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[PATCH] libdiskfs: fix and improve locking in nrefs/nput.


From: Flavio Cruz
Subject: [PATCH] libdiskfs: fix and improve locking in nrefs/nput.
Date: Sun, 14 Feb 2016 18:37:16 -0500
User-agent: Mutt/1.5.24 (2015-08-30)

* libnetfs/node-nput.c: Do not unlock the node since it will be unlocked
later.
* libnetfs/node-nrele.c: Do not lock the node twice if not needed.
---
 libdiskfs/node-nput.c  | 1 -
 libdiskfs/node-nrele.c | 8 ++++++--
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/libdiskfs/node-nput.c b/libdiskfs/node-nput.c
index d23c103..d59769b 100644
--- a/libdiskfs/node-nput.c
+++ b/libdiskfs/node-nput.c
@@ -56,7 +56,6 @@ diskfs_nput (struct node *np)
             hold a weak reference ourselves. */
          diskfs_try_dropping_softrefs (np);
        }
-      pthread_mutex_unlock (&np->lock);
     }
 
   /* Finally get rid of our reference.  */
diff --git a/libdiskfs/node-nrele.c b/libdiskfs/node-nrele.c
index d962846..a96d134 100644
--- a/libdiskfs/node-nrele.c
+++ b/libdiskfs/node-nrele.c
@@ -28,6 +28,7 @@
 void
 diskfs_nrele (struct node *np)
 {
+  int locked = FALSE;
   struct references result;
 
   /* While we call the diskfs_try_dropping_softrefs, we need to hold
@@ -37,6 +38,7 @@ diskfs_nrele (struct node *np)
 
   if (result.hard == 0)
     {
+      locked = TRUE;
       pthread_mutex_lock (&np->lock);
       diskfs_lost_hardrefs (np);
       if (!np->dn_stat.st_nlink)
@@ -49,7 +51,6 @@ diskfs_nrele (struct node *np)
             hold a weak reference ourselves. */
          diskfs_try_dropping_softrefs (np);
        }
-      pthread_mutex_unlock (&np->lock);
     }
 
   /* Finally get rid of our reference.  */
@@ -57,7 +58,10 @@ diskfs_nrele (struct node *np)
 
   if (result.hard == 0 && result.weak == 0)
     {
-      pthread_mutex_lock (&np->lock);
+      if (! locked)
+        pthread_mutex_lock (&np->lock);
       diskfs_drop_node (np);
     }
+  else if (locked)
+    pthread_mutex_unlock (&np->lock);
 }
-- 
2.6.4




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