buffer.c 86.1 KB
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/*
 *  linux/fs/buffer.c
 *
 *  Copyright (C) 1991, 1992, 2002  Linus Torvalds
 */

/*
 * Start bdflush() with kernel_thread not syscall - Paul Gortmaker, 12/95
 *
 * Removed a lot of unnecessary code and simplified things now that
 * the buffer cache isn't our primary cache - Andrew Tridgell 12/96
 *
 * Speed up hash, lru, and free list operations.  Use gfp() for allocating
 * hash table, use SLAB cache for buffer heads. SMP threading.  -DaveM
 *
 * Added 32k buffer block sizes - these are required older ARM systems. - RMK
 *
 * async buffer flushing, 1999 Andrea Arcangeli <andrea@suse.de>
 */

#include <linux/kernel.h>
#include <linux/syscalls.h>
#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/percpu.h>
#include <linux/slab.h>
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#include <linux/capability.h>
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#include <linux/blkdev.h>
#include <linux/file.h>
#include <linux/quotaops.h>
#include <linux/highmem.h>
#include <linux/module.h>
#include <linux/writeback.h>
#include <linux/hash.h>
#include <linux/suspend.h>
#include <linux/buffer_head.h>
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#include <linux/task_io_accounting_ops.h>
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#include <linux/bio.h>
#include <linux/notifier.h>
#include <linux/cpu.h>
#include <linux/bitops.h>
#include <linux/mpage.h>
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#include <linux/bit_spinlock.h>
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static int fsync_buffers_list(spinlock_t *lock, struct list_head *list);

#define BH_ENTRY(list) list_entry((list), struct buffer_head, b_assoc_buffers)

inline void
init_buffer(struct buffer_head *bh, bh_end_io_t *handler, void *private)
{
	bh->b_end_io = handler;
	bh->b_private = private;
}

static int sync_buffer(void *word)
{
	struct block_device *bd;
	struct buffer_head *bh
		= container_of(word, struct buffer_head, b_state);

	smp_mb();
	bd = bh->b_bdev;
	if (bd)
		blk_run_address_space(bd->bd_inode->i_mapping);
	io_schedule();
	return 0;
}

void fastcall __lock_buffer(struct buffer_head *bh)
{
	wait_on_bit_lock(&bh->b_state, BH_Lock, sync_buffer,
							TASK_UNINTERRUPTIBLE);
}
EXPORT_SYMBOL(__lock_buffer);

void fastcall unlock_buffer(struct buffer_head *bh)
{
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	smp_mb__before_clear_bit();
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	clear_buffer_locked(bh);
	smp_mb__after_clear_bit();
	wake_up_bit(&bh->b_state, BH_Lock);
}

/*
 * Block until a buffer comes unlocked.  This doesn't stop it
 * from becoming locked again - you have to lock it yourself
 * if you want to preserve its state.
 */
void __wait_on_buffer(struct buffer_head * bh)
{
	wait_on_bit(&bh->b_state, BH_Lock, sync_buffer, TASK_UNINTERRUPTIBLE);
}

static void
__clear_page_buffers(struct page *page)
{
	ClearPagePrivate(page);
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	set_page_private(page, 0);
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	page_cache_release(page);
}

static void buffer_io_error(struct buffer_head *bh)
{
	char b[BDEVNAME_SIZE];

	printk(KERN_ERR "Buffer I/O error on device %s, logical block %Lu\n",
			bdevname(bh->b_bdev, b),
			(unsigned long long)bh->b_blocknr);
}

/*
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 * End-of-IO handler helper function which does not touch the bh after
 * unlocking it.
 * Note: unlock_buffer() sort-of does touch the bh after unlocking it, but
 * a race there is benign: unlock_buffer() only use the bh's address for
 * hashing after unlocking the buffer, so it doesn't actually touch the bh
 * itself.
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 */
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static void __end_buffer_read_notouch(struct buffer_head *bh, int uptodate)
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{
	if (uptodate) {
		set_buffer_uptodate(bh);
	} else {
		/* This happens, due to failed READA attempts. */
		clear_buffer_uptodate(bh);
	}
	unlock_buffer(bh);
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}

/*
 * Default synchronous end-of-IO handler..  Just mark it up-to-date and
 * unlock the buffer. This is what ll_rw_block uses too.
 */
void end_buffer_read_sync(struct buffer_head *bh, int uptodate)
{
	__end_buffer_read_notouch(bh, uptodate);
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	put_bh(bh);
}

void end_buffer_write_sync(struct buffer_head *bh, int uptodate)
{
	char b[BDEVNAME_SIZE];

	if (uptodate) {
		set_buffer_uptodate(bh);
	} else {
		if (!buffer_eopnotsupp(bh) && printk_ratelimit()) {
			buffer_io_error(bh);
			printk(KERN_WARNING "lost page write due to "
					"I/O error on %s\n",
				       bdevname(bh->b_bdev, b));
		}
		set_buffer_write_io_error(bh);
		clear_buffer_uptodate(bh);
	}
	unlock_buffer(bh);
	put_bh(bh);
}

/*
 * Write out and wait upon all the dirty data associated with a block
 * device via its mapping.  Does not take the superblock lock.
 */
int sync_blockdev(struct block_device *bdev)
{
	int ret = 0;

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	if (bdev)
		ret = filemap_write_and_wait(bdev->bd_inode->i_mapping);
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	return ret;
}
EXPORT_SYMBOL(sync_blockdev);

/*
 * Write out and wait upon all dirty data associated with this
 * device.   Filesystem data as well as the underlying block
 * device.  Takes the superblock lock.
 */
int fsync_bdev(struct block_device *bdev)
{
	struct super_block *sb = get_super(bdev);
	if (sb) {
		int res = fsync_super(sb);
		drop_super(sb);
		return res;
	}
	return sync_blockdev(bdev);
}

/**
 * freeze_bdev  --  lock a filesystem and force it into a consistent state
 * @bdev:	blockdevice to lock
 *
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 * This takes the block device bd_mount_sem to make sure no new mounts
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 * happen on bdev until thaw_bdev() is called.
 * If a superblock is found on this device, we take the s_umount semaphore
 * on it to make sure nobody unmounts until the snapshot creation is done.
 */
struct super_block *freeze_bdev(struct block_device *bdev)
{
	struct super_block *sb;

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	down(&bdev->bd_mount_sem);
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	sb = get_super(bdev);
	if (sb && !(sb->s_flags & MS_RDONLY)) {
		sb->s_frozen = SB_FREEZE_WRITE;
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		smp_wmb();
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		__fsync_super(sb);
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		sb->s_frozen = SB_FREEZE_TRANS;
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		smp_wmb();
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		sync_blockdev(sb->s_bdev);

		if (sb->s_op->write_super_lockfs)
			sb->s_op->write_super_lockfs(sb);
	}

	sync_blockdev(bdev);
	return sb;	/* thaw_bdev releases s->s_umount and bd_mount_sem */
}
EXPORT_SYMBOL(freeze_bdev);

/**
 * thaw_bdev  -- unlock filesystem
 * @bdev:	blockdevice to unlock
 * @sb:		associated superblock
 *
 * Unlocks the filesystem and marks it writeable again after freeze_bdev().
 */
void thaw_bdev(struct block_device *bdev, struct super_block *sb)
{
	if (sb) {
		BUG_ON(sb->s_bdev != bdev);

		if (sb->s_op->unlockfs)
			sb->s_op->unlockfs(sb);
		sb->s_frozen = SB_UNFROZEN;
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		smp_wmb();
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		wake_up(&sb->s_wait_unfrozen);
		drop_super(sb);
	}

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	up(&bdev->bd_mount_sem);
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}
EXPORT_SYMBOL(thaw_bdev);

/*
 * Various filesystems appear to want __find_get_block to be non-blocking.
 * But it's the page lock which protects the buffers.  To get around this,
 * we get exclusion from try_to_free_buffers with the blockdev mapping's
 * private_lock.
 *
 * Hack idea: for the blockdev mapping, i_bufferlist_lock contention
 * may be quite high.  This code could TryLock the page, and if that
 * succeeds, there is no need to take private_lock. (But if
 * private_lock is contended then so is mapping->tree_lock).
 */
static struct buffer_head *
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__find_get_block_slow(struct block_device *bdev, sector_t block)
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{
	struct inode *bd_inode = bdev->bd_inode;
	struct address_space *bd_mapping = bd_inode->i_mapping;
	struct buffer_head *ret = NULL;
	pgoff_t index;
	struct buffer_head *bh;
	struct buffer_head *head;
	struct page *page;
	int all_mapped = 1;

	index = block >> (PAGE_CACHE_SHIFT - bd_inode->i_blkbits);
	page = find_get_page(bd_mapping, index);
	if (!page)
		goto out;

	spin_lock(&bd_mapping->private_lock);
	if (!page_has_buffers(page))
		goto out_unlock;
	head = page_buffers(page);
	bh = head;
	do {
		if (bh->b_blocknr == block) {
			ret = bh;
			get_bh(bh);
			goto out_unlock;
		}
		if (!buffer_mapped(bh))
			all_mapped = 0;
		bh = bh->b_this_page;
	} while (bh != head);

	/* we might be here because some of the buffers on this page are
	 * not mapped.  This is due to various races between
	 * file io on the block device and getblk.  It gets dealt with
	 * elsewhere, don't buffer_error if we had some unmapped buffers
	 */
	if (all_mapped) {
		printk("__find_get_block_slow() failed. "
			"block=%llu, b_blocknr=%llu\n",
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			(unsigned long long)block,
			(unsigned long long)bh->b_blocknr);
		printk("b_state=0x%08lx, b_size=%zu\n",
			bh->b_state, bh->b_size);
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		printk("device blocksize: %d\n", 1 << bd_inode->i_blkbits);
	}
out_unlock:
	spin_unlock(&bd_mapping->private_lock);
	page_cache_release(page);
out:
	return ret;
}

/* If invalidate_buffers() will trash dirty buffers, it means some kind
   of fs corruption is going on. Trashing dirty data always imply losing
   information that was supposed to be just stored on the physical layer
   by the user.

   Thus invalidate_buffers in general usage is not allwowed to trash
   dirty buffers. For example ioctl(FLSBLKBUF) expects dirty data to
   be preserved.  These buffers are simply skipped.
  
   We also skip buffers which are still in use.  For example this can
   happen if a userspace program is reading the block device.

   NOTE: In the case where the user removed a removable-media-disk even if
   there's still dirty data not synced on disk (due a bug in the device driver
   or due an error of the user), by not destroying the dirty buffers we could
   generate corruption also on the next media inserted, thus a parameter is
   necessary to handle this case in the most safe way possible (trying
   to not corrupt also the new disk inserted with the data belonging to
   the old now corrupted disk). Also for the ramdisk the natural thing
   to do in order to release the ramdisk memory is to destroy dirty buffers.

   These are two special cases. Normal usage imply the device driver
   to issue a sync on the device (without waiting I/O completion) and
   then an invalidate_buffers call that doesn't trash dirty buffers.

   For handling cache coherency with the blkdev pagecache the 'update' case
   is been introduced. It is needed to re-read from disk any pinned
   buffer. NOTE: re-reading from disk is destructive so we can do it only
   when we assume nobody is changing the buffercache under our I/O and when
   we think the disk contains more recent information than the buffercache.
   The update == 1 pass marks the buffers we need to update, the update == 2
   pass does the actual I/O. */
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void invalidate_bdev(struct block_device *bdev)
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{
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	struct address_space *mapping = bdev->bd_inode->i_mapping;

	if (mapping->nrpages == 0)
		return;

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	invalidate_bh_lrus();
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	invalidate_mapping_pages(mapping, 0, -1);
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}

/*
 * Kick pdflush then try to free up some ZONE_NORMAL memory.
 */
static void free_more_memory(void)
{
	struct zone **zones;
	pg_data_t *pgdat;

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	wakeup_pdflush(1024);
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	yield();

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	for_each_online_pgdat(pgdat) {
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		zones = pgdat->node_zonelists[gfp_zone(GFP_NOFS)].zones;
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		if (*zones)
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			try_to_free_pages(zones, 0, GFP_NOFS);
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	}
}

/*
 * I/O completion handler for block_read_full_page() - pages
 * which come unlocked at the end of I/O.
 */
static void end_buffer_async_read(struct buffer_head *bh, int uptodate)
{
	unsigned long flags;
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	struct buffer_head *first;
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	struct buffer_head *tmp;
	struct page *page;
	int page_uptodate = 1;

	BUG_ON(!buffer_async_read(bh));

	page = bh->b_page;
	if (uptodate) {
		set_buffer_uptodate(bh);
	} else {
		clear_buffer_uptodate(bh);
		if (printk_ratelimit())
			buffer_io_error(bh);
		SetPageError(page);
	}

	/*
	 * Be _very_ careful from here on. Bad things can happen if
	 * two buffer heads end IO at almost the same time and both
	 * decide that the page is now completely done.
	 */
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	first = page_buffers(page);
	local_irq_save(flags);
	bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
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	clear_buffer_async_read(bh);
	unlock_buffer(bh);
	tmp = bh;
	do {
		if (!buffer_uptodate(tmp))
			page_uptodate = 0;
		if (buffer_async_read(tmp)) {
			BUG_ON(!buffer_locked(tmp));
			goto still_busy;
		}
		tmp = tmp->b_this_page;
	} while (tmp != bh);
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	bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
	local_irq_restore(flags);
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	/*
	 * If none of the buffers had errors and they are all
	 * uptodate then we can set the page uptodate.
	 */
	if (page_uptodate && !PageError(page))
		SetPageUptodate(page);
	unlock_page(page);
	return;

still_busy:
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	bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
	local_irq_restore(flags);
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	return;
}

/*
 * Completion handler for block_write_full_page() - pages which are unlocked
 * during I/O, and which have PageWriteback cleared upon I/O completion.
 */
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static void end_buffer_async_write(struct buffer_head *bh, int uptodate)
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{
	char b[BDEVNAME_SIZE];
	unsigned long flags;
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	struct buffer_head *first;
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	struct buffer_head *tmp;
	struct page *page;

	BUG_ON(!buffer_async_write(bh));

	page = bh->b_page;
	if (uptodate) {
		set_buffer_uptodate(bh);
	} else {
		if (printk_ratelimit()) {
			buffer_io_error(bh);
			printk(KERN_WARNING "lost page write due to "
					"I/O error on %s\n",
			       bdevname(bh->b_bdev, b));
		}
		set_bit(AS_EIO, &page->mapping->flags);
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		set_buffer_write_io_error(bh);
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		clear_buffer_uptodate(bh);
		SetPageError(page);
	}

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	first = page_buffers(page);
	local_irq_save(flags);
	bit_spin_lock(BH_Uptodate_Lock, &first->b_state);

