wake up s_wait_unfrozen when ->freeze_fs fails
[linux-2.6.git] / fs / super.c
index 7943f04..6015c02 100644 (file)
@@ -61,7 +61,7 @@ static int prune_super(struct shrinker *shrink, struct shrink_control *sc)
                return -1;
 
        if (!grab_super_passive(sb))
-               return -1;
+               return !sc->nr_to_scan ? 0 : -1;
 
        if (sb->s_op && sb->s_op->nr_cached_objects)
                fs_objects = sb->s_op->nr_cached_objects(sb);
@@ -136,12 +136,13 @@ static struct super_block *alloc_super(struct file_system_type *type)
                INIT_LIST_HEAD(&s->s_files);
 #endif
                s->s_bdi = &default_backing_dev_info;
-               INIT_LIST_HEAD(&s->s_instances);
+               INIT_HLIST_NODE(&s->s_instances);
                INIT_HLIST_BL_HEAD(&s->s_anon);
                INIT_LIST_HEAD(&s->s_inodes);
                INIT_LIST_HEAD(&s->s_dentry_lru);
                INIT_LIST_HEAD(&s->s_inode_lru);
                spin_lock_init(&s->s_inode_lru_lock);
+               INIT_LIST_HEAD(&s->s_mounts);
                init_rwsem(&s->s_umount);
                mutex_init(&s->s_lock);
                lockdep_set_class(&s->s_umount, &type->s_umount_key);
@@ -200,6 +201,7 @@ static inline void destroy_super(struct super_block *s)
        free_percpu(s->s_files);
 #endif
        security_sb_free(s);
+       WARN_ON(!list_empty(&s->s_mounts));
        kfree(s->s_subtype);
        kfree(s->s_options);
        kfree(s);
@@ -210,7 +212,7 @@ static inline void destroy_super(struct super_block *s)
 /*
  * Drop a superblock's refcount.  The caller must hold sb_lock.
  */
-void __put_super(struct super_block *sb)
+static void __put_super(struct super_block *sb)
 {
        if (!--sb->s_count) {
                list_del_init(&sb->s_list);
@@ -225,7 +227,7 @@ void __put_super(struct super_block *sb)
  *     Drops a temporary reference, frees superblock if there's no
  *     references left.
  */
-void put_super(struct super_block *sb)
+static void put_super(struct super_block *sb)
 {
        spin_lock(&sb_lock);
        __put_super(sb);
@@ -328,7 +330,7 @@ static int grab_super(struct super_block *s) __releases(sb_lock)
 bool grab_super_passive(struct super_block *sb)
 {
        spin_lock(&sb_lock);
-       if (list_empty(&sb->s_instances)) {
+       if (hlist_unhashed(&sb->s_instances)) {
                spin_unlock(&sb_lock);
                return false;
        }
@@ -337,7 +339,7 @@ bool grab_super_passive(struct super_block *sb)
        spin_unlock(&sb_lock);
 
        if (down_read_trylock(&sb->s_umount)) {
-               if (sb->s_root)
+               if (sb->s_root && (sb->s_flags & MS_BORN))
                        return true;
                up_read(&sb->s_umount);
        }
@@ -351,13 +353,11 @@ bool grab_super_passive(struct super_block *sb)
  */
 void lock_super(struct super_block * sb)
 {
-       get_fs_excl();
        mutex_lock(&sb->s_lock);
 }
 
 void unlock_super(struct super_block * sb)
 {
-       put_fs_excl();
        mutex_unlock(&sb->s_lock);
 }
 
@@ -385,7 +385,6 @@ void generic_shutdown_super(struct super_block *sb)
        if (sb->s_root) {
                shrink_dcache_for_umount(sb);
                sync_filesystem(sb);
-               get_fs_excl();
                sb->s_flags &= ~MS_ACTIVE;
 
