get rid of ->mnt_longterm
Al Viro [Sat, 9 Jun 2012 04:59:08 +0000 (00:59 -0400)]
it's enough to set ->mnt_ns of internal vfsmounts to something
distinct from all struct mnt_namespace out there; then we can
just use the check for ->mnt_ns != NULL in the fast path of
mntput_no_expire()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/dcache.c
fs/fs_struct.c
fs/internal.h
fs/mount.h
fs/namespace.c

index 4046904..44acb5b 100644 (file)
@@ -2622,7 +2622,7 @@ global_root:
        if (!slash)
                error = prepend(buffer, buflen, "/", 1);
        if (!error)
-               error = real_mount(vfsmnt)->mnt_ns ? 1 : 2;
+               error = is_mounted(vfsmnt) ? 1 : 2;
        goto out;
 }
 
index e159e68..5df4775 100644 (file)
@@ -6,18 +6,6 @@
 #include <linux/fs_struct.h>
 #include "internal.h"
 
-static inline void path_get_longterm(struct path *path)
-{
-       path_get(path);
-       mnt_make_longterm(path->mnt);
-}
-
-static inline void path_put_longterm(struct path *path)
-{
-       mnt_make_shortterm(path->mnt);
-       path_put(path);
-}
-
 /*
  * Replace the fs->{rootmnt,root} with {mnt,dentry}. Put the old values.
  * It can block.
@@ -26,7 +14,7 @@ void set_fs_root(struct fs_struct *fs, struct path *path)
 {
        struct path old_root;
 
-       path_get_longterm(path);
+       path_get(path);
        spin_lock(&fs->lock);
        write_seqcount_begin(&fs->seq);
        old_root = fs->root;
@@ -34,7 +22,7 @@ void set_fs_root(struct fs_struct *fs, struct path *path)
        write_seqcount_end(&fs->seq);
        spin_unlock(&fs->lock);
        if (old_root.dentry)
-               path_put_longterm(&old_root);
+               path_put(&old_root);
 }
 
 /*
@@ -45,7 +33,7 @@ void set_fs_pwd(struct fs_struct *fs, struct path *path)
 {
        struct path old_pwd;
 
-       path_get_longterm(path);
+       path_get(path);
        spin_lock(&fs->lock);
        write_seqcount_begin(&fs->seq);
        old_pwd = fs->pwd;
@@ -54,7 +42,7 @@ void set_fs_pwd(struct fs_struct *fs, struct path *path)
        spin_unlock(&fs->lock);
 
        if (old_pwd.dentry)
-               path_put_longterm(&old_pwd);
+               path_put(&old_pwd);
 }
 
 static inline int replace_path(struct path *p, const struct path *old, const struct path *new)
@@ -84,7 +72,7 @@ void chroot_fs_refs(struct path *old_root, struct path *new_root)
                        write_seqcount_end(&fs->seq);
                        while (hits--) {
                                count++;
-                               path_get_longterm(new_root);
+                               path_get(new_root);
                        }
                        spin_unlock(&fs->lock);
                }
@@ -92,13 +80,13 @@ void chroot_fs_refs(struct path *old_root, struct path *new_root)
        } while_each_thread(g, p);
        read_unlock(&tasklist_lock);
        while (count--)
-               path_put_longterm(old_root);
+               path_put(old_root);
 }
 
 void free_fs_struct(struct fs_struct *fs)
 {
-       path_put_longterm(&fs->root);
-       path_put_longterm(&fs->pwd);
+       path_put(&fs->root);
+       path_put(&fs->pwd);
        kmem_cache_free(fs_cachep, fs);
 }
 
@@ -132,9 +120,9 @@ struct fs_struct *copy_fs_struct(struct fs_struct *old)
 
                spin_lock(&old->lock);
                fs->root = old->root;
-               path_get_longterm(&fs->root);
+               path_get(&fs->root);
                fs->pwd = old->pwd;
-               path_get_longterm(&fs->pwd);
+               path_get(&fs->pwd);
                spin_unlock(&old->lock);
        }
        return fs;
index 18bc216..d2a23ff 100644 (file)
@@ -50,8 +50,6 @@ extern int copy_mount_string(const void __user *, char **);
 extern struct vfsmount *lookup_mnt(struct path *);
 extern int finish_automount(struct vfsmount *, struct path *);
 
-extern void mnt_make_longterm(struct vfsmount *);
-extern void mnt_make_shortterm(struct vfsmount *);
 extern int sb_prepare_remount_readonly(struct super_block *);
 
 extern void __init mnt_init(void);
index 4ef36d9..05a2a11 100644 (file)
@@ -22,7 +22,6 @@ struct mount {
        struct vfsmount mnt;
 #ifdef CONFIG_SMP
        struct mnt_pcp __percpu *mnt_pcp;
-       atomic_t mnt_longterm;          /* how many of the refs are longterm */
 #else
        int mnt_count;
        int mnt_writers;
@@ -49,6 +48,8 @@ struct mount {
        int mnt_ghosts;
 };
 
+#define MNT_NS_INTERNAL ERR_PTR(-EINVAL) /* distinct from any mnt_namespace */
+
 static inline struct mount *real_mount(struct vfsmount *mnt)
 {
        return container_of(mnt, struct mount, mnt);
@@ -59,6 +60,12 @@ static inline int mnt_has_parent(struct mount *mnt)
        return mnt != mnt->mnt_parent;
 }
 