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	clear_buffer_async_write(bh);
	unlock_buffer(bh);
	tmp = bh->b_this_page;
	while (tmp != bh) {
		if (buffer_async_write(tmp)) {
			BUG_ON(!buffer_locked(tmp));
			goto still_busy;
		}
		tmp = tmp->b_this_page;
	}
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	bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
	local_irq_restore(flags);
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	end_page_writeback(page);
	return;

still_busy:
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	bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
	local_irq_restore(flags);
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	return;
}

/*
 * If a page's buffers are under async readin (end_buffer_async_read
 * completion) then there is a possibility that another thread of
 * control could lock one of the buffers after it has completed
 * but while some of the other buffers have not completed.  This
 * locked buffer would confuse end_buffer_async_read() into not unlocking
 * the page.  So the absence of BH_Async_Read tells end_buffer_async_read()
 * that this buffer is not under async I/O.
 *
 * The page comes unlocked when it has no locked buffer_async buffers
 * left.
 *
 * PageLocked prevents anyone starting new async I/O reads any of
 * the buffers.
 *
 * PageWriteback is used to prevent simultaneous writeout of the same
 * page.
 *
 * PageLocked prevents anyone from starting writeback of a page which is
 * under read I/O (PageWriteback is only ever set against a locked page).
 */
static void mark_buffer_async_read(struct buffer_head *bh)
{
	bh->b_end_io = end_buffer_async_read;
	set_buffer_async_read(bh);
}

void mark_buffer_async_write(struct buffer_head *bh)
{
	bh->b_end_io = end_buffer_async_write;
	set_buffer_async_write(bh);
}
EXPORT_SYMBOL(mark_buffer_async_write);


/*
 * fs/buffer.c contains helper functions for buffer-backed address space's
 * fsync functions.  A common requirement for buffer-based filesystems is
 * that certain data from the backing blockdev needs to be written out for
 * a successful fsync().  For example, ext2 indirect blocks need to be
 * written back and waited upon before fsync() returns.
 *
 * The functions mark_buffer_inode_dirty(), fsync_inode_buffers(),
 * inode_has_buffers() and invalidate_inode_buffers() are provided for the
 * management of a list of dependent buffers at ->i_mapping->private_list.
 *
 * Locking is a little subtle: try_to_free_buffers() will remove buffers
 * from their controlling inode's queue when they are being freed.  But
 * try_to_free_buffers() will be operating against the *blockdev* mapping
 * at the time, not against the S_ISREG file which depends on those buffers.
 * So the locking for private_list is via the private_lock in the address_space
 * which backs the buffers.  Which is different from the address_space 
 * against which the buffers are listed.  So for a particular address_space,
 * mapping->private_lock does *not* protect mapping->private_list!  In fact,
 * mapping->private_list will always be protected by the backing blockdev's
 * ->private_lock.
 *
 * Which introduces a requirement: all buffers on an address_space's
 * ->private_list must be from the same address_space: the blockdev's.
 *
 * address_spaces which do not place buffers at ->private_list via these
 * utility functions are free to use private_lock and private_list for
 * whatever they want.  The only requirement is that list_empty(private_list)
 * be true at clear_inode() time.
 *
 * FIXME: clear_inode should not call invalidate_inode_buffers().  The
 * filesystems should do that.  invalidate_inode_buffers() should just go
 * BUG_ON(!list_empty).
 *
 * FIXME: mark_buffer_dirty_inode() is a data-plane operation.  It should
 * take an address_space, not an inode.  And it should be called
 * mark_buffer_dirty_fsync() to clearly define why those buffers are being
 * queued up.
 *
 * FIXME: mark_buffer_dirty_inode() doesn't need to add the buffer to the
 * list if it is already on a list.  Because if the buffer is on a list,
 * it *must* already be on the right one.  If not, the filesystem is being
 * silly.  This will save a ton of locking.  But first we have to ensure
 * that buffers are taken *off* the old inode's list when they are freed
 * (presumably in truncate).  That requires careful auditing of all
 * filesystems (do it inside bforget()).  It could also be done by bringing
 * b_inode back.
 */

/*
 * The buffer's backing address_space's private_lock must be held
 */
static inline void __remove_assoc_queue(struct buffer_head *bh)
{
	list_del_init(&bh->b_assoc_buffers);
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	WARN_ON(!bh->b_assoc_map);
	if (buffer_write_io_error(bh))
		set_bit(AS_EIO, &bh->b_assoc_map->flags);
	bh->b_assoc_map = NULL;
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}

int inode_has_buffers(struct inode *inode)
{
	return !list_empty(&inode->i_data.private_list);
}

/*
 * osync is designed to support O_SYNC io.  It waits synchronously for
 * all already-submitted IO to complete, but does not queue any new
 * writes to the disk.
 *
 * To do O_SYNC writes, just queue the buffer writes with ll_rw_block as
 * you dirty the buffers, and then use osync_inode_buffers to wait for
 * completion.  Any other dirty buffers which are not yet queued for
 * write will not be flushed to disk by the osync.
 */
static int osync_buffers_list(spinlock_t *lock, struct list_head *list)
{
	struct buffer_head *bh;
	struct list_head *p;
	int err = 0;

	spin_lock(lock);
repeat:
	list_for_each_prev(p, list) {
		bh = BH_ENTRY(p);
		if (buffer_locked(bh)) {
			get_bh(bh);
			spin_unlock(lock);
			wait_on_buffer(bh);
			if (!buffer_uptodate(bh))
				err = -EIO;
			brelse(bh);
			spin_lock(lock);
			goto repeat;
		}
	}
	spin_unlock(lock);
	return err;
}

/**
 * sync_mapping_buffers - write out and wait upon a mapping's "associated"
 *                        buffers
632
 * @mapping: the mapping which wants those buffers written
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 *
 * Starts I/O against the buffers at mapping->private_list, and waits upon
 * that I/O.
 *
637 638 639
 * Basically, this is a convenience function for fsync().
 * @mapping is a file or directory which needs those buffers to be written for
 * a successful fsync().
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 */
int sync_mapping_buffers(struct address_space *mapping)
{
	struct address_space *buffer_mapping = mapping->assoc_mapping;

	if (buffer_mapping == NULL || list_empty(&mapping->private_list))
		return 0;

	return fsync_buffers_list(&buffer_mapping->private_lock,
					&mapping->private_list);
}
EXPORT_SYMBOL(sync_mapping_buffers);

/*
 * Called when we've recently written block `bblock', and it is known that
 * `bblock' was for a buffer_boundary() buffer.  This means that the block at
 * `bblock + 1' is probably a dirty indirect block.  Hunt it down and, if it's
 * dirty, schedule it for IO.  So that indirects merge nicely with their data.
 */
void write_boundary_block(struct block_device *bdev,
			sector_t bblock, unsigned blocksize)
{
	struct buffer_head *bh = __find_get_block(bdev, bblock + 1, blocksize);
	if (bh) {
		if (buffer_dirty(bh))
			ll_rw_block(WRITE, 1, &bh);
		put_bh(bh);
	}
}

void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode)
{
	struct address_space *mapping = inode->i_mapping;
	struct address_space *buffer_mapping = bh->b_page->mapping;

	mark_buffer_dirty(bh);
	if (!mapping->assoc_mapping) {
		mapping->assoc_mapping = buffer_mapping;
	} else {
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		BUG_ON(mapping->assoc_mapping != buffer_mapping);
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	}
	if (list_empty(&bh->b_assoc_buffers)) {
		spin_lock(&buffer_mapping->private_lock);
		list_move_tail(&bh->b_assoc_buffers,
				&mapping->private_list);
685
		bh->b_assoc_map = mapping;
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		spin_unlock(&buffer_mapping->private_lock);
	}
}
EXPORT_SYMBOL(mark_buffer_dirty_inode);

691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712
/*
 * Mark the page dirty, and set it dirty in the radix tree, and mark the inode
 * dirty.
 *
 * If warn is true, then emit a warning if the page is not uptodate and has
 * not been truncated.
 */
static int __set_page_dirty(struct page *page,
		struct address_space *mapping, int warn)
{
	if (unlikely(!mapping))
		return !TestSetPageDirty(page);

	if (TestSetPageDirty(page))
		return 0;

	write_lock_irq(&mapping->tree_lock);
	if (page->mapping) {	/* Race with truncate? */
		WARN_ON_ONCE(warn && !PageUptodate(page));

		if (mapping_cap_account_dirty(mapping)) {
			__inc_zone_page_state(page, NR_FILE_DIRTY);
713 714
			__inc_bdi_stat(mapping->backing_dev_info,
					BDI_RECLAIMABLE);
715 716 717 718 719 720 721 722 723 724 725
			task_io_account_write(PAGE_CACHE_SIZE);
		}
		radix_tree_tag_set(&mapping->page_tree,
				page_index(page), PAGECACHE_TAG_DIRTY);
	}
	write_unlock_irq(&mapping->tree_lock);
	__mark_inode_dirty(mapping->host, I_DIRTY_PAGES);

	return 1;
}

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/*
 * Add a page to the dirty page list.
 *
 * It is a sad fact of life that this function is called from several places
 * deeply under spinlocking.  It may not sleep.
 *
 * If the page has buffers, the uptodate buffers are set dirty, to preserve
 * dirty-state coherency between the page and the buffers.  It the page does
 * not have buffers then when they are later attached they will all be set
 * dirty.
 *
 * The buffers are dirtied before the page is dirtied.  There's a small race
 * window in which a writepage caller may see the page cleanness but not the
 * buffer dirtiness.  That's fine.  If this code were to set the page dirty
 * before the buffers, a concurrent writepage caller could clear the page dirty
 * bit, see a bunch of clean buffers and we'd end up with dirty buffers/clean
 * page on the dirty page list.
 *
 * We use private_lock to lock against try_to_free_buffers while using the
 * page's buffer list.  Also use this to protect against clean buffers being
 * added to the page after it was set dirty.
 *
 * FIXME: may need to call ->reservepage here as well.  That's rather up to the
 * address_space though.
 */
int __set_page_dirty_buffers(struct page *page)
{
753
	struct address_space *mapping = page_mapping(page);
754 755 756

	if (unlikely(!mapping))
		return !TestSetPageDirty(page);
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	spin_lock(&mapping->private_lock);
	if (page_has_buffers(page)) {
		struct buffer_head *head = page_buffers(page);
		struct buffer_head *bh = head;

		do {
			set_buffer_dirty(bh);
			bh = bh->b_this_page;
		} while (bh != head);
	}
	spin_unlock(&mapping->private_lock);

770
	return __set_page_dirty(page, mapping, 1);
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}
EXPORT_SYMBOL(__set_page_dirty_buffers);

/*
 * Write out and wait upon a list of buffers.
 *
 * We have conflicting pressures: we want to make sure that all
 * initially dirty buffers get waited on, but that any subsequently
 * dirtied buffers don't.  After all, we don't want fsync to last
 * forever if somebody is actively writing to the file.
 *
 * Do this in two main stages: first we copy dirty buffers to a
 * temporary inode list, queueing the writes as we go.  Then we clean
 * up, waiting for those writes to complete.
 * 
 * During this second stage, any subsequent updates to the file may end
 * up refiling the buffer on the original inode's dirty list again, so
 * there is a chance we will end up with a buffer queued for write but
 * not yet completed on that list.  So, as a final cleanup we go through
 * the osync code to catch these locked, dirty buffers without requeuing
 * any newly dirty buffers for write.
 */
static int fsync_buffers_list(spinlock_t *lock, struct list_head *list)
{
	struct buffer_head *bh;
	struct list_head tmp;
	int err = 0, err2;

	INIT_LIST_HEAD(&tmp);

	spin_lock(lock);
	while (!list_empty(list)) {
		bh = BH_ENTRY(list->next);
804
		__remove_assoc_queue(bh);
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		if (buffer_dirty(bh) || buffer_locked(bh)) {
			list_add(&bh->b_assoc_buffers, &tmp);
			if (buffer_dirty(bh)) {
				get_bh(bh);
				spin_unlock(lock);
				/*
				 * Ensure any pending I/O completes so that
				 * ll_rw_block() actually writes the current
				 * contents - it is a noop if I/O is still in
				 * flight on potentially older contents.
				 */
816
				ll_rw_block(SWRITE, 1, &bh);
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				brelse(bh);
				spin_lock(lock);
			}
		}
	}

	while (!list_empty(&tmp)) {
		bh = BH_ENTRY(tmp.prev);
825
		list_del_init(&bh->b_assoc_buffers);
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		get_bh(bh);
		spin_unlock(lock);
		wait_on_buffer(bh);
		if (!buffer_uptodate(bh))
			err = -EIO;
		brelse(bh);
		spin_lock(lock);
	}
	
	spin_unlock(lock);
	err2 = osync_buffers_list(lock, list);
	if (err)
		return err;
	else
		return err2;
}

/*
 * Invalidate any and all dirty buffers on a given inode.  We are
 * probably unmounting the fs, but that doesn't mean we have already
 * done a sync().  Just drop the buffers from the inode list.
 *
 * NOTE: we take the inode's blockdev's mapping's private_lock.  Which
 * assumes that all the buffers are against the blockdev.  Not true
 * for reiserfs.
 */
void invalidate_inode_buffers(struct inode *inode)
{
	if (inode_has_buffers(inode)) {
		struct address_space *mapping = &inode->i_data;
		struct list_head *list = &mapping->private_list;
		struct address_space *buffer_mapping = mapping->assoc_mapping;

		spin_lock(&buffer_mapping->private_lock);
		while (!list_empty(list))
			__remove_assoc_queue(BH_ENTRY(list->next));
		spin_unlock(&buffer_mapping->private_lock);
	}
}

/*
 * Remove any clean buffers from the inode's buffer list.  This is called
 * when we're trying to free the inode itself.  Those buffers can pin it.
 *
 * Returns true if all buffers were removed.
 */
int remove_inode_buffers(struct inode *inode)
{
	int ret = 1;

	if (inode_has_buffers(inode)) {
		struct address_space *mapping = &inode->i_data;
		struct list_head *list = &mapping->private_list;
		struct address_space *buffer_mapping = mapping->assoc_mapping;

		spin_lock(&buffer_mapping->private_lock);
		while (!list_empty(list)) {
			struct buffer_head *bh = BH_ENTRY(list->next);
			if (buffer_dirty(bh)) {
				ret = 0;
				break;
			}
			__remove_assoc_queue(bh);
		}
		spin_unlock(&buffer_mapping->private_lock);
	}
	return ret;
}

