removexattr(struct dentry *dentry, const char *name)
{
2629
	struct shmem_inode_info *info = SHMEM_I(d_inode(dentry));
2630 2631 2632 2633 2634 2635 2636 2637 2638 2639 2640 2641 2642 2643
	int err;

	/*
	 * If this is a request for a synthetic attribute in the system.*
	 * namespace use the generic infrastructure to resolve a handler
	 * for it via sb->s_xattr.
	 */
	if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
		return generic_removexattr(dentry, name);

	err = shmem_xattr_validate(name);
	if (err)
		return err;

2644
	return simple_xattr_remove(&info->xattrs, name);
2645 2646 2647 2648
}

static ssize_t shmem_listxattr(struct dentry *dentry, char *buffer, size_t size)
{
2649
	struct shmem_inode_info *info = SHMEM_I(d_inode(dentry));
2650
	return simple_xattr_list(&info->xattrs, buffer, size);
2651 2652 2653
}
#endif /* CONFIG_TMPFS_XATTR */

2654
static const struct inode_operations shmem_short_symlink_operations = {
2655
	.readlink	= generic_readlink,
A
Al Viro 已提交
2656
	.follow_link	= simple_follow_link,
2657 2658 2659 2660 2661 2662 2663 2664 2665 2666 2667 2668 2669 2670 2671 2672 2673
#ifdef CONFIG_TMPFS_XATTR
	.setxattr	= shmem_setxattr,
	.getxattr	= shmem_getxattr,
	.listxattr	= shmem_listxattr,
	.removexattr	= shmem_removexattr,
#endif
};

static const struct inode_operations shmem_symlink_inode_operations = {
	.readlink	= generic_readlink,
	.follow_link	= shmem_follow_link,
	.put_link	= shmem_put_link,
#ifdef CONFIG_TMPFS_XATTR
	.setxattr	= shmem_setxattr,
	.getxattr	= shmem_getxattr,
	.listxattr	= shmem_listxattr,
	.removexattr	= shmem_removexattr,
2674
#endif
2675
};
2676

2677 2678 2679 2680 2681 2682 2683 2684 2685 2686 2687 2688 2689
static struct dentry *shmem_get_parent(struct dentry *child)
{
	return ERR_PTR(-ESTALE);
}

static int shmem_match(struct inode *ino, void *vfh)
{
	__u32 *fh = vfh;
	__u64 inum = fh[2];
	inum = (inum << 32) | fh[1];
	return ino->i_ino == inum && fh[0] == ino->i_generation;
}

C
Christoph Hellwig 已提交
2690 2691
static struct dentry *shmem_fh_to_dentry(struct super_block *sb,
		struct fid *fid, int fh_len, int fh_type)
2692 2693
{
	struct inode *inode;
C
Christoph Hellwig 已提交
2694
	struct dentry *dentry = NULL;
2695
	u64 inum;
C
Christoph Hellwig 已提交
2696 2697 2698

	if (fh_len < 3)
		return NULL;
2699

2700 2701 2702
	inum = fid->raw[2];
	inum = (inum << 32) | fid->raw[1];

C
Christoph Hellwig 已提交
2703 2704
	inode = ilookup5(sb, (unsigned long)(inum + fid->raw[0]),
			shmem_match, fid->raw);
2705
	if (inode) {
C
Christoph Hellwig 已提交
2706
		dentry = d_find_alias(inode);
2707 2708 2709
		iput(inode);
	}

C
Christoph Hellwig 已提交
2710
	return dentry;
2711 2712
}

A
Al Viro 已提交
2713 2714
static int shmem_encode_fh(struct inode *inode, __u32 *fh, int *len,
				struct inode *parent)
2715
{
2716 2717
	if (*len < 3) {
		*len = 3;
2718
		return FILEID_INVALID;
2719
	}
2720

A
Al Viro 已提交
2721
	if (inode_unhashed(inode)) {
2722 2723 2724 2725 2726 2727 2728
		/* Unfortunately insert_inode_hash is not idempotent,
		 * so as we hash inodes here rather than at creation
		 * time, we need a lock to ensure we only try
		 * to do it once
		 */
		static DEFINE_SPINLOCK(lock);
		spin_lock(&lock);
A
Al Viro 已提交
2729
		if (inode_unhashed(inode))
2730 2731 2732 2733 2734 2735 2736 2737 2738 2739 2740 2741 2742
			__insert_inode_hash(inode,
					    inode->i_ino + inode->i_generation);
		spin_unlock(&lock);
	}

	fh[0] = inode->i_generation;
	fh[1] = inode->i_ino;
	fh[2] = ((__u64)inode->i_ino) >> 32;

	*len = 3;
	return 1;
}

2743
static const struct export_operations shmem_export_ops = {
2744 2745
	.get_parent     = shmem_get_parent,
	.encode_fh      = shmem_encode_fh,
C
Christoph Hellwig 已提交
2746
	.fh_to_dentry	= shmem_fh_to_dentry,
2747 2748
};

