[PATCH v3 06/15] selinux: Use simple_start_creating() / simple_done_creating()

[NeilBrown]

From: NeilBrown <neil@xxxxxxxxxx>

Instead of explicitly locking the parent and performing a lookup in
selinux, use simple_start_creating(), and then use
simple_done_creating() to unlock.

This extends the region that the directory is locked for, and also
performs a lookup.
The lock extension is of no real consequence.
The lookup uses simple_lookup() and so always succeeds.  Thus when
d_make_persistent() is called the dentry will already be hashed.
d_make_persistent() handles this case.

Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx>
Acked-by: Paul Moore <paul@xxxxxxxxxxxxxx>
Signed-off-by: NeilBrown <neil@xxxxxxxxxx>
---
 security/selinux/selinuxfs.c | 17 ++++++++---------
 1 file changed, 8 insertions(+), 9 deletions(-)

diff --git a/security/selinux/selinuxfs.c b/security/selinux/selinuxfs.c
index 3245cc531555..83aa765a09f9 100644
--- a/security/selinux/selinuxfs.c
+++ b/security/selinux/selinuxfs.c
@@ -1931,27 +1931,26 @@ static const struct inode_operations swapover_dir_inode_operations = {
 static struct dentry *sel_make_swapover_dir(struct super_block *sb,
 						unsigned long *ino)
 {
-	struct dentry *dentry = d_alloc_name(sb->s_root, ".swapover");
+	struct dentry *dentry;
 	struct inode *inode;
 
-	if (!dentry)
-		return ERR_PTR(-ENOMEM);
-
 	inode = sel_make_inode(sb, S_IFDIR);
-	if (!inode) {
-		dput(dentry);
+	if (!inode)
 		return ERR_PTR(-ENOMEM);
+
+	dentry = simple_start_creating(sb->s_root, ".swapover");
+	if (IS_ERR(dentry)) {
+		iput(inode);
+		return dentry;
 	}
 
 	inode->i_op = &swapover_dir_inode_operations;
 	inode->i_ino = ++(*ino);
 	/* directory inodes start off with i_nlink == 2 (for "." entry) */
 	inc_nlink(inode);
-	inode_lock(sb->s_root->d_inode);
 	d_make_persistent(dentry, inode);
 	inc_nlink(sb->s_root->d_inode);
-	inode_unlock(sb->s_root->d_inode);
-	dput(dentry);
+	simple_done_creating(dentry);
 	return dentry;	// borrowed
 }
 
-- 
2.50.0.107.gf914562f5916.dirty