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[PATCH 4/8] xfs: Move ilock before transaction start in xfs_setattr_size

To: linux-fsdevel@xxxxxxxxxxxxxxx
Subject: [PATCH 4/8] xfs: Move ilock before transaction start in xfs_setattr_size()
From: Jan Kara <jack@xxxxxxx>
Date: Fri, 20 Jan 2012 21:34:42 +0100
Cc: Eric Sandeen <sandeen@xxxxxxxxxxx>, Dave Chinner <dchinner@xxxxxxxxxx>, Surbhi Palande <csurbhi@xxxxxxxxx>, Kamal Mostafa <kamal@xxxxxxxxxxxxx>, Christoph Hellwig <hch@xxxxxxxxxxxxx>, LKML <linux-kernel@xxxxxxxxxxxxxxx>, xfs@xxxxxxxxxxx, linux-ext4@xxxxxxxxxxxxxxx, Jan Kara <jack@xxxxxxx>, Ben Myers <bpm@xxxxxxx>, Alex Elder <elder@xxxxxxxxxx>
In-reply-to: <1327091686-23177-1-git-send-email-jack@xxxxxxx>
References: <1327091686-23177-1-git-send-email-jack@xxxxxxx>
In xfs we first take ilock and start transaction afterwards. We should obey
this order in all places because otherwise we can create the following deadlock
with filesystem freezing: One process holds ilock and blocks on s_frozen ==
SB_FREEZE_TRANS in xfs_trans_alloc(), another process has a transaction started
(thus blocking freezing) and blocks on ilock. So we have to take ilock earlier
in xfs_setattr_size().

CC: Ben Myers <bpm@xxxxxxx>
CC: Alex Elder <elder@xxxxxxxxxx>
Signed-off-by: Jan Kara <jack@xxxxxxx>
---
 fs/xfs/xfs_iops.c |    6 +++---
 1 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
index 23ce927..3579bc8 100644
--- a/fs/xfs/xfs_iops.c
+++ b/fs/xfs/xfs_iops.c
@@ -850,6 +850,9 @@ xfs_setattr_size(
        if (error)
                goto out_unlock;
 
+       xfs_ilock(ip, XFS_ILOCK_EXCL);
+       lock_flags |= XFS_ILOCK_EXCL;
+
        tp = xfs_trans_alloc(mp, XFS_TRANS_SETATTR_SIZE);
        error = xfs_trans_reserve(tp, 0, XFS_ITRUNCATE_LOG_RES(mp), 0,
                                 XFS_TRANS_PERM_LOG_RES,
@@ -860,9 +863,6 @@ xfs_setattr_size(
        truncate_setsize(inode, iattr->ia_size);
 
        commit_flags = XFS_TRANS_RELEASE_LOG_RES;
-       lock_flags |= XFS_ILOCK_EXCL;
-
-       xfs_ilock(ip, XFS_ILOCK_EXCL);
 
        xfs_trans_ijoin(tp, ip, 0);
 
-- 
1.7.1

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