2749 2750
static int shmem_parse_options(char *options, struct shmem_sb_info *sbinfo,
			       bool remount)
L
Linus Torvalds 已提交
2751 2752
{
	char *this_char, *value, *rest;
G
Greg Thelen 已提交
2753
	struct mempolicy *mpol = NULL;
2754 2755
	uid_t uid;
	gid_t gid;
L
Linus Torvalds 已提交
2756

2757 2758 2759 2760 2761 2762 2763 2764 2765 2766 2767 2768 2769 2770 2771 2772 2773
	while (options != NULL) {
		this_char = options;
		for (;;) {
			/*
			 * NUL-terminate this option: unfortunately,
			 * mount options form a comma-separated list,
			 * but mpol's nodelist may also contain commas.
			 */
			options = strchr(options, ',');
			if (options == NULL)
				break;
			options++;
			if (!isdigit(*options)) {
				options[-1] = '\0';
				break;
			}
		}
L
Linus Torvalds 已提交
2774 2775 2776 2777 2778 2779 2780 2781
		if (!*this_char)
			continue;
		if ((value = strchr(this_char,'=')) != NULL) {
			*value++ = 0;
		} else {
			printk(KERN_ERR
			    "tmpfs: No value for mount option '%s'\n",
			    this_char);
G
Greg Thelen 已提交
2782
			goto error;
L
Linus Torvalds 已提交
2783 2784 2785 2786 2787 2788 2789 2790 2791 2792 2793 2794 2795
		}

		if (!strcmp(this_char,"size")) {
			unsigned long long size;
			size = memparse(value,&rest);
			if (*rest == '%') {
				size <<= PAGE_SHIFT;
				size *= totalram_pages;
				do_div(size, 100);
				rest++;
			}
			if (*rest)
				goto bad_val;
2796 2797
			sbinfo->max_blocks =
				DIV_ROUND_UP(size, PAGE_CACHE_SIZE);
L
Linus Torvalds 已提交
2798
		} else if (!strcmp(this_char,"nr_blocks")) {
2799
			sbinfo->max_blocks = memparse(value, &rest);
L
Linus Torvalds 已提交
2800 2801 2802
			if (*rest)
				goto bad_val;
		} else if (!strcmp(this_char,"nr_inodes")) {
2803
			sbinfo->max_inodes = memparse(value, &rest);
L
Linus Torvalds 已提交
2804 2805 2806
			if (*rest)
				goto bad_val;
		} else if (!strcmp(this_char,"mode")) {
2807
			if (remount)
L
Linus Torvalds 已提交
2808
				continue;
2809
			sbinfo->mode = simple_strtoul(value, &rest, 8) & 07777;
L
Linus Torvalds 已提交
2810 2811 2812
			if (*rest)
				goto bad_val;
		} else if (!strcmp(this_char,"uid")) {
2813
			if (remount)
L
Linus Torvalds 已提交
2814
				continue;
2815
			uid = simple_strtoul(value, &rest, 0);
L
Linus Torvalds 已提交
2816 2817
			if (*rest)
				goto bad_val;
2818 2819 2820
			sbinfo->uid = make_kuid(current_user_ns(), uid);
			if (!uid_valid(sbinfo->uid))
				goto bad_val;
L
Linus Torvalds 已提交
2821
		} else if (!strcmp(this_char,"gid")) {
2822
			if (remount)
L
Linus Torvalds 已提交
2823
				continue;
2824
			gid = simple_strtoul(value, &rest, 0);
L
Linus Torvalds 已提交
2825 2826
			if (*rest)
				goto bad_val;
2827 2828 2829
			sbinfo->gid = make_kgid(current_user_ns(), gid);
			if (!gid_valid(sbinfo->gid))
				goto bad_val;
2830
		} else if (!strcmp(this_char,"mpol")) {
G
Greg Thelen 已提交
2831 2832 2833
			mpol_put(mpol);
			mpol = NULL;
			if (mpol_parse_str(value, &mpol))
2834
				goto bad_val;
L
Linus Torvalds 已提交
2835 2836 2837
		} else {
			printk(KERN_ERR "tmpfs: Bad mount option %s\n",
			       this_char);
G
Greg Thelen 已提交
2838
			goto error;
L
Linus Torvalds 已提交
2839 2840
		}
	}
G
Greg Thelen 已提交
2841
	sbinfo->mpol = mpol;
L
Linus Torvalds 已提交
2842 2843 2844 2845 2846
	return 0;

bad_val:
	printk(KERN_ERR "tmpfs: Bad value '%s' for mount option '%s'\n",
	       value, this_char);
G
Greg Thelen 已提交
2847 2848
error:
	mpol_put(mpol);
L
Linus Torvalds 已提交
2849 2850 2851 2852 2853 2854 2855
	return 1;

