From: Chengguang Xu <cgxu519@icloud.com>
Date: Fri, 9 Feb 2018 20:40:59 +0800
Subject: ceph: fix dentry leak when failing to init debugfs
Git-commit: 18106734b512664a8541026519ce4b862498b6c3
Patch-mainline: v4.16-rc4
References: bsc#1084898

When failing from ceph_fs_debugfs_init() in ceph_real_mount(),
there is lack of dput of root_dentry and it causes slab errors,
so change the calling order of ceph_fs_debugfs_init() and
open_root_dentry() and do some cleanups to avoid this issue.

Signed-off-by: Chengguang Xu <cgxu519@icloud.com>
Reviewed-by: "Yan, Zheng" <zyan@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Acked-by: Luis Henriques <lhenriques@suse.com>
---
 fs/ceph/super.c | 16 +++++-----------
 1 file changed, 5 insertions(+), 11 deletions(-)

diff --git a/fs/ceph/super.c b/fs/ceph/super.c
index bfc85b22a190..1c470b453a9e 100644
--- a/fs/ceph/super.c
+++ b/fs/ceph/super.c
@@ -838,7 +838,6 @@ static struct dentry *ceph_real_mount(struct ceph_fs_client *fsc)
 	int err;
 	unsigned long started = jiffies;  /* note the start time */
 	struct dentry *root;
-	int first = 0;   /* first vfsmount for this super_block */
 
 	dout("mount start %p\n", fsc);
 	mutex_lock(&fsc->client->mount_mutex);
@@ -863,17 +862,17 @@ static struct dentry *ceph_real_mount(struct ceph_fs_client *fsc)
 			path = fsc->mount_options->server_path + 1;
 			dout("mount opening path %s\n", path);
 		}
+
+		err = ceph_fs_debugfs_init(fsc);
+		if (err < 0)
+			goto out;
+
 		root = open_root_dentry(fsc, path, started);
 		if (IS_ERR(root)) {
 			err = PTR_ERR(root);
 			goto out;
 		}
 		fsc->sb->s_root = dget(root);
-		first = 1;
-
-		err = ceph_fs_debugfs_init(fsc);
-		if (err < 0)
-			goto fail;
 	} else {
 		root = dget(fsc->sb->s_root);
 	}
@@ -883,11 +882,6 @@ static struct dentry *ceph_real_mount(struct ceph_fs_client *fsc)
 	mutex_unlock(&fsc->client->mount_mutex);
 	return root;
 
-fail:
-	if (first) {
-		dput(fsc->sb->s_root);
-		fsc->sb->s_root = NULL;
-	}
 out:
 	mutex_unlock(&fsc->client->mount_mutex);
 	return ERR_PTR(err);