                fsnotify_unmount_inodes(&sb->s_inodes);
@@ -400,11 +399,10 @@ void generic_shutdown_super(struct super_block *sb)
                           "Self-destruct in 5 seconds.  Have a nice day...\n",
                           sb->s_id);
                }
-               put_fs_excl();
        }
        spin_lock(&sb_lock);
        /* should be initialized for __put_super_and_need_restart() */
-       list_del_init(&sb->s_instances);
+       hlist_del_init(&sb->s_instances);
        spin_unlock(&sb_lock);
        up_write(&sb->s_umount);
 }
@@ -424,13 +422,14 @@ struct super_block *sget(struct file_system_type *type,
                        void *data)
 {
        struct super_block *s = NULL;
+       struct hlist_node *node;
        struct super_block *old;
        int err;
 
 retry:
        spin_lock(&sb_lock);
        if (test) {
-               list_for_each_entry(old, &type->fs_supers, s_instances) {
+               hlist_for_each_entry(old, node, &type->fs_supers, s_instances) {
                        if (!test(old, data))
                                continue;
                        if (!grab_super(old))
@@ -466,7 +465,7 @@ retry:
        s->s_type = type;
        strlcpy(s->s_id, type->name, sizeof(s->s_id));
        list_add_tail(&s->s_list, &super_blocks);
-       list_add(&s->s_instances, &type->fs_supers);
+       hlist_add_head(&s->s_instances, &type->fs_supers);
        spin_unlock(&sb_lock);
        get_filesystem(type);
        register_shrinker(&s->s_shrink);
@@ -501,14 +500,14 @@ void sync_supers(void)
 
        spin_lock(&sb_lock);
        list_for_each_entry(sb, &super_blocks, s_list) {
-               if (list_empty(&sb->s_instances))
+               if (hlist_unhashed(&sb->s_instances))
                        continue;
                if (sb->s_op->write_super && sb->s_dirt) {
                        sb->s_count++;
                        spin_unlock(&sb_lock);
 
                        down_read(&sb->s_umount);
-                       if (sb->s_root && sb->s_dirt)
+                       if (sb->s_root && sb->s_dirt && (sb->s_flags & MS_BORN))
                                sb->s_op->write_super(sb);
                        up_read(&sb->s_umount);
 
@@ -537,13 +536,13 @@ void iterate_supers(void (*f)(struct super_block *, void *), void *arg)
 
        spin_lock(&sb_lock);
        list_for_each_entry(sb, &super_blocks, s_list) {
-               if (list_empty(&sb->s_instances))
+               if (hlist_unhashed(&sb->s_instances))
                        continue;
                sb->s_count++;
                spin_unlock(&sb_lock);
 
                down_read(&sb->s_umount);
-               if (sb->s_root)
+               if (sb->s_root && (sb->s_flags & MS_BORN))
                        f(sb, arg);
                up_read(&sb->s_umount);
 
@@ -570,14 +569,15 @@ void iterate_supers_type(struct file_system_type *type,
        void (*f)(struct super_block *, void *), void *arg)
 {
        struct super_block *sb, *p = NULL;
+       struct hlist_node *node;
 
        spin_lock(&sb_lock);
-       list_for_each_entry(sb, &type->fs_supers, s_instances) {
+       hlist_for_each_entry(sb, node, &type->fs_supers, s_instances) {
                sb->s_count++;
                spin_unlock(&sb_lock);
 
                down_read(&sb->s_umount);
-               if (sb->s_root)
+               if (sb->s_root && (sb->s_flags & MS_BORN))
                        f(sb, arg);
                up_read(&sb->s_umount);
 
