3 files changed, 33 insertions, 1 deletions

diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index 1a052c0eee8e..054b90b682a7 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -91,6 +91,30 @@ struct workqueue_struct	*cifsiod_wq;
 __u8 cifs_client_guid[SMB2_CLIENT_GUID_SIZE];
 #endif
 
+/*
+ * Bumps refcount for cifs super block.
+ * Note that it should be only called if a referece to VFS super block is
+ * already held, e.g. in open-type syscalls context. Otherwise it can race with
+ * atomic_dec_and_test in deactivate_locked_super.
+ */
+void
+cifs_sb_active(struct super_block *sb)
+{
+        struct cifs_sb_info *server = CIFS_SB(sb);
+
+        if (atomic_inc_return(&server->active) == 1)
+                atomic_inc(&sb->s_active);
+}
+
+void
+cifs_sb_deactive(struct super_block *sb)
+{
+        struct cifs_sb_info *server = CIFS_SB(sb);
+
+        if (atomic_dec_and_test(&server->active))
+                deactivate_super(sb);
+}
+
 static int
 cifs_read_super(struct super_block *sb)
 {
diff --git a/fs/cifs/cifsfs.h b/fs/cifs/cifsfs.h
index 7163419cecd9..0e32c3446ce9 100644
--- a/fs/cifs/cifsfs.h
+++ b/fs/cifs/cifsfs.h
@@ -41,6 +41,10 @@ extern struct file_system_type cifs_fs_type;
 extern const struct address_space_operations cifs_addr_ops;
 extern const struct address_space_operations cifs_addr_ops_smallbuf;
 
+/* Functions related to super block operations */
+extern void cifs_sb_active(struct super_block *sb);
+extern void cifs_sb_deactive(struct super_block *sb);
+
 /* Functions related to inodes */
 extern const struct inode_operations cifs_dir_inode_ops;
 extern struct inode *cifs_root_iget(struct super_block *);
diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index 8c0d85577314..7a0dd99e4507 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -300,6 +300,8 @@ cifs_new_fileinfo(struct cifs_fid *fid, struct file *file,
         INIT_WORK(&cfile->oplock_break, cifs_oplock_break);
         mutex_init(&cfile->fh_mutex);
 
+        cifs_sb_active(inode->i_sb);
+
         /*
          * If the server returned a read oplock and we have mandatory brlocks,
          * set oplock level to None.
@@ -349,7 +351,8 @@ void cifsFileInfo_put(struct cifsFileInfo *cifs_file)
         struct cifs_tcon *tcon = tlink_tcon(cifs_file->tlink);
         struct TCP_Server_Info *server = tcon->ses->server;
         struct cifsInodeInfo *cifsi = CIFS_I(inode);
-        struct cifs_sb_info *cifs_sb = CIFS_SB(inode->i_sb);
+        struct super_block *sb = inode->i_sb;
+        struct cifs_sb_info *cifs_sb = CIFS_SB(sb);
         struct cifsLockInfo *li, *tmp;
         struct cifs_fid fid;
         struct cifs_pending_open open;
@@ -414,6 +417,7 @@ void cifsFileInfo_put(struct cifsFileInfo *cifs_file)
 
         cifs_put_tlink(cifs_file->tlink);
         dput(cifs_file->dentry);
+        cifs_sb_deactive(sb);
         kfree(cifs_file);
 }