}

static int shmem_remount_fs(struct super_block *sb, int *flags, char *data)
{
	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
2856
	struct shmem_sb_info config = *sbinfo;
2857 2858 2859
	unsigned long inodes;
	int error = -EINVAL;

2860
	config.mpol = NULL;
2861
	if (shmem_parse_options(data, &config, true))
2862
		return error;
L
Linus Torvalds 已提交
2863

2864 2865
	spin_lock(&sbinfo->stat_lock);
	inodes = sbinfo->max_inodes - sbinfo->free_inodes;
2866
	if (percpu_counter_compare(&sbinfo->used_blocks, config.max_blocks) > 0)
2867
		goto out;
2868
	if (config.max_inodes < inodes)
2869 2870
		goto out;
	/*
2871
	 * Those tests disallow limited->unlimited while any are in use;
2872 2873 2874
	 * but we must separately disallow unlimited->limited, because
	 * in that case we have no record of how much is already in use.
	 */
2875
	if (config.max_blocks && !sbinfo->max_blocks)
2876
		goto out;
2877
	if (config.max_inodes && !sbinfo->max_inodes)
2878 2879 2880
		goto out;

	error = 0;
2881 2882 2883
	sbinfo->max_blocks  = config.max_blocks;
	sbinfo->max_inodes  = config.max_inodes;
	sbinfo->free_inodes = config.max_inodes - inodes;
2884

2885 2886 2887 2888 2889 2890 2891
	/*
	 * Preserve previous mempolicy unless mpol remount option was specified.
	 */
	if (config.mpol) {
		mpol_put(sbinfo->mpol);
		sbinfo->mpol = config.mpol;	/* transfers initial ref */
	}
2892 2893 2894
out:
	spin_unlock(&sbinfo->stat_lock);
	return error;
L
Linus Torvalds 已提交
2895
}
2896

2897
static int shmem_show_options(struct seq_file *seq, struct dentry *root)
2898
{
2899
	struct shmem_sb_info *sbinfo = SHMEM_SB(root->d_sb);
2900 2901 2902 2903 2904 2905 2906

	if (sbinfo->max_blocks != shmem_default_max_blocks())
		seq_printf(seq, ",size=%luk",
			sbinfo->max_blocks << (PAGE_CACHE_SHIFT - 10));
	if (sbinfo->max_inodes != shmem_default_max_inodes())
		seq_printf(seq, ",nr_inodes=%lu", sbinfo->max_inodes);
	if (sbinfo->mode != (S_IRWXUGO | S_ISVTX))
2907
		seq_printf(seq, ",mode=%03ho", sbinfo->mode);
2908 2909 2910 2911 2912 2913
	if (!uid_eq(sbinfo->uid, GLOBAL_ROOT_UID))
		seq_printf(seq, ",uid=%u",
				from_kuid_munged(&init_user_ns, sbinfo->uid));
	if (!gid_eq(sbinfo->gid, GLOBAL_ROOT_GID))
		seq_printf(seq, ",gid=%u",
				from_kgid_munged(&init_user_ns, sbinfo->gid));
2914
	shmem_show_mpol(seq, sbinfo->mpol);
2915 2916
	return 0;
}
D
David Herrmann 已提交
2917 2918 2919 2920 2921 2922 2923 2924 2925 2926 2927 2928 2929 2930 2931 2932 2933 2934 2935 2936 2937 2938 2939 2940 2941 2942 2943 2944 2945 2946 2947 2948 2949 2950 2951 2952 2953 2954 2955 2956 2957 2958 2959 2960 2961 2962 2963 2964 2965 2966 2967 2968 2969 2970 2971 2972 2973 2974 2975 2976 2977 2978 2979 2980 2981 2982 2983 2984 2985 2986 2987

#define MFD_NAME_PREFIX "memfd:"
#define MFD_NAME_PREFIX_LEN (sizeof(MFD_NAME_PREFIX) - 1)
#define MFD_NAME_MAX_LEN (NAME_MAX - MFD_NAME_PREFIX_LEN)

#define MFD_ALL_FLAGS (MFD_CLOEXEC | MFD_ALLOW_SEALING)

SYSCALL_DEFINE2(memfd_create,
		const char __user *, uname,
		unsigned int, flags)
{
	struct shmem_inode_info *info;
	struct file *file;
	int fd, error;
	char *name;
	long len;

	if (flags & ~(unsigned int)MFD_ALL_FLAGS)
		return -EINVAL;

	/* length includes terminating zero */
	len = strnlen_user(uname, MFD_NAME_MAX_LEN + 1);
	if (len <= 0)
		return -EFAULT;
	if (len > MFD_NAME_MAX_LEN + 1)
		return -EINVAL;

	name = kmalloc(len + MFD_NAME_PREFIX_LEN, GFP_TEMPORARY);
	if (!name)
		return -ENOMEM;

	strcpy(name, MFD_NAME_PREFIX);
	if (copy_from_user(&name[MFD_NAME_PREFIX_LEN], uname, len)) {
		error = -EFAULT;
		goto err_name;
	}

