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authorLinus Torvalds <torvalds@linux-foundation.org>2009-08-21 17:40:08 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-08-21 17:40:08 -0700
commit8e9d78edea3ce5c0036f85b93091483f2f15443a (patch)
tree898c98daca2602f0df70558211f30ff1bd2bcf6c
parent4dfd79e7b42bff334128907e28c3b41f1ef1cec8 (diff)
Re-introduce page mapping check in mark_buffer_dirty()
In commit a8e7d49aa7be728c4ae241a75a2a124cdcabc0c5 ("Fix race in create_empty_buffers() vs __set_page_dirty_buffers()"), I removed a test for a NULL page mapping unintentionally when some of the code inside __set_page_dirty() was moved to the callers. That removal generally didn't matter, since a filesystem would serialize truncation (which clears the page mapping) against writing (which marks the buffer dirty), so locking at a higher level (either per-page or an inode at a time) should mean that the buffer page would be stable. And indeed, nothing bad seemed to happen. Except it turns out that apparently reiserfs does something odd when under load and writing out the journal, and we have a number of bugzilla entries that look similar: http://bugzilla.kernel.org/show_bug.cgi?id=13556 http://bugzilla.kernel.org/show_bug.cgi?id=13756 http://bugzilla.kernel.org/show_bug.cgi?id=13876 and it looks like reiserfs depended on that check (the common theme seems to be "data=journal", and a journal writeback during a truncate). I suspect reiserfs should have some additional locking, but in the meantime this should get us back to the pre-2.6.29 behavior. Pattern-pointed-out-by: Roland Kletzing <devzero@web.de> Cc: stable@kernel.org (2.6.29 and 2.6.30) Cc: Jeff Mahoney <jeffm@suse.com> Cc: Nick Piggin <npiggin@suse.de> Cc: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--fs/buffer.c7
1 files changed, 5 insertions, 2 deletions
diff --git a/fs/buffer.c b/fs/buffer.c
index a3ef091a45bd..28f320fac4d4 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -1165,8 +1165,11 @@ void mark_buffer_dirty(struct buffer_head *bh)
if (!test_set_buffer_dirty(bh)) {
struct page *page = bh->b_page;
- if (!TestSetPageDirty(page))
- __set_page_dirty(page, page_mapping(page), 0);
+ if (!TestSetPageDirty(page)) {
+ struct address_space *mapping = page_mapping(page);
+ if (mapping)
+ __set_page_dirty(page, mapping, 0);
+ }
}
}