[Devel] [PATCH RHEL7 COMMIT] ms/xfs: fix dquot isolation hang

[Konstantin Khorenko]

The commit is pushed to "temp1" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-327.3.1.el7
------>
commit f45a7773669121cacfd28a9081f0d68b80a99de3
Author: Vladimir Davydov <vdavydov at virtuozzo.com>
Date:   Fri Dec 25 13:48:41 2015 +0400

    ms/xfs: fix dquot isolation hang
    
    Patch series description:
    
    https://jira.sw.ru/browse/PSBM-42319
    
    Andrew Morton (1):
      xfs-convert-dquot-cache-lru-to-list_lru-fix
    
    Dave Chinner (2):
      xfs: convert dquot cache lru to list_lru
      xfs: fix dquot isolation hang
    
    Vladimir Davydov (3):
      xfs_qm: lost hunk from "ms/list_lru: dynamically adjust node arrays"
      xfs_qm: lost hunk from "ms/list_lru: introduce
        list_lru_shrink_{count,walk}"
      xfs_qm: lost hunk from "ms/list_lru: add helpers to isolate items"
    
    ================================
    This patch description:
    
    From: Dave Chinner <david at fromorbit.com>
    
    The new LRU list isolation code in xfs_qm_dquot_isolate() isn't
    completely up to date.  Firstly, it needs conversion to return enum
    lru_status values, not raw numbers. Secondly - most importantly - it
    fails to unlock the dquot and relock the LRU in the LRU_RETRY path.
    This leads to deadlocks in xfstests generic/232. Fix them.
    
    Signed-off-by: Dave Chinner <dchinner at redhat.com>
    Cc: Glauber Costa <glommer at gmail.com>
    Cc: Michal Hocko <mhocko at suse.cz>
    Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
    Signed-off-by: Al Viro <viro at zeniv.linux.org.uk>
    (cherry picked from commit 35163417fb7a55a24b6b0ebb102e9991adf309aa)
    Signed-off-by: Vladimir Davydov <vdavydov at virtuozzo.com>
---
 fs/xfs/xfs_qm.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/fs/xfs/xfs_qm.c b/fs/xfs/xfs_qm.c
index edf2349..1a454d1 100644
--- a/fs/xfs/xfs_qm.c
+++ b/fs/xfs/xfs_qm.c
@@ -451,7 +451,7 @@ xfs_qm_dquot_isolate(
 		trace_xfs_dqreclaim_want(dqp);
 		list_del_init(&dqp->q_lru);
 		XFS_STATS_DEC(xs_qm_dquot_unused);
-		return 0;
+		return LRU_REMOVED;
 	}
 
 	/*
@@ -497,17 +497,19 @@ xfs_qm_dquot_isolate(
 	XFS_STATS_DEC(xs_qm_dquot_unused);
 	trace_xfs_dqreclaim_done(dqp);
 	XFS_STATS_INC(xs_qm_dqreclaims);
-	return 0;
+	return LRU_REMOVED;
 
 out_miss_busy:
 	trace_xfs_dqreclaim_busy(dqp);
 	XFS_STATS_INC(xs_qm_dqreclaim_misses);
-	return 2;
+	return LRU_SKIP;
 
 out_unlock_dirty:
 	trace_xfs_dqreclaim_busy(dqp);
 	XFS_STATS_INC(xs_qm_dqreclaim_misses);
-	return 3;
+	xfs_dqunlock(dqp);
+	spin_lock(lru_lock);
+	return LRU_RETRY;
 }
 
 static unsigned long