1 files changed, 43 insertions, 52 deletions

diff --git a/fs/dcache.c b/fs/dcache.c
index 611ffe928c03..a39fe47c466f 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -296,8 +296,12 @@ static struct dentry *d_kill(struct dentry *dentry, struct dentry *parent)
         __releases(parent->d_lock)
         __releases(dentry->d_inode->i_lock)
 {
-        dentry->d_parent = NULL;
         list_del(&dentry->d_u.d_child);
+        /*
+         * Inform try_to_ascend() that we are no longer attached to the
+         * dentry tree
+         */
+        dentry->d_flags |= DCACHE_DISCONNECTED;
         if (parent)
                 spin_unlock(&parent->d_lock);
         dentry_iput(dentry);
@@ -1012,6 +1016,35 @@ void shrink_dcache_for_umount(struct super_block *sb)
 }
 
 /*
+ * This tries to ascend one level of parenthood, but
+ * we can race with renaming, so we need to re-check
+ * the parenthood after dropping the lock and check
+ * that the sequence number still matches.
+ */
+static struct dentry *try_to_ascend(struct dentry *old, int locked, unsigned seq)
+{
+        struct dentry *new = old->d_parent;
+
+        rcu_read_lock();
+        spin_unlock(&old->d_lock);
+        spin_lock(&new->d_lock);
+
+        /*
+         * might go back up the wrong parent if we have had a rename
+         * or deletion
+         */
+        if (new != old->d_parent ||
+                 (old->d_flags & DCACHE_DISCONNECTED) ||
+                 (!locked && read_seqretry(&rename_lock, seq))) {
+                spin_unlock(&new->d_lock);
+                new = NULL;
+        }
+        rcu_read_unlock();
+        return new;
+}
+
+
+/*
  * Search for at least 1 mount point in the dentry's subdirs.
  * We descend to the next level whenever the d_subdirs
  * list is non-empty and continue searching.
@@ -1066,24 +1099,10 @@ resume:
          * All done at this level ... ascend and resume the search.
          */
         if (this_parent != parent) {
-                struct dentry *tmp;
-                struct dentry *child;
-
-                tmp = this_parent->d_parent;
-                rcu_read_lock();
-                spin_unlock(&this_parent->d_lock);
-                child = this_parent;
-                this_parent = tmp;
-                spin_lock(&this_parent->d_lock);
-                /* might go back up the wrong parent if we have had a rename
-                 * or deletion */
-                if (this_parent != child->d_parent ||
-                         (!locked && read_seqretry(&rename_lock, seq))) {
-                        spin_unlock(&this_parent->d_lock);
-                        rcu_read_unlock();
+                struct dentry *child = this_parent;
+                this_parent = try_to_ascend(this_parent, locked, seq);
+                if (!this_parent)
                         goto rename_retry;
-                }
-                rcu_read_unlock();
                 next = child->d_u.d_child.next;
                 goto resume;
         }
@@ -1181,24 +1200,10 @@ resume:
          * All done at this level ... ascend and resume the search.
          */
         if (this_parent != parent) {
-                struct dentry *tmp;
-                struct dentry *child;
-
-                tmp = this_parent->d_parent;
-                rcu_read_lock();
-                spin_unlock(&this_parent->d_lock);
-                child = this_parent;
-                this_parent = tmp;
-                spin_lock(&this_parent->d_lock);
-                /* might go back up the wrong parent if we have had a rename
-                 * or deletion */
-                if (this_parent != child->d_parent ||
-                        (!locked && read_seqretry(&rename_lock, seq))) {
-                        spin_unlock(&this_parent->d_lock);
-                        rcu_read_unlock();
+                struct dentry *child = this_parent;
+                this_parent = try_to_ascend(this_parent, locked, seq);
+                if (!this_parent)
                         goto rename_retry;
-                }
-                rcu_read_unlock();
                 next = child->d_u.d_child.next;
                 goto resume;
         }
@@ -2942,28 +2947,14 @@ resume:
                 spin_unlock(&dentry->d_lock);
         }
         if (this_parent != root) {
-                struct dentry *tmp;
-                struct dentry *child;
-
-                tmp = this_parent->d_parent;
+                struct dentry *child = this_parent;
                 if (!(this_parent->d_flags & DCACHE_GENOCIDE)) {
                         this_parent->d_flags |= DCACHE_GENOCIDE;
                         this_parent->d_count--;
                 }
-                rcu_read_lock();
-                spin_unlock(&this_parent->d_lock);
-                child = this_parent;
-                this_parent = tmp;
-                spin_lock(&this_parent->d_lock);
-                /* might go back up the wrong parent if we have had a rename
-                 * or deletion */
-                if (this_parent != child->d_parent ||
-                         (!locked && read_seqretry(&rename_lock, seq))) {
-                        spin_unlock(&this_parent->d_lock);
-                        rcu_read_unlock();
+                this_parent = try_to_ascend(this_parent, locked, seq);
+                if (!this_parent)
                         goto rename_retry;
-                }
-                rcu_read_unlock();
                 next = child->d_u.d_child.next;
                 goto resume;
         }