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Date:	Thu, 12 Jan 2012 02:20:53 +0100
From:	Jan Kara <jack@...e.cz>
To:	linux-fsdevel@...r.kernel.org
Cc:	LKML <linux-kernel@...r.kernel.org>, linux-ext4@...r.kernel.org,
	xfs@....sgi.com, Eric Sandeen <sandeen@...deen.net>,
	Dave Chinner <dchinner@...hat.com>,
	Surbhi Palande <csurbhi@...il.com>,
	Kamal Mostafa <kamal@...onical.com>,
	Christoph Hellwig <hch@...radead.org>, Jan Kara <jack@...e.cz>,
	Ben Myers <bpm@....com>, Alex Elder <elder@...nel.org>
Subject: [PATCH 4/4] xfs: Protect xfs_file_aio_write() with sb_start_write - sb_end_write

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@....com>
CC: Alex Elder <elder@...nel.org>
Signed-off-by: Jan Kara <jack@...e.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);
 
 	/* 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;
 
-- 
1.7.1

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