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

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Submitter Jan Kara
Date Jan. 12, 2012, 1:20 a.m.
Message ID <1326331253-6497-5-git-send-email-jack@suse.cz>
Download mbox | patch
Permalink /patch/135539/
State New
Headers show

Comments

Jan Kara - Jan. 12, 2012, 1:20 a.m.
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(-)
Al Viro - Jan. 12, 2012, 9:29 p.m.
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...
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Jan Kara - Jan. 12, 2012, 9:36 p.m.
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

Patch

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);
 
 	/* No fallback to buffered IO on errors for XFS. */
 	ASSERT(ret < 0 || ret == count);
@@ -899,6 +901,7 @@  xfs_file_buffered_aio_write(
 	/* We can write back this queue in page reclaim */
 	current->backing_dev_info = mapping->backing_dev_info;
 
+	sb_start_write(inode->i_sb);
 write_retry:
 	trace_xfs_file_buffered_write(ip, count, iocb->ki_pos, 0);
 	ret = generic_file_buffered_write(iocb, iovp, nr_segs,
@@ -914,6 +917,7 @@  write_retry:
 		enospc = 1;
 		goto write_retry;
 	}
+	sb_end_write(inode->i_sb);
 	current->backing_dev_info = NULL;
 	return ret;
 }
@@ -945,8 +949,6 @@  xfs_file_aio_write(
 	if (ocount == 0)
 		return 0;
 
-	xfs_wait_for_freeze(ip->i_mount, SB_FREEZE_WRITE);
-
 	if (XFS_FORCED_SHUTDOWN(ip->i_mount))
 		return -EIO;