/*
 * Create the appropriate buffers when given a page for data area and
 * the size of each buffer.. Use the bh->b_this_page linked list to
 * follow the buffers created.  Return NULL if unable to create more
 * buffers.
 *
 * The retry flag is used to differentiate async IO (paging, swapping)
 * which may not fail from ordinary buffer allocations.
 */
struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
		int retry)
{
	struct buffer_head *bh, *head;
	long offset;

try_again:
	head = NULL;
	offset = PAGE_SIZE;
	while ((offset -= size) >= 0) {
		bh = alloc_buffer_head(GFP_NOFS);
		if (!bh)
			goto no_grow;

		bh->b_bdev = NULL;
		bh->b_this_page = head;
		bh->b_blocknr = -1;
		head = bh;

		bh->b_state = 0;
		atomic_set(&bh->b_count, 0);
925
		bh->b_private = NULL;
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		bh->b_size = size;

		/* Link the buffer to its page */
		set_bh_page(bh, page, offset);

931
		init_buffer(bh, NULL, NULL);
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	}
	return head;
/*
 * In case anything failed, we just free everything we got.
 */
no_grow:
	if (head) {
		do {
			bh = head;
			head = head->b_this_page;
			free_buffer_head(bh);
		} while (head);
	}

	/*
	 * Return failure for non-async IO requests.  Async IO requests
	 * are not allowed to fail, so we have to wait until buffer heads
	 * become available.  But we don't want tasks sleeping with 
	 * partially complete buffers, so all were released above.
	 */
	if (!retry)
		return NULL;

	/* We're _really_ low on memory. Now we just
	 * wait for old buffer heads to become free due to
	 * finishing IO.  Since this is an async request and
	 * the reserve list is empty, we're sure there are 
	 * async buffer heads in use.
	 */
	free_more_memory();
	goto try_again;
}
EXPORT_SYMBOL_GPL(alloc_page_buffers);

static inline void
link_dev_buffers(struct page *page, struct buffer_head *head)
{
	struct buffer_head *bh, *tail;

	bh = head;
	do {
		tail = bh;
		bh = bh->b_this_page;
	} while (bh);
	tail->b_this_page = head;
	attach_page_buffers(page, head);
}

/*
 * Initialise the state of a blockdev page's buffers.
 */ 
static void
init_page_buffers(struct page *page, struct block_device *bdev,
			sector_t block, int size)
{
	struct buffer_head *head = page_buffers(page);
	struct buffer_head *bh = head;
	int uptodate = PageUptodate(page);

	do {
		if (!buffer_mapped(bh)) {
			init_buffer(bh, NULL, NULL);
			bh->b_bdev = bdev;
			bh->b_blocknr = block;
			if (uptodate)
				set_buffer_uptodate(bh);
			set_buffer_mapped(bh);
		}
		block++;
		bh = bh->b_this_page;
	} while (bh != head);
}

/*
 * Create the page-cache page that contains the requested block.
 *
 * This is user purely for blockdev mappings.
 */
static struct page *
grow_dev_page(struct block_device *bdev, sector_t block,
		pgoff_t index, int size)
{
	struct inode *inode = bdev->bd_inode;
	struct page *page;
	struct buffer_head *bh;

1018
	page = find_or_create_page(inode->i_mapping, index,
1019
		(mapping_gfp_mask(inode->i_mapping) & ~__GFP_FS)|__GFP_MOVABLE);
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	if (!page)
		return NULL;

1023
	BUG_ON(!PageLocked(page));
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	if (page_has_buffers(page)) {
		bh = page_buffers(page);
		if (bh->b_size == size) {
			init_page_buffers(page, bdev, block, size);
			return page;
		}
		if (!try_to_free_buffers(page))
			goto failed;
	}

	/*
	 * Allocate some buffers for this page
	 */
	bh = alloc_page_buffers(page, size, 0);
	if (!bh)
		goto failed;

	/*
	 * Link the page to the buffers and initialise them.  Take the
	 * lock to be atomic wrt __find_get_block(), which does not
	 * run under the page lock.
	 */
	spin_lock(&inode->i_mapping->private_lock);
	link_dev_buffers(page, bh);
	init_page_buffers(page, bdev, block, size);
	spin_unlock(&inode->i_mapping->private_lock);
	return page;

failed:
	BUG();
	unlock_page(page);
	page_cache_release(page);
	return NULL;
}

/*
 * Create buffers for the specified block device block's page.  If
 * that page was dirty, the buffers are set dirty also.
 */
1064
static int
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grow_buffers(struct block_device *bdev, sector_t block, int size)
{
	struct page *page;
	pgoff_t index;
	int sizebits;

	sizebits = -1;
	do {
		sizebits++;
	} while ((size << sizebits) < PAGE_SIZE);

	index = block >> sizebits;

1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091
	/*
	 * Check for a block which wants to lie outside our maximum possible
	 * pagecache index.  (this comparison is done using sector_t types).
	 */
	if (unlikely(index != block >> sizebits)) {
		char b[BDEVNAME_SIZE];

		printk(KERN_ERR "%s: requested out-of-range block %llu for "
			"device %s\n",
			__FUNCTION__, (unsigned long long)block,
			bdevname(bdev, b));
		return -EIO;
	}
	block = index << sizebits;
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	/* Create a page with the proper size buffers.. */
	page = grow_dev_page(bdev, block, index, size);
	if (!page)
		return 0;
	unlock_page(page);
	page_cache_release(page);
	return 1;
}

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static struct buffer_head *
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__getblk_slow(struct block_device *bdev, sector_t block, int size)
{
	/* Size must be multiple of hard sectorsize */
	if (unlikely(size & (bdev_hardsect_size(bdev)-1) ||
			(size < 512 || size > PAGE_SIZE))) {
		printk(KERN_ERR "getblk(): invalid block size %d requested\n",
					size);
		printk(KERN_ERR "hardsect size: %d\n",
					bdev_hardsect_size(bdev));

		dump_stack();
		return NULL;
	}

	for (;;) {
		struct buffer_head * bh;
1118
		int ret;
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		bh = __find_get_block(bdev, block, size);
		if (bh)
			return bh;

1124 1125 1126 1127
		ret = grow_buffers(bdev, block, size);
		if (ret < 0)
			return NULL;
		if (ret == 0)
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			free_more_memory();
	}
}

/*
 * The relationship between dirty buffers and dirty pages:
 *
 * Whenever a page has any dirty buffers, the page's dirty bit is set, and
 * the page is tagged dirty in its radix tree.
 *
 * At all times, the dirtiness of the buffers represents the dirtiness of
 * subsections of the page.  If the page has buffers, the page dirty bit is
 * merely a hint about the true dirty state.
 *
 * When a page is set dirty in its entirety, all its buffers are marked dirty
 * (if the page has buffers).
 *
 * When a buffer is marked dirty, its page is dirtied, but the page's other
 * buffers are not.
 *
 * Also.  When blockdev buffers are explicitly read with bread(), they
 * individually become uptodate.  But their backing page remains not
 * uptodate - even if all of its buffers are uptodate.  A subsequent
 * block_read_full_page() against that page will discover all the uptodate
 * buffers, will set the page uptodate and will perform no I/O.
 */

/**
 * mark_buffer_dirty - mark a buffer_head as needing writeout
1157
 * @bh: the buffer_head to mark dirty
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 *
 * mark_buffer_dirty() will set the dirty bit against the buffer, then set its
 * backing page dirty, then tag the page as dirty in its address_space's radix
 * tree and then attach the address_space's inode to its superblock's dirty
 * inode list.
 *
 * mark_buffer_dirty() is atomic.  It takes bh->b_page->mapping->private_lock,
 * mapping->tree_lock and the global inode_lock.
 */
void fastcall mark_buffer_dirty(struct buffer_head *bh)
{
1169
	WARN_ON_ONCE(!buffer_uptodate(bh));
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	if (!buffer_dirty(bh) && !test_set_buffer_dirty(bh))
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		__set_page_dirty(bh->b_page, page_mapping(bh->b_page), 0);
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}

/*
 * Decrement a buffer_head's reference count.  If all buffers against a page
 * have zero reference count, are clean and unlocked, and if the page is clean
 * and unlocked then try_to_free_buffers() may strip the buffers from the page
 * in preparation for freeing it (sometimes, rarely, buffers are removed from
 * a page but it ends up not being freed, and buffers may later be reattached).
 */
void __brelse(struct buffer_head * buf)
{
	if (atomic_read(&buf->b_count)) {
		put_bh(buf);
		return;
	}
	printk(KERN_ERR "VFS: brelse: Trying to free free buffer\n");
	WARN_ON(1);
}

/*
 * bforget() is like brelse(), except it discards any
 * potentially dirty data.
 */
void __bforget(struct buffer_head *bh)
{
	clear_buffer_dirty(bh);
	if (!list_empty(&bh->b_assoc_buffers)) {
		struct address_space *buffer_mapping = bh->b_page->mapping;

		spin_lock(&buffer_mapping->private_lock);
		list_del_init(&bh->b_assoc_buffers);
1203
		bh->b_assoc_map = NULL;
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		spin_unlock(&buffer_mapping->private_lock);
	}
	__brelse(bh);
}

static struct buffer_head *__bread_slow(struct buffer_head *bh)
{
	lock_buffer(bh);
	if (buffer_uptodate(bh)) {
		unlock_buffer(bh);
		return bh;
	} else {
		get_bh(bh);
		bh->b_end_io = end_buffer_read_sync;
		submit_bh(READ, bh);
		wait_on_buffer(bh);
		if (buffer_uptodate(bh))
			return bh;
	}
	brelse(bh);
	return NULL;
}

/*
 * Per-cpu buffer LRU implementation.  To reduce the cost of __find_get_block().
 * The bhs[] array is sorted - newest buffer is at bhs[0].  Buffers have their
 * refcount elevated by one when they're in an LRU.  A buffer can only appear
 * once in a particular CPU's LRU.  A single buffer can be present in multiple
 * CPU's LRUs at the same time.
 *
 * This is a transparent caching front-end to sb_bread(), sb_getblk() and
 * sb_find_get_block().
 *
 * The LRUs themselves only need locking against invalidate_bh_lrus.  We use
 * a local interrupt disable for that.
 */

#define BH_LRU_SIZE	8

struct bh_lru {
	struct buffer_head *bhs[BH_LRU_SIZE];
};

static DEFINE_PER_CPU(struct bh_lru, bh_lrus) = {{ NULL }};

#ifdef CONFIG_SMP
#define bh_lru_lock()	local_irq_disable()
#define bh_lru_unlock()	local_irq_enable()
#else
#define bh_lru_lock()	preempt_disable()
#define bh_lru_unlock()	preempt_enable()
#endif

static inline void check_irqs_on(void)
{
#ifdef irqs_disabled
	BUG_ON(irqs_disabled());
#endif
}

/*
 * The LRU management algorithm is dopey-but-simple.  Sorry.
 */
static void bh_lru_install(struct buffer_head *bh)
{
	struct buffer_head *evictee = NULL;
	struct bh_lru *lru;

	check_irqs_on();
	bh_lru_lock();
	lru = &__get_cpu_var(bh_lrus);
	if (lru->bhs[0] != bh) {
		struct buffer_head *bhs[BH_LRU_SIZE];
		int in;
		int out = 0;

		get_bh(bh);
		bhs[out++] = bh;
		for (in = 0; in < BH_LRU_SIZE; in++) {
			struct buffer_head *bh2 = lru->bhs[in];

			if (bh2 == bh) {
				__brelse(bh2);
			} else {
				if (out >= BH_LRU_SIZE) {
					BUG_ON(evictee != NULL);
					evictee = bh2;
				} else {
					bhs[out++] = bh2;
				}
			}
		}
		while (out < BH_LRU_SIZE)
			bhs[out++] = NULL;
		memcpy(lru->bhs, bhs, sizeof(bhs));
	}
	bh_lru_unlock();

	if (evictee)
		__brelse(evictee);
}

/*
 * Look up the bh in this cpu's LRU.  If it's there, move it to the head.
 */
1309
static struct buffer_head *
1310
lookup_bh_lru(struct block_device *bdev, sector_t block, unsigned size)
L
Linus Torvalds 已提交
1311 1312 1313
{
	struct buffer_head *ret = NULL;
	struct bh_lru *lru;
1314
	unsigned int i;
L
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1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344 1345

	check_irqs_on();
	bh_lru_lock();
	lru = &__get_cpu_var(bh_lrus);
	for (i = 0; i < BH_LRU_SIZE; i++) {
		struct buffer_head *bh = lru->bhs[i];

		if (bh && bh->b_bdev == bdev &&
				bh->b_blocknr == block && bh->b_size == size) {
			if (i) {
				while (i) {
					lru->bhs[i] = lru->bhs[i - 1];
					i--;
				}
				lru->bhs[0] = bh;
			}
			get_bh(bh);
			ret = bh;
			break;
		}
	}
	bh_lru_unlock();
	return ret;
}

/*
 * Perform a pagecache lookup for the matching buffer.  If it's there, refresh
 * it in the LRU and mark it as accessed.  If it is not present then return
 * NULL
 */
struct buffer_head *
1346
__find_get_block(struct block_device *bdev, sector_t block, unsigned size)
L
Linus Torvalds 已提交
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{
	struct buffer_head *bh = lookup_bh_lru(bdev, block, size);

	if (bh == NULL) {
1351
		bh = __find_get_block_slow(bdev, block);
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		if (bh)
			bh_lru_install(bh);
	}
	if (bh)
		touch_buffer(bh);
	return bh;
}
EXPORT_SYMBOL(__find_get_block);

/*
 * __getblk will locate (and, if necessary, create) the buffer_head
 * which corresponds to the passed block_device, block and size. The
 * returned buffer has its reference count incremented.
 *
 * __getblk() cannot fail - it just keeps trying.  If you pass it an
 * illegal block number, __getblk() will happily return a buffer_head
 * which represents the non-existent block.  Very weird.
 *
 * __getblk() will lock up the machine if grow_dev_page's try_to_free_buffers()
 * attempt is failing.  FIXME, perhaps?
 */
struct buffer_head *
1374
__getblk(struct block_device *bdev, sector_t block, unsigned size)
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{
	struct buffer_head *bh = __find_get_block(bdev, block, size);

	might_sleep();
	if (bh == NULL)
		bh = __getblk_slow(bdev, block, size);
	return bh;
}
EXPORT_SYMBOL(__getblk);

/*
 * Do async read-ahead on a buffer..
 */
1388
void __breadahead(struct block_device *bdev, sector_t block, unsigned size)
L
Linus Torvalds 已提交
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{
	struct buffer_head *bh = __getblk(bdev, block, size);
A
Andrew Morton 已提交
1391 1392 1393 1394
	if (likely(bh)) {
		ll_rw_block(READA, 1, &bh);
		brelse(bh);
	}
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}
EXPORT_SYMBOL(__breadahead);

/**
 *  __bread() - reads a specified block and returns the bh
1400
 *  @bdev: the block_device to read from
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 *  @block: number of block
 *  @size: size (in bytes) to read
 * 
 *  Reads a specified block, and returns buffer head that contains it.
 *  It returns NULL if the block was unreadable.
 */
struct buffer_head *
1408
__bread(struct block_device *bdev, sector_t block, unsigned size)
L
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{
	struct buffer_head *bh = __getblk(bdev, block, size);

