jbd: fix race between free buffer and commit transaction

journal_try_to_free_buffers() could race with jbd commit transaction when
the later is holding the buffer reference while waiting for the data
buffer to flush to disk.  If the caller of journal_try_to_free_buffers()
request tries hard to release the buffers, it will treat the failure as
error and return back to the caller.  We have seen the directo IO failed
due to this race.  Some of the caller of releasepage() also expecting the
buffer to be dropped when passed with GFP_KERNEL mask to the
releasepage()->journal_try_to_free_buffers().

With this patch, if the caller is passing the __GFP_WAIT and __GFP_FS to
indicating this call could wait, in case of try_to_free_buffers() failed,
let's waiting for journal_commit_transaction() to finish commit the
current committing transaction, then try to free those buffers again.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Mingming Cao <cmm@us.ibm.com>
Reviewed-by: Badari Pulavarty <pbadari@us.ibm.com>
Acked-by: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 1 insertions, 2 deletions

diff --git a/mm/filemap.c b/mm/filemap.c
index 7675b91..5d4c880 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2563,9 +2563,8 @@ EXPORT_SYMBOL(generic_file_aio_write);
  * Otherwise return zero.
  *
  * The @gfp_mask argument specifies whether I/O may be performed to release
- * this page (__GFP_IO), and whether the call may block (__GFP_WAIT).
+ * this page (__GFP_IO), and whether the call may block (__GFP_WAIT & __GFP_FS).
  *
- * NOTE: @gfp_mask may go away, and this function may become non-blocking.
  */
 int try_to_release_page(struct page *page, gfp_t gfp_mask)
 {