buffer.c 90.0 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>
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#include <linux/sched/signal.h>
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#include <linux/syscalls.h>
#include <linux/fs.h>
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#include <linux/iomap.h>
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#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>
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#include <linux/export.h>
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#include <linux/backing-dev.h>
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#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/cpu.h>
#include <linux/bitops.h>
#include <linux/mpage.h>
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#include <linux/bit_spinlock.h>
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#include <linux/pagevec.h>
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#include <linux/sched/mm.h>
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#include <trace/events/block.h>
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static int fsync_buffers_list(spinlock_t *lock, struct list_head *list);
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static int submit_bh_wbc(int op, int op_flags, struct buffer_head *bh,
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			 enum rw_hint hint, struct writeback_control *wbc);
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#define BH_ENTRY(list) list_entry((list), struct buffer_head, b_assoc_buffers)

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inline void touch_buffer(struct buffer_head *bh)
{
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	trace_block_touch_buffer(bh);
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	mark_page_accessed(bh->b_page);
}
EXPORT_SYMBOL(touch_buffer);

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

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void unlock_buffer(struct buffer_head *bh)
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{
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	clear_bit_unlock(BH_Lock, &bh->b_state);
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	smp_mb__after_atomic();
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	wake_up_bit(&bh->b_state, BH_Lock);
}
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EXPORT_SYMBOL(unlock_buffer);
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/*
 * Returns if the page has dirty or writeback buffers. If all the buffers
 * are unlocked and clean then the PageDirty information is stale. If
 * any of the pages are locked, it is assumed they are locked for IO.
 */
void buffer_check_dirty_writeback(struct page *page,
				     bool *dirty, bool *writeback)
{
	struct buffer_head *head, *bh;
	*dirty = false;
	*writeback = false;

	BUG_ON(!PageLocked(page));

	if (!page_has_buffers(page))
		return;

	if (PageWriteback(page))
		*writeback = true;

	head = page_buffers(page);
	bh = head;
	do {
		if (buffer_locked(bh))
			*writeback = true;

		if (buffer_dirty(bh))
			*dirty = true;

		bh = bh->b_this_page;
	} while (bh != head);
}
EXPORT_SYMBOL(buffer_check_dirty_writeback);

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/*
 * 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)
{
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	wait_on_bit_io(&bh->b_state, BH_Lock, TASK_UNINTERRUPTIBLE);
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}
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EXPORT_SYMBOL(__wait_on_buffer);
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static void
__clear_page_buffers(struct page *page)
{
	ClearPagePrivate(page);
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	set_page_private(page, 0);
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	put_page(page);
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}

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static void buffer_io_error(struct buffer_head *bh, char *msg)
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{
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	if (!test_bit(BH_Quiet, &bh->b_state))
		printk_ratelimited(KERN_ERR
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			"Buffer I/O error on dev %pg, logical block %llu%s\n",
			bh->b_bdev, (unsigned long long)bh->b_blocknr, msg);
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}

/*
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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 {
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		/* This happens, due to failed read-ahead attempts. */
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		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);
}
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EXPORT_SYMBOL(end_buffer_read_sync);
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void end_buffer_write_sync(struct buffer_head *bh, int uptodate)
{
	if (uptodate) {
		set_buffer_uptodate(bh);
	} else {
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		buffer_io_error(bh, ", lost sync page write");
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		mark_buffer_write_io_error(bh);
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		clear_buffer_uptodate(bh);
	}
	unlock_buffer(bh);
	put_bh(bh);
}
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EXPORT_SYMBOL(end_buffer_write_sync);
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/*
 * 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.
 *
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 * Hack idea: for the blockdev mapping, private_lock contention
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 * may be quite high.  This code could TryLock the page, and if that
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 * succeeds, there is no need to take private_lock.
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 */
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;
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	static DEFINE_RATELIMIT_STATE(last_warned, HZ, 1);
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	index = block >> (PAGE_SHIFT - bd_inode->i_blkbits);
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	page = find_get_page_flags(bd_mapping, index, FGP_ACCESSED);
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	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 {
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		if (!buffer_mapped(bh))
			all_mapped = 0;
		else if (bh->b_blocknr == block) {
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			ret = bh;
			get_bh(bh);
			goto out_unlock;
		}
		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
	 */
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	ratelimit_set_flags(&last_warned, RATELIMIT_MSG_ON_RELEASE);
	if (all_mapped && __ratelimit(&last_warned)) {
		printk("__find_get_block_slow() failed. block=%llu, "
		       "b_blocknr=%llu, b_state=0x%08lx, b_size=%zu, "
		       "device %pg blocksize: %d\n",
		       (unsigned long long)block,
		       (unsigned long long)bh->b_blocknr,
		       bh->b_state, bh->b_size, bdev,
		       1 << bd_inode->i_blkbits);
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	}
out_unlock:
	spin_unlock(&bd_mapping->private_lock);
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	put_page(page);
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out:
	return ret;
}

/*
 * 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);
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		buffer_io_error(bh, ", async page read");
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		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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void end_buffer_async_write(struct buffer_head *bh, int uptodate)
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{
	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 {
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		buffer_io_error(bh, ", lost async page write");
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		mark_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;
}
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EXPORT_SYMBOL(end_buffer_async_write);
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/*
 * 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);
}

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static void mark_buffer_async_write_endio(struct buffer_head *bh,
					  bh_end_io_t *handler)
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{
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	bh->b_end_io = handler;
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	set_buffer_async_write(bh);
}
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void mark_buffer_async_write(struct buffer_head *bh)
{
	mark_buffer_async_write_endio(bh, end_buffer_async_write);
}
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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
 */
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static void __remove_assoc_queue(struct buffer_head *bh)
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{
	list_del_init(&bh->b_assoc_buffers);
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	WARN_ON(!bh->b_assoc_map);
	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;
}

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void emergency_thaw_bdev(struct super_block *sb)
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{
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	while (sb->s_bdev && !thaw_bdev(sb->s_bdev, sb))
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		printk(KERN_WARNING "Emergency Thaw on %pg\n", sb->s_bdev);
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}
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/**
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 * sync_mapping_buffers - write out & wait upon a mapping's "associated" buffers
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 * @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.
 *
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 * 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)
{
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	struct address_space *buffer_mapping = mapping->private_data;
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	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))
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			ll_rw_block(REQ_OP_WRITE, 0, 1, &bh);
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		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);
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	if (!mapping->private_data) {
		mapping->private_data = buffer_mapping;
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	} else {
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		BUG_ON(mapping->private_data != buffer_mapping);
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	}
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	if (!bh->b_assoc_map) {
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		spin_lock(&buffer_mapping->private_lock);
		list_move_tail(&bh->b_assoc_buffers,
				&mapping->private_list);
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		bh->b_assoc_map = mapping;
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		spin_unlock(&buffer_mapping->private_lock);
	}
}
EXPORT_SYMBOL(mark_buffer_dirty_inode);

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/*
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 * Mark the page dirty, and set it dirty in the page cache, and mark the inode
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 * dirty.
 *
 * If warn is true, then emit a warning if the page is not uptodate and has
 * not been truncated.
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 *
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 * The caller must hold lock_page_memcg().
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 */
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void __set_page_dirty(struct page *page, struct address_space *mapping,
J
Johannes Weiner 已提交
575
			     int warn)
576
{
577 578
	unsigned long flags;

M
Matthew Wilcox 已提交
579
	xa_lock_irqsave(&mapping->i_pages, flags);
580 581
	if (page->mapping) {	/* Race with truncate? */
		WARN_ON_ONCE(warn && !PageUptodate(page));
J
Johannes Weiner 已提交
582
		account_page_dirtied(page, mapping);
M
Matthew Wilcox 已提交
583 584
		__xa_set_mark(&mapping->i_pages, page_index(page),
				PAGECACHE_TAG_DIRTY);
585
	}
M
Matthew Wilcox 已提交
586
	xa_unlock_irqrestore(&mapping->i_pages, flags);
587
}
M
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588
EXPORT_SYMBOL_GPL(__set_page_dirty);
589

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590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616
/*
 * 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)
{
617
	int newly_dirty;
618
	struct address_space *mapping = page_mapping(page);
619 620 621

	if (unlikely(!mapping))
		return !TestSetPageDirty(page);
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Linus Torvalds 已提交
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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);
	}
633
	/*
634 635
	 * Lock out page->mem_cgroup migration to keep PageDirty
	 * synchronized with per-memcg dirty page counters.
636
	 */
J
Johannes Weiner 已提交
637
	lock_page_memcg(page);
638
	newly_dirty = !TestSetPageDirty(page);
L
Linus Torvalds 已提交
639 640
	spin_unlock(&mapping->private_lock);

641
	if (newly_dirty)
J
Johannes Weiner 已提交
642
		__set_page_dirty(page, mapping, 1);
643

J
Johannes Weiner 已提交
644
	unlock_page_memcg(page);
645 646 647 648

	if (newly_dirty)
		__mark_inode_dirty(mapping->host, I_DIRTY_PAGES);

649
	return newly_dirty;
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650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675
}
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;
J
Jens Axboe 已提交
676
	struct address_space *mapping;
L
Linus Torvalds 已提交
677
	int err = 0, err2;
J
Jens Axboe 已提交
678
	struct blk_plug plug;
L
Linus Torvalds 已提交
679 680

	INIT_LIST_HEAD(&tmp);
J
Jens Axboe 已提交
681
	blk_start_plug(&plug);
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682 683 684 685

	spin_lock(lock);
	while (!list_empty(list)) {
		bh = BH_ENTRY(list->next);
686
		mapping = bh->b_assoc_map;
687
		__remove_assoc_queue(bh);
688 689 690
		/* Avoid race with mark_buffer_dirty_inode() which does
		 * a lockless check and we rely on seeing the dirty bit */
		smp_mb();
L
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		if (buffer_dirty(bh) || buffer_locked(bh)) {
			list_add(&bh->b_assoc_buffers, &tmp);
693
			bh->b_assoc_map = mapping;
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			if (buffer_dirty(bh)) {
				get_bh(bh);
				spin_unlock(lock);
				/*
				 * Ensure any pending I/O completes so that
C
Christoph Hellwig 已提交
699 700 701 702
				 * write_dirty_buffer() actually writes the
				 * current contents - it is a noop if I/O is
				 * still in flight on potentially older
				 * contents.
L
Linus Torvalds 已提交
703
				 */
704
				write_dirty_buffer(bh, REQ_SYNC);
705 706 707 708 709 710 711

				/*
				 * Kick off IO for the previous mapping. Note
				 * that we will not run the very last mapping,
				 * wait_on_buffer() will do that for us
				 * through sync_buffer().
				 */
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				brelse(bh);
				spin_lock(lock);
			}
		}
	}

J
Jens Axboe 已提交
718 719 720 721
	spin_unlock(lock);
	blk_finish_plug(&plug);
	spin_lock(lock);

L
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722 723 724
	while (!list_empty(&tmp)) {
		bh = BH_ENTRY(tmp.prev);
		get_bh(bh);
725 726 727 728 729 730 731
		mapping = bh->b_assoc_map;
		__remove_assoc_queue(bh);
		/* Avoid race with mark_buffer_dirty_inode() which does
		 * a lockless check and we rely on seeing the dirty bit */
		smp_mb();
		if (buffer_dirty(bh)) {
			list_add(&bh->b_assoc_buffers,
732
				 &mapping->private_list);
733 734
			bh->b_assoc_map = mapping;
		}
L
Linus Torvalds 已提交
735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764
		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;
765
		struct address_space *buffer_mapping = mapping->private_data;
L
Linus Torvalds 已提交
766 767 768 769 770 771 772

		spin_lock(&buffer_mapping->private_lock);
		while (!list_empty(list))
			__remove_assoc_queue(BH_ENTRY(list->next));
		spin_unlock(&buffer_mapping->private_lock);
	}
}
J
Jan Kara 已提交
773
EXPORT_SYMBOL(invalidate_inode_buffers);
L
Linus Torvalds 已提交
774 775 776 777 778 779 780 781 782 783 784 785 786 787

