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[PATCH] Fix try_to_free_buffer() locking

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Fix commit ecdfc9787f

Not to put too fine a point on it, but in a nutshell...

	__set_page_dirty_buffers() | try_to_free_buffers()
	---------------------------+---------------------------
	                           | spin_lock(private_lock);
	                           | drop_bufers()
	                           | spin_unlock(private_lock);
	spin_lock(private_lock)    |
	!page_has_buffers()        |
	spin_unlock(private_lock)  |
	SetPageDirty()             |
	                           | cancel_dirty_page()

                          oops!

Signed-off-by: Nick Piggin <npiggin@suse.de>
Acked-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Nick Piggin 2007-01-30 14:36:27 +11:00 committed by Linus Torvalds
parent 4cbf2aa35e
commit 87df7241bd
1 changed files with 5 additions and 1 deletions
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6
fs/buffer.c
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@ -2844,7 +2844,6 @@ int try_to_free_buffers(struct page *page)
spin_lock(&mapping->private_lock); spin_lock(&mapping->private_lock);
ret = drop_buffers(page, &buffers_to_free); ret = drop_buffers(page, &buffers_to_free);
spin_unlock(&mapping->private_lock);
/* /*
* If the filesystem writes its buffers by hand (eg ext3) * If the filesystem writes its buffers by hand (eg ext3)
@ -2855,9 +2854,14 @@ int try_to_free_buffers(struct page *page)
* Also, during truncate, discard_buffer will have marked all * Also, during truncate, discard_buffer will have marked all
* the page's buffers clean. We discover that here and clean * the page's buffers clean. We discover that here and clean
* the page also. * the page also.
*
* 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.
*/ */
if (ret) if (ret)
cancel_dirty_page(page, PAGE_CACHE_SIZE); cancel_dirty_page(page, PAGE_CACHE_SIZE);
spin_unlock(&mapping->private_lock);
out: out:
if (buffers_to_free) { if (buffers_to_free) {
struct buffer_head *bh = buffers_to_free; struct buffer_head *bh = buffers_to_free;