ocfs2: don't use iocb when EIOCBQUEUED returns
authorChangwei Ge <ge.changwei@h3c.com>
Fri, 2 Nov 2018 22:48:11 +0000 (15:48 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Sat, 3 Nov 2018 17:09:37 +0000 (10:09 -0700)
commit9e985787750db8aae87f02b67e908f28ac4d6b83
treeb7693d418aa7201f4bc290774c5b8540350356c9
parent21158ca85b73ddd0088076a5209cfd040513a8b5
ocfs2: don't use iocb when EIOCBQUEUED returns

When -EIOCBQUEUED returns, it means that aio_complete() will be called
from dio_complete(), which is an asynchronous progress against
write_iter.  Generally, IO is a very slow progress than executing
instruction, but we still can't take the risk to access a freed iocb.

And we do face a BUG crash issue.  Using the crash tool, iocb is
obviously freed already.

  crash> struct -x kiocb ffff881a350f5900
  struct kiocb {
    ki_filp = 0xffff881a350f5a80,
    ki_pos = 0x0,
    ki_complete = 0x0,
    private = 0x0,
    ki_flags = 0x0
  }

And the backtrace shows:
  ocfs2_file_write_iter+0xcaa/0xd00 [ocfs2]
  aio_run_iocb+0x229/0x2f0
  do_io_submit+0x291/0x540
  SyS_io_submit+0x10/0x20
  system_call_fastpath+0x16/0x75

Link: http://lkml.kernel.org/r/1523361653-14439-1-git-send-email-ge.changwei@h3c.com
Signed-off-by: Changwei Ge <ge.changwei@h3c.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Joseph Qi <jiangqi903@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
fs/ocfs2/file.c