linux-kernel - [PATCH] vfs: update d_make

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Date:   Thu, 11 Apr 2019 12:28:02 +0800
From:   Ian Kent <raven@...maw.net>
To:     Al Viro <viro@...IV.linux.org.uk>
Cc:     Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>
Subject: [PATCH] vfs: update d_make_root() description

Clearify d_make_root() usage, error handling and cleanup
requirements.

Signed-off-by: Ian Kent <raven@...maw.net>
---
 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.
 --
 [mandatory]
 	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;
+	...
 
 --
 [mandatory]