Merge branch 'work.dcache' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

Pull dcache updates from Al Viro:
 "Neil Brown's d_move()/d_path() race fix"

* 'work.dcache' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  VFS: close race between getcwd() and d_move()

1 files changed, 16 insertions, 7 deletions

diff --git a/fs/dcache.c b/fs/dcache.c
index c6d996ee2d61..d93872d425d6 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -466,9 +466,11 @@ static void dentry_lru_add(struct dentry *dentry)
  * d_drop() is used mainly for stuff that wants to invalidate a dentry for some
  * reason (NFS timeouts or autofs deletes).
  *
- * __d_drop requires dentry->d_lock.
+ * __d_drop requires dentry->d_lock
+ * ___d_drop doesn't mark dentry as "unhashed"
+ *   (dentry->d_hash.pprev will be LIST_POISON2, not NULL).
  */
-void __d_drop(struct dentry *dentry)
+static void ___d_drop(struct dentry *dentry)
 {
 	if (!d_unhashed(dentry)) {
 		struct hlist_bl_head *b;
@@ -484,12 +486,17 @@ void __d_drop(struct dentry *dentry)
 
 		hlist_bl_lock(b);
 		__hlist_bl_del(&dentry->d_hash);
-		dentry->d_hash.pprev = NULL;
 		hlist_bl_unlock(b);
 		/* After this call, in-progress rcu-walk path lookup will fail. */
 		write_seqcount_invalidate(&dentry->d_seq);
 	}
 }
+
+void __d_drop(struct dentry *dentry)
+{
+	___d_drop(dentry);
+	dentry->d_hash.pprev = NULL;
+}
 EXPORT_SYMBOL(__d_drop);
 
 void d_drop(struct dentry *dentry)
@@ -2380,7 +2387,7 @@ EXPORT_SYMBOL(d_delete);
 static void __d_rehash(struct dentry *entry)
 {
 	struct hlist_bl_head *b = d_hash(entry->d_name.hash);
-	BUG_ON(!d_unhashed(entry));
+
 	hlist_bl_lock(b);
 	hlist_bl_add_head_rcu(&entry->d_hash, b);
 	hlist_bl_unlock(b);
@@ -2815,9 +2822,9 @@ static void __d_move(struct dentry *dentry, struct dentry *target,
 	write_seqcount_begin_nested(&target->d_seq, DENTRY_D_LOCK_NESTED);
 
 	/* unhash both */
-	/* __d_drop does write_seqcount_barrier, but they're OK to nest. */
-	__d_drop(dentry);
-	__d_drop(target);
+	/* ___d_drop does write_seqcount_barrier, but they're OK to nest. */
+	___d_drop(dentry);
+	___d_drop(target);
 
 	/* Switch the names.. */
 	if (exchange)
@@ -2829,6 +2836,8 @@ static void __d_move(struct dentry *dentry, struct dentry *target,
 	__d_rehash(dentry);
 	if (exchange)
 		__d_rehash(target);
+	else
+		target->d_hash.pprev = NULL;
 
 	/* ... and switch them in the tree */
 	if (IS_ROOT(dentry)) {