Ocfs2 devel - Sep 2014 - [PATCH] ocfs2/dlm: call dlm_lockres_put without resource spinlock

dlm_lockres_put should be called without &res->spinlock, otherwise a
deadlock case may happen.

spin_lock(&res->spinlock)
...
dlm_lockres_put
  ->dlm_lockres_release
    ->dlm_print_one_lock_resource
      ->spin_lock(&res->spinlock)

Signed-off-by: Alex Chen <alex.chen at huawei.com>
Reviewed-by: Joseph Qi <joseph.qi at huawei.com>
---
 fs/ocfs2/dlm/dlmrecovery.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/fs/ocfs2/dlm/dlmrecovery.c b/fs/ocfs2/dlm/dlmrecovery.c
index 45067fa..3365839 100644
--- a/fs/ocfs2/dlm/dlmrecovery.c
+++ b/fs/ocfs2/dlm/dlmrecovery.c
@@ -1710,9 +1710,12 @@ int dlm_master_requery_handler(struct o2net_msg *msg, u32
len, void *data,
 				BUG();
 			} else
 				__dlm_lockres_grab_inflight_worker(dlm, res);
-		} else /* put.. incase we are not the master */
+			spin_unlock(&res->spinlock);
+		} else {
+			/* put.. incase we are not the master */
+			spin_unlock(&res->spinlock);
 			dlm_lockres_put(res);
-		spin_unlock(&res->spinlock);
+		}
 	}
 	spin_unlock(&dlm->spinlock);

-- 
1.8.4.3

On Fri, 26 Sep 2014 16:41:39 +0800 alex chen <alex.chen at huawei.com>
wrote:
> dlm_lockres_put should be called without &res->spinlock, otherwise a
> deadlock case may happen.
> 
> spin_lock(&res->spinlock)
> ...
> dlm_lockres_put
>   ->dlm_lockres_release
>     ->dlm_print_one_lock_resource
>       ->spin_lock(&res->spinlock)
> 
> Signed-off-by: Alex Chen <alex.chen at huawei.com>
> Reviewed-by: Joseph Qi <joseph.qi at huawei.com>
> ---
>  fs/ocfs2/dlm/dlmrecovery.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/ocfs2/dlm/dlmrecovery.c b/fs/ocfs2/dlm/dlmrecovery.c
> index 45067fa..3365839 100644
> --- a/fs/ocfs2/dlm/dlmrecovery.c
> +++ b/fs/ocfs2/dlm/dlmrecovery.c
> @@ -1710,9 +1710,12 @@ int dlm_master_requery_handler(struct o2net_msg
*msg, u32 len, void *data,
>  				BUG();
This code does a GFP_ATOMIC allocation attempt and if that fails, it
goes BUG().

Guys, GFP_ATOMIC is unreliable.  This isn't production quality code :(