	/* terminating-zero may have changed after strnlen_user() returned */
	if (name[len + MFD_NAME_PREFIX_LEN - 1]) {
		error = -EFAULT;
		goto err_name;
	}

	fd = get_unused_fd_flags((flags & MFD_CLOEXEC) ? O_CLOEXEC : 0);
	if (fd < 0) {
		error = fd;
		goto err_name;
	}

	file = shmem_file_setup(name, 0, VM_NORESERVE);
	if (IS_ERR(file)) {
		error = PTR_ERR(file);
		goto err_fd;
	}
	info = SHMEM_I(file_inode(file));
	file->f_mode |= FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE;
	file->f_flags |= O_RDWR | O_LARGEFILE;
	if (flags & MFD_ALLOW_SEALING)
		info->seals &= ~F_SEAL_SEAL;

	fd_install(fd, file);
	kfree(name);
	return fd;

err_fd:
	put_unused_fd(fd);
err_name:
	kfree(name);
	return error;
}

2988
#endif /* CONFIG_TMPFS */
L
Linus Torvalds 已提交
2989 2990 2991

static void shmem_put_super(struct super_block *sb)
{
2992 2993 2994
	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);

	percpu_counter_destroy(&sbinfo->used_blocks);
G
Greg Thelen 已提交
2995
	mpol_put(sbinfo->mpol);
2996
	kfree(sbinfo);
L
Linus Torvalds 已提交
2997 2998 2999
	sb->s_fs_info = NULL;
}

3000
int shmem_fill_super(struct super_block *sb, void *data, int silent)
L
Linus Torvalds 已提交
3001 3002
{
	struct inode *inode;
3003
	struct shmem_sb_info *sbinfo;
3004 3005 3006
	int err = -ENOMEM;

	/* Round up to L1_CACHE_BYTES to resist false sharing */
3007
	sbinfo = kzalloc(max((int)sizeof(struct shmem_sb_info),
3008 3009 3010 3011 3012
				L1_CACHE_BYTES), GFP_KERNEL);
	if (!sbinfo)
		return -ENOMEM;

	sbinfo->mode = S_IRWXUGO | S_ISVTX;
3013 3014
	sbinfo->uid = current_fsuid();
	sbinfo->gid = current_fsgid();
3015
	sb->s_fs_info = sbinfo;
L
Linus Torvalds 已提交
3016

3017
#ifdef CONFIG_TMPFS
L
Linus Torvalds 已提交
3018 3019 3020 3021 3022
	/*
	 * Per default we only allow half of the physical ram per
	 * tmpfs instance, limiting inodes to one per page of lowmem;
	 * but the internal instance is left unlimited.
	 */
3023
	if (!(sb->s_flags & MS_KERNMOUNT)) {
3024 3025 3026 3027 3028 3029
		sbinfo->max_blocks = shmem_default_max_blocks();
		sbinfo->max_inodes = shmem_default_max_inodes();
		if (shmem_parse_options(data, sbinfo, false)) {
			err = -EINVAL;
			goto failed;
		}
3030 3031
	} else {
		sb->s_flags |= MS_NOUSER;
L
Linus Torvalds 已提交
3032
	}
3033
	sb->s_export_op = &shmem_export_ops;
H
Hugh Dickins 已提交
3034
	sb->s_flags |= MS_NOSEC;
L
Linus Torvalds 已提交
3035 3036 3037 3038
#else
	sb->s_flags |= MS_NOUSER;
#endif

3039
	spin_lock_init(&sbinfo->stat_lock);
3040
	if (percpu_counter_init(&sbinfo->used_blocks, 0, GFP_KERNEL))
3041
		goto failed;
3042
	sbinfo->free_inodes = sbinfo->max_inodes;
3043

3044
	sb->s_maxbytes = MAX_LFS_FILESIZE;
L
Linus Torvalds 已提交
3045 3046 3047 3048
	sb->s_blocksize = PAGE_CACHE_SIZE;
	sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
	sb->s_magic = TMPFS_MAGIC;
	sb->s_op = &shmem_ops;
3049
	sb->s_time_gran = 1;
3050
#ifdef CONFIG_TMPFS_XATTR
3051
	sb->s_xattr = shmem_xattr_handlers;
3052 3053
#endif
#ifdef CONFIG_TMPFS_POSIX_ACL
3054 3055
	sb->s_flags |= MS_POSIXACL;
#endif
3056

