Btrfs: resume balance on rw (re)mounts properly

This introduces btrfs_resume_balance_async(), which, given that
restriper state was recovered earlier by btrfs_recover_balance(),
resumes balance in btrfs-balance kthread.

Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

4 files changed, 47 insertions, 18 deletions

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 3a7961ba161e..8cc47103a32e 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -2490,17 +2490,23 @@ retry_root_backup:
                 goto fail_trans_kthread;
         }
 
-        if (!(sb->s_flags & MS_RDONLY)) {
-                down_read(&fs_info->cleanup_work_sem);
-                err = btrfs_orphan_cleanup(fs_info->fs_root);
-                if (!err)
-                        err = btrfs_orphan_cleanup(fs_info->tree_root);
+        if (sb->s_flags & MS_RDONLY)
+                return 0;
+
+        down_read(&fs_info->cleanup_work_sem);
+        if ((ret = btrfs_orphan_cleanup(fs_info->fs_root)) ||
+            (ret = btrfs_orphan_cleanup(fs_info->tree_root))) {
                 up_read(&fs_info->cleanup_work_sem);
+                close_ctree(tree_root);
+                return ret;
+        }
+        up_read(&fs_info->cleanup_work_sem);
 
-                if (err) {
-                        close_ctree(tree_root);
-                        return err;
-                }
+        ret = btrfs_resume_balance_async(fs_info);
+        if (ret) {
+                printk(KERN_WARNING "btrfs: failed to resume balance\n");
+                close_ctree(tree_root);
+                return ret;
         }
 
         return 0;
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 0eb9a4da069e..e23991574fdf 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -1187,6 +1187,10 @@ static int btrfs_remount(struct super_block *sb, int *flags, char *data)
                 if (ret)
                         goto restore;
 
+                ret = btrfs_resume_balance_async(fs_info);
+                if (ret)
+                        goto restore;
+
                 sb->s_flags &= ~MS_RDONLY;
         }
 
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 48943d0f861a..ecaad40e7ef4 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -2845,28 +2845,46 @@ out:
 
 static int balance_kthread(void *data)
 {
-        struct btrfs_balance_control *bctl =
-                        (struct btrfs_balance_control *)data;
-        struct btrfs_fs_info *fs_info = bctl->fs_info;
+        struct btrfs_fs_info *fs_info = data;
         int ret = 0;
 
         mutex_lock(&fs_info->volume_mutex);
         mutex_lock(&fs_info->balance_mutex);
 
-        set_balance_control(bctl);
-
-        if (btrfs_test_opt(fs_info->tree_root, SKIP_BALANCE)) {
-                printk(KERN_INFO "btrfs: force skipping balance\n");
-        } else {
+        if (fs_info->balance_ctl) {
                 printk(KERN_INFO "btrfs: continuing balance\n");
-                ret = btrfs_balance(bctl, NULL);
+                ret = btrfs_balance(fs_info->balance_ctl, NULL);
         }
 
         mutex_unlock(&fs_info->balance_mutex);
         mutex_unlock(&fs_info->volume_mutex);
+
         return ret;
 }
 
+int btrfs_resume_balance_async(struct btrfs_fs_info *fs_info)
+{
+        struct task_struct *tsk;
+
+        spin_lock(&fs_info->balance_lock);
+        if (!fs_info->balance_ctl) {
+                spin_unlock(&fs_info->balance_lock);
+                return 0;
+        }
+        spin_unlock(&fs_info->balance_lock);
+
+        if (btrfs_test_opt(fs_info->tree_root, SKIP_BALANCE)) {
+                printk(KERN_INFO "btrfs: force skipping balance\n");
+                return 0;
+        }
+
+        tsk = kthread_run(balance_kthread, fs_info, "btrfs-balance");
+        if (IS_ERR(tsk))
+                return PTR_ERR(tsk);
+
+        return 0;
+}
+
 int btrfs_recover_balance(struct btrfs_fs_info *fs_info)
 {
         struct btrfs_balance_control *bctl;
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index e1b1a649fc5a..95f6637614db 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -281,6 +281,7 @@ int btrfs_shrink_device(struct btrfs_device *device, u64 new_size);
 int btrfs_init_new_device(struct btrfs_root *root, char *path);
 int btrfs_balance(struct btrfs_balance_control *bctl,
                   struct btrfs_ioctl_balance_args *bargs);
+int btrfs_resume_balance_async(struct btrfs_fs_info *fs_info);
 int btrfs_recover_balance(struct btrfs_fs_info *fs_info);
 int btrfs_pause_balance(struct btrfs_fs_info *fs_info);
 int btrfs_cancel_balance(struct btrfs_fs_info *fs_info);