A
Andrew Morton 已提交
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	if (likely(bh) && !buffer_uptodate(bh))
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		bh = __bread_slow(bh);
	return bh;
}
EXPORT_SYMBOL(__bread);

/*
 * invalidate_bh_lrus() is called rarely - but not only at unmount.
 * This doesn't race because it runs in each cpu either in irq
 * or with preempt disabled.
 */
static void invalidate_bh_lru(void *arg)
{
	struct bh_lru *b = &get_cpu_var(bh_lrus);
	int i;

	for (i = 0; i < BH_LRU_SIZE; i++) {
		brelse(b->bhs[i]);
		b->bhs[i] = NULL;
	}
	put_cpu_var(bh_lrus);
}
	
P
Peter Zijlstra 已提交
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void invalidate_bh_lrus(void)
L
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1436 1437 1438
{
	on_each_cpu(invalidate_bh_lru, NULL, 1, 1);
}
N
Nick Piggin 已提交
1439
EXPORT_SYMBOL_GPL(invalidate_bh_lrus);
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void set_bh_page(struct buffer_head *bh,
		struct page *page, unsigned long offset)
{
	bh->b_page = page;
1445
	BUG_ON(offset >= PAGE_SIZE);
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	if (PageHighMem(page))
		/*
		 * This catches illegal uses and preserves the offset:
		 */
		bh->b_data = (char *)(0 + offset);
	else
		bh->b_data = page_address(page) + offset;
}
EXPORT_SYMBOL(set_bh_page);

/*
 * Called when truncating a buffer on a page completely.
 */
1459
static void discard_buffer(struct buffer_head * bh)
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{
	lock_buffer(bh);
	clear_buffer_dirty(bh);
	bh->b_bdev = NULL;
	clear_buffer_mapped(bh);
	clear_buffer_req(bh);
	clear_buffer_new(bh);
	clear_buffer_delay(bh);
1468
	clear_buffer_unwritten(bh);
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	unlock_buffer(bh);
}

/**
 * block_invalidatepage - invalidate part of all of a buffer-backed page
 *
 * @page: the page which is affected
 * @offset: the index of the truncation point
 *
 * block_invalidatepage() is called when all or part of the page has become
 * invalidatedby a truncate operation.
 *
 * block_invalidatepage() does not have to release all buffers, but it must
 * ensure that no dirty buffer is left outside @offset and that no I/O
 * is underway against any of the blocks which are outside the truncation
 * point.  Because the caller is about to free (and possibly reuse) those
 * blocks on-disk.
 */
1487
void block_invalidatepage(struct page *page, unsigned long offset)
L
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{
	struct buffer_head *head, *bh, *next;
	unsigned int curr_off = 0;

	BUG_ON(!PageLocked(page));
	if (!page_has_buffers(page))
		goto out;

	head = page_buffers(page);
	bh = head;
	do {
		unsigned int next_off = curr_off + bh->b_size;
		next = bh->b_this_page;

		/*
		 * is this block fully invalidated?
		 */
		if (offset <= curr_off)
			discard_buffer(bh);
		curr_off = next_off;
		bh = next;
	} while (bh != head);

	/*
	 * We release buffers only if the entire page is being invalidated.
	 * The get_block cached value has been unconditionally invalidated,
	 * so real IO is not possible anymore.
	 */
	if (offset == 0)
1517
		try_to_release_page(page, 0);
L
Linus Torvalds 已提交
1518
out:
1519
	return;
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}
EXPORT_SYMBOL(block_invalidatepage);

/*
 * We attach and possibly dirty the buffers atomically wrt
 * __set_page_dirty_buffers() via private_lock.  try_to_free_buffers
 * is already excluded via the page lock.
 */
void create_empty_buffers(struct page *page,
			unsigned long blocksize, unsigned long b_state)
{
	struct buffer_head *bh, *head, *tail;

	head = alloc_page_buffers(page, blocksize, 1);
	bh = head;
	do {
		bh->b_state |= b_state;
		tail = bh;
		bh = bh->b_this_page;
	} while (bh);
	tail->b_this_page = head;

	spin_lock(&page->mapping->private_lock);
	if (PageUptodate(page) || PageDirty(page)) {
		bh = head;
		do {
			if (PageDirty(page))
				set_buffer_dirty(bh);
			if (PageUptodate(page))
				set_buffer_uptodate(bh);
			bh = bh->b_this_page;
		} while (bh != head);
	}
	attach_page_buffers(page, head);
	spin_unlock(&page->mapping->private_lock);
}
EXPORT_SYMBOL(create_empty_buffers);

/*
 * We are taking a block for data and we don't want any output from any
 * buffer-cache aliases starting from return from that function and
 * until the moment when something will explicitly mark the buffer
 * dirty (hopefully that will not happen until we will free that block ;-)
 * We don't even need to mark it not-uptodate - nobody can expect
 * anything from a newly allocated buffer anyway. We used to used
 * unmap_buffer() for such invalidation, but that was wrong. We definitely
 * don't want to mark the alias unmapped, for example - it would confuse
 * anyone who might pick it with bread() afterwards...
 *
 * Also..  Note that bforget() doesn't lock the buffer.  So there can
 * be writeout I/O going on against recently-freed buffers.  We don't
 * wait on that I/O in bforget() - it's more efficient to wait on the I/O
 * only if we really need to.  That happens here.
 */
void unmap_underlying_metadata(struct block_device *bdev, sector_t block)
{
	struct buffer_head *old_bh;

	might_sleep();

1580
	old_bh = __find_get_block_slow(bdev, block);
L
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1581 1582 1583 1584 1585 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 1613 1614 1615 1616 1617 1618 1619 1620
	if (old_bh) {
		clear_buffer_dirty(old_bh);
		wait_on_buffer(old_bh);
		clear_buffer_req(old_bh);
		__brelse(old_bh);
	}
}
EXPORT_SYMBOL(unmap_underlying_metadata);

/*
 * NOTE! All mapped/uptodate combinations are valid:
 *
 *	Mapped	Uptodate	Meaning
 *
 *	No	No		"unknown" - must do get_block()
 *	No	Yes		"hole" - zero-filled
 *	Yes	No		"allocated" - allocated on disk, not read in
 *	Yes	Yes		"valid" - allocated and up-to-date in memory.
 *
 * "Dirty" is valid only with the last case (mapped+uptodate).
 */

/*
 * While block_write_full_page is writing back the dirty buffers under
 * the page lock, whoever dirtied the buffers may decide to clean them
 * again at any time.  We handle that by only looking at the buffer
 * state inside lock_buffer().
 *
 * If block_write_full_page() is called for regular writeback
 * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a
 * locked buffer.   This only can happen if someone has written the buffer
 * directly, with submit_bh().  At the address_space level PageWriteback
 * prevents this contention from occurring.
 */
static int __block_write_full_page(struct inode *inode, struct page *page,
			get_block_t *get_block, struct writeback_control *wbc)
{
	int err;
	sector_t block;
	sector_t last_block;
1621
	struct buffer_head *bh, *head;
1622
	const unsigned blocksize = 1 << inode->i_blkbits;
L
Linus Torvalds 已提交
1623 1624 1625 1626 1627 1628 1629
	int nr_underway = 0;

	BUG_ON(!PageLocked(page));

	last_block = (i_size_read(inode) - 1) >> inode->i_blkbits;

	if (!page_has_buffers(page)) {
1630
		create_empty_buffers(page, blocksize,
L
Linus Torvalds 已提交
1631 1632 1633 1634 1635 1636 1637 1638 1639 1640 1641 1642 1643
					(1 << BH_Dirty)|(1 << BH_Uptodate));
	}

	/*
	 * Be very careful.  We have no exclusion from __set_page_dirty_buffers
	 * here, and the (potentially unmapped) buffers may become dirty at
	 * any time.  If a buffer becomes dirty here after we've inspected it
	 * then we just miss that fact, and the page stays dirty.
	 *
	 * Buffers outside i_size may be dirtied by __set_page_dirty_buffers;
	 * handle that here by just cleaning them.
	 */

1644
	block = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
L
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1645 1646 1647 1648 1649 1650 1651 1652 1653 1654 1655 1656 1657 1658 1659 1660 1661 1662 1663 1664
	head = page_buffers(page);
	bh = head;

	/*
	 * Get all the dirty buffers mapped to disk addresses and
	 * handle any aliases from the underlying blockdev's mapping.
	 */
	do {
		if (block > last_block) {
			/*
			 * mapped buffers outside i_size will occur, because
			 * this page can be outside i_size when there is a
			 * truncate in progress.
			 */
			/*
			 * The buffer was zeroed by block_write_full_page()
			 */
			clear_buffer_dirty(bh);
			set_buffer_uptodate(bh);
		} else if (!buffer_mapped(bh) && buffer_dirty(bh)) {
1665
			WARN_ON(bh->b_size != blocksize);
L
Linus Torvalds 已提交
1666 1667 1668 1669 1670 1671 1672 1673 1674 1675 1676 1677 1678 1679 1680 1681 1682 1683 1684 1685 1686 1687 1688 1689 1690 1691 1692 1693 1694 1695 1696 1697 1698 1699 1700 1701 1702 1703 1704 1705 1706 1707 1708 1709 1710 1711 1712 1713 1714 1715 1716 1717
			err = get_block(inode, block, bh, 1);
			if (err)
				goto recover;
			if (buffer_new(bh)) {
				/* blockdev mappings never come here */
				clear_buffer_new(bh);
				unmap_underlying_metadata(bh->b_bdev,
							bh->b_blocknr);
			}
		}
		bh = bh->b_this_page;
		block++;
	} while (bh != head);

	do {
		if (!buffer_mapped(bh))
			continue;
		/*
		 * If it's a fully non-blocking write attempt and we cannot
		 * lock the buffer then redirty the page.  Note that this can
		 * potentially cause a busy-wait loop from pdflush and kswapd
		 * activity, but those code paths have their own higher-level
		 * throttling.
		 */
		if (wbc->sync_mode != WB_SYNC_NONE || !wbc->nonblocking) {
			lock_buffer(bh);
		} else if (test_set_buffer_locked(bh)) {
			redirty_page_for_writepage(wbc, page);
			continue;
		}
		if (test_clear_buffer_dirty(bh)) {
			mark_buffer_async_write(bh);
		} else {
			unlock_buffer(bh);
		}
	} while ((bh = bh->b_this_page) != head);

	/*
	 * The page and its buffers are protected by PageWriteback(), so we can
	 * drop the bh refcounts early.
	 */
	BUG_ON(PageWriteback(page));
	set_page_writeback(page);

	do {
		struct buffer_head *next = bh->b_this_page;
		if (buffer_async_write(bh)) {
			submit_bh(WRITE, bh);
			nr_underway++;
		}
		bh = next;
	} while (bh != head);
1718
	unlock_page(page);
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Linus Torvalds 已提交
1719 1720 1721 1722 1723 1724 1725 1726 1727 1728

	err = 0;
done:
	if (nr_underway == 0) {
		/*
		 * The page was marked dirty, but the buffers were
		 * clean.  Someone wrote them back by hand with
		 * ll_rw_block/submit_bh.  A rare case.
		 */
		end_page_writeback(page);
1729

L
Linus Torvalds 已提交
1730 1731 1732 1733 1734 1735 1736 1737 1738 1739 1740 1741 1742 1743 1744 1745 1746 1747 1748 1749 1750 1751 1752 1753 1754 1755 1756 1757 1758 1759
		/*
		 * The page and buffer_heads can be released at any time from
		 * here on.
		 */
	}
	return err;

recover:
	/*
	 * ENOSPC, or some other error.  We may already have added some
	 * blocks to the file, so we need to write these out to avoid
	 * exposing stale data.
	 * The page is currently locked and not marked for writeback
	 */
	bh = head;
	/* Recovery: lock and submit the mapped buffers */
	do {
		if (buffer_mapped(bh) && buffer_dirty(bh)) {
			lock_buffer(bh);
			mark_buffer_async_write(bh);
		} else {
			/*
			 * The buffer may have been set dirty during
			 * attachment to a dirty page.
			 */
			clear_buffer_dirty(bh);
		}
	} while ((bh = bh->b_this_page) != head);
	SetPageError(page);
	BUG_ON(PageWriteback(page));
1760
	mapping_set_error(page->mapping, err);
L
Linus Torvalds 已提交
1761 1762 1763 1764 1765 1766 1767 1768 1769 1770
	set_page_writeback(page);
	do {
		struct buffer_head *next = bh->b_this_page;
		if (buffer_async_write(bh)) {
			clear_buffer_dirty(bh);
			submit_bh(WRITE, bh);
			nr_underway++;
		}
		bh = next;
	} while (bh != head);
1771
	unlock_page(page);
L
Linus Torvalds 已提交
1772 1773 1774
	goto done;
}

1775 1776 1777 1778 1779 1780 1781 1782 1783 1784 1785 1786 1787 1788 1789 1790 1791 1792 1793 1794 1795 1796 1797 1798 1799 1800 1801
/*
 * If a page has any new buffers, zero them out here, and mark them uptodate
 * and dirty so they'll be written out (in order to prevent uninitialised
 * block data from leaking). And clear the new bit.
 */
void page_zero_new_buffers(struct page *page, unsigned from, unsigned to)
{
	unsigned int block_start, block_end;
	struct buffer_head *head, *bh;

	BUG_ON(!PageLocked(page));
	if (!page_has_buffers(page))
		return;

	bh = head = page_buffers(page);
	block_start = 0;
	do {
		block_end = block_start + bh->b_size;

		if (buffer_new(bh)) {
			if (block_end > from && block_start < to) {
				if (!PageUptodate(page)) {
					unsigned start, size;

					start = max(from, block_start);
					size = min(to, block_end) - start;

1802
					zero_user(page, start, size);
1803 1804 1805 1806 1807 1808 1809 1810 1811 1812 1813 1814 1815 1816
					set_buffer_uptodate(bh);
				}

				clear_buffer_new(bh);
				mark_buffer_dirty(bh);
			}
		}

		block_start = block_end;
		bh = bh->b_this_page;
	} while (bh != head);
}
EXPORT_SYMBOL(page_zero_new_buffers);

L
Linus Torvalds 已提交
1817 1818 1819 1820 1821 1822 1823 1824 1825 1826 1827 1828 1829 1830 1831 1832 1833 1834 1835 1836 1837 1838 1839 1840 1841 1842 1843 1844 1845 1846 1847 1848 1849 1850 1851
static int __block_prepare_write(struct inode *inode, struct page *page,
		unsigned from, unsigned to, get_block_t *get_block)
{
	unsigned block_start, block_end;
	sector_t block;
	int err = 0;
	unsigned blocksize, bbits;
	struct buffer_head *bh, *head, *wait[2], **wait_bh=wait;