/*
 * 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;
788
		struct address_space *buffer_mapping = mapping->private_data;
L
Linus Torvalds 已提交
789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813

		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,
814
		bool retry)
L
Linus Torvalds 已提交
815 816
{
	struct buffer_head *bh, *head;
817
	gfp_t gfp = GFP_NOFS | __GFP_ACCOUNT;
L
Linus Torvalds 已提交
818
	long offset;
819
	struct mem_cgroup *memcg;
L
Linus Torvalds 已提交
820

821 822 823
	if (retry)
		gfp |= __GFP_NOFAIL;

824 825 826
	memcg = get_mem_cgroup_from_page(page);
	memalloc_use_memcg(memcg);

L
Linus Torvalds 已提交
827 828 829
	head = NULL;
	offset = PAGE_SIZE;
	while ((offset -= size) >= 0) {
830
		bh = alloc_buffer_head(gfp);
L
Linus Torvalds 已提交
831 832 833 834 835 836 837 838 839 840 841 842
		if (!bh)
			goto no_grow;

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

		bh->b_size = size;

		/* Link the buffer to its page */
		set_bh_page(bh, page, offset);
	}
843 844 845
out:
	memalloc_unuse_memcg();
	mem_cgroup_put(memcg);
L
Linus Torvalds 已提交
846 847 848 849 850 851 852 853 854 855 856 857 858
	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);
	}

859
	goto out;
L
Linus Torvalds 已提交
860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876
}
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);
}

877 878 879 880 881 882 883 884 885 886 887 888
static sector_t blkdev_max_block(struct block_device *bdev, unsigned int size)
{
	sector_t retval = ~((sector_t)0);
	loff_t sz = i_size_read(bdev->bd_inode);

	if (sz) {
		unsigned int sizebits = blksize_bits(size);
		retval = (sz >> sizebits);
	}
	return retval;
}

L
Linus Torvalds 已提交
889 890 891
/*
 * Initialise the state of a blockdev page's buffers.
 */ 
892
static sector_t
L
Linus Torvalds 已提交
893 894 895 896 897 898
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);
899
	sector_t end_block = blkdev_max_block(I_BDEV(bdev->bd_inode), size);
L
Linus Torvalds 已提交
900 901 902

	do {
		if (!buffer_mapped(bh)) {
903 904
			bh->b_end_io = NULL;
			bh->b_private = NULL;
L
Linus Torvalds 已提交
905 906 907 908
			bh->b_bdev = bdev;
			bh->b_blocknr = block;
			if (uptodate)
				set_buffer_uptodate(bh);
909 910
			if (block < end_block)
				set_buffer_mapped(bh);
L
Linus Torvalds 已提交
911 912 913 914
		}
		block++;
		bh = bh->b_this_page;
	} while (bh != head);
915 916 917 918 919

	/*
	 * Caller needs to validate requested block against end of device.
	 */
	return end_block;
L
Linus Torvalds 已提交
920 921 922 923 924
}

/*
 * Create the page-cache page that contains the requested block.
 *
925
 * This is used purely for blockdev mappings.
L
Linus Torvalds 已提交
926
 */
927
static int
L
Linus Torvalds 已提交
928
grow_dev_page(struct block_device *bdev, sector_t block,
929
	      pgoff_t index, int size, int sizebits, gfp_t gfp)
L
Linus Torvalds 已提交
930 931 932 933
{
	struct inode *inode = bdev->bd_inode;
	struct page *page;
	struct buffer_head *bh;
934 935
	sector_t end_block;
	int ret = 0;		/* Will call free_more_memory() */
936
	gfp_t gfp_mask;
L
Linus Torvalds 已提交
937

938
	gfp_mask = mapping_gfp_constraint(inode->i_mapping, ~__GFP_FS) | gfp;
939

940 941 942 943 944 945 946 947 948
	/*
	 * XXX: __getblk_slow() can not really deal with failure and
	 * will endlessly loop on improvised global reclaim.  Prefer
	 * looping in the allocator rather than here, at least that
	 * code knows what it's doing.
	 */
	gfp_mask |= __GFP_NOFAIL;

	page = find_or_create_page(inode->i_mapping, index, gfp_mask);
L
Linus Torvalds 已提交
949

950
	BUG_ON(!PageLocked(page));
L
Linus Torvalds 已提交
951 952 953 954

	if (page_has_buffers(page)) {
		bh = page_buffers(page);
		if (bh->b_size == size) {
955
			end_block = init_page_buffers(page, bdev,
956 957
						(sector_t)index << sizebits,
						size);
958
			goto done;
L
Linus Torvalds 已提交
959 960 961 962 963 964 965 966
		}
		if (!try_to_free_buffers(page))
			goto failed;
	}

	/*
	 * Allocate some buffers for this page
	 */
967
	bh = alloc_page_buffers(page, size, true);
L
Linus Torvalds 已提交
968 969 970 971 972 973 974 975

	/*
	 * 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);
976 977
	end_block = init_page_buffers(page, bdev, (sector_t)index << sizebits,
			size);
L
Linus Torvalds 已提交
978
	spin_unlock(&inode->i_mapping->private_lock);
979 980
done:
	ret = (block < end_block) ? 1 : -ENXIO;
L
Linus Torvalds 已提交
981 982
failed:
	unlock_page(page);
983
	put_page(page);
984
	return ret;
L
Linus Torvalds 已提交
985 986 987 988 989 990
}

/*
 * Create buffers for the specified block device block's page.  If
 * that page was dirty, the buffers are set dirty also.
 */
991
static int
992
grow_buffers(struct block_device *bdev, sector_t block, int size, gfp_t gfp)
L
Linus Torvalds 已提交
993 994 995 996 997 998 999 1000 1001 1002 1003
{
	pgoff_t index;
	int sizebits;

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

	index = block >> sizebits;

1004 1005 1006 1007 1008 1009
	/*
	 * 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)) {
		printk(KERN_ERR "%s: requested out-of-range block %llu for "
1010
			"device %pg\n",
1011
			__func__, (unsigned long long)block,
1012
			bdev);
1013 1014
		return -EIO;
	}
1015

L
Linus Torvalds 已提交
1016
	/* Create a page with the proper size buffers.. */
1017
	return grow_dev_page(bdev, block, index, size, sizebits, gfp);
L
Linus Torvalds 已提交
1018 1019
}

1020
static struct buffer_head *
1021 1022
__getblk_slow(struct block_device *bdev, sector_t block,
	     unsigned size, gfp_t gfp)
L
Linus Torvalds 已提交
1023 1024
{
	/* Size must be multiple of hard sectorsize */
1025
	if (unlikely(size & (bdev_logical_block_size(bdev)-1) ||
L
Linus Torvalds 已提交
1026 1027 1028
			(size < 512 || size > PAGE_SIZE))) {
		printk(KERN_ERR "getblk(): invalid block size %d requested\n",
					size);
1029 1030
		printk(KERN_ERR "logical block size: %d\n",
					bdev_logical_block_size(bdev));
L
Linus Torvalds 已提交
1031 1032 1033 1034 1035

		dump_stack();
		return NULL;
	}

1036 1037 1038
	for (;;) {
		struct buffer_head *bh;
		int ret;
L
Linus Torvalds 已提交
1039 1040 1041 1042

		bh = __find_get_block(bdev, block, size);
		if (bh)
			return bh;
1043

1044
		ret = grow_buffers(bdev, block, size, gfp);
1045 1046
		if (ret < 0)
			return NULL;
L
Linus Torvalds 已提交
1047 1048 1049 1050 1051 1052 1053
	}
}

/*
 * The relationship between dirty buffers and dirty pages:
 *
 * Whenever a page has any dirty buffers, the page's dirty bit is set, and
M
Matthew Wilcox 已提交
1054
 * the page is tagged dirty in the page cache.
L
Linus Torvalds 已提交
1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074
 *
 * 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
1075
 * @bh: the buffer_head to mark dirty
L
Linus Torvalds 已提交
1076
 *
M
Matthew Wilcox 已提交
1077 1078 1079
 * mark_buffer_dirty() will set the dirty bit against the buffer, then set
 * its backing page dirty, then tag the page as dirty in the page cache
 * and then attach the address_space's inode to its superblock's dirty
L
Linus Torvalds 已提交
1080 1081 1082
 * inode list.
 *
 * mark_buffer_dirty() is atomic.  It takes bh->b_page->mapping->private_lock,
M
Matthew Wilcox 已提交
1083
 * i_pages lock and mapping->host->i_lock.
L
Linus Torvalds 已提交
1084
 */
1085
void mark_buffer_dirty(struct buffer_head *bh)
L
Linus Torvalds 已提交
1086
{
1087
	WARN_ON_ONCE(!buffer_uptodate(bh));
1088

1089 1090
	trace_block_dirty_buffer(bh);

1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102
	/*
	 * Very *carefully* optimize the it-is-already-dirty case.
	 *
	 * Don't let the final "is it dirty" escape to before we
	 * perhaps modified the buffer.
	 */
	if (buffer_dirty(bh)) {
		smp_mb();
		if (buffer_dirty(bh))
			return;
	}

1103 1104
	if (!test_set_buffer_dirty(bh)) {
		struct page *page = bh->b_page;
1105 1106
		struct address_space *mapping = NULL;

J
Johannes Weiner 已提交
1107
		lock_page_memcg(page);
1108
		if (!TestSetPageDirty(page)) {
1109
			mapping = page_mapping(page);
1110
			if (mapping)
J
Johannes Weiner 已提交
1111
				__set_page_dirty(page, mapping, 0);
1112
		}
J
Johannes Weiner 已提交
1113
		unlock_page_memcg(page);
1114 1115
		if (mapping)
			__mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
1116
	}
L
Linus Torvalds 已提交
1117
}
1118
EXPORT_SYMBOL(mark_buffer_dirty);
L
Linus Torvalds 已提交
1119

1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130
void mark_buffer_write_io_error(struct buffer_head *bh)
{
	set_buffer_write_io_error(bh);
	/* FIXME: do we need to set this in both places? */
	if (bh->b_page && bh->b_page->mapping)
		mapping_set_error(bh->b_page->mapping, -EIO);
	if (bh->b_assoc_map)
		mapping_set_error(bh->b_assoc_map, -EIO);
}
EXPORT_SYMBOL(mark_buffer_write_io_error);

L
Linus Torvalds 已提交
1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143
/*
 * 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;
	}
A
Arjan van de Ven 已提交
1144
	WARN(1, KERN_ERR "VFS: brelse: Trying to free free buffer\n");
L
Linus Torvalds 已提交
1145
}
1146
EXPORT_SYMBOL(__brelse);
L
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1147 1148 1149 1150 1151 1152 1153 1154

/*
 * bforget() is like brelse(), except it discards any
 * potentially dirty data.
 */
void __bforget(struct buffer_head *bh)
{
	clear_buffer_dirty(bh);
1155
	if (bh->b_assoc_map) {
L
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1156 1157 1158 1159
		struct address_space *buffer_mapping = bh->b_page->mapping;

		spin_lock(&buffer_mapping->private_lock);
		list_del_init(&bh->b_assoc_buffers);
1160
		bh->b_assoc_map = NULL;
L
Linus Torvalds 已提交
1161 1162 1163 1164
		spin_unlock(&buffer_mapping->private_lock);
	}
	__brelse(bh);
}
1165
EXPORT_SYMBOL(__bforget);
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1166 1167 1168 1169 1170 1171 1172 1173 1174 1175

