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authorNick Piggin <nickpiggin@yahoo.com.au>2007-01-30 14:36:27 +1100
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-01-29 20:20:42 -0800
commit87df7241bd547da5d4d4a4e5397866dfe422e439 (patch)
treeffe1e90a761aa358ef95e351e0718cb3c377ad37
parent4cbf2aa35e1c189db234190fefc6c83b139ef963 (diff)
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[PATCH] Fix try_to_free_buffer() locking
Fix commit ecdfc9787fe527491baefc22dce8b2dbd5b2908d 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>
-rw-r--r--fs/buffer.c6
1 files changed, 5 insertions, 1 deletions
diff --git a/fs/buffer.c b/fs/buffer.c
index 460f1c43238..1ad674fd348 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -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;