	BUG_ON(!PageLocked(page));
	BUG_ON(from > PAGE_CACHE_SIZE);
	BUG_ON(to > PAGE_CACHE_SIZE);
	BUG_ON(from > to);

	blocksize = 1 << inode->i_blkbits;
	if (!page_has_buffers(page))
		create_empty_buffers(page, blocksize, 0);
	head = page_buffers(page);

	bbits = inode->i_blkbits;
	block = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits);

	for(bh = head, block_start = 0; bh != head || !block_start;
	    block++, block_start=block_end, bh = bh->b_this_page) {
		block_end = block_start + blocksize;
		if (block_end <= from || block_start >= to) {
			if (PageUptodate(page)) {
				if (!buffer_uptodate(bh))
					set_buffer_uptodate(bh);
			}
			continue;
		}
		if (buffer_new(bh))
			clear_buffer_new(bh);
		if (!buffer_mapped(bh)) {
1852
			WARN_ON(bh->b_size != blocksize);
L
Linus Torvalds 已提交
1853 1854
			err = get_block(inode, block, bh, 1);
			if (err)
1855
				break;
L
Linus Torvalds 已提交
1856 1857 1858 1859
			if (buffer_new(bh)) {
				unmap_underlying_metadata(bh->b_bdev,
							bh->b_blocknr);
				if (PageUptodate(page)) {
N
Nick Piggin 已提交
1860
					clear_buffer_new(bh);
L
Linus Torvalds 已提交
1861
					set_buffer_uptodate(bh);
N
Nick Piggin 已提交
1862
					mark_buffer_dirty(bh);
L
Linus Torvalds 已提交
1863 1864
					continue;
				}
1865 1866 1867 1868
				if (block_end > to || block_start < from)
					zero_user_segments(page,
						to, block_end,
						block_start, from);
L
Linus Torvalds 已提交
1869 1870 1871 1872 1873 1874 1875 1876 1877
				continue;
			}
		}
		if (PageUptodate(page)) {
			if (!buffer_uptodate(bh))
				set_buffer_uptodate(bh);
			continue; 
		}
		if (!buffer_uptodate(bh) && !buffer_delay(bh) &&
1878
		    !buffer_unwritten(bh) &&
L
Linus Torvalds 已提交
1879 1880 1881 1882 1883 1884 1885 1886 1887 1888 1889
		     (block_start < from || block_end > to)) {
			ll_rw_block(READ, 1, &bh);
			*wait_bh++=bh;
		}
	}
	/*
	 * If we issued read requests - let them complete.
	 */
	while(wait_bh > wait) {
		wait_on_buffer(*--wait_bh);
		if (!buffer_uptodate(*wait_bh))
1890
			err = -EIO;
L
Linus Torvalds 已提交
1891
	}
1892 1893
	if (unlikely(err))
		page_zero_new_buffers(page, from, to);
L
Linus Torvalds 已提交
1894 1895 1896 1897 1898 1899 1900 1901 1902 1903 1904 1905 1906 1907 1908 1909 1910 1911 1912 1913 1914 1915 1916 1917
	return err;
}

static int __block_commit_write(struct inode *inode, struct page *page,
		unsigned from, unsigned to)
{
	unsigned block_start, block_end;
	int partial = 0;
	unsigned blocksize;
	struct buffer_head *bh, *head;

	blocksize = 1 << inode->i_blkbits;

	for(bh = head = page_buffers(page), block_start = 0;
	    bh != head || !block_start;
	    block_start=block_end, bh = bh->b_this_page) {
		block_end = block_start + blocksize;
		if (block_end <= from || block_start >= to) {
			if (!buffer_uptodate(bh))
				partial = 1;
		} else {
			set_buffer_uptodate(bh);
			mark_buffer_dirty(bh);
		}
1918
		clear_buffer_new(bh);
L
Linus Torvalds 已提交
1919 1920 1921 1922 1923 1924 1925 1926 1927 1928 1929 1930 1931
	}

	/*
	 * If this is a partial write which happened to make all buffers
	 * uptodate then we can optimize away a bogus readpage() for
	 * the next read(). Here we 'discover' whether the page went
	 * uptodate as a result of this (potentially partial) write.
	 */
	if (!partial)
		SetPageUptodate(page);
	return 0;
}

1932 1933 1934 1935 1936 1937 1938 1939 1940 1941 1942 1943 1944 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954 1955 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
/*
 * block_write_begin takes care of the basic task of block allocation and
 * bringing partial write blocks uptodate first.
 *
 * If *pagep is not NULL, then block_write_begin uses the locked page
 * at *pagep rather than allocating its own. In this case, the page will
 * not be unlocked or deallocated on failure.
 */
int block_write_begin(struct file *file, struct address_space *mapping,
			loff_t pos, unsigned len, unsigned flags,
			struct page **pagep, void **fsdata,
			get_block_t *get_block)
{
	struct inode *inode = mapping->host;
	int status = 0;
	struct page *page;
	pgoff_t index;
	unsigned start, end;
	int ownpage = 0;

	index = pos >> PAGE_CACHE_SHIFT;
	start = pos & (PAGE_CACHE_SIZE - 1);
	end = start + len;

	page = *pagep;
	if (page == NULL) {
		ownpage = 1;
		page = __grab_cache_page(mapping, index);
		if (!page) {
			status = -ENOMEM;
			goto out;
		}
		*pagep = page;
	} else
		BUG_ON(!PageLocked(page));

	status = __block_prepare_write(inode, page, start, end, get_block);
	if (unlikely(status)) {
		ClearPageUptodate(page);

		if (ownpage) {
			unlock_page(page);
			page_cache_release(page);
			*pagep = NULL;

			/*
			 * prepare_write() may have instantiated a few blocks
			 * outside i_size.  Trim these off again. Don't need
			 * i_size_read because we hold i_mutex.
			 */
			if (pos + len > inode->i_size)
				vmtruncate(inode, inode->i_size);
		}
		goto out;
	}

out:
	return status;
}
EXPORT_SYMBOL(block_write_begin);

int block_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;
	unsigned start;

	start = pos & (PAGE_CACHE_SIZE - 1);

	if (unlikely(copied < len)) {
		/*
		 * The buffers that were written will now be uptodate, so we
		 * don't have to worry about a readpage reading them and
		 * overwriting a partial write. However if we have encountered
		 * a short write and only partially written into a buffer, it
		 * will not be marked uptodate, so a readpage might come in and
		 * destroy our partial write.
		 *
		 * Do the simplest thing, and just treat any short write to a
		 * non uptodate page as a zero-length write, and force the
		 * caller to redo the whole thing.
		 */
		if (!PageUptodate(page))
			copied = 0;

		page_zero_new_buffers(page, start+copied, start+len);
	}
	flush_dcache_page(page);

	/* This could be a short (even 0-length) commit */
	__block_commit_write(inode, page, start, start+copied);

	return copied;
}
EXPORT_SYMBOL(block_write_end);

int generic_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;

	copied = block_write_end(file, mapping, pos, len, copied, page, fsdata);

	/*
	 * No need to use i_size_read() here, the i_size
	 * cannot change under us because we hold i_mutex.
	 *
	 * But it's important to update i_size while still holding page lock:
	 * page writeout could otherwise come in and zero beyond i_size.
	 */
	if (pos+copied > inode->i_size) {
		i_size_write(inode, pos+copied);
		mark_inode_dirty(inode);
	}

	unlock_page(page);
	page_cache_release(page);

	return copied;
}
EXPORT_SYMBOL(generic_write_end);

L
Linus Torvalds 已提交
2056 2057 2058 2059 2060 2061 2062 2063 2064 2065 2066 2067 2068 2069 2070 2071
/*
 * Generic "read page" function for block devices that have the normal
 * get_block functionality. This is most of the block device filesystems.
 * Reads the page asynchronously --- the unlock_buffer() and
 * set/clear_buffer_uptodate() functions propagate buffer state into the
 * page struct once IO has completed.
 */
int block_read_full_page(struct page *page, get_block_t *get_block)
{
	struct inode *inode = page->mapping->host;
	sector_t iblock, lblock;
	struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE];
	unsigned int blocksize;
	int nr, i;
	int fully_mapped = 1;

M
Matt Mackall 已提交
2072
	BUG_ON(!PageLocked(page));
L
Linus Torvalds 已提交
2073 2074 2075 2076 2077 2078 2079 2080 2081 2082 2083 2084 2085 2086 2087 2088
	blocksize = 1 << inode->i_blkbits;
	if (!page_has_buffers(page))
		create_empty_buffers(page, blocksize, 0);
	head = page_buffers(page);

	iblock = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
	lblock = (i_size_read(inode)+blocksize-1) >> inode->i_blkbits;
	bh = head;
	nr = 0;
	i = 0;

	do {
		if (buffer_uptodate(bh))
			continue;

		if (!buffer_mapped(bh)) {
2089 2090
			int err = 0;

L
Linus Torvalds 已提交
2091 2092
			fully_mapped = 0;
			if (iblock < lblock) {
2093
				WARN_ON(bh->b_size != blocksize);
2094 2095
				err = get_block(inode, iblock, bh, 0);
				if (err)
L
Linus Torvalds 已提交
2096 2097 2098
					SetPageError(page);
			}
			if (!buffer_mapped(bh)) {
2099
				zero_user(page, i * blocksize, blocksize);
2100 2101
				if (!err)
					set_buffer_uptodate(bh);
L
Linus Torvalds 已提交
2102 2103 2104 2105 2106 2107 2108 2109 2110 2111 2112 2113 2114 2115 2116 2117 2118 2119 2120 2121 2122 2123 2124 2125 2126 2127 2128 2129 2130 2131 2132 2133 2134 2135 2136 2137 2138 2139 2140 2141 2142 2143 2144 2145 2146 2147 2148 2149 2150
				continue;
			}
			/*
			 * get_block() might have updated the buffer
			 * synchronously
			 */
			if (buffer_uptodate(bh))
				continue;
		}
		arr[nr++] = bh;
	} while (i++, iblock++, (bh = bh->b_this_page) != head);

	if (fully_mapped)
		SetPageMappedToDisk(page);

	if (!nr) {
		/*
		 * All buffers are uptodate - we can set the page uptodate
		 * as well. But not if get_block() returned an error.
		 */
		if (!PageError(page))
			SetPageUptodate(page);
		unlock_page(page);
		return 0;
	}

	/* Stage two: lock the buffers */
	for (i = 0; i < nr; i++) {
		bh = arr[i];
		lock_buffer(bh);
		mark_buffer_async_read(bh);
	}

	/*
	 * Stage 3: start the IO.  Check for uptodateness
	 * inside the buffer lock in case another process reading
	 * the underlying blockdev brought it uptodate (the sct fix).
	 */
	for (i = 0; i < nr; i++) {
		bh = arr[i];
		if (buffer_uptodate(bh))
			end_buffer_async_read(bh, 1);
		else
			submit_bh(READ, bh);
	}
	return 0;
}

/* utility function for filesystems that need to do work on expanding
N
Nick Piggin 已提交
2151
 * truncates.  Uses filesystem pagecache writes to allow the filesystem to
L
Linus Torvalds 已提交
2152 2153
 * deal with the hole.  
 */
N
Nick Piggin 已提交
2154
int generic_cont_expand_simple(struct inode *inode, loff_t size)
L
Linus Torvalds 已提交
2155 2156 2157
{
	struct address_space *mapping = inode->i_mapping;
	struct page *page;
N
Nick Piggin 已提交
2158
	void *fsdata;
2159
	unsigned long limit;
L
Linus Torvalds 已提交
2160 2161 2162 2163 2164 2165 2166 2167 2168 2169 2170
	int err;

	err = -EFBIG;
        limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur;
	if (limit != RLIM_INFINITY && size > (loff_t)limit) {
		send_sig(SIGXFSZ, current, 0);
		goto out;
	}
	if (size > inode->i_sb->s_maxbytes)
		goto out;

N
Nick Piggin 已提交
2171 2172 2173 2174
	err = pagecache_write_begin(NULL, mapping, size, 0,
				AOP_FLAG_UNINTERRUPTIBLE|AOP_FLAG_CONT_EXPAND,
				&page, &fsdata);
	if (err)
2175 2176
		goto out;

N
Nick Piggin 已提交
2177 2178
	err = pagecache_write_end(NULL, mapping, size, 0, 0, page, fsdata);
	BUG_ON(err > 0);
2179

L
Linus Torvalds 已提交
2180 2181 2182 2183
out:
	return err;
}

N
Nick Piggin 已提交
2184 2185
int cont_expand_zero(struct file *file, struct address_space *mapping,
			loff_t pos, loff_t *bytes)
L
Linus Torvalds 已提交
2186 2187 2188
{
	struct inode *inode = mapping->host;
	unsigned blocksize = 1 << inode->i_blkbits;
N
Nick Piggin 已提交
2189 2190 2191 2192 2193 2194
	struct page *page;
	void *fsdata;
	pgoff_t index, curidx;
	loff_t curpos;
	unsigned zerofrom, offset, len;
	int err = 0;
L
Linus Torvalds 已提交
2195

N
Nick Piggin 已提交
2196 2197 2198 2199 2200
	index = pos >> PAGE_CACHE_SHIFT;
	offset = pos & ~PAGE_CACHE_MASK;

	while (index > (curidx = (curpos = *bytes)>>PAGE_CACHE_SHIFT)) {
		zerofrom = curpos & ~PAGE_CACHE_MASK;
L
Linus Torvalds 已提交
2201 2202 2203 2204
		if (zerofrom & (blocksize-1)) {
			*bytes |= (blocksize-1);
			(*bytes)++;
		}
N
Nick Piggin 已提交
2205
		len = PAGE_CACHE_SIZE - zerofrom;
L
Linus Torvalds 已提交
2206

N
Nick Piggin 已提交
2207 2208 2209 2210 2211
		err = pagecache_write_begin(file, mapping, curpos, len,
						AOP_FLAG_UNINTERRUPTIBLE,
						&page, &fsdata);
		if (err)
			goto out;
2212
		zero_user(page, zerofrom, len);
N
Nick Piggin 已提交
2213 2214 2215 2216 2217 2218 2219
		err = pagecache_write_end(file, mapping, curpos, len, len,
						page, fsdata);
		if (err < 0)
			goto out;
		BUG_ON(err != len);
		err = 0;
	}
L
Linus Torvalds 已提交
2220

N
Nick Piggin 已提交
2221 2222 2223
	/* page covers the boundary, find the boundary offset */
	if (index == curidx) {
		zerofrom = curpos & ~PAGE_CACHE_MASK;
L
Linus Torvalds 已提交
2224
		/* if we will expand the thing last block will be filled */
N
Nick Piggin 已提交
2225 2226 2227 2228
		if (offset <= zerofrom) {
			goto out;
		}
		if (zerofrom & (blocksize-1)) {
L
Linus Torvalds 已提交
2229 2230 2231
			*bytes |= (blocksize-1);
			(*bytes)++;
		}
N
Nick Piggin 已提交
2232
		len = offset - zerofrom;
L
Linus Torvalds 已提交
2233

N
Nick Piggin 已提交
2234 2235 2236 2237 2238
		err = pagecache_write_begin(file, mapping, curpos, len,
						AOP_FLAG_UNINTERRUPTIBLE,
						&page, &fsdata);
		if (err)
			goto out;
2239
		zero_user(page, zerofrom, len);
N
Nick Piggin 已提交
2240 2241 2242 2243 2244 2245
		err = pagecache_write_end(file, mapping, curpos, len, len,
						page, fsdata);
		if (err < 0)
			goto out;
		BUG_ON(err != len);
		err = 0;
L
Linus Torvalds 已提交
2246
	}
N
Nick Piggin 已提交
2247 2248 2249 2250 2251 2252 2253 2254 2255 2256 2257 2258 2259 2260 2261 2262 2263 2264 2265 2266 2267 2268 2269 2270 2271 2272
out:
	return err;
}

/*
 * For moronic filesystems that do not allow holes in file.
 * We may have to extend the file.
 */
int cont_write_begin(struct file *file, struct address_space *mapping,
			loff_t pos, unsigned len, unsigned flags,
			struct page **pagep, void **fsdata,
			get_block_t *get_block, loff_t *bytes)
{
	struct inode *inode = mapping->host;
	unsigned blocksize = 1 << inode->i_blkbits;
	unsigned zerofrom;
	int err;

	err = cont_expand_zero(file, mapping, pos, bytes);
	if (err)
		goto out;

	zerofrom = *bytes & ~PAGE_CACHE_MASK;
	if (pos+len > *bytes && zerofrom & (blocksize-1)) {
		*bytes |= (blocksize-1);
		(*bytes)++;
L
Linus Torvalds 已提交
2273 2274
	}

N
Nick Piggin 已提交
2275 2276 2277
	*pagep = NULL;
	err = block_write_begin(file, mapping, pos, len,
				flags, pagep, fsdata, get_block);
L
Linus Torvalds 已提交
2278
out:
N
Nick Piggin 已提交
2279
	return err;
L
Linus Torvalds 已提交
2280 2281 2282 2283 2284 2285 2286 2287 2288 2289 2290 2291 2292 2293 2294 2295 2296 2297 2298 2299 2300 2301 2302 2303 2304 2305 2306
}

int block_prepare_write(struct page *page, unsigned from, unsigned to,
			get_block_t *get_block)
{
	struct inode *inode = page->mapping->host;
	int err = __block_prepare_write(inode, page, from, to, get_block);
	if (err)
		ClearPageUptodate(page);
	return err;
}

int block_commit_write(struct page *page, unsigned from, unsigned to)
{
	struct inode *inode = page->mapping->host;
	__block_commit_write(inode,page,from,to);
	return 0;
}

int generic_commit_write(struct file *file, struct page *page,
		unsigned from, unsigned to)
{
	struct inode *inode = page->mapping->host;
	loff_t pos = ((loff_t)page->index << PAGE_CACHE_SHIFT) + to;
	__block_commit_write(inode,page,from,to);
	/*
	 * No need to use i_size_read() here, the i_size
2307
	 * cannot change under us because we hold i_mutex.
L
Linus Torvalds 已提交
2308 2309 2310 2311 2312 2313 2314 2315
	 */
	if (pos > inode->i_size) {
		i_size_write(inode, pos);
		mark_inode_dirty(inode);
	}
	return 0;
}

2316 2317 2318 2319 2320 2321 2322 2323 2324 2325 2326 2327 2328 2329 2330 2331 2332 2333 2334 2335 2336 2337 2338 2339 2340 2341 2342
/*
 * block_page_mkwrite() is not allowed to change the file size as it gets
 * called from a page fault handler when a page is first dirtied. Hence we must
 * be careful to check for EOF conditions here. We set the page up correctly
 * for a written page which means we get ENOSPC checking when writing into
 * holes and correct delalloc and unwritten extent mapping on filesystems that
 * support these features.
 *
 * We are not allowed to take the i_mutex here so we have to play games to
 * protect against truncate races as the page could now be beyond EOF.  Because
 * vmtruncate() writes the inode size before removing pages, once we have the
 * page lock we can determine safely if the page is beyond EOF. If it is not
 * beyond EOF, then the page is guaranteed safe against truncation until we
 * unlock the page.
 */
int
block_page_mkwrite(struct vm_area_struct *vma, struct page *page,
		   get_block_t get_block)
{
	struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
	unsigned long end;
	loff_t size;
	int ret = -EINVAL;

	lock_page(page);
	size = i_size_read(inode);
	if ((page->mapping != inode->i_mapping) ||
N
Nick Piggin 已提交
2343
	    (page_offset(page) > size)) {
2344 2345 2346 2347 2348 2349 2350 2351 2352 2353 2354 2355 2356 2357 2358 2359 2360 2361
		/* page got truncated out from underneath us */
		goto out_unlock;
	}

	/* page is wholly or partially inside EOF */
	if (((page->index + 1) << PAGE_CACHE_SHIFT) > size)
		end = size & ~PAGE_CACHE_MASK;
	else
		end = PAGE_CACHE_SIZE;

	ret = block_prepare_write(page, 0, end, get_block);
	if (!ret)
		ret = block_commit_write(page, 0, end);

out_unlock:
	unlock_page(page);
	return ret;
}
L
Linus Torvalds 已提交
2362 2363

/*
N
Nick Piggin 已提交
2364
 * nobh_write_begin()'s prereads are special: the buffer_heads are freed
L
Linus Torvalds 已提交
2365 2366 2367 2368 2369
 * immediately, while under the page lock.  So it needs a special end_io
 * handler which does not touch the bh after unlocking it.
 */
static void end_buffer_read_nobh(struct buffer_head *bh, int uptodate)
{
2370
	__end_buffer_read_notouch(bh, uptodate);
L
Linus Torvalds 已提交
2371 2372
}

N
Nick Piggin 已提交
2373 2374 2375 2376 2377 2378 2379 2380 2381 2382 2383 2384 2385 2386 2387 2388 2389 2390 2391 2392 2393 2394 2395 2396
/*
 * Attach the singly-linked list of buffers created by nobh_write_begin, to
 * the page (converting it to circular linked list and taking care of page
 * dirty races).
 */
static void attach_nobh_buffers(struct page *page, struct buffer_head *head)
{
	struct buffer_head *bh;

	BUG_ON(!PageLocked(page));

	spin_lock(&page->mapping->private_lock);
	bh = head;
	do {
		if (PageDirty(page))
			set_buffer_dirty(bh);
		if (!bh->b_this_page)
			bh->b_this_page = head;
		bh = bh->b_this_page;
	} while (bh != head);
	attach_page_buffers(page, head);
	spin_unlock(&page->mapping->private_lock);
}

L
Linus Torvalds 已提交
2397 2398 2399 2400
/*
 * On entry, the page is fully not uptodate.
 * On exit the page is fully uptodate in the areas outside (from,to)
 */
N
Nick Piggin 已提交
2401 2402 2403
int nobh_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
2404 2405
			get_block_t *get_block)
{
N
Nick Piggin 已提交
2406
	struct inode *inode = mapping->host;
L
Linus Torvalds 已提交
2407 2408
	const unsigned blkbits = inode->i_blkbits;
	const unsigned blocksize = 1 << blkbits;
N
Nick Piggin 已提交
2409
	struct buffer_head *head, *bh;
N
Nick Piggin 已提交
2410 2411 2412
	struct page *page;
	pgoff_t index;
	unsigned from, to;
L
Linus Torvalds 已提交
2413
	unsigned block_in_page;
N
Nick Piggin 已提交
2414
	unsigned block_start, block_end;
L
Linus Torvalds 已提交
2415 2416 2417 2418 2419
	sector_t block_in_file;
	int nr_reads = 0;
	int ret = 0;
	int is_mapped_to_disk = 1;

N
Nick Piggin 已提交
2420 2421 2422 2423 2424 2425 2426 2427 2428 2429 2430 2431 2432 2433 2434 2435 2436
	index = pos >> PAGE_CACHE_SHIFT;
	from = pos & (PAGE_CACHE_SIZE - 1);
	to = from + len;

	page = __grab_cache_page(mapping, index);
	if (!page)
		return -ENOMEM;
	*pagep = page;
	*fsdata = NULL;

	if (page_has_buffers(page)) {
		unlock_page(page);
		page_cache_release(page);
		*pagep = NULL;
		return block_write_begin(file, mapping, pos, len, flags, pagep,
					fsdata, get_block);
	}
N
Nick Piggin 已提交
2437

L
Linus Torvalds 已提交
2438 2439 2440
	if (PageMappedToDisk(page))
		return 0;

N
Nick Piggin 已提交
2441 2442 2443 2444 2445 2446 2447 2448 2449 2450
	/*
	 * Allocate buffers so that we can keep track of state, and potentially
	 * attach them to the page if an error occurs. In the common case of
	 * no error, they will just be freed again without ever being attached
	 * to the page (which is all OK, because we're under the page lock).
	 *
	 * Be careful: the buffer linked list is a NULL terminated one, rather
	 * than the circular one we're used to.
	 */
	head = alloc_page_buffers(page, blocksize, 0);
N
Nick Piggin 已提交
2451 2452 2453 2454
	if (!head) {
		ret = -ENOMEM;
		goto out_release;
	}
N
Nick Piggin 已提交
2455

L
Linus Torvalds 已提交
2456 2457 2458 2459 2460 2461 2462
	block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits);

	/*
	 * We loop across all blocks in the page, whether or not they are
	 * part of the affected region.  This is so we can discover if the
	 * page is fully mapped-to-disk.
	 */
N
Nick Piggin 已提交
2463
	for (block_start = 0, block_in_page = 0, bh = head;
L
Linus Torvalds 已提交
2464
		  block_start < PAGE_CACHE_SIZE;
N
Nick Piggin 已提交
2465
		  block_in_page++, block_start += blocksize, bh = bh->b_this_page) {
L
Linus Torvalds 已提交
2466 2467
		int create;

N
Nick Piggin 已提交
2468 2469
		block_end = block_start + blocksize;
		bh->b_state = 0;
L
Linus Torvalds 已提交
2470 2471 2472 2473
		create = 1;
		if (block_start >= to)
			create = 0;
		ret = get_block(inode, block_in_file + block_in_page,
N
Nick Piggin 已提交
2474
					bh, create);
L
Linus Torvalds 已提交
2475 2476
		if (ret)
			goto failed;
N
Nick Piggin 已提交
2477
		if (!buffer_mapped(bh))
L
Linus Torvalds 已提交
2478
			is_mapped_to_disk = 0;
N
Nick Piggin 已提交
2479 2480 2481 2482
		if (buffer_new(bh))
			unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr);
		if (PageUptodate(page)) {
			set_buffer_uptodate(bh);
L
Linus Torvalds 已提交
2483
			continue;
N
Nick Piggin 已提交
2484 2485
		}
		if (buffer_new(bh) || !buffer_mapped(bh)) {
2486 2487
			zero_user_segments(page, block_start, from,
							to, block_end);
L
Linus Torvalds 已提交
2488 2489
			continue;
		}
N
Nick Piggin 已提交
2490
		if (buffer_uptodate(bh))
L
Linus Torvalds 已提交
2491 2492
			continue;	/* reiserfs does this */
		if (block_start < from || block_end > to) {
N
Nick Piggin 已提交
2493 2494 2495 2496
			lock_buffer(bh);
			bh->b_end_io = end_buffer_read_nobh;
			submit_bh(READ, bh);
			nr_reads++;
L
Linus Torvalds 已提交
2497 2498 2499 2500 2501 2502 2503 2504 2505
		}
	}

	if (nr_reads) {
		/*
		 * The page is locked, so these buffers are protected from
		 * any VM or truncate activity.  Hence we don't need to care
		 * for the buffer_head refcounts.
		 */
N
Nick Piggin 已提交
2506
		for (bh = head; bh; bh = bh->b_this_page) {
L
Linus Torvalds 已提交
2507 2508 2509 2510 2511 2512 2513 2514 2515 2516 2517
			wait_on_buffer(bh);
			if (!buffer_uptodate(bh))
				ret = -EIO;
		}
		if (ret)
			goto failed;
	}

	if (is_mapped_to_disk)
		SetPageMappedToDisk(page);

N
Nick Piggin 已提交
2518
	*fsdata = head; /* to be released by nobh_write_end */
N
Nick Piggin 已提交
2519

L
Linus Torvalds 已提交
2520 2521 2522
	return 0;

failed:
N
Nick Piggin 已提交
2523
	BUG_ON(!ret);
L
Linus Torvalds 已提交
2524
	/*
N
Nick Piggin 已提交
2525 2526 2527 2528 2529
	 * Error recovery is a bit difficult. We need to zero out blocks that
	 * were newly allocated, and dirty them to ensure they get written out.
	 * Buffers need to be attached to the page at this point, otherwise
	 * the handling of potential IO errors during writeout would be hard
	 * (could try doing synchronous writeout, but what if that fails too?)
L
Linus Torvalds 已提交
2530
	 */
N
Nick Piggin 已提交
2531 2532
	attach_nobh_buffers(page, head);
	page_zero_new_buffers(page, from, to);
N
Nick Piggin 已提交
2533

N
Nick Piggin 已提交
2534 2535 2536 2537
out_release:
	unlock_page(page);
	page_cache_release(page);
	*pagep = NULL;
N
Nick Piggin 已提交
2538

N
Nick Piggin 已提交
2539 2540
	if (pos + len > inode->i_size)
		vmtruncate(inode, inode->i_size);
N
Nick Piggin 已提交
2541

L
Linus Torvalds 已提交
2542 2543
	return ret;
}
N
Nick Piggin 已提交
2544
EXPORT_SYMBOL(nobh_write_begin);
L
Linus Torvalds 已提交
2545

N
Nick Piggin 已提交
2546 2547 2548
int nobh_write_end(struct file *file, struct address_space *mapping,
			loff_t pos, unsigned len, unsigned copied,
			struct page *page, void *fsdata)
L
Linus Torvalds 已提交
2549 2550
{
	struct inode *inode = page->mapping->host;
N
Nick Piggin 已提交
2551
	struct buffer_head *head = fsdata;
N
Nick Piggin 已提交
2552
	struct buffer_head *bh;
L
Linus Torvalds 已提交
2553