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;
1176
		submit_bh(REQ_OP_READ, 0, bh);
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		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.
 */

1199
#define BH_LRU_SIZE	16
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1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221 1222

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
}

/*
1223 1224 1225
 * Install a buffer_head into this cpu's LRU.  If not already in the LRU, it is
 * inserted at the front, and the buffer_head at the back if any is evicted.
 * Or, if already in the LRU it is moved to the front.
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1226 1227 1228
 */
static void bh_lru_install(struct buffer_head *bh)
{
1229 1230 1231
	struct buffer_head *evictee = bh;
	struct bh_lru *b;
	int i;
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1232 1233 1234 1235

	check_irqs_on();
	bh_lru_lock();

1236 1237 1238 1239 1240 1241
	b = this_cpu_ptr(&bh_lrus);
	for (i = 0; i < BH_LRU_SIZE; i++) {
		swap(evictee, b->bhs[i]);
		if (evictee == bh) {
			bh_lru_unlock();
			return;
L
Linus Torvalds 已提交
1242 1243 1244
		}
	}

1245 1246 1247
	get_bh(bh);
	bh_lru_unlock();
	brelse(evictee);
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1248 1249 1250 1251 1252
}

/*
 * Look up the bh in this cpu's LRU.  If it's there, move it to the head.
 */
1253
static struct buffer_head *
1254
lookup_bh_lru(struct block_device *bdev, sector_t block, unsigned size)
L
Linus Torvalds 已提交
1255 1256
{
	struct buffer_head *ret = NULL;
1257
	unsigned int i;
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1258 1259 1260 1261

	check_irqs_on();
	bh_lru_lock();
	for (i = 0; i < BH_LRU_SIZE; i++) {
1262
		struct buffer_head *bh = __this_cpu_read(bh_lrus.bhs[i]);
L
Linus Torvalds 已提交
1263

1264 1265
		if (bh && bh->b_blocknr == block && bh->b_bdev == bdev &&
		    bh->b_size == size) {
L
Linus Torvalds 已提交
1266 1267
			if (i) {
				while (i) {
1268 1269
					__this_cpu_write(bh_lrus.bhs[i],
						__this_cpu_read(bh_lrus.bhs[i - 1]));
L
Linus Torvalds 已提交
1270 1271
					i--;
				}
1272
				__this_cpu_write(bh_lrus.bhs[0], bh);
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1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288
			}
			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 *
1289
__find_get_block(struct block_device *bdev, sector_t block, unsigned size)
L
Linus Torvalds 已提交
1290 1291 1292 1293
{
	struct buffer_head *bh = lookup_bh_lru(bdev, block, size);

	if (bh == NULL) {
1294
		/* __find_get_block_slow will mark the page accessed */
1295
		bh = __find_get_block_slow(bdev, block);
L
Linus Torvalds 已提交
1296 1297
		if (bh)
			bh_lru_install(bh);
1298
	} else
L
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1299
		touch_buffer(bh);
1300

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1301 1302 1303 1304 1305
	return bh;
}
EXPORT_SYMBOL(__find_get_block);

/*
1306
 * __getblk_gfp() will locate (and, if necessary, create) the buffer_head
L
Linus Torvalds 已提交
1307 1308 1309
 * which corresponds to the passed block_device, block and size. The
 * returned buffer has its reference count incremented.
 *
1310 1311
 * __getblk_gfp() will lock up the machine if grow_dev_page's
 * try_to_free_buffers() attempt is failing.  FIXME, perhaps?
L
Linus Torvalds 已提交
1312 1313
 */
struct buffer_head *
1314 1315
__getblk_gfp(struct block_device *bdev, sector_t block,
	     unsigned size, gfp_t gfp)
L
Linus Torvalds 已提交
1316 1317 1318 1319 1320
{
	struct buffer_head *bh = __find_get_block(bdev, block, size);

	might_sleep();
	if (bh == NULL)
1321
		bh = __getblk_slow(bdev, block, size, gfp);
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1322 1323
	return bh;
}
1324
EXPORT_SYMBOL(__getblk_gfp);
L
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1325 1326 1327 1328

/*
 * Do async read-ahead on a buffer..
 */
1329
void __breadahead(struct block_device *bdev, sector_t block, unsigned size)
L
Linus Torvalds 已提交
1330 1331
{
	struct buffer_head *bh = __getblk(bdev, block, size);
A
Andrew Morton 已提交
1332
	if (likely(bh)) {
1333
		ll_rw_block(REQ_OP_READ, REQ_RAHEAD, 1, &bh);
A
Andrew Morton 已提交
1334 1335
		brelse(bh);
	}
L
Linus Torvalds 已提交
1336 1337 1338 1339
}
EXPORT_SYMBOL(__breadahead);

/**
1340
 *  __bread_gfp() - reads a specified block and returns the bh
1341
 *  @bdev: the block_device to read from
L
Linus Torvalds 已提交
1342 1343
 *  @block: number of block
 *  @size: size (in bytes) to read
1344 1345
 *  @gfp: page allocation flag
 *
L
Linus Torvalds 已提交
1346
 *  Reads a specified block, and returns buffer head that contains it.
1347 1348
 *  The page cache can be allocated from non-movable area
 *  not to prevent page migration if you set gfp to zero.
L
Linus Torvalds 已提交
1349 1350 1351
 *  It returns NULL if the block was unreadable.
 */
struct buffer_head *
1352 1353
__bread_gfp(struct block_device *bdev, sector_t block,
		   unsigned size, gfp_t gfp)
L
Linus Torvalds 已提交
1354
{
1355
	struct buffer_head *bh = __getblk_gfp(bdev, block, size, gfp);
L
Linus Torvalds 已提交
1356

A
Andrew Morton 已提交
1357
	if (likely(bh) && !buffer_uptodate(bh))
L
Linus Torvalds 已提交
1358 1359 1360
		bh = __bread_slow(bh);
	return bh;
}
1361
EXPORT_SYMBOL(__bread_gfp);
L
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1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378

/*
 * 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);
}
1379 1380 1381 1382 1383

static bool has_bh_in_lru(int cpu, void *dummy)
{
	struct bh_lru *b = per_cpu_ptr(&bh_lrus, cpu);
	int i;
L
Linus Torvalds 已提交
1384
	
1385 1386 1387 1388 1389 1390 1391 1392
	for (i = 0; i < BH_LRU_SIZE; i++) {
		if (b->bhs[i])
			return 1;
	}

	return 0;
}

P
Peter Zijlstra 已提交
1393
void invalidate_bh_lrus(void)
L
Linus Torvalds 已提交
1394
{
1395
	on_each_cpu_cond(has_bh_in_lru, invalidate_bh_lru, NULL, 1, GFP_KERNEL);
L
Linus Torvalds 已提交
1396
}
N
Nick Piggin 已提交
1397
EXPORT_SYMBOL_GPL(invalidate_bh_lrus);
L
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1398 1399 1400 1401 1402

void set_bh_page(struct buffer_head *bh,
		struct page *page, unsigned long offset)
{
	bh->b_page = page;
1403
	BUG_ON(offset >= PAGE_SIZE);
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Linus Torvalds 已提交
1404 1405 1406 1407 1408 1409 1410 1411 1412 1413 1414 1415 1416
	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.
 */
1417 1418 1419 1420 1421 1422

/* Bits that are cleared during an invalidate */
#define BUFFER_FLAGS_DISCARD \
	(1 << BH_Mapped | 1 << BH_New | 1 << BH_Req | \
	 1 << BH_Delay | 1 << BH_Unwritten)

1423
static void discard_buffer(struct buffer_head * bh)
L
Linus Torvalds 已提交
1424
{
1425 1426
	unsigned long b_state, b_state_old;

L
Linus Torvalds 已提交
1427 1428 1429
	lock_buffer(bh);
	clear_buffer_dirty(bh);
	bh->b_bdev = NULL;
1430 1431 1432 1433 1434 1435 1436 1437
	b_state = bh->b_state;
	for (;;) {
		b_state_old = cmpxchg(&bh->b_state, b_state,
				      (b_state & ~BUFFER_FLAGS_DISCARD));
		if (b_state_old == b_state)
			break;
		b_state = b_state_old;
	}
L
Linus Torvalds 已提交
1438 1439 1440 1441
	unlock_buffer(bh);
}

/**
1442
 * block_invalidatepage - invalidate part or all of a buffer-backed page
L
Linus Torvalds 已提交
1443 1444
 *
 * @page: the page which is affected
1445 1446
 * @offset: start of the range to invalidate
 * @length: length of the range to invalidate
L
Linus Torvalds 已提交
1447 1448
 *
 * block_invalidatepage() is called when all or part of the page has become
1449
 * invalidated by a truncate operation.
L
Linus Torvalds 已提交
1450 1451 1452 1453 1454 1455 1456
 *
 * 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.
 */
1457 1458
void block_invalidatepage(struct page *page, unsigned int offset,
			  unsigned int length)
L
Linus Torvalds 已提交
1459 1460 1461
{
	struct buffer_head *head, *bh, *next;
	unsigned int curr_off = 0;
1462
	unsigned int stop = length + offset;
L
Linus Torvalds 已提交
1463 1464 1465 1466 1467

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

1468 1469 1470
	/*
	 * Check for overflow
	 */
1471
	BUG_ON(stop > PAGE_SIZE || stop < length);
1472

L
Linus Torvalds 已提交
1473 1474 1475 1476 1477 1478
	head = page_buffers(page);
	bh = head;
	do {
		unsigned int next_off = curr_off + bh->b_size;
		next = bh->b_this_page;

1479 1480 1481 1482 1483 1484
		/*
		 * Are we still fully in range ?
		 */
		if (next_off > stop)
			goto out;

L
Linus Torvalds 已提交
1485 1486 1487 1488 1489 1490 1491 1492 1493 1494 1495 1496 1497 1498
		/*
		 * 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.
	 */
1499
	if (length == PAGE_SIZE)
1500
		try_to_release_page(page, 0);
L
Linus Torvalds 已提交
1501
out:
1502
	return;
L
Linus Torvalds 已提交
1503 1504 1505
}
EXPORT_SYMBOL(block_invalidatepage);

1506

L
Linus Torvalds 已提交
1507 1508 1509 1510 1511 1512 1513 1514 1515 1516
/*
 * 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;

1517
	head = alloc_page_buffers(page, blocksize, true);
L
Linus Torvalds 已提交
1518 1519 1520 1521 1522 1523 1524 1525 1526 1527 1528 1529 1530 1531 1532 1533 1534 1535 1536 1537 1538 1539 1540 1541
	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);

1542 1543 1544 1545 1546
/**
 * clean_bdev_aliases: clean a range of buffers in block device
 * @bdev: Block device to clean buffers in
 * @block: Start of a range of blocks to clean
 * @len: Number of blocks to clean
L
Linus Torvalds 已提交
1547
 *
1548 1549 1550 1551 1552 1553 1554 1555 1556 1557 1558 1559 1560
 * We are taking a range of blocks for data and we don't want writeback of any
 * buffer-cache aliases starting from return from this 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 use 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.
L
Linus Torvalds 已提交
1561
 */
1562
void clean_bdev_aliases(struct block_device *bdev, sector_t block, sector_t len)
L
Linus Torvalds 已提交
1563
{
1564 1565 1566 1567 1568
	struct inode *bd_inode = bdev->bd_inode;
	struct address_space *bd_mapping = bd_inode->i_mapping;
	struct pagevec pvec;
	pgoff_t index = block >> (PAGE_SHIFT - bd_inode->i_blkbits);
	pgoff_t end;
1569
	int i, count;
1570 1571
	struct buffer_head *bh;
	struct buffer_head *head;
L
Linus Torvalds 已提交
1572

