[Ocfs2-devel] [PATCH] ocfs2/cluster: unlock the o2hb_live_lock before the o2nm_depend_item()

From: alex chen <alex.chen@huawei.com>
To: ocfs2-devel@oss.oracle.com
Subject: [Ocfs2-devel] [PATCH] ocfs2/cluster: unlock the o2hb_live_lock before the o2nm_depend_item()
Date: Tue, 31 Oct 2017 20:41:39 +0800	[thread overview]
Message-ID: <59F86F83.7010501@huawei.com> (raw)

In the following situation, the down_write() will be called under
the spin_lock(), which may lead a soft lockup:
o2hb_region_inc_user
 spin_lock(&o2hb_live_lock)
  o2hb_region_pin
   o2nm_depend_item
    configfs_depend_item
     inode_lock
      down_write
      -->here may sleep and reschedule

So we should unlock the o2hb_live_lock before the o2nm_depend_item(), and
get item reference in advance to prevent the region to be released.

Signed-off-by: Alex Chen <alex.chen@huawei.com>
Reviewed-by: Yiwen Jiang <jiangyiwen@huawei.com>
Reviewed-by: Jun Piao <piaojun@huawei.com>
---
 fs/ocfs2/cluster/heartbeat.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/fs/ocfs2/cluster/heartbeat.c b/fs/ocfs2/cluster/heartbeat.c
index d020604..f1142a9 100644
--- a/fs/ocfs2/cluster/heartbeat.c
+++ b/fs/ocfs2/cluster/heartbeat.c
@@ -2399,6 +2399,9 @@ static int o2hb_region_pin(const char *region_uuid)
 		if (reg->hr_item_pinned || reg->hr_item_dropped)
 			goto skip_pin;

+		config_item_get(&reg->hr_item);
+		spin_unlock(&o2hb_live_lock);
+
 		/* Ignore ENOENT only for local hb (userdlm domain) */
 		ret = o2nm_depend_item(&reg->hr_item);
 		if (!ret) {
@@ -2410,9 +2413,14 @@ static int o2hb_region_pin(const char *region_uuid)
 			else {
 				mlog(ML_ERROR, "Pin region %s fails with %d\n",
 				     uuid, ret);
+				config_item_put(&reg->hr_item);
+				spin_lock(&o2hb_live_lock);
 				break;
 			}
 		}
+
+		config_item_put(&reg->hr_item);
+		spin_lock(&o2hb_live_lock);
 skip_pin:
 		if (found)
 			break;
-- 1.9.5.msysgit.1