N
Nick Piggin 已提交
2554 2555 2556 2557 2558 2559 2560
	if (!PageMappedToDisk(page)) {
		if (unlikely(copied < len) && !page_has_buffers(page))
			attach_nobh_buffers(page, head);
		if (page_has_buffers(page))
			return generic_write_end(file, mapping, pos, len,
						copied, page, fsdata);
	}
N
Nick Piggin 已提交
2561

N
Nick Piggin 已提交
2562
	SetPageUptodate(page);
L
Linus Torvalds 已提交
2563
	set_page_dirty(page);
N
Nick Piggin 已提交
2564 2565
	if (pos+copied > inode->i_size) {
		i_size_write(inode, pos+copied);
L
Linus Torvalds 已提交
2566 2567
		mark_inode_dirty(inode);
	}
N
Nick Piggin 已提交
2568 2569 2570 2571 2572 2573 2574 2575 2576 2577 2578

	unlock_page(page);
	page_cache_release(page);

	while (head) {
		bh = head;
		head = head->b_this_page;
		free_buffer_head(bh);
	}

	return copied;
L
Linus Torvalds 已提交
2579
}
N
Nick Piggin 已提交
2580
EXPORT_SYMBOL(nobh_write_end);
L
Linus Torvalds 已提交
2581 2582 2583 2584 2585 2586 2587 2588 2589 2590 2591 2592 2593 2594 2595 2596 2597 2598 2599 2600 2601 2602 2603 2604 2605 2606 2607 2608 2609 2610 2611 2612 2613 2614 2615 2616 2617 2618 2619 2620 2621 2622 2623

/*
 * nobh_writepage() - based on block_full_write_page() except
 * that it tries to operate without attaching bufferheads to
 * the page.
 */
int nobh_writepage(struct page *page, get_block_t *get_block,
			struct writeback_control *wbc)
{
	struct inode * const inode = page->mapping->host;
	loff_t i_size = i_size_read(inode);
	const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
	unsigned offset;
	int ret;

	/* Is the page fully inside i_size? */
	if (page->index < end_index)
		goto out;

	/* Is the page fully outside i_size? (truncate in progress) */
	offset = i_size & (PAGE_CACHE_SIZE-1);
	if (page->index >= end_index+1 || !offset) {
		/*
		 * The page may have dirty, unmapped buffers.  For example,
		 * they may have been added in ext3_writepage().  Make them
		 * freeable here, so the page does not leak.
		 */
#if 0
		/* Not really sure about this  - do we need this ? */
		if (page->mapping->a_ops->invalidatepage)
			page->mapping->a_ops->invalidatepage(page, offset);
#endif
		unlock_page(page);
		return 0; /* don't care */
	}

	/*
	 * The page straddles i_size.  It must be zeroed out on each and every
	 * writepage invocation because it may be mmapped.  "A file is mapped
	 * in multiples of the page size.  For a file that is not a multiple of
	 * the  page size, the remaining memory is zeroed when mapped, and
	 * writes to that region are not written out to the file."
	 */
2624
	zero_user_segment(page, offset, PAGE_CACHE_SIZE);
L
Linus Torvalds 已提交
2625 2626 2627 2628 2629 2630 2631 2632
out:
	ret = mpage_writepage(page, get_block, wbc);
	if (ret == -EAGAIN)
		ret = __block_write_full_page(inode, page, get_block, wbc);
	return ret;
}
EXPORT_SYMBOL(nobh_writepage);

N
Nick Piggin 已提交
2633 2634
int nobh_truncate_page(struct address_space *mapping,
			loff_t from, get_block_t *get_block)
L
Linus Torvalds 已提交
2635 2636 2637
{
	pgoff_t index = from >> PAGE_CACHE_SHIFT;
	unsigned offset = from & (PAGE_CACHE_SIZE-1);
N
Nick Piggin 已提交
2638 2639 2640 2641
	unsigned blocksize;
	sector_t iblock;
	unsigned length, pos;
	struct inode *inode = mapping->host;
L
Linus Torvalds 已提交
2642
	struct page *page;
N
Nick Piggin 已提交
2643 2644
	struct buffer_head map_bh;
	int err;
L
Linus Torvalds 已提交
2645

N
Nick Piggin 已提交
2646 2647 2648 2649 2650 2651 2652 2653 2654
	blocksize = 1 << inode->i_blkbits;
	length = offset & (blocksize - 1);

	/* Block boundary? Nothing to do */
	if (!length)
		return 0;

	length = blocksize - length;
	iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
L
Linus Torvalds 已提交
2655 2656

	page = grab_cache_page(mapping, index);
N
Nick Piggin 已提交
2657
	err = -ENOMEM;
L
Linus Torvalds 已提交
2658 2659 2660
	if (!page)
		goto out;

N
Nick Piggin 已提交
2661 2662 2663 2664 2665 2666 2667 2668 2669 2670 2671 2672 2673 2674 2675 2676 2677 2678 2679 2680 2681 2682 2683 2684 2685 2686 2687 2688 2689 2690 2691 2692 2693 2694 2695
	if (page_has_buffers(page)) {
has_buffers:
		unlock_page(page);
		page_cache_release(page);
		return block_truncate_page(mapping, from, get_block);
	}

	/* Find the buffer that contains "offset" */
	pos = blocksize;
	while (offset >= pos) {
		iblock++;
		pos += blocksize;
	}

	err = get_block(inode, iblock, &map_bh, 0);
	if (err)
		goto unlock;
	/* unmapped? It's a hole - nothing to do */
	if (!buffer_mapped(&map_bh))
		goto unlock;

	/* Ok, it's mapped. Make sure it's up-to-date */
	if (!PageUptodate(page)) {
		err = mapping->a_ops->readpage(NULL, page);
		if (err) {
			page_cache_release(page);
			goto out;
		}
		lock_page(page);
		if (!PageUptodate(page)) {
			err = -EIO;
			goto unlock;
		}
		if (page_has_buffers(page))
			goto has_buffers;
L
Linus Torvalds 已提交
2696
	}
2697
	zero_user(page, offset, length);
N
Nick Piggin 已提交
2698 2699 2700 2701
	set_page_dirty(page);
	err = 0;

unlock:
L
Linus Torvalds 已提交
2702 2703 2704
	unlock_page(page);
	page_cache_release(page);
out:
N
Nick Piggin 已提交
2705
	return err;
L
Linus Torvalds 已提交
2706 2707 2708 2709 2710 2711 2712 2713 2714
}
EXPORT_SYMBOL(nobh_truncate_page);

int block_truncate_page(struct address_space *mapping,
			loff_t from, get_block_t *get_block)
{
	pgoff_t index = from >> PAGE_CACHE_SHIFT;
	unsigned offset = from & (PAGE_CACHE_SIZE-1);
	unsigned blocksize;
2715
	sector_t iblock;
L
Linus Torvalds 已提交
2716 2717 2718 2719 2720 2721 2722 2723 2724 2725 2726 2727 2728 2729
	unsigned length, pos;
	struct inode *inode = mapping->host;
	struct page *page;
	struct buffer_head *bh;
	int err;

	blocksize = 1 << inode->i_blkbits;
	length = offset & (blocksize - 1);

	/* Block boundary? Nothing to do */
	if (!length)
		return 0;

	length = blocksize - length;
2730
	iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
L
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2731 2732 2733 2734 2735 2736 2737 2738 2739 2740 2741 2742 2743 2744 2745 2746 2747 2748 2749 2750
	
	page = grab_cache_page(mapping, index);
	err = -ENOMEM;
	if (!page)
		goto out;

	if (!page_has_buffers(page))
		create_empty_buffers(page, blocksize, 0);

	/* Find the buffer that contains "offset" */
	bh = page_buffers(page);
	pos = blocksize;
	while (offset >= pos) {
		bh = bh->b_this_page;
		iblock++;
		pos += blocksize;
	}

	err = 0;
	if (!buffer_mapped(bh)) {
2751
		WARN_ON(bh->b_size != blocksize);
L
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2752 2753 2754 2755 2756 2757 2758 2759 2760 2761 2762 2763
		err = get_block(inode, iblock, bh, 0);
		if (err)
			goto unlock;
		/* unmapped? It's a hole - nothing to do */
		if (!buffer_mapped(bh))
			goto unlock;
	}

	/* Ok, it's mapped. Make sure it's up-to-date */
	if (PageUptodate(page))
		set_buffer_uptodate(bh);

2764
	if (!buffer_uptodate(bh) && !buffer_delay(bh) && !buffer_unwritten(bh)) {
L
Linus Torvalds 已提交
2765 2766 2767 2768 2769 2770 2771 2772
		err = -EIO;
		ll_rw_block(READ, 1, &bh);
		wait_on_buffer(bh);
		/* Uhhuh. Read error. Complain and punt. */
		if (!buffer_uptodate(bh))
			goto unlock;
	}

2773
	zero_user(page, offset, length);
L
Linus Torvalds 已提交
2774 2775 2776 2777 2778 2779 2780 2781 2782 2783 2784 2785 2786 2787 2788 2789 2790 2791 2792 2793 2794 2795 2796 2797 2798 2799 2800 2801 2802 2803 2804 2805 2806
	mark_buffer_dirty(bh);
	err = 0;

unlock:
	unlock_page(page);
	page_cache_release(page);
out:
	return err;
}

/*
 * The generic ->writepage function for buffer-backed address_spaces
 */
int block_write_full_page(struct page *page, get_block_t *get_block,
			struct writeback_control *wbc)
{
	struct inode * const inode = page->mapping->host;
	loff_t i_size = i_size_read(inode);
	const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
	unsigned offset;

	/* Is the page fully inside i_size? */
	if (page->index < end_index)
		return __block_write_full_page(inode, page, get_block, wbc);

	/* Is the page fully outside i_size? (truncate in progress) */
	offset = i_size & (PAGE_CACHE_SIZE-1);
	if (page->index >= end_index+1 || !offset) {
		/*
		 * The page may have dirty, unmapped buffers.  For example,
		 * they may have been added in ext3_writepage().  Make them
		 * freeable here, so the page does not leak.
		 */
2807
		do_invalidatepage(page, 0);
L
Linus Torvalds 已提交
2808 2809 2810 2811 2812 2813 2814 2815 2816 2817 2818
		unlock_page(page);
		return 0; /* don't care */
	}

	/*
	 * The page straddles i_size.  It must be zeroed out on each and every
	 * writepage invokation because it may be mmapped.  "A file is mapped
	 * in multiples of the page size.  For a file that is not a multiple of
	 * the  page size, the remaining memory is zeroed when mapped, and
	 * writes to that region are not written out to the file."
	 */
2819
	zero_user_segment(page, offset, PAGE_CACHE_SIZE);
L
Linus Torvalds 已提交
2820 2821 2822 2823 2824 2825 2826 2827 2828 2829
	return __block_write_full_page(inode, page, get_block, wbc);
}

sector_t generic_block_bmap(struct address_space *mapping, sector_t block,
			    get_block_t *get_block)
{
	struct buffer_head tmp;
	struct inode *inode = mapping->host;
	tmp.b_state = 0;
	tmp.b_blocknr = 0;
2830
	tmp.b_size = 1 << inode->i_blkbits;
L
Linus Torvalds 已提交
2831 2832 2833 2834
	get_block(inode, block, &tmp, 0);
	return tmp.b_blocknr;
}

2835
static void end_bio_bh_io_sync(struct bio *bio, int err)
L
Linus Torvalds 已提交
2836 2837 2838 2839 2840 2841 2842 2843 2844 2845 2846 2847 2848 2849 2850 2851 2852 2853 2854 2855 2856 2857 2858 2859 2860 2861 2862 2863 2864 2865 2866 2867 2868 2869 2870 2871 2872 2873 2874 2875 2876 2877 2878 2879 2880 2881 2882 2883 2884 2885 2886 2887 2888 2889 2890 2891 2892 2893 2894 2895 2896 2897
{
	struct buffer_head *bh = bio->bi_private;

	if (err == -EOPNOTSUPP) {
		set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
		set_bit(BH_Eopnotsupp, &bh->b_state);
	}

	bh->b_end_io(bh, test_bit(BIO_UPTODATE, &bio->bi_flags));
	bio_put(bio);
}

int submit_bh(int rw, struct buffer_head * bh)
{
	struct bio *bio;
	int ret = 0;

	BUG_ON(!buffer_locked(bh));
	BUG_ON(!buffer_mapped(bh));
	BUG_ON(!bh->b_end_io);

	if (buffer_ordered(bh) && (rw == WRITE))
		rw = WRITE_BARRIER;

	/*
	 * Only clear out a write error when rewriting, should this
	 * include WRITE_SYNC as well?
	 */
	if (test_set_buffer_req(bh) && (rw == WRITE || rw == WRITE_BARRIER))
		clear_buffer_write_io_error(bh);

	/*
	 * from here on down, it's all bio -- do the initial mapping,
	 * submit_bio -> generic_make_request may further map this bio around
	 */
	bio = bio_alloc(GFP_NOIO, 1);

	bio->bi_sector = bh->b_blocknr * (bh->b_size >> 9);
	bio->bi_bdev = bh->b_bdev;
	bio->bi_io_vec[0].bv_page = bh->b_page;
	bio->bi_io_vec[0].bv_len = bh->b_size;
	bio->bi_io_vec[0].bv_offset = bh_offset(bh);

	bio->bi_vcnt = 1;
	bio->bi_idx = 0;
	bio->bi_size = bh->b_size;

	bio->bi_end_io = end_bio_bh_io_sync;
	bio->bi_private = bh;

	bio_get(bio);
	submit_bio(rw, bio);

	if (bio_flagged(bio, BIO_EOPNOTSUPP))
		ret = -EOPNOTSUPP;

	bio_put(bio);
	return ret;
}

/**
 * ll_rw_block: low-level access to block devices (DEPRECATED)
2898
 * @rw: whether to %READ or %WRITE or %SWRITE or maybe %READA (readahead)
L
Linus Torvalds 已提交
2899 2900 2901
 * @nr: number of &struct buffer_heads in the array
 * @bhs: array of pointers to &struct buffer_head
 *
2902 2903 2904 2905 2906
 * ll_rw_block() takes an array of pointers to &struct buffer_heads, and
 * requests an I/O operation on them, either a %READ or a %WRITE.  The third
 * %SWRITE is like %WRITE only we make sure that the *current* data in buffers
 * are sent to disk. The fourth %READA option is described in the documentation
 * for generic_make_request() which ll_rw_block() calls.
L
Linus Torvalds 已提交
2907 2908
 *
 * This function drops any buffer that it cannot get a lock on (with the
2909 2910 2911 2912 2913
 * BH_Lock state bit) unless SWRITE is required, any buffer that appears to be
 * clean when doing a write request, and any buffer that appears to be
 * up-to-date when doing read request.  Further it marks as clean buffers that
 * are processed for writing (the buffer cache won't assume that they are
 * actually clean until the buffer gets unlocked).
L
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2914 2915 2916 2917 2918 2919 2920 2921 2922 2923 2924 2925 2926 2927 2928
 *
 * ll_rw_block sets b_end_io to simple completion handler that marks
 * the buffer up-to-date (if approriate), unlocks the buffer and wakes
 * any waiters. 
 *
 * All of the buffers must be for the same device, and must also be a
 * multiple of the current approved size for the device.
 */
void ll_rw_block(int rw, int nr, struct buffer_head *bhs[])
{
	int i;

	for (i = 0; i < nr; i++) {
		struct buffer_head *bh = bhs[i];

