fs/namespace.c: fix the namespace_sem guard mess

If anything, namespace_lock should be DEFINE_LOCK_GUARD_0, not DEFINE_GUARD.
That way we
	* do not need to feed it a bogus argument
	* do not get gcc trying to compare an address of static in
file variable with -4097 - and, if we are unlucky, trying to keep
it in a register, with spills and all such.

The same problems apply to grabbing namespace_sem shared.

Rename it to namespace_excl, add namespace_shared, convert the existing users:

    guard(namespace_lock, &namespace_sem) => guard(namespace_excl)()
    guard(rwsem_read, &namespace_sem) => guard(namespace_shared)()
    scoped_guard(namespace_lock, &namespace_sem) => scoped_guard(namespace_excl)
    scoped_guard(rwsem_read, &namespace_sem) => scoped_guard(namespace_shared)

Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/fs/namespace.c b/fs/namespace.c
index ae6d1312b1849cdfe11ee1bb1d98e96d6db8f2db..fcea65587ff9146ae296eaa72d2f9cbccf375abd 100644 (file)
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -82,6 +82,12 @@ static LIST_HEAD(ex_mountpoints); /* protected by namespace_sem */
 static struct mnt_namespace *emptied_ns; /* protected by namespace_sem */
 static DEFINE_SEQLOCK(mnt_ns_tree_lock);
 
+static inline void namespace_lock(void);
+static void namespace_unlock(void);
+DEFINE_LOCK_GUARD_0(namespace_excl, namespace_lock(), namespace_unlock())
+DEFINE_LOCK_GUARD_0(namespace_shared, down_read(&namespace_sem),
+                                     up_read(&namespace_sem))
+
 #ifdef CONFIG_FSNOTIFY
 LIST_HEAD(notify_list); /* protected by namespace_sem */
 #endif
@@ -1776,8 +1782,6 @@ static inline void namespace_lock(void)
        down_write(&namespace_sem);
 }
 
-DEFINE_GUARD(namespace_lock, struct rw_semaphore *, namespace_lock(), namespace_unlock())
-
 enum umount_tree_flags {
        UMOUNT_SYNC = 1,
        UMOUNT_PROPAGATE = 2,
@@ -2306,7 +2310,7 @@ struct path *collect_paths(const struct path *path,
        struct path *res = prealloc, *to_free = NULL;
        unsigned n = 0;
 
-       guard(rwsem_read)(&namespace_sem);
+       guard(namespace_shared)();
 
        if (!check_mnt(root))
                return ERR_PTR(-EINVAL);
@@ -2361,7 +2365,7 @@ void dissolve_on_fput(struct vfsmount *mnt)
                        return;
        }
 
-       scoped_guard(namespace_lock, &namespace_sem) {
+       scoped_guard(namespace_excl) {
                if (!anon_ns_root(m))
                        return;
 
@@ -2435,7 +2439,7 @@ struct vfsmount *clone_private_mount(const struct path *path)
        struct mount *old_mnt = real_mount(path->mnt);
        struct mount *new_mnt;
 
-       guard(rwsem_read)(&namespace_sem);
+       guard(namespace_shared)();
 
        if (IS_MNT_UNBINDABLE(old_mnt))
                return ERR_PTR(-EINVAL);
@@ -5957,7 +5961,7 @@ retry:
        if (ret)
                return ret;
 
-       scoped_guard(rwsem_read, &namespace_sem)
+       scoped_guard(namespace_shared)
                ret = do_statmount(ks, kreq.mnt_id, kreq.mnt_ns_id, ns);
 
        if (!ret)
@@ -6079,7 +6083,7 @@ SYSCALL_DEFINE4(listmount, const struct mnt_id_req __user *, req,
         * We only need to guard against mount topology changes as
         * listmount() doesn't care about any mount properties.
         */
-       scoped_guard(rwsem_read, &namespace_sem)
+       scoped_guard(namespace_shared)
                ret = do_listmount(ns, kreq.mnt_id, last_mnt_id, kmnt_ids,
                                   nr_mnt_ids, (flags & LISTMOUNT_REVERSE));
        if (ret <= 0)