Merge tag 'pull-rename' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

Pull rename updates from Al Viro:
 "Fix directory locking scheme on rename

  This was broken in 6.5; we really can't lock two unrelated directories
  without holding ->s_vfs_rename_mutex first and in case of same-parent
  rename of a subdirectory 6.5 ends up doing just that"

* tag 'pull-rename' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  rename(): avoid a deadlock in the case of parents having no common ancestor
  kill lock_two_inodes()
  rename(): fix the locking of subdirectories
  f2fs: Avoid reading renamed directory if parent does not change
  ext4: don't access the source subdirectory content on same-directory rename
  ext2: Avoid reading renamed directory if parent does not change
  udf_rename(): only access the child content on cross-directory rename
  ocfs2: Avoid touching renamed directory if parent does not change
  reiserfs: Avoid touching renamed directory if parent does not change

1 files changed, 27 insertions, 0 deletions

diff --git a/Documentation/filesystems/porting.rst b/Documentation/filesystems/porting.rst
index ced3a6761329..c549fb2fc3ba 100644
--- a/Documentation/filesystems/porting.rst
+++ b/Documentation/filesystems/porting.rst
@@ -1064,6 +1064,33 @@ generic_encode_ino32_fh() explicitly.
 
 ---
 
+**mandatory**
+
+If ->rename() update of .. on cross-directory move needs an exclusion with
+directory modifications, do *not* lock the subdirectory in question in your
+->rename() - it's done by the caller now [that item should've been added in
+28eceeda130f "fs: Lock moved directories"].
+
+---
+
+**mandatory**
+
+On same-directory ->rename() the (tautological) update of .. is not protected
+by any locks; just don't do it if the old parent is the same as the new one.
+We really can't lock two subdirectories in same-directory rename - not without
+deadlocks.
+
+---
+
+**mandatory**
+
+lock_rename() and lock_rename_child() may fail in cross-directory case, if
+their arguments do not have a common ancestor.  In that case ERR_PTR(-EXDEV)
+is returned, with no locks taken.  In-tree users updated; out-of-tree ones
+would need to do so.
+
+---
+
 **recommended**
 
 Block device freezing and thawing have been moved to holder operations.