1573
	end = (block + len - 1) >> (PAGE_SHIFT - bd_inode->i_blkbits);
1574
	pagevec_init(&pvec);
1575
	while (pagevec_lookup_range(&pvec, bd_mapping, &index, end)) {
1576 1577
		count = pagevec_count(&pvec);
		for (i = 0; i < count; i++) {
1578
			struct page *page = pvec.pages[i];
L
Linus Torvalds 已提交
1579

1580 1581 1582 1583 1584 1585 1586 1587 1588 1589 1590 1591 1592 1593
			if (!page_has_buffers(page))
				continue;
			/*
			 * We use page lock instead of bd_mapping->private_lock
			 * to pin buffers here since we can afford to sleep and
			 * it scales better than a global spinlock lock.
			 */
			lock_page(page);
			/* Recheck when the page is locked which pins bhs */
			if (!page_has_buffers(page))
				goto unlock_page;
			head = page_buffers(page);
			bh = head;
			do {
1594
				if (!buffer_mapped(bh) || (bh->b_blocknr < block))
1595 1596 1597 1598 1599 1600 1601 1602 1603 1604 1605 1606 1607 1608
					goto next;
				if (bh->b_blocknr >= block + len)
					break;
				clear_buffer_dirty(bh);
				wait_on_buffer(bh);
				clear_buffer_req(bh);
next:
				bh = bh->b_this_page;
			} while (bh != head);
unlock_page:
			unlock_page(page);
		}
		pagevec_release(&pvec);
		cond_resched();
1609 1610 1611
		/* End of range already reached? */
		if (index > end || !index)
			break;
L
Linus Torvalds 已提交
1612 1613
	}
}
1614
EXPORT_SYMBOL(clean_bdev_aliases);
L
Linus Torvalds 已提交
1615

1616 1617 1618 1619 1620 1621 1622 1623 1624 1625 1626 1627 1628 1629 1630 1631 1632 1633
/*
 * Size is a power-of-two in the range 512..PAGE_SIZE,
 * and the case we care about most is PAGE_SIZE.
 *
 * So this *could* possibly be written with those
 * constraints in mind (relevant mostly if some
 * architecture has a slow bit-scan instruction)
 */
static inline int block_size_bits(unsigned int blocksize)
{
	return ilog2(blocksize);
}

static struct buffer_head *create_page_buffers(struct page *page, struct inode *inode, unsigned int b_state)
{
	BUG_ON(!PageLocked(page));

	if (!page_has_buffers(page))
1634 1635
		create_empty_buffers(page, 1 << READ_ONCE(inode->i_blkbits),
				     b_state);
1636 1637 1638
	return page_buffers(page);
}

L
Linus Torvalds 已提交
1639 1640 1641 1642 1643 1644 1645 1646 1647 1648 1649 1650 1651 1652 1653 1654 1655 1656 1657 1658 1659 1660 1661 1662
/*
 * 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.
1663 1664
 *
 * If block_write_full_page() is called with wbc->sync_mode ==
1665
 * WB_SYNC_ALL, the writes are posted using REQ_SYNC; this
J
Jens Axboe 已提交
1666
 * causes the writes to be flagged as synchronous writes.
L
Linus Torvalds 已提交
1667
 */
1668
int __block_write_full_page(struct inode *inode, struct page *page,
1669 1670
			get_block_t *get_block, struct writeback_control *wbc,
			bh_end_io_t *handler)
L
Linus Torvalds 已提交
1671 1672 1673 1674
{
	int err;
	sector_t block;
	sector_t last_block;
1675
	struct buffer_head *bh, *head;
1676
	unsigned int blocksize, bbits;
L
Linus Torvalds 已提交
1677
	int nr_underway = 0;
J
Jens Axboe 已提交
1678
	int write_flags = wbc_to_write_flags(wbc);
L
Linus Torvalds 已提交
1679

1680
	head = create_page_buffers(page, inode,
L
Linus Torvalds 已提交
1681 1682 1683 1684 1685 1686 1687 1688 1689 1690 1691 1692 1693
					(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.
	 */

	bh = head;
1694 1695 1696
	blocksize = bh->b_size;
	bbits = block_size_bits(blocksize);

1697
	block = (sector_t)page->index << (PAGE_SHIFT - bbits);
1698
	last_block = (i_size_read(inode) - 1) >> bbits;
L
Linus Torvalds 已提交
1699 1700 1701 1702 1703 1704 1705 1706 1707 1708 1709 1710 1711 1712 1713 1714 1715

	/*
	 * 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);
1716 1717
		} else if ((!buffer_mapped(bh) || buffer_delay(bh)) &&
			   buffer_dirty(bh)) {
1718
			WARN_ON(bh->b_size != blocksize);
L
Linus Torvalds 已提交
1719 1720 1721
			err = get_block(inode, block, bh, 1);
			if (err)
				goto recover;
1722
			clear_buffer_delay(bh);
L
Linus Torvalds 已提交
1723 1724 1725
			if (buffer_new(bh)) {
				/* blockdev mappings never come here */
				clear_buffer_new(bh);
1726
				clean_bdev_bh_alias(bh);
L
Linus Torvalds 已提交
1727 1728 1729 1730 1731 1732 1733 1734 1735 1736 1737 1738
			}
		}
		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
1739 1740 1741
		 * potentially cause a busy-wait loop from writeback threads
		 * and kswapd activity, but those code paths have their own
		 * higher-level throttling.
L
Linus Torvalds 已提交
1742
		 */
1743
		if (wbc->sync_mode != WB_SYNC_NONE) {
L
Linus Torvalds 已提交
1744
			lock_buffer(bh);
N
Nick Piggin 已提交
1745
		} else if (!trylock_buffer(bh)) {
L
Linus Torvalds 已提交
1746 1747 1748 1749
			redirty_page_for_writepage(wbc, page);
			continue;
		}
		if (test_clear_buffer_dirty(bh)) {
1750
			mark_buffer_async_write_endio(bh, handler);
L
Linus Torvalds 已提交
1751 1752 1753 1754 1755 1756 1757 1758 1759 1760 1761 1762 1763 1764 1765
		} 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)) {
1766 1767
			submit_bh_wbc(REQ_OP_WRITE, write_flags, bh,
					inode->i_write_hint, wbc);
L
Linus Torvalds 已提交
1768 1769 1770 1771
			nr_underway++;
		}
		bh = next;
	} while (bh != head);
1772
	unlock_page(page);
L
Linus Torvalds 已提交
1773 1774 1775 1776 1777 1778 1779 1780 1781 1782

	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);
1783

L
Linus Torvalds 已提交
1784 1785 1786 1787 1788 1789 1790 1791 1792 1793 1794 1795 1796 1797 1798 1799 1800
		/*
		 * 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 {
1801 1802
		if (buffer_mapped(bh) && buffer_dirty(bh) &&
		    !buffer_delay(bh)) {
L
Linus Torvalds 已提交
1803
			lock_buffer(bh);
1804
			mark_buffer_async_write_endio(bh, handler);
L
Linus Torvalds 已提交
1805 1806 1807 1808 1809 1810 1811 1812 1813 1814
		} 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));
1815
	mapping_set_error(page->mapping, err);
L
Linus Torvalds 已提交
1816 1817 1818 1819 1820
	set_page_writeback(page);
	do {
		struct buffer_head *next = bh->b_this_page;
		if (buffer_async_write(bh)) {
			clear_buffer_dirty(bh);
1821 1822
			submit_bh_wbc(REQ_OP_WRITE, write_flags, bh,
					inode->i_write_hint, wbc);
L
Linus Torvalds 已提交
1823 1824 1825 1826
			nr_underway++;
		}
		bh = next;
	} while (bh != head);
1827
	unlock_page(page);
L
Linus Torvalds 已提交
1828 1829
	goto done;
}
1830
EXPORT_SYMBOL(__block_write_full_page);
L
Linus Torvalds 已提交
1831

1832 1833 1834 1835 1836 1837 1838 1839 1840 1841 1842 1843 1844 1845 1846 1847 1848 1849 1850 1851 1852 1853 1854 1855 1856 1857 1858
/*
 * 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;

1859
					zero_user(page, start, size);
1860 1861 1862 1863 1864 1865 1866 1867 1868 1869 1870 1871 1872 1873
					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);

1874 1875 1876 1877 1878 1879 1880 1881 1882 1883 1884 1885 1886 1887 1888 1889 1890 1891 1892 1893 1894 1895 1896 1897 1898 1899 1900 1901 1902 1903 1904 1905 1906 1907 1908 1909 1910
static void
iomap_to_bh(struct inode *inode, sector_t block, struct buffer_head *bh,
		struct iomap *iomap)
{
	loff_t offset = block << inode->i_blkbits;

	bh->b_bdev = iomap->bdev;

	/*
	 * Block points to offset in file we need to map, iomap contains
	 * the offset at which the map starts. If the map ends before the
	 * current block, then do not map the buffer and let the caller
	 * handle it.
	 */
	BUG_ON(offset >= iomap->offset + iomap->length);

	switch (iomap->type) {
	case IOMAP_HOLE:
		/*
		 * If the buffer is not up to date or beyond the current EOF,
		 * we need to mark it as new to ensure sub-block zeroing is
		 * executed if necessary.
		 */
		if (!buffer_uptodate(bh) ||
		    (offset >= i_size_read(inode)))
			set_buffer_new(bh);
		break;
	case IOMAP_DELALLOC:
		if (!buffer_uptodate(bh) ||
		    (offset >= i_size_read(inode)))
			set_buffer_new(bh);
		set_buffer_uptodate(bh);
		set_buffer_mapped(bh);
		set_buffer_delay(bh);
		break;
	case IOMAP_UNWRITTEN:
		/*
1911 1912 1913
		 * For unwritten regions, we always need to ensure that regions
		 * in the block we are not writing to are zeroed. Mark the
		 * buffer as new to ensure this.
1914 1915 1916 1917 1918
		 */
		set_buffer_new(bh);
		set_buffer_unwritten(bh);
		/* FALLTHRU */
	case IOMAP_MAPPED:
1919 1920
		if ((iomap->flags & IOMAP_F_NEW) ||
		    offset >= i_size_read(inode))
1921
			set_buffer_new(bh);
1922 1923
		bh->b_blocknr = (iomap->addr + offset - iomap->offset) >>
				inode->i_blkbits;
1924 1925 1926 1927 1928 1929 1930
		set_buffer_mapped(bh);
		break;
	}
}

int __block_write_begin_int(struct page *page, loff_t pos, unsigned len,
		get_block_t *get_block, struct iomap *iomap)
L
Linus Torvalds 已提交
1931
{
1932
	unsigned from = pos & (PAGE_SIZE - 1);
C
Christoph Hellwig 已提交
1933
	unsigned to = from + len;
1934
	struct inode *inode = page->mapping->host;
L
Linus Torvalds 已提交
1935 1936 1937 1938 1939 1940 1941
	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));
1942 1943
	BUG_ON(from > PAGE_SIZE);
	BUG_ON(to > PAGE_SIZE);
L
Linus Torvalds 已提交
1944 1945
	BUG_ON(from > to);

1946 1947 1948
	head = create_page_buffers(page, inode, 0);
	blocksize = head->b_size;
	bbits = block_size_bits(blocksize);
L
Linus Torvalds 已提交
1949

