dcache: Prevent d_genocide() from decrementing d_count more than once

When d_genocide is called, it traverses the dentries decrementing the
d_count. After the loops, a check is made to see if a rename or other
change has been made, if so, it traverse the tree again. Unfortunately,
this will decrement the same dentries that it decremented the first
time.

To avoid this multiple decrement, I added a DCACHE_GENOCIDE flag that
will be set to a dentry when the d_genocide has decremented its counter.
It will only decrement the counter if this flag is not set.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Nick Piggin <npiggin@suse.de>
Cc: John Kacur <jkacur@redhat.com>
Cc: "Luis Claudio R. Goncalves" <lclaudio@uudg.org>
Cc: Clark Williams <williams@redhat.com>
Acked-by: john stultz <johnstul@us.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 8 insertions, 2 deletions

diff --git a/fs/dcache.c b/fs/dcache.c
index 673cdc22ca46..18a3b762297c 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -2568,7 +2568,10 @@ resume:
 			spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_);
 			goto repeat;
 		}
-		atomic_dec(&dentry->d_count);
+		if (!(dentry->d_flags & DCACHE_GENOCIDE)) {
+			atomic_dec(&dentry->d_count);
+			dentry->d_flags |= DCACHE_GENOCIDE;
+		}
 		spin_unlock(&dentry->d_lock);
 	}
 	if (this_parent != root) {
@@ -2576,7 +2579,10 @@ resume:
 		struct dentry *child;
 
 		tmp = this_parent->d_parent;
-		atomic_dec(&this_parent->d_count);
+		if (!(this_parent->d_flags & DCACHE_GENOCIDE)) {
+			atomic_dec(&this_parent->d_count);
+			this_parent->d_flags |= DCACHE_GENOCIDE;
+		}
 		rcu_read_lock();
 		spin_unlock(&this_parent->d_lock);
 		child = this_parent;