1 files changed, 19 insertions, 55 deletions

diff --git a/ipc/mqueue.c b/ipc/mqueue.c
index d7f309f74dec..a808f29d4c5a 100644
--- a/ipc/mqueue.c
+++ b/ipc/mqueue.c
@@ -325,9 +325,8 @@ err:
 static int mqueue_fill_super(struct super_block *sb, void *data, int silent)
 {
         struct inode *inode;
-        struct ipc_namespace *ns = data;
+        struct ipc_namespace *ns = sb->s_fs_info;
 
-        sb->s_fs_info = ns;
         sb->s_iflags |= SB_I_NOEXEC | SB_I_NODEV;
         sb->s_blocksize = PAGE_SIZE;
         sb->s_blocksize_bits = PAGE_SHIFT;
@@ -344,44 +343,18 @@ static int mqueue_fill_super(struct super_block *sb, void *data, int silent)
         return 0;
 }
 
-static struct file_system_type mqueue_fs_type;
-/*
- * Return value is pinned only by reference in ->mq_mnt; it will
- * live until ipcns dies.  Caller does not need to drop it.
- */
-static struct vfsmount *mq_internal_mount(void)
-{
-        struct ipc_namespace *ns = current->nsproxy->ipc_ns;
-        struct vfsmount *m = ns->mq_mnt;
-        if (m)
-                return m;
-        m = kern_mount_data(&mqueue_fs_type, ns);
-        spin_lock(&mq_lock);
-        if (unlikely(ns->mq_mnt)) {
-                spin_unlock(&mq_lock);
-                if (!IS_ERR(m))
-                        kern_unmount(m);
-                return ns->mq_mnt;
-        }
-        if (!IS_ERR(m))
-                ns->mq_mnt = m;
-        spin_unlock(&mq_lock);
-        return m;
-}
-
 static struct dentry *mqueue_mount(struct file_system_type *fs_type,
                          int flags, const char *dev_name,
                          void *data)
 {
-        struct vfsmount *m;
-        if (flags & SB_KERNMOUNT)
-                return mount_nodev(fs_type, flags, data, mqueue_fill_super);
-        m = mq_internal_mount();
-        if (IS_ERR(m))
-                return ERR_CAST(m);
-        atomic_inc(&m->mnt_sb->s_active);
-        down_write(&m->mnt_sb->s_umount);
-        return dget(m->mnt_root);
+        struct ipc_namespace *ns;
+        if (flags & SB_KERNMOUNT) {
+                ns = data;
+                data = NULL;
+        } else {
+                ns = current->nsproxy->ipc_ns;
+        }
+        return mount_ns(fs_type, flags, data, ns, ns->user_ns, mqueue_fill_super);
 }
 
 static void init_once(void *foo)
@@ -771,16 +744,13 @@ static int prepare_open(struct dentry *dentry, int oflag, int ro,
 static int do_mq_open(const char __user *u_name, int oflag, umode_t mode,
                       struct mq_attr *attr)
 {
-        struct vfsmount *mnt = mq_internal_mount();
-        struct dentry *root;
+        struct vfsmount *mnt = current->nsproxy->ipc_ns->mq_mnt;
+        struct dentry *root = mnt->mnt_root;
         struct filename *name;
         struct path path;
         int fd, error;
         int ro;
 
-        if (IS_ERR(mnt))
-                return PTR_ERR(mnt);
-
         audit_mq_open(oflag, mode, attr);
 
         if (IS_ERR(name = getname(u_name)))
@@ -791,7 +761,6 @@ static int do_mq_open(const char __user *u_name, int oflag, umode_t mode,
                 goto out_putname;
 
         ro = mnt_want_write(mnt);       /* we'll drop it in any case */
-        root = mnt->mnt_root;
         inode_lock(d_inode(root));
         path.dentry = lookup_one_len(name->name, root, strlen(name->name));
         if (IS_ERR(path.dentry)) {
@@ -840,9 +809,6 @@ SYSCALL_DEFINE1(mq_unlink, const char __user *, u_name)
         struct ipc_namespace *ipc_ns = current->nsproxy->ipc_ns;
         struct vfsmount *mnt = ipc_ns->mq_mnt;
 
-        if (!mnt)
-                return -ENOENT;
-
         name = getname(u_name);
         if (IS_ERR(name))
                 return PTR_ERR(name);
@@ -1569,26 +1535,28 @@ int mq_init_ns(struct ipc_namespace *ns)
         ns->mq_msgsize_max   = DFLT_MSGSIZEMAX;
         ns->mq_msg_default   = DFLT_MSG;
         ns->mq_msgsize_default  = DFLT_MSGSIZE;
-        ns->mq_mnt = NULL;
 
+        ns->mq_mnt = kern_mount_data(&mqueue_fs_type, ns);
+        if (IS_ERR(ns->mq_mnt)) {
+                int err = PTR_ERR(ns->mq_mnt);
+                ns->mq_mnt = NULL;
+                return err;
+        }
         return 0;
 }
 
 void mq_clear_sbinfo(struct ipc_namespace *ns)
 {
-        if (ns->mq_mnt)
-                ns->mq_mnt->mnt_sb->s_fs_info = NULL;
+        ns->mq_mnt->mnt_sb->s_fs_info = NULL;
 }
 
 void mq_put_mnt(struct ipc_namespace *ns)
 {
-        if (ns->mq_mnt)
-                kern_unmount(ns->mq_mnt);
+        kern_unmount(ns->mq_mnt);
 }
 
 static int __init init_mqueue_fs(void)
 {
-        struct vfsmount *m;
         int error;
 
         mqueue_inode_cachep = kmem_cache_create("mqueue_inode_cache",
@@ -1610,10 +1578,6 @@ static int __init init_mqueue_fs(void)
         if (error)
                 goto out_filesystem;
 
-        m = kern_mount_data(&mqueue_fs_type, &init_ipc_ns);
-        if (IS_ERR(m))
-                goto out_filesystem;
-        init_ipc_ns.mq_mnt = m;
         return 0;
 
 out_filesystem: