]> err.no Git - linux-2.6/commit
[PATCH] Fix race in do_get_write_access()
authorJan Kara <jack@suse.cz>
Tue, 6 Sep 2005 22:19:17 +0000 (15:19 -0700)
committerLinus Torvalds <torvalds@g5.osdl.org>
Wed, 7 Sep 2005 23:57:57 +0000 (16:57 -0700)
commit4407c2b6b297339e296facf62e020cf66e55053d
tree485d60b1cb5c6013d09a0327355e216b202bd8ed
parente39f07c83bac96850265b87a69dfc5c90ed4f1f5
[PATCH] Fix race in do_get_write_access()

  attached patch should fix the following race:
     Proc 1                               Proc 2

     __flush_batch()
       ll_rw_block()
                                        do_get_write_access()
   lock_buffer
                                             jh is only waiting for checkpoint
     -> b_transaction == NULL ->
     do nothing
                                           unlock_buffer
    test_set_buffer_locked()
    test_clear_buffer_dirty()
                                           __journal_file_buffer()
                                        change the data
    submit_bh()

and we have sent wrong data to disk...  We now clean the dirty buffer flag
under buffer lock in all cases and hence we know that whenever a buffer is
starting to be journaled we either finish the pending write-out before
attaching a buffer to a transaction or we won't write the buffer until the
transaction is going to be committed.

The test in jbd_unexpected_dirty_buffer() is redundant - remove it.
Furthermore we have to clear the buffer dirty bit under the buffer lock to
prevent races with buffer write-out (and hence prevent returning a buffer with
IO happening).

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
fs/jbd/transaction.c