[PATCH v6 7/7] kernfs: dont call d_splice_alias() under kernfs node lock

From: Ian Kent <raven@themaw.net>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Tejun Heo <tj@kernel.org>
Cc: Eric Sandeen <sandeen@sandeen.net>,
	Fox Chen <foxhlchen@gmail.com>,
	Brice Goglin <brice.goglin@gmail.com>,
	Al Viro <viro@ZenIV.linux.org.uk>,
	Rick Lindsley <ricklind@linux.vnet.ibm.com>,
	David Howells <dhowells@redhat.com>,
	Miklos Szeredi <miklos@szeredi.hu>,
	Marcelo Tosatti <mtosatti@redhat.com>,
	"Eric W. Biederman" <ebiederm@xmission.com>,
	Carlos Maiolino <cmaiolino@redhat.com>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: [PATCH v6 7/7] kernfs: dont call d_splice_alias() under kernfs node lock
Date: Wed, 09 Jun 2021 16:52:25 +0800	[thread overview]
Message-ID: <162322874509.361452.3143376113190093370.stgit@web.messagingengine.com> (raw)
In-Reply-To: <162322846765.361452.17051755721944717990.stgit@web.messagingengine.com>

The call to d_splice_alias() in kernfs_iop_lookup() doesn't depend on
any kernfs node so there's no reason to hold the kernfs node lock when
calling it.

Signed-off-by: Ian Kent <raven@themaw.net>
---
 fs/kernfs/dir.c |    6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index 195561c08439a..a5820a8c139a2 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -1097,7 +1097,6 @@ static struct dentry *kernfs_iop_lookup(struct inode *dir,
 					struct dentry *dentry,
 					unsigned int flags)
 {
-	struct dentry *ret;
 	struct kernfs_node *parent = dir->i_private;
 	struct kernfs_node *kn;
 	struct inode *inode = NULL;
@@ -1117,11 +1116,10 @@ static struct dentry *kernfs_iop_lookup(struct inode *dir,
 	/* Needed only for negative dentry validation */
 	if (!inode)
 		kernfs_set_rev(parent, dentry);
-	/* instantiate and hash (possibly negative) dentry */
-	ret = d_splice_alias(inode, dentry);
 	up_read(&kernfs_rwsem);
 
-	return ret;
+	/* instantiate and hash (possibly negative) dentry */
+	return d_splice_alias(inode, dentry);
 }
 
 static int kernfs_iop_mkdir(struct user_namespace *mnt_userns,


