1 files changed, 18 insertions, 9 deletions

diff --git a/fs/dcache.c b/fs/dcache.c
index 7599d35b4ae5..cb25a1a5e307 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -2372,7 +2372,8 @@ void dentry_update_name_case(struct dentry *dentry, struct qstr *name)
 }
 EXPORT_SYMBOL(dentry_update_name_case);
 
-static void switch_names(struct dentry *dentry, struct dentry *target)
+static void switch_names(struct dentry *dentry, struct dentry *target,
+                         bool exchange)
 {
         if (dname_external(target)) {
                 if (dname_external(dentry)) {
@@ -2406,6 +2407,12 @@ static void switch_names(struct dentry *dentry, struct dentry *target)
                          */
                         unsigned int i;
                         BUILD_BUG_ON(!IS_ALIGNED(DNAME_INLINE_LEN, sizeof(long)));
+                        if (!exchange) {
+                                memcpy(dentry->d_iname, target->d_name.name,
+                                                target->d_name.len + 1);
+                                dentry->d_name.hash_len = target->d_name.hash_len;
+                                return;
+                        }
                         for (i = 0; i < DNAME_INLINE_LEN / sizeof(long); i++) {
                                 swap(((long *) &dentry->d_iname)[i],
                                      ((long *) &target->d_iname)[i]);
@@ -2456,12 +2463,15 @@ static void dentry_unlock_for_move(struct dentry *dentry, struct dentry *target)
  * When switching names, the actual string doesn't strictly have to
  * be preserved in the target - because we're dropping the target
  * anyway. As such, we can just do a simple memcpy() to copy over
- * the new name before we switch.
- *
- * Note that we have to be a lot more careful about getting the hash
- * switched - we have to switch the hash value properly even if it
- * then no longer matches the actual (corrupted) string of the target.
- * The hash value has to match the hash queue that the dentry is on..
+ * the new name before we switch, unless we are going to rehash
+ * it.  Note that if we *do* unhash the target, we are not allowed
+ * to rehash it without giving it a new name/hash key - whether
+ * we swap or overwrite the names here, resulting name won't match
+ * the reality in filesystem; it's only there for d_path() purposes.
+ * Note that all of this is happening under rename_lock, so the
+ * any hash lookup seeing it in the middle of manipulations will
+ * be discarded anyway.  So we do not care what happens to the hash
+ * key in that case.
  */
 /*
  * __d_move - move a dentry
@@ -2507,9 +2517,8 @@ static void __d_move(struct dentry *dentry, struct dentry *target,
                            d_hash(dentry->d_parent, dentry->d_name.hash));
         }
 
-
         /* Switch the names.. */
-        switch_names(dentry, target);
+        switch_names(dentry, target, exchange);
 
         /* ... and switch them in the tree */
         if (IS_ROOT(dentry)) {