From: Ronnie Sahlberg <lsahlber@redhat.com>
Date: Tue, 9 Mar 2021 09:07:30 +1000
Subject: [PATCH] cifs: store a pointer to the root dentry in cifs_sb_info once
 we have completed mounting the share
Git-commit: 269f67e1ffead61777b1b0cf2ea0f61d06f8c56d
References: bsc#1190317
Patch-mainline: v5.13-rc1

And use this to only allow to take out a shared handle once the mount has completed and the
sb becomes available.
This will become important in follow up patches where we will start holding a reference to the
directory dentry for the shared handle during the lifetime of the handle.

Signed-off-by: Ronnie Sahlberg <lsahlber@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Acked-by: Enzo Matsumiya <ematsumiya@suse.de>
---
 fs/cifs/cifs_fs_sb.h | 4 ++++
 fs/cifs/cifsfs.c     | 9 +++++++++
 fs/cifs/smb2ops.c    | 5 ++++-
 3 files changed, 17 insertions(+), 1 deletion(-)

--- a/fs/cifs/cifs_fs_sb.h
+++ b/fs/cifs/cifs_fs_sb.h
@@ -91,5 +91,9 @@ struct cifs_sb_info {
 	 * (cifs_autodisable_serverino) in order to match new mounts.
 	 */
 	bool mnt_cifs_serverino_autodisabled;
+	/*
+	 * Available once the mount has completed.
+	 */
+	struct dentry *root;
 };
 #endif				/* _CIFS_FS_SB_H */
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -220,6 +220,12 @@ out_no_root:
 static void cifs_kill_sb(struct super_block *sb)
 {
 	struct cifs_sb_info *cifs_sb = CIFS_SB(sb);
+
+	if (cifs_sb->root) {
+		dput(cifs_sb->root);
+		cifs_sb->root = NULL;
+	}
+
 	kill_anon_super(sb);
 	cifs_umount(cifs_sb);
 }
@@ -828,6 +834,9 @@ cifs_smb3_do_mount(struct file_system_ty
 	if (IS_ERR(root))
 		goto out_super;
 
+	if (cifs_sb)
+		cifs_sb->root = dget(root);
+
 	cifs_dbg(FYI, "dentry root is: %p\n", root);
 	goto out;
 
--- a/fs/cifs/smb2ops.c
+++ b/fs/cifs/smb2ops.c
@@ -709,8 +709,11 @@ int open_cached_dir(unsigned int xid, st
 	if (tcon->nohandlecache)
 		return -ENOTSUPP;
 
+	if (cifs_sb->root == NULL)
+		return -ENOENT;
+
 	if (strlen(path))
-		return -ENOTSUPP;
+		return -ENOENT;
 
 	mutex_lock(&tcon->crfid.fid_mutex);
 	if (tcon->crfid.is_valid) {