[Ocfs2-devel] [PATCH v2] ocfs2/cluster: unlock the o2hb_live_lock before the o2nm_depend_item()

[alex chen]

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.c...@huawei.com>
Reviewed-by: Yiwen Jiang <jiangyi...@huawei.com>
Reviewed-by: Jun Piao <piao...@huawei.com>
---
 fs/ocfs2/cluster/heartbeat.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/fs/ocfs2/cluster/heartbeat.c b/fs/ocfs2/cluster/heartbeat.c
index d020604..07b2fdc 100644
--- a/fs/ocfs2/cluster/heartbeat.c
+++ b/fs/ocfs2/cluster/heartbeat.c
@@ -2399,8 +2399,15 @@ 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);
+
+               config_item_put(&reg->hr_item);
+               spin_lock(&o2hb_live_lock);
+
                if (!ret) {
                        mlog(ML_CLUSTER, "Pin region %s\n", uuid);
                        reg->hr_item_pinned = 1;
-- 
1.9.5.msysgit.1


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