Re: [PATCH 4/4] xfs: Protect xfs_file_aio_write() with sb_start_write - sb_end_write

Jan Kara
2012-01-12T21:37:01Z

On Thu 12-01-12 21:29:41, Al Viro wrote:
> On Thu, Jan 12, 2012 at 02:20:53AM +0100, Jan Kara wrote:
> > Replace racy xfs_wait_for_freeze() check with reliable sb_start_write()
> > - sb_end_write() locking. Due to lock ranking dictated by the page fault
> > code we have to call sb_start_write() after we acquire ilock.
> >
> > CC: Ben Myers <bpm@sgi.com>
> > CC: Alex Elder <elder@kernel.org>
> > Signed-off-by: Jan Kara <jack@suse.cz>
> > ---
> > fs/xfs/xfs_file.c | 6 ++++--
> > 1 files changed, 4 insertions(+), 2 deletions(-)
> >
> > diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
> > index 753ed9b..c5f879b 100644
> > --- a/fs/xfs/xfs_file.c
> > +++ b/fs/xfs/xfs_file.c
> > @@ -862,9 +862,11 @@ xfs_file_dio_aio_write(
> > *iolock = XFS_IOLOCK_SHARED;
> > }
> >
> > + sb_start_write(inode->i_sb);
> > trace_xfs_file_direct_write(ip, count, iocb->ki_pos, 0);
> > ret = generic_file_direct_write(iocb, iovp,
> > &nr_segs, pos, &iocb->ki_pos, count, ocount);
> > + sb_end_write(inode->i_sb);
>
> What lock ordering do you have in mind? Explicit description in fs/super.c,
> please...
Good point. Will add explanatory comment. Thanks.

Honza
--
Jan Kara <jack@suse.cz>
SUSE Labs, CR