1950
	block = (sector_t)page->index << (PAGE_SHIFT - bbits);
L
Linus Torvalds 已提交
1951 1952 1953 1954 1955 1956 1957 1958 1959 1960 1961 1962 1963 1964

	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)) {
1965
			WARN_ON(bh->b_size != blocksize);
1966 1967 1968 1969 1970 1971 1972 1973
			if (get_block) {
				err = get_block(inode, block, bh, 1);
				if (err)
					break;
			} else {
				iomap_to_bh(inode, block, bh, iomap);
			}

L
Linus Torvalds 已提交
1974
			if (buffer_new(bh)) {
1975
				clean_bdev_bh_alias(bh);
L
Linus Torvalds 已提交
1976
				if (PageUptodate(page)) {
N
Nick Piggin 已提交
1977
					clear_buffer_new(bh);
L
Linus Torvalds 已提交
1978
					set_buffer_uptodate(bh);
N
Nick Piggin 已提交
1979
					mark_buffer_dirty(bh);
L
Linus Torvalds 已提交
1980 1981
					continue;
				}
1982 1983 1984 1985
				if (block_end > to || block_start < from)
					zero_user_segments(page,
						to, block_end,
						block_start, from);
L
Linus Torvalds 已提交
1986 1987 1988 1989 1990 1991 1992 1993 1994
				continue;
			}
		}
		if (PageUptodate(page)) {
			if (!buffer_uptodate(bh))
				set_buffer_uptodate(bh);
			continue; 
		}
		if (!buffer_uptodate(bh) && !buffer_delay(bh) &&
1995
		    !buffer_unwritten(bh) &&
L
Linus Torvalds 已提交
1996
		     (block_start < from || block_end > to)) {
1997
			ll_rw_block(REQ_OP_READ, 0, 1, &bh);
L
Linus Torvalds 已提交
1998 1999 2000 2001 2002 2003 2004 2005 2006
			*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))
2007
			err = -EIO;
L
Linus Torvalds 已提交
2008
	}
2009
	if (unlikely(err))
2010
		page_zero_new_buffers(page, from, to);
L
Linus Torvalds 已提交
2011 2012
	return err;
}
2013 2014 2015 2016 2017 2018

int __block_write_begin(struct page *page, loff_t pos, unsigned len,
		get_block_t *get_block)
{
	return __block_write_begin_int(page, pos, len, get_block, NULL);
}
C
Christoph Hellwig 已提交
2019
EXPORT_SYMBOL(__block_write_begin);
L
Linus Torvalds 已提交
2020 2021 2022 2023 2024 2025 2026 2027 2028

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;

2029 2030
	bh = head = page_buffers(page);
	blocksize = bh->b_size;
L
Linus Torvalds 已提交
2031

2032 2033
	block_start = 0;
	do {
L
Linus Torvalds 已提交
2034 2035 2036 2037 2038 2039 2040 2041
		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);
		}
2042
		clear_buffer_new(bh);
2043 2044 2045 2046

		block_start = block_end;
		bh = bh->b_this_page;
	} while (bh != head);
L
Linus Torvalds 已提交
2047 2048 2049 2050 2051 2052 2053 2054 2055 2056 2057 2058

	/*
	 * 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;
}

2059
/*
2060 2061 2062
 * block_write_begin takes care of the basic task of block allocation and
 * bringing partial write blocks uptodate first.
 *
2063
 * The filesystem needs to handle block truncation upon failure.
2064
 */
2065 2066
int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len,
		unsigned flags, struct page **pagep, get_block_t *get_block)
2067
{
2068
	pgoff_t index = pos >> PAGE_SHIFT;
2069
	struct page *page;
2070
	int status;
2071

2072 2073 2074
	page = grab_cache_page_write_begin(mapping, index, flags);
	if (!page)
		return -ENOMEM;
2075

2076
	status = __block_write_begin(page, pos, len, get_block);
2077
	if (unlikely(status)) {
2078
		unlock_page(page);
2079
		put_page(page);
2080
		page = NULL;
2081 2082
	}

2083
	*pagep = page;
2084 2085 2086 2087
	return status;
}
EXPORT_SYMBOL(block_write_begin);

2088 2089 2090 2091 2092 2093 2094 2095 2096 2097 2098 2099 2100 2101 2102 2103 2104 2105 2106 2107 2108 2109 2110 2111 2112 2113 2114 2115 2116 2117 2118 2119 2120 2121
int __generic_write_end(struct inode *inode, loff_t pos, unsigned copied,
		struct page *page)
{
	loff_t old_size = inode->i_size;
	bool i_size_changed = false;

	/*
	 * No need to use i_size_read() here, the i_size cannot change under us
	 * because we hold i_rwsem.
	 *
	 * 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);
		i_size_changed = true;
	}

	unlock_page(page);
	put_page(page);

	if (old_size < pos)
		pagecache_isize_extended(inode, old_size, pos);
	/*
	 * Don't mark the inode dirty under page lock. First, it unnecessarily
	 * makes the holding time of page lock longer. Second, it forces lock
	 * ordering of page lock and transaction start for journaling
	 * filesystems.
	 */
	if (i_size_changed)
		mark_inode_dirty(inode);
	return copied;
}

2122 2123 2124 2125 2126 2127 2128
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;

2129
	start = pos & (PAGE_SIZE - 1);
2130 2131 2132 2133 2134 2135 2136 2137 2138 2139 2140 2141 2142 2143 2144 2145 2146 2147 2148 2149 2150 2151 2152 2153 2154 2155 2156 2157 2158 2159 2160 2161 2162

	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)
{
	copied = block_write_end(file, mapping, pos, len, copied, page, fsdata);
2163
	return __generic_write_end(mapping->host, pos, copied, page);
2164 2165 2166
}
EXPORT_SYMBOL(generic_write_end);

2167 2168 2169 2170 2171 2172 2173
/*
 * block_is_partially_uptodate checks whether buffers within a page are
 * uptodate or not.
 *
 * Returns true if all buffers which correspond to a file portion
 * we want to read are uptodate.
 */
2174 2175
int block_is_partially_uptodate(struct page *page, unsigned long from,
					unsigned long count)
2176 2177 2178 2179 2180 2181 2182 2183 2184
{
	unsigned block_start, block_end, blocksize;
	unsigned to;
	struct buffer_head *bh, *head;
	int ret = 1;

	if (!page_has_buffers(page))
		return 0;

2185 2186
	head = page_buffers(page);
	blocksize = head->b_size;
2187
	to = min_t(unsigned, PAGE_SIZE - from, count);
2188
	to = from + to;
2189
	if (from < blocksize && to > PAGE_SIZE - blocksize)
2190 2191 2192 2193 2194 2195 2196 2197 2198 2199 2200 2201 2202 2203 2204 2205 2206 2207 2208 2209 2210 2211
		return 0;

	bh = head;
	block_start = 0;
	do {
		block_end = block_start + blocksize;
		if (block_end > from && block_start < to) {
			if (!buffer_uptodate(bh)) {
				ret = 0;
				break;
			}
			if (block_end >= to)
				break;
		}
		block_start = block_end;
		bh = bh->b_this_page;
	} while (bh != head);

	return ret;
}
EXPORT_SYMBOL(block_is_partially_uptodate);

L
Linus Torvalds 已提交
2212 2213 2214 2215 2216 2217 2218 2219 2220 2221 2222 2223
/*
 * 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];
2224
	unsigned int blocksize, bbits;
L
Linus Torvalds 已提交
2225 2226 2227
	int nr, i;
	int fully_mapped = 1;

2228 2229 2230
	head = create_page_buffers(page, inode, 0);
	blocksize = head->b_size;
	bbits = block_size_bits(blocksize);
L
Linus Torvalds 已提交
2231

2232
	iblock = (sector_t)page->index << (PAGE_SHIFT - bbits);
2233
	lblock = (i_size_read(inode)+blocksize-1) >> bbits;
L
Linus Torvalds 已提交
2234 2235 2236 2237 2238 2239 2240 2241 2242
	bh = head;
	nr = 0;
	i = 0;

	do {
		if (buffer_uptodate(bh))
			continue;

		if (!buffer_mapped(bh)) {
2243 2244
			int err = 0;

L
Linus Torvalds 已提交
2245 2246
			fully_mapped = 0;
			if (iblock < lblock) {
2247
				WARN_ON(bh->b_size != blocksize);
2248 2249
				err = get_block(inode, iblock, bh, 0);
				if (err)
L
Linus Torvalds 已提交
2250 2251 2252
					SetPageError(page);
			}
			if (!buffer_mapped(bh)) {
2253
				zero_user(page, i * blocksize, blocksize);
2254 2255
				if (!err)
					set_buffer_uptodate(bh);
L
Linus Torvalds 已提交
2256 2257 2258 2259 2260 2261 2262 2263 2264 2265 2266 2267 2268 2269 2270 2271 2272 2273 2274 2275 2276 2277 2278 2279 2280 2281 2282 2283 2284 2285 2286 2287 2288 2289 2290 2291 2292 2293 2294 2295 2296 2297 2298
				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
2299
			submit_bh(REQ_OP_READ, 0, bh);
L
Linus Torvalds 已提交
2300 2301 2302
	}
	return 0;
}
2303
EXPORT_SYMBOL(block_read_full_page);
L
Linus Torvalds 已提交
2304 2305

/* utility function for filesystems that need to do work on expanding
N
Nick Piggin 已提交
2306
 * truncates.  Uses filesystem pagecache writes to allow the filesystem to
L
Linus Torvalds 已提交
2307 2308
 * deal with the hole.  
 */
N
Nick Piggin 已提交
2309
int generic_cont_expand_simple(struct inode *inode, loff_t size)
L
Linus Torvalds 已提交
2310 2311 2312
{
	struct address_space *mapping = inode->i_mapping;
	struct page *page;
N
Nick Piggin 已提交
2313
	void *fsdata;
L
Linus Torvalds 已提交
2314 2315
	int err;

N
npiggin@suse.de 已提交
2316 2317
	err = inode_newsize_ok(inode, size);
	if (err)
L
Linus Torvalds 已提交
2318 2319
		goto out;

N
Nick Piggin 已提交
2320
	err = pagecache_write_begin(NULL, mapping, size, 0,
2321
				    AOP_FLAG_CONT_EXPAND, &page, &fsdata);
N
Nick Piggin 已提交
2322
	if (err)
2323 2324
		goto out;

N
Nick Piggin 已提交
2325 2326
	err = pagecache_write_end(NULL, mapping, size, 0, 0, page, fsdata);
	BUG_ON(err > 0);
2327

L
Linus Torvalds 已提交
2328 2329 2330
out:
	return err;
}
2331
EXPORT_SYMBOL(generic_cont_expand_simple);
L
Linus Torvalds 已提交
2332

2333 2334
static int cont_expand_zero(struct file *file, struct address_space *mapping,
			    loff_t pos, loff_t *bytes)
L
Linus Torvalds 已提交
2335 2336
{
	struct inode *inode = mapping->host;
F
Fabian Frederick 已提交
2337
	unsigned int blocksize = i_blocksize(inode);
N
Nick Piggin 已提交
2338 2339 2340 2341 2342 2343
	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
2344

2345 2346
	index = pos >> PAGE_SHIFT;
	offset = pos & ~PAGE_MASK;
N
Nick Piggin 已提交
2347

2348 2349
	while (index > (curidx = (curpos = *bytes)>>PAGE_SHIFT)) {
		zerofrom = curpos & ~PAGE_MASK;
L
Linus Torvalds 已提交
2350 2351 2352 2353
		if (zerofrom & (blocksize-1)) {
			*bytes |= (blocksize-1);
			(*bytes)++;
		}
2354
		len = PAGE_SIZE - zerofrom;
L
Linus Torvalds 已提交
2355

