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ext4: fix deadlock in journal_unmap_buffer()

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We cannot wait for transaction commit in journal_unmap_buffer()
because we hold page lock which ranks below transaction start.  We
solve the issue by bailing out of journal_unmap_buffer() and
jbd2_journal_invalidatepage() with -EBUSY.  Caller is then responsible
for waiting for transaction commit to finish and try invalidation
again. Since the issue can happen only for page stradding i_size, it
is simple enough to manually call jbd2_journal_invalidatepage() for
such page from ext4_setattr(), check the return value and wait if
necessary.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
This commit is contained in:
Jan Kara
2012-12-25 13:29:52 -05:00
committed by Theodore Ts'o
parent 4520fb3c36
commit 53e872681f
3 changed files with 86 additions and 25 deletions
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include/linux/jbd2.h
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@@ -1098,7 +1098,7 @@ void jbd2_journal_set_triggers(struct buffer_head *,
extern int jbd2_journal_dirty_metadata (handle_t *, struct buffer_head *);
extern int jbd2_journal_forget (handle_t *, struct buffer_head *);
extern void journal_sync_buffer (struct buffer_head *);
extern void jbd2_journal_invalidatepage(journal_t *,
extern int jbd2_journal_invalidatepage(journal_t *,
struct page *, unsigned long);
extern int jbd2_journal_try_to_free_buffers(journal_t *, struct page *, gfp_t);
extern int jbd2_journal_stop(handle_t *);