[PATCH] vfs: update d_make_root() description

From: Ian Kent
Date: Thu Apr 11 2019 - 00:28:16 EST

Clearify d_make_root() usage, error handling and cleanup

Signed-off-by: Ian Kent <raven@xxxxxxxxxx>
Documentation/filesystems/porting | 15 +++++++++++++--
1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/Documentation/filesystems/porting b/Documentation/filesystems/porting
index cf43bc4dbf31..1ebc1c6eb64b 100644
--- a/Documentation/filesystems/porting
+++ b/Documentation/filesystems/porting
@@ -428,8 +428,19 @@ release it yourself.
d_alloc_root() is gone, along with a lot of bugs caused by code
-misusing it. Replacement: d_make_root(inode). The difference is,
-d_make_root() drops the reference to inode if dentry allocation fails.
+misusing it. Replacement: d_make_root(inode). On success d_make_root(inode)
+allocates and returns a new dentry instantiated with the passed in inode.
+On failure NULL is returned and the passed in inode is dropped so failure
+handling need not do any cleanup for the inode. If d_make_root(inode)
+is passed a NULL inode it returns NULL and also requires no further
+error handling. Typical usage is:
+ inode = foofs_new_inode(....);
+ s->s_root = d_make_inode(inode);
+ if (!s->s_root)
+ /* Nothing needed for the inode cleanup */
+ return -ENOMEM;
+ ...