2356 2357
		err = pagecache_write_begin(file, mapping, curpos, len, 0,
					    &page, &fsdata);
N
Nick Piggin 已提交
2358 2359
		if (err)
			goto out;
2360
		zero_user(page, zerofrom, len);
N
Nick Piggin 已提交
2361 2362 2363 2364 2365 2366
		err = pagecache_write_end(file, mapping, curpos, len, len,
						page, fsdata);
		if (err < 0)
			goto out;
		BUG_ON(err != len);
		err = 0;
2367 2368

		balance_dirty_pages_ratelimited(mapping);
2369

2370
		if (fatal_signal_pending(current)) {
2371 2372 2373
			err = -EINTR;
			goto out;
		}
N
Nick Piggin 已提交
2374
	}
L
Linus Torvalds 已提交
2375

N
Nick Piggin 已提交
2376 2377
	/* page covers the boundary, find the boundary offset */
	if (index == curidx) {
2378
		zerofrom = curpos & ~PAGE_MASK;
L
Linus Torvalds 已提交
2379
		/* if we will expand the thing last block will be filled */
N
Nick Piggin 已提交
2380 2381 2382 2383
		if (offset <= zerofrom) {
			goto out;
		}
		if (zerofrom & (blocksize-1)) {
L
Linus Torvalds 已提交
2384 2385 2386
			*bytes |= (blocksize-1);
			(*bytes)++;
		}
N
Nick Piggin 已提交
2387
		len = offset - zerofrom;
L
Linus Torvalds 已提交
2388

2389 2390
		err = pagecache_write_begin(file, mapping, curpos, len, 0,
					    &page, &fsdata);
N
Nick Piggin 已提交
2391 2392
		if (err)
			goto out;
2393
		zero_user(page, zerofrom, len);
N
Nick Piggin 已提交
2394 2395 2396 2397 2398 2399
		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
2400
	}
N
Nick Piggin 已提交
2401 2402 2403 2404 2405 2406 2407 2408
out:
	return err;
}

/*
 * For moronic filesystems that do not allow holes in file.
 * We may have to extend the file.
 */
2409
int cont_write_begin(struct file *file, struct address_space *mapping,
N
Nick Piggin 已提交
2410 2411 2412 2413 2414
			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;
F
Fabian Frederick 已提交
2415 2416
	unsigned int blocksize = i_blocksize(inode);
	unsigned int zerofrom;
N
Nick Piggin 已提交
2417 2418 2419 2420
	int err;

	err = cont_expand_zero(file, mapping, pos, bytes);
	if (err)
2421
		return err;
N
Nick Piggin 已提交
2422

2423
	zerofrom = *bytes & ~PAGE_MASK;
N
Nick Piggin 已提交
2424 2425 2426
	if (pos+len > *bytes && zerofrom & (blocksize-1)) {
		*bytes |= (blocksize-1);
		(*bytes)++;
L
Linus Torvalds 已提交
2427 2428
	}

2429
	return block_write_begin(mapping, pos, len, flags, pagep, get_block);
L
Linus Torvalds 已提交
2430
}
2431
EXPORT_SYMBOL(cont_write_begin);
L
Linus Torvalds 已提交
2432 2433 2434 2435 2436 2437 2438

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;
}
2439
EXPORT_SYMBOL(block_commit_write);
L
Linus Torvalds 已提交
2440

2441 2442 2443 2444 2445 2446 2447 2448 2449 2450
/*
 * 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
2451
 * truncate writes the inode size before removing pages, once we have the
2452 2453 2454
 * 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.
2455
 *
2456
 * Direct callers of this function should protect against filesystem freezing
2457
 * using sb_start_pagefault() - sb_end_pagefault() functions.
2458
 */
2459
int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
2460
			 get_block_t get_block)
2461
{
2462
	struct page *page = vmf->page;
A
Al Viro 已提交
2463
	struct inode *inode = file_inode(vma->vm_file);
2464 2465
	unsigned long end;
	loff_t size;
2466
	int ret;
2467 2468 2469 2470

	lock_page(page);
	size = i_size_read(inode);
	if ((page->mapping != inode->i_mapping) ||
N
Nick Piggin 已提交
2471
	    (page_offset(page) > size)) {
2472 2473 2474
		/* We overload EFAULT to mean page got truncated */
		ret = -EFAULT;
		goto out_unlock;
2475 2476 2477
	}

	/* page is wholly or partially inside EOF */
2478 2479
	if (((page->index + 1) << PAGE_SHIFT) > size)
		end = size & ~PAGE_MASK;
2480
	else
2481
		end = PAGE_SIZE;
2482

C
Christoph Hellwig 已提交
2483
	ret = __block_write_begin(page, 0, end, get_block);
2484 2485 2486
	if (!ret)
		ret = block_commit_write(page, 0, end);

2487 2488
	if (unlikely(ret < 0))
		goto out_unlock;
2489
	set_page_dirty(page);
2490
	wait_for_stable_page(page);
2491 2492 2493
	return 0;
out_unlock:
	unlock_page(page);
2494
	return ret;
2495
}
2496
EXPORT_SYMBOL(block_page_mkwrite);
L
Linus Torvalds 已提交
2497 2498

/*
N
Nick Piggin 已提交
2499
 * nobh_write_begin()'s prereads are special: the buffer_heads are freed
L
Linus Torvalds 已提交
2500 2501 2502 2503 2504
 * 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)
{
2505
	__end_buffer_read_notouch(bh, uptodate);
L
Linus Torvalds 已提交
2506 2507
}

N
Nick Piggin 已提交
2508 2509 2510 2511 2512 2513 2514 2515 2516 2517 2518 2519 2520 2521 2522 2523 2524 2525 2526 2527 2528 2529 2530 2531
/*
 * 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
2532
/*
2533 2534
 * On entry, the page is fully not uptodate.
 * On exit the page is fully uptodate in the areas outside (from,to)
2535
 * The filesystem needs to handle block truncation upon failure.
L
Linus Torvalds 已提交
2536
 */
2537
int nobh_write_begin(struct address_space *mapping,
N
Nick Piggin 已提交
2538 2539
			loff_t pos, unsigned len, unsigned flags,
			struct page **pagep, void **fsdata,
L
Linus Torvalds 已提交
2540 2541
			get_block_t *get_block)
{
N
Nick Piggin 已提交
2542
	struct inode *inode = mapping->host;
L
Linus Torvalds 已提交
2543 2544
	const unsigned blkbits = inode->i_blkbits;
	const unsigned blocksize = 1 << blkbits;
N
Nick Piggin 已提交
2545
	struct buffer_head *head, *bh;
N
Nick Piggin 已提交
2546 2547 2548
	struct page *page;
	pgoff_t index;
	unsigned from, to;
L
Linus Torvalds 已提交
2549
	unsigned block_in_page;
N
Nick Piggin 已提交
2550
	unsigned block_start, block_end;
L
Linus Torvalds 已提交
2551 2552 2553 2554 2555
	sector_t block_in_file;
	int nr_reads = 0;
	int ret = 0;
	int is_mapped_to_disk = 1;

2556 2557
	index = pos >> PAGE_SHIFT;
	from = pos & (PAGE_SIZE - 1);
N
Nick Piggin 已提交
2558 2559
	to = from + len;

2560
	page = grab_cache_page_write_begin(mapping, index, flags);
N
Nick Piggin 已提交
2561 2562 2563 2564 2565 2566
	if (!page)
		return -ENOMEM;
	*pagep = page;
	*fsdata = NULL;

	if (page_has_buffers(page)) {
2567 2568 2569 2570
		ret = __block_write_begin(page, pos, len, get_block);
		if (unlikely(ret))
			goto out_release;
		return ret;
N
Nick Piggin 已提交
2571
	}
N
Nick Piggin 已提交
2572

L
Linus Torvalds 已提交
2573 2574 2575
	if (PageMappedToDisk(page))
		return 0;

N
Nick Piggin 已提交
2576 2577 2578 2579 2580 2581 2582 2583 2584
	/*
	 * 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.
	 */
2585
	head = alloc_page_buffers(page, blocksize, false);
N
Nick Piggin 已提交
2586 2587 2588 2589
	if (!head) {
		ret = -ENOMEM;
		goto out_release;
	}
N
Nick Piggin 已提交
2590

2591
	block_in_file = (sector_t)page->index << (PAGE_SHIFT - blkbits);
L
Linus Torvalds 已提交
2592 2593 2594 2595 2596 2597

	/*
	 * 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
2598
	for (block_start = 0, block_in_page = 0, bh = head;
2599
		  block_start < PAGE_SIZE;
N
Nick Piggin 已提交
2600
		  block_in_page++, block_start += blocksize, bh = bh->b_this_page) {
L
Linus Torvalds 已提交
2601 2602
		int create;

N
Nick Piggin 已提交
2603 2604
		block_end = block_start + blocksize;
		bh->b_state = 0;
L
Linus Torvalds 已提交
2605 2606 2607 2608
		create = 1;
		if (block_start >= to)
			create = 0;
		ret = get_block(inode, block_in_file + block_in_page,
N
Nick Piggin 已提交
2609
					bh, create);
L
Linus Torvalds 已提交
2610 2611
		if (ret)
			goto failed;
N
Nick Piggin 已提交
2612
		if (!buffer_mapped(bh))
L
Linus Torvalds 已提交
2613
			is_mapped_to_disk = 0;
N
Nick Piggin 已提交
2614
		if (buffer_new(bh))
2615
			clean_bdev_bh_alias(bh);
N
Nick Piggin 已提交
2616 2617
		if (PageUptodate(page)) {
			set_buffer_uptodate(bh);
L
Linus Torvalds 已提交
2618
			continue;
N
Nick Piggin 已提交
2619 2620
		}
		if (buffer_new(bh) || !buffer_mapped(bh)) {
2621 2622
			zero_user_segments(page, block_start, from,
							to, block_end);
L
Linus Torvalds 已提交
2623 2624
			continue;
		}
N
Nick Piggin 已提交
2625
		if (buffer_uptodate(bh))
L
Linus Torvalds 已提交
2626 2627
			continue;	/* reiserfs does this */
		if (block_start < from || block_end > to) {
N
Nick Piggin 已提交
2628 2629
			lock_buffer(bh);
			bh->b_end_io = end_buffer_read_nobh;
2630
			submit_bh(REQ_OP_READ, 0, bh);
N
Nick Piggin 已提交
2631
			nr_reads++;
L
Linus Torvalds 已提交
2632 2633 2634 2635 2636 2637 2638 2639 2640
		}
	}

	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
2641
		for (bh = head; bh; bh = bh->b_this_page) {
L
Linus Torvalds 已提交
2642 2643 2644 2645 2646 2647 2648 2649 2650 2651 2652
			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
2653
	*fsdata = head; /* to be released by nobh_write_end */
N
Nick Piggin 已提交
2654

L
Linus Torvalds 已提交
2655 2656 2657
	return 0;

failed:
N
Nick Piggin 已提交
2658
	BUG_ON(!ret);
L
Linus Torvalds 已提交
2659
	/*
N
Nick Piggin 已提交
2660 2661 2662 2663 2664
	 * 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
2665
	 */
N
Nick Piggin 已提交
2666 2667
	attach_nobh_buffers(page, head);
	page_zero_new_buffers(page, from, to);
N
Nick Piggin 已提交
2668

N
Nick Piggin 已提交
2669 2670
out_release:
	unlock_page(page);
2671
	put_page(page);
N
Nick Piggin 已提交
2672
	*pagep = NULL;
N
Nick Piggin 已提交
2673