+static inline int is_mounted(struct vfsmount *mnt)
+{
+       /* neither detached nor internal? */
+       return !IS_ERR_OR_NULL(real_mount(mnt));
+}
+
 extern struct mount *__lookup_mnt(struct vfsmount *, struct dentry *, int);
 
 static inline void get_mnt_ns(struct mnt_namespace *ns)
index 1e4a5fe..a524ea4 100644 (file)
@@ -621,21 +621,6 @@ static void attach_mnt(struct mount *mnt, struct path *path)
        list_add_tail(&mnt->mnt_child, &real_mount(path->mnt)->mnt_mounts);
 }
 
-static inline void __mnt_make_longterm(struct mount *mnt)
-{
-#ifdef CONFIG_SMP
-       atomic_inc(&mnt->mnt_longterm);
-#endif
-}
-
-/* needs vfsmount lock for write */
-static inline void __mnt_make_shortterm(struct mount *mnt)
-{
-#ifdef CONFIG_SMP
-       atomic_dec(&mnt->mnt_longterm);
-#endif
-}
-
 /*
  * vfsmount lock must be held for write
  */
@@ -649,10 +634,8 @@ static void commit_tree(struct mount *mnt)
        BUG_ON(parent == mnt);
 
        list_add_tail(&head, &mnt->mnt_list);
-       list_for_each_entry(m, &head, mnt_list) {
+       list_for_each_entry(m, &head, mnt_list)
                m->mnt_ns = n;
-               __mnt_make_longterm(m);
-       }
 
        list_splice(&head, n->list.prev);
 
@@ -804,7 +787,8 @@ static void mntput_no_expire(struct mount *mnt)
 put_again:
 #ifdef CONFIG_SMP
        br_read_lock(&vfsmount_lock);
-       if (likely(atomic_read(&mnt->mnt_longterm))) {
+       if (likely(mnt->mnt_ns)) {
+               /* shouldn't be the last one */
                mnt_add_count(mnt, -1);
                br_read_unlock(&vfsmount_lock);
                return;
@@ -1074,8 +1058,6 @@ void umount_tree(struct mount *mnt, int propagate, struct list_head *kill)
                list_del_init(&p->mnt_expire);
                list_del_init(&p->mnt_list);
                __touch_mnt_namespace(p->mnt_ns);
-               if (p->mnt_ns)
-                       __mnt_make_shortterm(p);
                p->mnt_ns = NULL;
                list_del_init(&p->mnt_child);
                if (mnt_has_parent(p)) {
@@ -2209,23 +2191,6 @@ static struct mnt_namespace *alloc_mnt_ns(void)
        return new_ns;
 }
 
-void mnt_make_longterm(struct vfsmount *mnt)
-{
-       __mnt_make_longterm(real_mount(mnt));
-}
-
-void mnt_make_shortterm(struct vfsmount *m)
-{
-#ifdef CONFIG_SMP
-       struct mount *mnt = real_mount(m);
-       if (atomic_add_unless(&mnt->mnt_longterm, -1, 1))
-               return;
-       br_write_lock(&vfsmount_lock);
-       atomic_dec(&mnt->mnt_longterm);
-       br_write_unlock(&vfsmount_lock);
-#endif
-}
-
 /*
  * Allocate a new namespace structure and populate it with contents
  * copied from the namespace of the passed in task structure.
@@ -2265,18 +2230,13 @@ static struct mnt_namespace *dup_mnt_ns(struct mnt_namespace *mnt_ns,
        q = new;
        while (p) {
                q->mnt_ns = new_ns;
-               __mnt_make_longterm(q);
                if (fs) {
                        if (&p->mnt == fs->root.mnt) {
                                fs->root.mnt = mntget(&q->mnt);
-                               __mnt_make_longterm(q);
-                               mnt_make_shortterm(&p->mnt);
                                rootmnt = &p->mnt;
                        }
                        if (&p->mnt == fs->pwd.mnt) {
                                fs->pwd.mnt = mntget(&q->mnt);
-                               __mnt_make_longterm(q);
-                               mnt_make_shortterm(&p->mnt);
                                pwdmnt = &p->mnt;
                        }
                }
@@ -2320,7 +2280,6 @@ static struct mnt_namespace *create_mnt_ns(struct vfsmount *m)
        if (!IS_ERR(new_ns)) {
                struct mount *mnt = real_mount(m);
                mnt->mnt_ns = new_ns;
-               __mnt_make_longterm(mnt);
                new_ns->root = mnt;
                list_add(&new_ns->list, &mnt->mnt_list);
        } else {
@@ -2615,7 +2574,7 @@ struct vfsmount *kern_mount_data(struct file_system_type *type, void *data)
                 * it is a longterm mount, don't release mnt until
                 * we unmount before file sys is unregistered
                */
-               mnt_make_longterm(mnt);
+               real_mount(mnt)->mnt_ns = MNT_NS_INTERNAL;
        }
        return mnt;
 }
@@ -2625,7 +2584,9 @@ void kern_unmount(struct vfsmount *mnt)
 {
        /* release long term mount so mount point can be released */
        if (!IS_ERR_OR_NULL(mnt)) {
-               mnt_make_shortterm(mnt);
+               br_write_lock(&vfsmount_lock);
+               real_mount(mnt)->mnt_ns = NULL;
+               br_write_unlock(&vfsmount_lock);
                mntput(mnt);
        }
 }