Merge branch 'cross-rename' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs

Pull renameat2 system call from Miklos Szeredi:
 "This adds a new syscall, renameat2(), which is the same as renameat()
  but with a flags argument.

  The purpose of extending rename is to add cross-rename, a symmetric
  variant of rename, which exchanges the two files.  This allows
  interesting things, which were not possible before, for example
  atomically replacing a directory tree with a symlink, etc...  This
  also allows overlayfs and friends to operate on whiteouts atomically.

  Andy Lutomirski also suggested a "noreplace" flag, which disables the
  overwriting behavior of rename.

  These two flags, RENAME_EXCHANGE and RENAME_NOREPLACE are only
  implemented for ext4 as an example and for testing"

* 'cross-rename' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs:
  ext4: add cross rename support
  ext4: rename: split out helper functions
  ext4: rename: move EMLINK check up
  ext4: rename: create ext4_renament structure for local vars
  vfs: add cross-rename
  vfs: lock_two_nondirectories: allow directory args
  security: add flags to rename hooks
  vfs: add RENAME_NOREPLACE flag
  vfs: add renameat2 syscall
  vfs: rename: use common code for dir and non-dir
  vfs: rename: move d_move() up
  vfs: add d_is_dir()

1 files changed, 12 insertions, 13 deletions

diff --git a/fs/inode.c b/fs/inode.c
index e6905152c39f..fb59ba7967f1 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -944,24 +944,22 @@ EXPORT_SYMBOL(unlock_new_inode);
 
 /**
  * lock_two_nondirectories - take two i_mutexes on non-directory objects
+ *
+ * Lock any non-NULL argument that is not a directory.
+ * Zero, one or two objects may be locked by this function.
+ *
  * @inode1: first inode to lock
  * @inode2: second inode to lock
  */
 void lock_two_nondirectories(struct inode *inode1, struct inode *inode2)
 {
-	WARN_ON_ONCE(S_ISDIR(inode1->i_mode));
-	if (inode1 == inode2 || !inode2) {
-		mutex_lock(&inode1->i_mutex);
-		return;
-	}
-	WARN_ON_ONCE(S_ISDIR(inode2->i_mode));
-	if (inode1 < inode2) {
+	if (inode1 > inode2)
+		swap(inode1, inode2);
+
+	if (inode1 && !S_ISDIR(inode1->i_mode))
 		mutex_lock(&inode1->i_mutex);
+	if (inode2 && !S_ISDIR(inode2->i_mode) && inode2 != inode1)
 		mutex_lock_nested(&inode2->i_mutex, I_MUTEX_NONDIR2);
-	} else {
-		mutex_lock(&inode2->i_mutex);
-		mutex_lock_nested(&inode1->i_mutex, I_MUTEX_NONDIR2);
-	}
 }
 EXPORT_SYMBOL(lock_two_nondirectories);
 
@@ -972,8 +970,9 @@ EXPORT_SYMBOL(lock_two_nondirectories);
  */
 void unlock_two_nondirectories(struct inode *inode1, struct inode *inode2)
 {
-	mutex_unlock(&inode1->i_mutex);
-	if (inode2 && inode2 != inode1)
+	if (inode1 && !S_ISDIR(inode1->i_mode))
+		mutex_unlock(&inode1->i_mutex);
+	if (inode2 && !S_ISDIR(inode2->i_mode) && inode2 != inode1)
 		mutex_unlock(&inode2->i_mutex);
 }
 EXPORT_SYMBOL(unlock_two_nondirectories);