3057
	inode = shmem_get_inode(sb, NULL, S_IFDIR | sbinfo->mode, 0, VM_NORESERVE);
L
Linus Torvalds 已提交
3058 3059
	if (!inode)
		goto failed;
3060 3061
	inode->i_uid = sbinfo->uid;
	inode->i_gid = sbinfo->gid;
A
Al Viro 已提交
3062 3063
	sb->s_root = d_make_root(inode);
	if (!sb->s_root)
3064
		goto failed;
L
Linus Torvalds 已提交
3065 3066 3067 3068 3069 3070 3071
	return 0;

failed:
	shmem_put_super(sb);
	return err;
}

3072
static struct kmem_cache *shmem_inode_cachep;
L
Linus Torvalds 已提交
3073 3074 3075

static struct inode *shmem_alloc_inode(struct super_block *sb)
{
3076 3077 3078
	struct shmem_inode_info *info;
	info = kmem_cache_alloc(shmem_inode_cachep, GFP_KERNEL);
	if (!info)
L
Linus Torvalds 已提交
3079
		return NULL;
3080
	return &info->vfs_inode;
L
Linus Torvalds 已提交
3081 3082
}

3083
static void shmem_destroy_callback(struct rcu_head *head)
N
Nick Piggin 已提交
3084 3085 3086 3087 3088
{
	struct inode *inode = container_of(head, struct inode, i_rcu);
	kmem_cache_free(shmem_inode_cachep, SHMEM_I(inode));
}

L
Linus Torvalds 已提交
3089 3090
static void shmem_destroy_inode(struct inode *inode)
{
3091
	if (S_ISREG(inode->i_mode))
L
Linus Torvalds 已提交
3092
		mpol_free_shared_policy(&SHMEM_I(inode)->policy);
3093
	call_rcu(&inode->i_rcu, shmem_destroy_callback);
L
Linus Torvalds 已提交
3094 3095
}

3096
static void shmem_init_inode(void *foo)
L
Linus Torvalds 已提交
3097
{
3098 3099
	struct shmem_inode_info *info = foo;
	inode_init_once(&info->vfs_inode);
L
Linus Torvalds 已提交
3100 3101
}

3102
static int shmem_init_inodecache(void)
L
Linus Torvalds 已提交
3103 3104 3105
{
	shmem_inode_cachep = kmem_cache_create("shmem_inode_cache",
				sizeof(struct shmem_inode_info),
3106
				0, SLAB_PANIC, shmem_init_inode);
L
Linus Torvalds 已提交
3107 3108 3109
	return 0;
}

3110
static void shmem_destroy_inodecache(void)
L
Linus Torvalds 已提交
3111
{
3112
	kmem_cache_destroy(shmem_inode_cachep);
L
Linus Torvalds 已提交
3113 3114
}

3115
static const struct address_space_operations shmem_aops = {
L
Linus Torvalds 已提交
3116
	.writepage	= shmem_writepage,
3117
	.set_page_dirty	= __set_page_dirty_no_writeback,
L
Linus Torvalds 已提交
3118
#ifdef CONFIG_TMPFS
N
Nick Piggin 已提交
3119 3120
	.write_begin	= shmem_write_begin,
	.write_end	= shmem_write_end,
L
Linus Torvalds 已提交
3121
#endif
3122
#ifdef CONFIG_MIGRATION
3123
	.migratepage	= migrate_page,
3124
#endif
3125
	.error_remove_page = generic_error_remove_page,
L
Linus Torvalds 已提交
3126 3127
};

3128
static const struct file_operations shmem_file_operations = {
L
Linus Torvalds 已提交
3129 3130
	.mmap		= shmem_mmap,
#ifdef CONFIG_TMPFS
3131
	.llseek		= shmem_file_llseek,
A
Al Viro 已提交
3132
	.read_iter	= shmem_file_read_iter,
3133
	.write_iter	= generic_file_write_iter,
3134
	.fsync		= noop_fsync,
3135
	.splice_read	= shmem_file_splice_read,
3136
	.splice_write	= iter_file_splice_write,
3137
	.fallocate	= shmem_fallocate,
L
Linus Torvalds 已提交
3138 3139 3140
#endif
};

3141
static const struct inode_operations shmem_inode_operations = {
3142
	.getattr	= shmem_getattr,
3143
	.setattr	= shmem_setattr,
3144 3145 3146 3147 3148
#ifdef CONFIG_TMPFS_XATTR
	.setxattr	= shmem_setxattr,
	.getxattr	= shmem_getxattr,
	.listxattr	= shmem_listxattr,
	.removexattr	= shmem_removexattr,
C
Christoph Hellwig 已提交
3149
	.set_acl	= simple_set_acl,
3150
#endif
L
Linus Torvalds 已提交
3151 3152
};

