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

Pull more ->lookup() cleanups from Al Viro:
 "Some ->lookup() instances are still overcomplicating the life
  for themselves, open-coding the stuff that would be handled by
  d_splice_alias() just fine.

  Simplify a couple of such cases caught this cycle and document
  d_splice_alias() intended use"

* 'work.lookup' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  Document d_splice_alias() calling conventions for ->lookup() users.
  simplify btrfs_lookup()
  clean erofs_lookup()

1 files changed, 11 insertions, 0 deletions

diff --git a/Documentation/filesystems/porting b/Documentation/filesystems/porting
index 7b7b845c490a..321d74b73937 100644
--- a/Documentation/filesystems/porting
+++ b/Documentation/filesystems/porting
@@ -622,3 +622,14 @@ in your dentry operations instead.
 	alloc_file_clone(file, flags, ops) does not affect any caller's references.
 	On success you get a new struct file sharing the mount/dentry with the
 	original, on failure - ERR_PTR().
+--
+[recommended]
+	->lookup() instances doing an equivalent of
+		if (IS_ERR(inode))
+			return ERR_CAST(inode);
+		return d_splice_alias(inode, dentry);
+	don't need to bother with the check - d_splice_alias() will do the
+	right thing when given ERR_PTR(...) as inode.  Moreover, passing NULL
+	inode to d_splice_alias() will also do the right thing (equivalent of
+	d_add(dentry, NULL); return NULL;), so that kind of special cases
+	also doesn't need a separate treatment.