2674 2675
	return ret;
}
N
Nick Piggin 已提交
2676
EXPORT_SYMBOL(nobh_write_begin);
L
Linus Torvalds 已提交
2677

N
Nick Piggin 已提交
2678 2679 2680
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
2681 2682
{
	struct inode *inode = page->mapping->host;
N
Nick Piggin 已提交
2683
	struct buffer_head *head = fsdata;
N
Nick Piggin 已提交
2684
	struct buffer_head *bh;
2685
	BUG_ON(fsdata != NULL && page_has_buffers(page));
L
Linus Torvalds 已提交
2686

2687
	if (unlikely(copied < len) && head)
2688 2689 2690 2691
		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
2692

N
Nick Piggin 已提交
2693
	SetPageUptodate(page);
L
Linus Torvalds 已提交
2694
	set_page_dirty(page);
N
Nick Piggin 已提交
2695 2696
	if (pos+copied > inode->i_size) {
		i_size_write(inode, pos+copied);
L
Linus Torvalds 已提交
2697 2698
		mark_inode_dirty(inode);
	}
N
Nick Piggin 已提交
2699 2700

	unlock_page(page);
2701
	put_page(page);
N
Nick Piggin 已提交
2702 2703 2704 2705 2706 2707 2708 2709

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

	return copied;
L
Linus Torvalds 已提交
2710
}
N
Nick Piggin 已提交
2711
EXPORT_SYMBOL(nobh_write_end);
L
Linus Torvalds 已提交
2712 2713 2714 2715 2716 2717 2718 2719 2720 2721 2722

/*
 * 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);
2723
	const pgoff_t end_index = i_size >> PAGE_SHIFT;
L
Linus Torvalds 已提交
2724 2725 2726 2727 2728 2729 2730 2731
	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) */
2732
	offset = i_size & (PAGE_SIZE-1);
L
Linus Torvalds 已提交
2733 2734 2735 2736 2737 2738 2739 2740 2741 2742 2743 2744 2745 2746 2747 2748 2749 2750 2751 2752 2753 2754
	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."
	 */
2755
	zero_user_segment(page, offset, PAGE_SIZE);
L
Linus Torvalds 已提交
2756 2757 2758
out:
	ret = mpage_writepage(page, get_block, wbc);
	if (ret == -EAGAIN)
2759 2760
		ret = __block_write_full_page(inode, page, get_block, wbc,
					      end_buffer_async_write);
L
Linus Torvalds 已提交
2761 2762 2763 2764
	return ret;
}
EXPORT_SYMBOL(nobh_writepage);

N
Nick Piggin 已提交
2765 2766
int nobh_truncate_page(struct address_space *mapping,
			loff_t from, get_block_t *get_block)
L
Linus Torvalds 已提交
2767
{
2768 2769
	pgoff_t index = from >> PAGE_SHIFT;
	unsigned offset = from & (PAGE_SIZE-1);
N
Nick Piggin 已提交
2770 2771 2772 2773
	unsigned blocksize;
	sector_t iblock;
	unsigned length, pos;
	struct inode *inode = mapping->host;
L
Linus Torvalds 已提交
2774
	struct page *page;
N
Nick Piggin 已提交
2775 2776
	struct buffer_head map_bh;
	int err;
L
Linus Torvalds 已提交
2777

F
Fabian Frederick 已提交
2778
	blocksize = i_blocksize(inode);
N
Nick Piggin 已提交
2779 2780 2781 2782 2783 2784 2785
	length = offset & (blocksize - 1);

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

	length = blocksize - length;
2786
	iblock = (sector_t)index << (PAGE_SHIFT - inode->i_blkbits);
L
Linus Torvalds 已提交
2787 2788

	page = grab_cache_page(mapping, index);
N
Nick Piggin 已提交
2789
	err = -ENOMEM;
L
Linus Torvalds 已提交
2790 2791 2792
	if (!page)
		goto out;

N
Nick Piggin 已提交
2793 2794 2795
	if (page_has_buffers(page)) {
has_buffers:
		unlock_page(page);
2796
		put_page(page);
N
Nick Piggin 已提交
2797 2798 2799 2800 2801 2802 2803 2804 2805 2806
		return block_truncate_page(mapping, from, get_block);
	}

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

2807 2808
	map_bh.b_size = blocksize;
	map_bh.b_state = 0;
N
Nick Piggin 已提交
2809 2810 2811 2812 2813 2814 2815 2816 2817 2818 2819
	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) {
2820
			put_page(page);
N
Nick Piggin 已提交
2821 2822 2823 2824 2825 2826 2827 2828 2829
			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
2830
	}
2831
	zero_user(page, offset, length);
N
Nick Piggin 已提交
2832 2833 2834 2835
	set_page_dirty(page);
	err = 0;

unlock:
L
Linus Torvalds 已提交
2836
	unlock_page(page);
2837
	put_page(page);
L
Linus Torvalds 已提交
2838
out:
N
Nick Piggin 已提交
2839
	return err;
L
Linus Torvalds 已提交
2840 2841 2842 2843 2844 2845
}
EXPORT_SYMBOL(nobh_truncate_page);

int block_truncate_page(struct address_space *mapping,
			loff_t from, get_block_t *get_block)
{
2846 2847
	pgoff_t index = from >> PAGE_SHIFT;
	unsigned offset = from & (PAGE_SIZE-1);
L
Linus Torvalds 已提交
2848
	unsigned blocksize;
2849
	sector_t iblock;
L
Linus Torvalds 已提交
2850 2851 2852 2853 2854 2855
	unsigned length, pos;
	struct inode *inode = mapping->host;
	struct page *page;
	struct buffer_head *bh;
	int err;

F
Fabian Frederick 已提交
2856
	blocksize = i_blocksize(inode);
L
Linus Torvalds 已提交
2857 2858 2859 2860 2861 2862 2863
	length = offset & (blocksize - 1);

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

	length = blocksize - length;
2864
	iblock = (sector_t)index << (PAGE_SHIFT - inode->i_blkbits);
L
Linus Torvalds 已提交
2865 2866 2867 2868 2869 2870 2871 2872 2873 2874 2875 2876 2877 2878 2879 2880 2881 2882 2883 2884
	
	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)) {
2885
		WARN_ON(bh->b_size != blocksize);
L
Linus Torvalds 已提交
2886 2887 2888 2889 2890 2891 2892 2893 2894 2895 2896 2897
		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);

2898
	if (!buffer_uptodate(bh) && !buffer_delay(bh) && !buffer_unwritten(bh)) {
L
Linus Torvalds 已提交
2899
		err = -EIO;
2900
		ll_rw_block(REQ_OP_READ, 0, 1, &bh);
L
Linus Torvalds 已提交
2901 2902 2903 2904 2905 2906
		wait_on_buffer(bh);
		/* Uhhuh. Read error. Complain and punt. */
		if (!buffer_uptodate(bh))
			goto unlock;
	}

2907
	zero_user(page, offset, length);
L
Linus Torvalds 已提交
2908 2909 2910 2911 2912
	mark_buffer_dirty(bh);
	err = 0;

unlock:
	unlock_page(page);
2913
	put_page(page);
L
Linus Torvalds 已提交
2914 2915 2916
out:
	return err;
}
2917
EXPORT_SYMBOL(block_truncate_page);
L
Linus Torvalds 已提交
2918 2919 2920 2921

/*
 * The generic ->writepage function for buffer-backed address_spaces
 */
2922 2923
int block_write_full_page(struct page *page, get_block_t *get_block,
			struct writeback_control *wbc)
L
Linus Torvalds 已提交
2924 2925 2926
{
	struct inode * const inode = page->mapping->host;
	loff_t i_size = i_size_read(inode);
2927
	const pgoff_t end_index = i_size >> PAGE_SHIFT;
L
Linus Torvalds 已提交
2928 2929 2930 2931
	unsigned offset;

	/* Is the page fully inside i_size? */
	if (page->index < end_index)
2932
		return __block_write_full_page(inode, page, get_block, wbc,
2933
					       end_buffer_async_write);
L
Linus Torvalds 已提交
2934 2935

	/* Is the page fully outside i_size? (truncate in progress) */
2936
	offset = i_size & (PAGE_SIZE-1);
L
Linus Torvalds 已提交
2937 2938 2939 2940 2941 2942
	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.
		 */
2943
		do_invalidatepage(page, 0, PAGE_SIZE);
L
Linus Torvalds 已提交
2944 2945 2946 2947 2948 2949
		unlock_page(page);
		return 0; /* don't care */
	}

	/*
	 * The page straddles i_size.  It must be zeroed out on each and every
2950
	 * writepage invocation because it may be mmapped.  "A file is mapped
L
Linus Torvalds 已提交
2951 2952 2953 2954
	 * 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."
	 */
2955
	zero_user_segment(page, offset, PAGE_SIZE);
2956 2957
	return __block_write_full_page(inode, page, get_block, wbc,
							end_buffer_async_write);
2958
}
2959
EXPORT_SYMBOL(block_write_full_page);
2960

L
Linus Torvalds 已提交
2961 2962 2963 2964
sector_t generic_block_bmap(struct address_space *mapping, sector_t block,
			    get_block_t *get_block)
{
	struct inode *inode = mapping->host;
2965 2966 2967 2968
	struct buffer_head tmp = {
		.b_size = i_blocksize(inode),
	};

L
Linus Torvalds 已提交
2969 2970 2971
	get_block(inode, block, &tmp, 0);
	return tmp.b_blocknr;
}
2972
EXPORT_SYMBOL(generic_block_bmap);
L
Linus Torvalds 已提交
2973

2974
static void end_bio_bh_io_sync(struct bio *bio)
L
Linus Torvalds 已提交
2975 2976 2977
{
	struct buffer_head *bh = bio->bi_private;

2978
	if (unlikely(bio_flagged(bio, BIO_QUIET)))
2979 2980
		set_bit(BH_Quiet, &bh->b_state);

2981
	bh->b_end_io(bh, !bio->bi_status);
L
Linus Torvalds 已提交
2982 2983 2984
	bio_put(bio);
}

2985 2986
/*
 * This allows us to do IO even on the odd last sectors
2987
 * of a device, even if the block size is some multiple
2988 2989 2990 2991 2992 2993 2994 2995 2996
 * of the physical sector size.
 *
 * We'll just truncate the bio to the size of the device,
 * and clear the end of the buffer head manually.
 *
 * Truly out-of-range accesses will turn into actual IO
 * errors, this only handles the "we need to be able to
 * do IO at the final sector" case.
 */
2997
void guard_bio_eod(int op, struct bio *bio)
2998 2999
{
	sector_t maxsector;
M
Ming Lei 已提交
3000
	struct bio_vec *bvec = bio_last_bvec_all(bio);
3001
	unsigned truncated_bytes;
3002 3003 3004 3005 3006 3007 3008 3009 3010
	struct hd_struct *part;

	rcu_read_lock();
	part = __disk_get_part(bio->bi_disk, bio->bi_partno);
	if (part)
		maxsector = part_nr_sects_read(part);
	else
		maxsector = get_capacity(bio->bi_disk);
	rcu_read_unlock();
3011 3012 3013 3014 3015 3016 3017 3018 3019

	if (!maxsector)
		return;

	/*
	 * If the *whole* IO is past the end of the device,
	 * let it through, and the IO layer will turn it into
	 * an EIO.
	 */
3020
	if (unlikely(bio->bi_iter.bi_sector >= maxsector))
3021 3022
		return;