3153
static const struct inode_operations shmem_dir_inode_operations = {
L
Linus Torvalds 已提交
3154 3155 3156 3157 3158 3159 3160 3161 3162
#ifdef CONFIG_TMPFS
	.create		= shmem_create,
	.lookup		= simple_lookup,
	.link		= shmem_link,
	.unlink		= shmem_unlink,
	.symlink	= shmem_symlink,
	.mkdir		= shmem_mkdir,
	.rmdir		= shmem_rmdir,
	.mknod		= shmem_mknod,
M
Miklos Szeredi 已提交
3163
	.rename2	= shmem_rename2,
3164
	.tmpfile	= shmem_tmpfile,
L
Linus Torvalds 已提交
3165
#endif
3166 3167 3168 3169 3170 3171
#ifdef CONFIG_TMPFS_XATTR
	.setxattr	= shmem_setxattr,
	.getxattr	= shmem_getxattr,
	.listxattr	= shmem_listxattr,
	.removexattr	= shmem_removexattr,
#endif
3172
#ifdef CONFIG_TMPFS_POSIX_ACL
3173
	.setattr	= shmem_setattr,
C
Christoph Hellwig 已提交
3174
	.set_acl	= simple_set_acl,
3175 3176 3177
#endif
};

3178
static const struct inode_operations shmem_special_inode_operations = {
3179 3180 3181 3182 3183 3184
#ifdef CONFIG_TMPFS_XATTR
	.setxattr	= shmem_setxattr,
	.getxattr	= shmem_getxattr,
	.listxattr	= shmem_listxattr,
	.removexattr	= shmem_removexattr,
#endif
3185
#ifdef CONFIG_TMPFS_POSIX_ACL
3186
	.setattr	= shmem_setattr,
C
Christoph Hellwig 已提交
3187
	.set_acl	= simple_set_acl,
3188
#endif
L
Linus Torvalds 已提交
3189 3190
};

3191
static const struct super_operations shmem_ops = {
L
Linus Torvalds 已提交
3192 3193 3194 3195 3196
	.alloc_inode	= shmem_alloc_inode,
	.destroy_inode	= shmem_destroy_inode,
#ifdef CONFIG_TMPFS
	.statfs		= shmem_statfs,
	.remount_fs	= shmem_remount_fs,
3197
	.show_options	= shmem_show_options,
L
Linus Torvalds 已提交
3198
#endif
A
Al Viro 已提交
3199
	.evict_inode	= shmem_evict_inode,
L
Linus Torvalds 已提交
3200 3201 3202 3203
	.drop_inode	= generic_delete_inode,
	.put_super	= shmem_put_super,
};

3204
static const struct vm_operations_struct shmem_vm_ops = {
3205
	.fault		= shmem_fault,
3206
	.map_pages	= filemap_map_pages,
L
Linus Torvalds 已提交
3207 3208 3209 3210 3211 3212
#ifdef CONFIG_NUMA
	.set_policy     = shmem_set_policy,
	.get_policy     = shmem_get_policy,
#endif
};

A
Al Viro 已提交
3213 3214
static struct dentry *shmem_mount(struct file_system_type *fs_type,
	int flags, const char *dev_name, void *data)
L
Linus Torvalds 已提交
3215
{
A
Al Viro 已提交
3216
	return mount_nodev(fs_type, flags, data, shmem_fill_super);
L
Linus Torvalds 已提交
3217 3218
}

3219
static struct file_system_type shmem_fs_type = {
L
Linus Torvalds 已提交
3220 3221
	.owner		= THIS_MODULE,
	.name		= "tmpfs",
A
Al Viro 已提交
3222
	.mount		= shmem_mount,
L
Linus Torvalds 已提交
3223
	.kill_sb	= kill_litter_super,
3224
	.fs_flags	= FS_USERNS_MOUNT,
L
Linus Torvalds 已提交
3225 3226
};

3227
int __init shmem_init(void)
L
Linus Torvalds 已提交
3228 3229 3230
{
	int error;

3231 3232 3233 3234
	/* If rootfs called this, don't re-init */
	if (shmem_inode_cachep)
		return 0;

3235
	error = shmem_init_inodecache();
L
Linus Torvalds 已提交
3236 3237 3238
	if (error)
		goto out3;

3239
	error = register_filesystem(&shmem_fs_type);
L
Linus Torvalds 已提交
3240 3241 3242 3243
	if (error) {
		printk(KERN_ERR "Could not register tmpfs\n");
		goto out2;
	}
3244

3245
	shm_mnt = kern_mount(&shmem_fs_type);
L
Linus Torvalds 已提交
3246 3247 3248 3249 3250 3251 3252 3253
	if (IS_ERR(shm_mnt)) {
		error = PTR_ERR(shm_mnt);
		printk(KERN_ERR "Could not kern_mount tmpfs\n");
		goto out1;
	}
	return 0;

out1:
3254
	unregister_filesystem(&shmem_fs_type);
L
Linus Torvalds 已提交
3255
out2:
3256
	shmem_destroy_inodecache();
L
Linus Torvalds 已提交
3257 3258 3259 3260
out3:
	shm_mnt = ERR_PTR(error);
	return error;
}
3261 3262 3263 3264 3265 3266 3267 3268 3269 3270 3271 3272

