ext4: fix deadlock in journal_unmap_buffer()

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>

1 files changed, 1 insertions, 1 deletions

diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h
index 1be23d9fdacb..e30b66346942 100644
--- a/include/linux/jbd2.h
+++ b/include/linux/jbd2.h
@@ -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 *);