@@ -611,14 +611,14 @@ struct super_block *get_super(struct block_device *bdev)
        spin_lock(&sb_lock);
 rescan:
        list_for_each_entry(sb, &super_blocks, s_list) {
-               if (list_empty(&sb->s_instances))
+               if (hlist_unhashed(&sb->s_instances))
                        continue;
                if (sb->s_bdev == bdev) {
                        sb->s_count++;
                        spin_unlock(&sb_lock);
                        down_read(&sb->s_umount);
                        /* still alive? */
-                       if (sb->s_root)
+                       if (sb->s_root && (sb->s_flags & MS_BORN))
                                return sb;
                        up_read(&sb->s_umount);
                        /* nope, got unmounted */
@@ -651,7 +651,7 @@ struct super_block *get_active_super(struct block_device *bdev)
 restart:
        spin_lock(&sb_lock);
        list_for_each_entry(sb, &super_blocks, s_list) {
-               if (list_empty(&sb->s_instances))
+               if (hlist_unhashed(&sb->s_instances))
                        continue;
                if (sb->s_bdev == bdev) {
                        if (grab_super(sb)) /* drops sb_lock */
@@ -671,14 +671,14 @@ struct super_block *user_get_super(dev_t dev)
        spin_lock(&sb_lock);
 rescan:
        list_for_each_entry(sb, &super_blocks, s_list) {
-               if (list_empty(&sb->s_instances))
+               if (hlist_unhashed(&sb->s_instances))
                        continue;
                if (sb->s_dev ==  dev) {
                        sb->s_count++;
                        spin_unlock(&sb_lock);
                        down_read(&sb->s_umount);
                        /* still alive? */
-                       if (sb->s_root)
+                       if (sb->s_root && (sb->s_flags & MS_BORN))
                                return sb;
                        up_read(&sb->s_umount);
                        /* nope, got unmounted */
@@ -723,18 +723,29 @@ int do_remount_sb(struct super_block *sb, int flags, void *data, int force)
        /* If we are remounting RDONLY and current sb is read/write,
           make sure there are no rw files opened */
        if (remount_ro) {
-               if (force)
+               if (force) {
                        mark_files_ro(sb);
-               else if (!fs_may_remount_ro(sb))
-                       return -EBUSY;
+               } else {
+                       retval = sb_prepare_remount_readonly(sb);
+                       if (retval)
+                               return retval;
+               }
        }
 
        if (sb->s_op->remount_fs) {
                retval = sb->s_op->remount_fs(sb, &flags, data);
-               if (retval)
-                       return retval;
+               if (retval) {
+                       if (!force)
+                               goto cancel_readonly;
+                       /* If forced remount, go ahead despite any errors */
+                       WARN(1, "forced remount of a %s fs returned %i\n",
+                            sb->s_type->name, retval);
+               }
        }
        sb->s_flags = (sb->s_flags & ~MS_RMT_MASK) | (flags & MS_RMT_MASK);
+       /* Needs to be ordered wrt mnt_is_readonly() */
+       smp_wmb();
+       sb->s_readonly_remount = 0;
 
        /*
         * Some filesystems modify their metadata via some other path than the
@@ -747,6 +758,10 @@ int do_remount_sb(struct super_block *sb, int flags, void *data, int force)
        if (remount_ro && sb->s_bdev)
                invalidate_bdev(sb->s_bdev);
        return 0;
+
+cancel_readonly:
+       sb->s_readonly_remount = 0;
+       return retval;
 }
 
 static void do_emergency_remount(struct work_struct *work)
@@ -755,12 +770,13 @@ static void do_emergency_remount(struct work_struct *work)
 
        spin_lock(&sb_lock);
        list_for_each_entry(sb, &super_blocks, s_list) {
-               if (list_empty(&sb->s_instances))
+               if (hlist_unhashed(&sb->s_instances))
                        continue;
                sb->s_count++;
                spin_unlock(&sb_lock);
                down_write(&sb->s_umount);
-               if (sb->s_root && sb->s_bdev && !(sb->s_flags & MS_RDONLY)) {
+               if (sb->s_root && sb->s_bdev && (sb->s_flags & MS_BORN) &&
+                   !(sb->s_flags & MS_RDONLY)) {
                        /*
                         * What lock protects sb->s_flags??
                         */
@@ -1143,6 +1159,11 @@ int freeze_super(struct super_block *sb)
                return -EBUSY;
        }
 
+       if (!(sb->s_flags & MS_BORN)) {
+               up_write(&sb->s_umount);
+               return 0;       /* sic - it's "nothing to do" */
+       }
+
        if (sb->s_flags & MS_RDONLY) {
                sb->s_frozen = SB_FREEZE_TRANS;
                smp_wmb();
@@ -1165,6 +1186,8 @@ int freeze_super(struct super_block *sb)
                        printk(KERN_ERR
                                "VFS:Filesystem freeze failed\n");
                        sb->s_frozen = SB_UNFROZEN;
+                       smp_wmb();
+                       wake_up(&sb->s_wait_unfrozen);
                        deactivate_locked_super(sb);
                        return ret;
                }