2929 2930 2931
		if (rw == SWRITE)
			lock_buffer(bh);
		else if (test_set_buffer_locked(bh))
L
Linus Torvalds 已提交
2932 2933
			continue;

2934
		if (rw == WRITE || rw == SWRITE) {
L
Linus Torvalds 已提交
2935
			if (test_clear_buffer_dirty(bh)) {
2936
				bh->b_end_io = end_buffer_write_sync;
2937
				get_bh(bh);
L
Linus Torvalds 已提交
2938 2939 2940 2941 2942
				submit_bh(WRITE, bh);
				continue;
			}
		} else {
			if (!buffer_uptodate(bh)) {
2943
				bh->b_end_io = end_buffer_read_sync;
2944
				get_bh(bh);
L
Linus Torvalds 已提交
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 2988 2989 2990 2991 2992 2993 2994 2995 2996 2997 2998 2999 3000 3001 3002 3003 3004 3005 3006 3007 3008 3009 3010 3011 3012 3013 3014
				submit_bh(rw, bh);
				continue;
			}
		}
		unlock_buffer(bh);
	}
}

/*
 * For a data-integrity writeout, we need to wait upon any in-progress I/O
 * and then start new I/O and then wait upon it.  The caller must have a ref on
 * the buffer_head.
 */
int sync_dirty_buffer(struct buffer_head *bh)
{
	int ret = 0;

	WARN_ON(atomic_read(&bh->b_count) < 1);
	lock_buffer(bh);
	if (test_clear_buffer_dirty(bh)) {
		get_bh(bh);
		bh->b_end_io = end_buffer_write_sync;
		ret = submit_bh(WRITE, bh);
		wait_on_buffer(bh);
		if (buffer_eopnotsupp(bh)) {
			clear_buffer_eopnotsupp(bh);
			ret = -EOPNOTSUPP;
		}
		if (!ret && !buffer_uptodate(bh))
			ret = -EIO;
	} else {
		unlock_buffer(bh);
	}
	return ret;
}

/*
 * try_to_free_buffers() checks if all the buffers on this particular page
 * are unused, and releases them if so.
 *
 * Exclusion against try_to_free_buffers may be obtained by either
 * locking the page or by holding its mapping's private_lock.
 *
 * If the page is dirty but all the buffers are clean then we need to
 * be sure to mark the page clean as well.  This is because the page
 * may be against a block device, and a later reattachment of buffers
 * to a dirty page will set *all* buffers dirty.  Which would corrupt
 * filesystem data on the same device.
 *
 * The same applies to regular filesystem pages: if all the buffers are
 * clean then we set the page clean and proceed.  To do that, we require
 * total exclusion from __set_page_dirty_buffers().  That is obtained with
 * private_lock.
 *
 * try_to_free_buffers() is non-blocking.
 */
static inline int buffer_busy(struct buffer_head *bh)
{
	return atomic_read(&bh->b_count) |
		(bh->b_state & ((1 << BH_Dirty) | (1 << BH_Lock)));
}

static int
drop_buffers(struct page *page, struct buffer_head **buffers_to_free)
{
	struct buffer_head *head = page_buffers(page);
	struct buffer_head *bh;

	bh = head;
	do {
A
akpm@osdl.org 已提交
3015
		if (buffer_write_io_error(bh) && page->mapping)
L
Linus Torvalds 已提交
3016 3017 3018 3019 3020 3021 3022 3023 3024 3025 3026 3027 3028 3029 3030 3031 3032 3033 3034 3035 3036 3037 3038 3039 3040 3041 3042
			set_bit(AS_EIO, &page->mapping->flags);
		if (buffer_busy(bh))
			goto failed;
		bh = bh->b_this_page;
	} while (bh != head);

	do {
		struct buffer_head *next = bh->b_this_page;

		if (!list_empty(&bh->b_assoc_buffers))
			__remove_assoc_queue(bh);
		bh = next;
	} while (bh != head);
	*buffers_to_free = head;
	__clear_page_buffers(page);
	return 1;
failed:
	return 0;
}

int try_to_free_buffers(struct page *page)
{
	struct address_space * const mapping = page->mapping;
	struct buffer_head *buffers_to_free = NULL;
	int ret = 0;

	BUG_ON(!PageLocked(page));
3043
	if (PageWriteback(page))
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Linus Torvalds 已提交
3044 3045 3046 3047 3048 3049 3050 3051 3052
		return 0;

	if (mapping == NULL) {		/* can this still happen? */
		ret = drop_buffers(page, &buffers_to_free);
		goto out;
	}

	spin_lock(&mapping->private_lock);
	ret = drop_buffers(page, &buffers_to_free);
3053 3054 3055 3056 3057 3058 3059 3060 3061 3062

	/*
	 * If the filesystem writes its buffers by hand (eg ext3)
	 * then we can have clean buffers against a dirty page.  We
	 * clean the page here; otherwise the VM will never notice
	 * that the filesystem did any IO at all.
	 *
	 * Also, during truncate, discard_buffer will have marked all
	 * the page's buffers clean.  We discover that here and clean
	 * the page also.
3063 3064 3065 3066
	 *
	 * private_lock must be held over this entire operation in order
	 * to synchronise against __set_page_dirty_buffers and prevent the
	 * dirty bit from being lost.
3067 3068 3069
	 */
	if (ret)
		cancel_dirty_page(page, PAGE_CACHE_SIZE);
3070
	spin_unlock(&mapping->private_lock);
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Linus Torvalds 已提交
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out:
	if (buffers_to_free) {
		struct buffer_head *bh = buffers_to_free;

		do {
			struct buffer_head *next = bh->b_this_page;
			free_buffer_head(bh);
			bh = next;
		} while (bh != buffers_to_free);
	}
	return ret;
}
EXPORT_SYMBOL(try_to_free_buffers);

3085
void block_sync_page(struct page *page)
L
Linus Torvalds 已提交
3086 3087 3088 3089 3090 3091 3092 3093 3094 3095 3096 3097 3098 3099 3100 3101 3102 3103 3104 3105 3106 3107 3108 3109 3110 3111 3112 3113 3114 3115 3116 3117 3118 3119 3120 3121 3122 3123 3124
{
	struct address_space *mapping;

	smp_mb();
	mapping = page_mapping(page);
	if (mapping)
		blk_run_backing_dev(mapping->backing_dev_info, page);
}

/*
 * There are no bdflush tunables left.  But distributions are
 * still running obsolete flush daemons, so we terminate them here.
 *
 * Use of bdflush() is deprecated and will be removed in a future kernel.
 * The `pdflush' kernel threads fully replace bdflush daemons and this call.
 */
asmlinkage long sys_bdflush(int func, long data)
{
	static int msg_count;

	if (!capable(CAP_SYS_ADMIN))
		return -EPERM;

	if (msg_count < 5) {
		msg_count++;
		printk(KERN_INFO
			"warning: process `%s' used the obsolete bdflush"
			" system call\n", current->comm);
		printk(KERN_INFO "Fix your initscripts?\n");
	}

	if (func == 1)
		do_exit(0);
	return 0;
}

/*
 * Buffer-head allocation
 */
3125
static struct kmem_cache *bh_cachep;
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/*
 * Once the number of bh's in the machine exceeds this level, we start
 * stripping them in writeback.
 */
static int max_buffer_heads;

int buffer_heads_over_limit;

struct bh_accounting {
	int nr;			/* Number of live bh's */
	int ratelimit;		/* Limit cacheline bouncing */
};

static DEFINE_PER_CPU(struct bh_accounting, bh_accounting) = {0, 0};

static void recalc_bh_state(void)
{
	int i;
	int tot = 0;

	if (__get_cpu_var(bh_accounting).ratelimit++ < 4096)
		return;
	__get_cpu_var(bh_accounting).ratelimit = 0;
3150
	for_each_online_cpu(i)
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Linus Torvalds 已提交
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		tot += per_cpu(bh_accounting, i).nr;
	buffer_heads_over_limit = (tot > max_buffer_heads);
}
	
A
Al Viro 已提交
3155
struct buffer_head *alloc_buffer_head(gfp_t gfp_flags)
L
Linus Torvalds 已提交
3156
{
3157
	struct buffer_head *ret = kmem_cache_alloc(bh_cachep,
3158
				set_migrateflags(gfp_flags, __GFP_RECLAIMABLE));
L
Linus Torvalds 已提交
3159
	if (ret) {
C
Christoph Lameter 已提交
3160
		INIT_LIST_HEAD(&ret->b_assoc_buffers);
3161
		get_cpu_var(bh_accounting).nr++;
L
Linus Torvalds 已提交
3162
		recalc_bh_state();
3163
		put_cpu_var(bh_accounting);
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	}
	return ret;
}
EXPORT_SYMBOL(alloc_buffer_head);

void free_buffer_head(struct buffer_head *bh)
{
	BUG_ON(!list_empty(&bh->b_assoc_buffers));
	kmem_cache_free(bh_cachep, bh);
3173
	get_cpu_var(bh_accounting).nr--;
L
Linus Torvalds 已提交
3174
	recalc_bh_state();
3175
	put_cpu_var(bh_accounting);
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3176 3177 3178 3179 3180 3181 3182 3183 3184 3185 3186 3187
}
EXPORT_SYMBOL(free_buffer_head);

static void buffer_exit_cpu(int cpu)
{
	int i;
	struct bh_lru *b = &per_cpu(bh_lrus, cpu);

	for (i = 0; i < BH_LRU_SIZE; i++) {
		brelse(b->bhs[i]);
		b->bhs[i] = NULL;
	}
3188 3189 3190
	get_cpu_var(bh_accounting).nr += per_cpu(bh_accounting, cpu).nr;
	per_cpu(bh_accounting, cpu).nr = 0;
	put_cpu_var(bh_accounting);
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Linus Torvalds 已提交
3191 3192 3193 3194 3195
}

static int buffer_cpu_notify(struct notifier_block *self,
			      unsigned long action, void *hcpu)
{
3196
	if (action == CPU_DEAD || action == CPU_DEAD_FROZEN)
L
Linus Torvalds 已提交
3197 3198 3199 3200
		buffer_exit_cpu((unsigned long)hcpu);
	return NOTIFY_OK;
}

3201 3202 3203 3204 3205 3206 3207 3208 3209 3210 3211 3212 3213 3214 3215 3216 3217 3218 3219 3220 3221 3222 3223 3224 3225 3226 3227 3228 3229 3230 3231 3232 3233 3234 3235 3236 3237 3238 3239 3240 3241 3242 3243 3244
/**
 * bh_uptodate_or_lock: Test whether the buffer is uptodate
 * @bh: struct buffer_head
 *
 * Return true if the buffer is up-to-date and false,
 * with the buffer locked, if not.
 */
int bh_uptodate_or_lock(struct buffer_head *bh)
{
	if (!buffer_uptodate(bh)) {
		lock_buffer(bh);
		if (!buffer_uptodate(bh))
			return 0;
		unlock_buffer(bh);
	}
	return 1;
}
EXPORT_SYMBOL(bh_uptodate_or_lock);

/**
 * bh_submit_read: Submit a locked buffer for reading
 * @bh: struct buffer_head
 *
 * Returns zero on success and -EIO on error.
 */
int bh_submit_read(struct buffer_head *bh)
{
	BUG_ON(!buffer_locked(bh));

	if (buffer_uptodate(bh)) {
		unlock_buffer(bh);
		return 0;
	}

	get_bh(bh);
	bh->b_end_io = end_buffer_read_sync;
	submit_bh(READ, bh);
	wait_on_buffer(bh);
	if (buffer_uptodate(bh))
		return 0;
	return -EIO;
}
EXPORT_SYMBOL(bh_submit_read);

3245 3246 3247 3248 3249 3250 3251 3252 3253
static void
init_buffer_head(struct kmem_cache *cachep, void *data)
{
	struct buffer_head *bh = data;

	memset(bh, 0, sizeof(*bh));
	INIT_LIST_HEAD(&bh->b_assoc_buffers);
}

L
Linus Torvalds 已提交
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void __init buffer_init(void)
{
	int nrpages;

3258 3259 3260 3261 3262
	bh_cachep = kmem_cache_create("buffer_head",
			sizeof(struct buffer_head), 0,
				(SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|
				SLAB_MEM_SPREAD),
				init_buffer_head);
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	/*
	 * Limit the bh occupancy to 10% of ZONE_NORMAL
	 */
	nrpages = (nr_free_buffer_pages() * 10) / 100;
	max_buffer_heads = nrpages * (PAGE_SIZE / sizeof(struct buffer_head));
	hotcpu_notifier(buffer_cpu_notify, 0);
}

EXPORT_SYMBOL(__bforget);
EXPORT_SYMBOL(__brelse);
EXPORT_SYMBOL(__wait_on_buffer);
EXPORT_SYMBOL(block_commit_write);
EXPORT_SYMBOL(block_prepare_write);
3277
EXPORT_SYMBOL(block_page_mkwrite);
L
Linus Torvalds 已提交
3278 3279 3280 3281
EXPORT_SYMBOL(block_read_full_page);
EXPORT_SYMBOL(block_sync_page);
EXPORT_SYMBOL(block_truncate_page);
EXPORT_SYMBOL(block_write_full_page);
N
Nick Piggin 已提交
3282
EXPORT_SYMBOL(cont_write_begin);
L
Linus Torvalds 已提交
3283 3284 3285 3286 3287 3288
EXPORT_SYMBOL(end_buffer_read_sync);
EXPORT_SYMBOL(end_buffer_write_sync);
EXPORT_SYMBOL(file_fsync);
EXPORT_SYMBOL(fsync_bdev);
EXPORT_SYMBOL(generic_block_bmap);
EXPORT_SYMBOL(generic_commit_write);
3289
EXPORT_SYMBOL(generic_cont_expand_simple);
L
Linus Torvalds 已提交
3290 3291 3292 3293 3294 3295 3296
EXPORT_SYMBOL(init_buffer);
EXPORT_SYMBOL(invalidate_bdev);
EXPORT_SYMBOL(ll_rw_block);
EXPORT_SYMBOL(mark_buffer_dirty);
EXPORT_SYMBOL(submit_bh);
EXPORT_SYMBOL(sync_dirty_buffer);
EXPORT_SYMBOL(unlock_buffer);