From 1a16dbaf798c5b68ac767444eb045e6f3adaa16d Mon Sep 17 00:00:00 2001 From: Al Viro Date: Wed, 10 Oct 2018 16:52:37 -0400 Subject: Document d_splice_alias() calling conventions for ->lookup() users. Short version: it does the right thing when given NULL or ERR_PTR(...) and its calling conventions are chosen to have minimal PITA when used in ->lookup() instances. Signed-off-by: Al Viro --- Documentation/filesystems/porting | 11 +++++++++++ 1 file changed, 11 insertions(+) (limited to 'Documentation/filesystems') 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. -- cgit v1.2.3-59-g8ed1b