#else /* !CONFIG_SHMEM */

/*
 * tiny-shmem: simple shmemfs and tmpfs using ramfs code
 *
 * This is intended for small system where the benefits of the full
 * shmem code (swap-backed and resource-limited) are outweighed by
 * their complexity. On systems without swap this code should be
 * effectively equivalent, but much lighter weight.
 */

3273
static struct file_system_type shmem_fs_type = {
3274
	.name		= "tmpfs",
A
Al Viro 已提交
3275
	.mount		= ramfs_mount,
3276
	.kill_sb	= kill_litter_super,
3277
	.fs_flags	= FS_USERNS_MOUNT,
3278 3279
};

3280
int __init shmem_init(void)
3281
{
3282
	BUG_ON(register_filesystem(&shmem_fs_type) != 0);
3283

3284
	shm_mnt = kern_mount(&shmem_fs_type);
3285 3286 3287 3288 3289
	BUG_ON(IS_ERR(shm_mnt));

	return 0;
}

3290
int shmem_unuse(swp_entry_t swap, struct page *page)
3291 3292 3293 3294
{
	return 0;
}

H
Hugh Dickins 已提交
3295 3296 3297 3298 3299
int shmem_lock(struct file *file, int lock, struct user_struct *user)
{
	return 0;
}

3300 3301 3302 3303
void shmem_unlock_mapping(struct address_space *mapping)
{
}

3304
void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
3305
{
3306
	truncate_inode_pages_range(inode->i_mapping, lstart, lend);
3307 3308 3309
}
EXPORT_SYMBOL_GPL(shmem_truncate_range);

3310 3311
#define shmem_vm_ops				generic_file_vm_ops
#define shmem_file_operations			ramfs_file_operations
3312
#define shmem_get_inode(sb, dir, mode, dev, flags)	ramfs_get_inode(sb, dir, mode, dev)
3313 3314
#define shmem_acct_size(flags, size)		0
#define shmem_unacct_size(flags, size)		do {} while (0)
3315 3316 3317 3318

#endif /* CONFIG_SHMEM */

/* common code */
L
Linus Torvalds 已提交
3319

3320
static struct dentry_operations anon_ops = {
3321
	.d_dname = simple_dname
3322 3323
};

3324 3325
static struct file *__shmem_file_setup(const char *name, loff_t size,
				       unsigned long flags, unsigned int i_flags)
L
Linus Torvalds 已提交
3326
{
A
Al Viro 已提交
3327
	struct file *res;
L
Linus Torvalds 已提交
3328
	struct inode *inode;
3329
	struct path path;
3330
	struct super_block *sb;
L
Linus Torvalds 已提交
3331 3332 3333
	struct qstr this;

	if (IS_ERR(shm_mnt))
A
Al Viro 已提交
3334
		return ERR_CAST(shm_mnt);
L
Linus Torvalds 已提交
3335

3336
	if (size < 0 || size > MAX_LFS_FILESIZE)
L
Linus Torvalds 已提交
3337 3338 3339 3340 3341
		return ERR_PTR(-EINVAL);

	if (shmem_acct_size(flags, size))
		return ERR_PTR(-ENOMEM);

A
Al Viro 已提交
3342
	res = ERR_PTR(-ENOMEM);
L
Linus Torvalds 已提交
3343 3344 3345
	this.name = name;
	this.len = strlen(name);
	this.hash = 0; /* will go */
3346
	sb = shm_mnt->mnt_sb;
3347
	path.mnt = mntget(shm_mnt);
3348
	path.dentry = d_alloc_pseudo(sb, &this);
3349
	if (!path.dentry)
L
Linus Torvalds 已提交
3350
		goto put_memory;
3351
	d_set_d_op(path.dentry, &anon_ops);
L
Linus Torvalds 已提交
3352

A
Al Viro 已提交
3353
	res = ERR_PTR(-ENOSPC);
3354
	inode = shmem_get_inode(sb, NULL, S_IFREG | S_IRWXUGO, 0, flags);
L
Linus Torvalds 已提交
3355
	if (!inode)
3356
		goto put_memory;
L
Linus Torvalds 已提交
3357

3358
	inode->i_flags |= i_flags;
3359
	d_instantiate(path.dentry, inode);
L
Linus Torvalds 已提交
3360
	inode->i_size = size;
3361
	clear_nlink(inode);	/* It is unlinked */
A
Al Viro 已提交
3362 3363
	res = ERR_PTR(ramfs_nommu_expand_for_mapping(inode, size));
	if (IS_ERR(res))
3364
		goto put_path;
3365

A
Al Viro 已提交
3366
	res = alloc_file(&path, FMODE_WRITE | FMODE_READ,
3367
		  &shmem_file_operations);
A
Al Viro 已提交
3368
	if (IS_ERR(res))
3369
		goto put_path;
3370

