cifs: Properly handle auto disabling of serverino option

Fix mount options comparison when serverino option is turned off later
in cifs_autodisable_serverino() and thus avoiding mismatch of new cifs
mounts.

Cc: stable@vger.kernel.org
Signed-off-by: Paulo Alcantara (SUSE) <paulo@paulo.ac>
Signed-off-by: Steve French <stfrench@microsoft.com>
Reviewed-by: Pavel Shilovsky <pshilove@microsoft.com>

fs/cifs/cifs_fs_sb.h

@@ -83,5 +83,10 @@ struct cifs_sb_info {
 	 * failover properly.
 	 */
 	char *origin_fullpath; /* \\HOST\SHARE\[OPTIONAL PATH] */
+	/*
+	 * Indicate whether serverino option was turned off later
+	 * (cifs_autodisable_serverino) in order to match new mounts.
+	 */
+	bool mnt_cifs_serverino_autodisabled;
 };
 #endif				/* _CIFS_FS_SB_H */

fs/cifs/connect.c

@@ -3467,12 +3467,16 @@ compare_mount_options(struct super_block *sb, struct cifs_mnt_data *mnt_data)
 {
 	struct cifs_sb_info *old = CIFS_SB(sb);
 	struct cifs_sb_info *new = mnt_data->cifs_sb;
+	unsigned int oldflags = old->mnt_cifs_flags & CIFS_MOUNT_MASK;
+	unsigned int newflags = new->mnt_cifs_flags & CIFS_MOUNT_MASK;
 
 	if ((sb->s_flags & CIFS_MS_MASK) != (mnt_data->flags & CIFS_MS_MASK))
 		return 0;
 
-	if ((old->mnt_cifs_flags & CIFS_MOUNT_MASK) !=
-	    (new->mnt_cifs_flags & CIFS_MOUNT_MASK))
+	if (old->mnt_cifs_serverino_autodisabled)
+		newflags &= ~CIFS_MOUNT_SERVER_INUM;
+
+	if (oldflags != newflags)
 		return 0;
 
 	/*

fs/cifs/misc.c

@@ -539,6 +539,7 @@ cifs_autodisable_serverino(struct cifs_sb_info *cifs_sb)
 			tcon = cifs_sb_master_tcon(cifs_sb);
 
 		cifs_sb->mnt_cifs_flags &= ~CIFS_MOUNT_SERVER_INUM;
+		cifs_sb->mnt_cifs_serverino_autodisabled = true;
 		cifs_dbg(VFS, "Autodisabling the use of server inode numbers on %s.\n",
 			 tcon ? tcon->treeName : "new server");
 		cifs_dbg(VFS, "The server doesn't seem to support them properly or the files might be on different servers (DFS).\n");