3023
	maxsector -= bio->bi_iter.bi_sector;
3024
	if (likely((bio->bi_iter.bi_size >> 9) <= maxsector))
3025 3026
		return;

3027 3028
	/* Uhhuh. We've got a bio that straddles the device size! */
	truncated_bytes = bio->bi_iter.bi_size - (maxsector << 9);
3029 3030

	/* Truncate the bio.. */
3031 3032
	bio->bi_iter.bi_size -= truncated_bytes;
	bvec->bv_len -= truncated_bytes;
3033 3034

	/* ..and clear the end of the buffer for reads */
3035
	if (op == REQ_OP_READ) {
3036 3037
		zero_user(bvec->bv_page, bvec->bv_offset + bvec->bv_len,
				truncated_bytes);
3038 3039 3040
	}
}

3041
static int submit_bh_wbc(int op, int op_flags, struct buffer_head *bh,
3042
			 enum rw_hint write_hint, struct writeback_control *wbc)
L
Linus Torvalds 已提交
3043 3044 3045 3046 3047 3048
{
	struct bio *bio;

	BUG_ON(!buffer_locked(bh));
	BUG_ON(!buffer_mapped(bh));
	BUG_ON(!bh->b_end_io);
3049 3050
	BUG_ON(buffer_delay(bh));
	BUG_ON(buffer_unwritten(bh));
L
Linus Torvalds 已提交
3051 3052

	/*
3053
	 * Only clear out a write error when rewriting
L
Linus Torvalds 已提交
3054
	 */
3055
	if (test_set_buffer_req(bh) && (op == REQ_OP_WRITE))
L
Linus Torvalds 已提交
3056 3057 3058 3059 3060 3061 3062 3063
		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);

3064
	bio->bi_iter.bi_sector = bh->b_blocknr * (bh->b_size >> 9);
3065
	bio_set_dev(bio, bh->b_bdev);
3066
	bio->bi_write_hint = write_hint;
L
Linus Torvalds 已提交
3067

3068 3069
	bio_add_page(bio, bh->b_page, bh->b_size, bh_offset(bh));
	BUG_ON(bio->bi_iter.bi_size != bh->b_size);
L
Linus Torvalds 已提交
3070 3071 3072 3073

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

3074
	/* Take care of bh's that straddle the end of the device */
3075
	guard_bio_eod(op, bio);
3076

3077
	if (buffer_meta(bh))
3078
		op_flags |= REQ_META;
3079
	if (buffer_prio(bh))
3080 3081
		op_flags |= REQ_PRIO;
	bio_set_op_attrs(bio, op, op_flags);
3082

3083 3084 3085 3086 3087
	if (wbc) {
		wbc_init_bio(wbc, bio);
		wbc_account_io(wbc, bh->b_page, bh->b_size);
	}

3088
	submit_bio(bio);
3089
	return 0;
L
Linus Torvalds 已提交
3090
}
3091

E
Eric Biggers 已提交
3092
int submit_bh(int op, int op_flags, struct buffer_head *bh)
3093
{
3094
	return submit_bh_wbc(op, op_flags, bh, 0, NULL);
3095
}
3096
EXPORT_SYMBOL(submit_bh);
L
Linus Torvalds 已提交
3097 3098 3099

/**
 * ll_rw_block: low-level access to block devices (DEPRECATED)
3100
 * @op: whether to %READ or %WRITE
3101
 * @op_flags: req_flag_bits
L
Linus Torvalds 已提交
3102 3103 3104
 * @nr: number of &struct buffer_heads in the array
 * @bhs: array of pointers to &struct buffer_head
 *
3105
 * ll_rw_block() takes an array of pointers to &struct buffer_heads, and
3106 3107 3108
 * requests an I/O operation on them, either a %REQ_OP_READ or a %REQ_OP_WRITE.
 * @op_flags contains flags modifying the detailed I/O behavior, most notably
 * %REQ_RAHEAD.
L
Linus Torvalds 已提交
3109 3110
 *
 * This function drops any buffer that it cannot get a lock on (with the
C
Christoph Hellwig 已提交
3111 3112 3113 3114 3115
 * BH_Lock state bit), 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
Linus Torvalds 已提交
3116 3117
 *
 * ll_rw_block sets b_end_io to simple completion handler that marks
3118
 * the buffer up-to-date (if appropriate), unlocks the buffer and wakes
L
Linus Torvalds 已提交
3119 3120 3121 3122 3123
 * 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.
 */
3124
void ll_rw_block(int op, int op_flags,  int nr, struct buffer_head *bhs[])
L
Linus Torvalds 已提交
3125 3126 3127 3128 3129 3130
{
	int i;

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

C
Christoph Hellwig 已提交
3131
		if (!trylock_buffer(bh))
L
Linus Torvalds 已提交
3132
			continue;
3133
		if (op == WRITE) {
L
Linus Torvalds 已提交
3134
			if (test_clear_buffer_dirty(bh)) {
3135
				bh->b_end_io = end_buffer_write_sync;
3136
				get_bh(bh);
3137
				submit_bh(op, op_flags, bh);
L
Linus Torvalds 已提交
3138 3139 3140 3141
				continue;
			}
		} else {
			if (!buffer_uptodate(bh)) {
3142
				bh->b_end_io = end_buffer_read_sync;
3143
				get_bh(bh);
3144
				submit_bh(op, op_flags, bh);
L
Linus Torvalds 已提交
3145 3146 3147 3148 3149 3150
				continue;
			}
		}
		unlock_buffer(bh);
	}
}
3151
EXPORT_SYMBOL(ll_rw_block);
L
Linus Torvalds 已提交
3152

3153
void write_dirty_buffer(struct buffer_head *bh, int op_flags)
C
Christoph Hellwig 已提交
3154 3155 3156 3157 3158 3159 3160 3161
{
	lock_buffer(bh);
	if (!test_clear_buffer_dirty(bh)) {
		unlock_buffer(bh);
		return;
	}
	bh->b_end_io = end_buffer_write_sync;
	get_bh(bh);
3162
	submit_bh(REQ_OP_WRITE, op_flags, bh);
C
Christoph Hellwig 已提交
3163 3164 3165
}
EXPORT_SYMBOL(write_dirty_buffer);

L
Linus Torvalds 已提交
3166 3167 3168 3169 3170
/*
 * 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.
 */
3171
int __sync_dirty_buffer(struct buffer_head *bh, int op_flags)
L
Linus Torvalds 已提交
3172 3173 3174 3175 3176 3177 3178 3179
{
	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;
3180
		ret = submit_bh(REQ_OP_WRITE, op_flags, bh);
L
Linus Torvalds 已提交
3181 3182 3183 3184 3185 3186 3187 3188
		wait_on_buffer(bh);
		if (!ret && !buffer_uptodate(bh))
			ret = -EIO;
	} else {
		unlock_buffer(bh);
	}
	return ret;
}
C
Christoph Hellwig 已提交
3189 3190 3191 3192
EXPORT_SYMBOL(__sync_dirty_buffer);

int sync_dirty_buffer(struct buffer_head *bh)
{
3193
	return __sync_dirty_buffer(bh, REQ_SYNC);
C
Christoph Hellwig 已提交
3194
}
3195
EXPORT_SYMBOL(sync_dirty_buffer);
L
Linus Torvalds 已提交
3196 3197 3198 3199 3200 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

/*
 * 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 {
		if (buffer_busy(bh))
			goto failed;
		bh = bh->b_this_page;
	} while (bh != head);

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

3239
		if (bh->b_assoc_map)
L
Linus Torvalds 已提交
3240 3241 3242 3243 3244 3245 3246 3247 3248 3249 3250 3251 3252 3253 3254 3255 3256
			__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));
3257
	if (PageWriteback(page))
L
Linus Torvalds 已提交
3258 3259 3260 3261 3262 3263 3264 3265 3266
		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);
3267 3268 3269 3270 3271 3272 3273 3274 3275 3276

	/*
	 * 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.
3277 3278 3279 3280
	 *
	 * 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.
3281
	 */
3282 3283
	if (ret)
		cancel_dirty_page(page);
3284
	spin_unlock(&mapping->private_lock);
L
Linus Torvalds 已提交
3285 3286 3287 3288 3289 3290 3291 3292 3293 3294 3295 3296 3297 3298 3299 3300 3301 3302 3303
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);

/*
 * 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.
3304
 * The `flush-X' kernel threads fully replace bdflush daemons and this call.
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Linus Torvalds 已提交
3305
 */
3306
SYSCALL_DEFINE2(bdflush, int, func, long, data)
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3307 3308 3309 3310 3311 3312 3313 3314 3315 3316 3317 3318 3319 3320 3321 3322 3323 3324 3325 3326 3327 3328
{
	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
 */
3329
static struct kmem_cache *bh_cachep __read_mostly;
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/*
 * Once the number of bh's in the machine exceeds this level, we start
 * stripping them in writeback.
 */
3335
static unsigned long max_buffer_heads;
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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;

3351
	if (__this_cpu_inc_return(bh_accounting.ratelimit) - 1 < 4096)
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Linus Torvalds 已提交
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		return;
3353
	__this_cpu_write(bh_accounting.ratelimit, 0);
3354
	for_each_online_cpu(i)
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		tot += per_cpu(bh_accounting, i).nr;
	buffer_heads_over_limit = (tot > max_buffer_heads);
}
3358

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Al Viro 已提交
3359
struct buffer_head *alloc_buffer_head(gfp_t gfp_flags)
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3360
{
3361
	struct buffer_head *ret = kmem_cache_zalloc(bh_cachep, gfp_flags);
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3362
	if (ret) {
C
Christoph Lameter 已提交
3363
		INIT_LIST_HEAD(&ret->b_assoc_buffers);
3364 3365
		preempt_disable();
		__this_cpu_inc(bh_accounting.nr);
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3366
		recalc_bh_state();
3367
		preempt_enable();
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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);
3377 3378
	preempt_disable();
	__this_cpu_dec(bh_accounting.nr);
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3379
	recalc_bh_state();
3380
	preempt_enable();
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}
EXPORT_SYMBOL(free_buffer_head);

3384
static int buffer_exit_cpu_dead(unsigned int cpu)
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{
	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;
	}
3393
	this_cpu_add(bh_accounting.nr, per_cpu(bh_accounting, cpu).nr);
3394
	per_cpu(bh_accounting, cpu).nr = 0;
3395
	return 0;
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}

3398
/**
3399
 * bh_uptodate_or_lock - Test whether the buffer is uptodate
3400 3401 3402 3403 3404 3405 3406 3407 3408 3409 3410 3411 3412 3413 3414 3415 3416 3417
 * @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);

/**
3418
 * bh_submit_read - Submit a locked buffer for reading
3419 3420 3421 3422 3423 3424 3425 3426 3427 3428 3429 3430 3431 3432 3433
 * @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;
3434
	submit_bh(REQ_OP_READ, 0, bh);
3435 3436 3437 3438 3439 3440 3441
	wait_on_buffer(bh);
	if (buffer_uptodate(bh))
		return 0;
	return -EIO;
}
EXPORT_SYMBOL(bh_submit_read);

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void __init buffer_init(void)
{
3444
	unsigned long nrpages;
3445
	int ret;
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Linus Torvalds 已提交
3446

3447 3448 3449 3450
	bh_cachep = kmem_cache_create("buffer_head",
			sizeof(struct buffer_head), 0,
				(SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|
				SLAB_MEM_SPREAD),
3451
				NULL);
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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));
3458 3459 3460
	ret = cpuhp_setup_state_nocalls(CPUHP_FS_BUFF_DEAD, "fs/buffer:dead",
					NULL, buffer_exit_cpu_dead);
	WARN_ON(ret < 0);
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}