A
Al Viro 已提交
3371
	return res;
L
Linus Torvalds 已提交
3372 3373 3374

put_memory:
	shmem_unacct_size(flags, size);
3375 3376
put_path:
	path_put(&path);
A
Al Viro 已提交
3377
	return res;
L
Linus Torvalds 已提交
3378
}
3379 3380 3381 3382 3383

/**
 * shmem_kernel_file_setup - get an unlinked file living in tmpfs which must be
 * 	kernel internal.  There will be NO LSM permission checks against the
 * 	underlying inode.  So users of this interface must do LSM checks at a
3384 3385
 *	higher layer.  The users are the big_key and shm implementations.  LSM
 *	checks are provided at the key or shm level rather than the inode.
3386 3387 3388 3389 3390 3391 3392 3393 3394 3395 3396 3397 3398 3399 3400 3401 3402 3403 3404
 * @name: name for dentry (to be seen in /proc/<pid>/maps
 * @size: size to be set for the file
 * @flags: VM_NORESERVE suppresses pre-accounting of the entire object size
 */
struct file *shmem_kernel_file_setup(const char *name, loff_t size, unsigned long flags)
{
	return __shmem_file_setup(name, size, flags, S_PRIVATE);
}

/**
 * shmem_file_setup - get an unlinked file living in tmpfs
 * @name: name for dentry (to be seen in /proc/<pid>/maps
 * @size: size to be set for the file
 * @flags: VM_NORESERVE suppresses pre-accounting of the entire object size
 */
struct file *shmem_file_setup(const char *name, loff_t size, unsigned long flags)
{
	return __shmem_file_setup(name, size, flags, 0);
}
3405
EXPORT_SYMBOL_GPL(shmem_file_setup);
L
Linus Torvalds 已提交
3406

3407
/**
L
Linus Torvalds 已提交
3408 3409 3410 3411 3412 3413 3414 3415
 * shmem_zero_setup - setup a shared anonymous mapping
 * @vma: the vma to be mmapped is prepared by do_mmap_pgoff
 */
int shmem_zero_setup(struct vm_area_struct *vma)
{
	struct file *file;
	loff_t size = vma->vm_end - vma->vm_start;

3416 3417 3418 3419 3420 3421 3422
	/*
	 * Cloning a new file under mmap_sem leads to a lock ordering conflict
	 * between XFS directory reading and selinux: since this file is only
	 * accessible to the user through its mapping, use S_PRIVATE flag to
	 * bypass file security, in the same way as shmem_kernel_file_setup().
	 */
	file = __shmem_file_setup("dev/zero", size, vma->vm_flags, S_PRIVATE);
L
Linus Torvalds 已提交
3423 3424 3425 3426 3427 3428 3429 3430 3431
	if (IS_ERR(file))
		return PTR_ERR(file);

	if (vma->vm_file)
		fput(vma->vm_file);
	vma->vm_file = file;
	vma->vm_ops = &shmem_vm_ops;
	return 0;
}
3432 3433 3434 3435 3436 3437 3438 3439 3440 3441 3442 3443 3444

/**
 * shmem_read_mapping_page_gfp - read into page cache, using specified page allocation flags.
 * @mapping:	the page's address_space
 * @index:	the page index
 * @gfp:	the page allocator flags to use if allocating
 *
 * This behaves as a tmpfs "read_cache_page_gfp(mapping, index, gfp)",
 * with any new page allocations done using the specified allocation flags.
 * But read_cache_page_gfp() uses the ->readpage() method: which does not
 * suit tmpfs, since it may have pages in swapcache, and needs to find those
 * for itself; although drivers/gpu/drm i915 and ttm rely upon this support.
 *
3445 3446
 * i915_gem_object_get_pages_gtt() mixes __GFP_NORETRY | __GFP_NOWARN in
 * with the mapping_gfp_mask(), to avoid OOMing the machine unnecessarily.
3447 3448 3449 3450
 */
struct page *shmem_read_mapping_page_gfp(struct address_space *mapping,
					 pgoff_t index, gfp_t gfp)
{
3451 3452
#ifdef CONFIG_SHMEM
	struct inode *inode = mapping->host;
H
Hugh Dickins 已提交
3453
	struct page *page;
3454 3455 3456 3457 3458 3459 3460 3461 3462 3463 3464 3465 3466
	int error;

	BUG_ON(mapping->a_ops != &shmem_aops);
	error = shmem_getpage_gfp(inode, index, &page, SGP_CACHE, gfp, NULL);
	if (error)
		page = ERR_PTR(error);
	else
		unlock_page(page);
	return page;
#else
	/*
	 * The tiny !SHMEM case uses ramfs without swap
	 */
3467
	return read_cache_page_gfp(mapping, index, gfp);
3468
#endif
3469 3470
}
EXPORT_SYMBOL_GPL(shmem_read_mapping_page_gfp);