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Commit 87df7241 authored by Nick Piggin's avatar Nick Piggin Committed by Linus Torvalds
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[PATCH] Fix try_to_free_buffer() locking 



Fix commit ecdfc978

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: default avatarNick Piggin <npiggin@suse.de>
Acked-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 4cbf2aa3

fs/buffer.c

+5 −1
Original line number Diff line number Diff line
@@ -2844,7 +2844,6 @@ int try_to_free_buffers(struct page *page) 


	spin_lock(&mapping->private_lock);

	ret = drop_buffers(page, &buffers_to_free);

	spin_unlock(&mapping->private_lock);



	/*

	 * 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

	 * the page's buffers clean.  We discover that here and clean

	 * 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)

		cancel_dirty_page(page, PAGE_CACHE_SIZE);

	spin_unlock(&mapping->private_lock);

out:

	if (buffers_to_free) {

		struct buffer_head *bh = buffers_to_free;