Commit ed0fb78f authored by Ilya Dryomov's avatar Ilya Dryomov
Browse files

Btrfs: bring back balance pause/resume logic 



Balance pause/resume logic got broken by 5ac00add (went in into 3.8-rc1
as part of dev-replace merge).  Offending commit took a stab at making
mutually exclusive volume operations (add_dev, rm_dev, resize, balance,
replace_dev) not block behind volume_mutex if another such operation is
in progress and instead return an error right away.  Balancing front-end
relied on the blocking behaviour, so the fix is ugly, but short of a
complete rework, it's the best we can do.

Reported-by: default avatarLiu Bo <bo.li.liu@oracle.com>
Signed-off-by: default avatarIlya Dryomov <idryomov@gmail.com>
parent 3972f260

fs/btrfs/ioctl.c

+64 −14
Original line number Diff line number Diff line
@@ -3440,8 +3440,8 @@ static long btrfs_ioctl_balance(struct file *file, void __user *arg) 
	struct btrfs_fs_info *fs_info = root->fs_info;

	struct btrfs_ioctl_balance_args *bargs;

	struct btrfs_balance_control *bctl;

	bool need_unlock; /* for mut. excl. ops lock */

	int ret;

	int need_to_clear_lock = 0;



	if (!capable(CAP_SYS_ADMIN))

		return -EPERM;
@@ -3450,14 +3450,61 @@ static long btrfs_ioctl_balance(struct file *file, void __user *arg) 
	if (ret)

		return ret;



again:

	if (!atomic_xchg(&fs_info->mutually_exclusive_operation_running, 1)) {

		mutex_lock(&fs_info->volume_mutex);

		mutex_lock(&fs_info->balance_mutex);

		need_unlock = true;

		goto locked;

	}



	/*

	 * mut. excl. ops lock is locked.  Three possibilites:

	 *   (1) some other op is running

	 *   (2) balance is running

	 *   (3) balance is paused -- special case (think resume)

	 */

	mutex_lock(&fs_info->balance_mutex);

	if (fs_info->balance_ctl) {

		/* this is either (2) or (3) */

		if (!atomic_read(&fs_info->balance_running)) {

			mutex_unlock(&fs_info->balance_mutex);

			if (!mutex_trylock(&fs_info->volume_mutex))

				goto again;

			mutex_lock(&fs_info->balance_mutex);



			if (fs_info->balance_ctl &&

			    !atomic_read(&fs_info->balance_running)) {

				/* this is (3) */

				need_unlock = false;

				goto locked;

			}



			mutex_unlock(&fs_info->balance_mutex);

			mutex_unlock(&fs_info->volume_mutex);

			goto again;

		} else {

			/* this is (2) */

			mutex_unlock(&fs_info->balance_mutex);

			ret = -EINPROGRESS;

			goto out;

		}

	} else {

		/* this is (1) */

		mutex_unlock(&fs_info->balance_mutex);

		pr_info("btrfs: dev add/delete/balance/replace/resize operation in progress\n");

		ret = -EINVAL;

		goto out;

	}



locked:

	BUG_ON(!atomic_read(&fs_info->mutually_exclusive_operation_running));



	if (arg) {

		bargs = memdup_user(arg, sizeof(*bargs));

		if (IS_ERR(bargs)) {

			ret = PTR_ERR(bargs);

			goto out;

			goto out_unlock;

		}



		if (bargs->flags & BTRFS_BALANCE_RESUME) {
@@ -3477,13 +3524,10 @@ static long btrfs_ioctl_balance(struct file *file, void __user *arg) 
		bargs = NULL;

	}



	if (atomic_xchg(&root->fs_info->mutually_exclusive_operation_running,

			1)) {

		pr_info("btrfs: dev add/delete/balance/replace/resize operation in progress\n");

	if (fs_info->balance_ctl) {

		ret = -EINPROGRESS;

		goto out_bargs;

	}

	need_to_clear_lock = 1;



	bctl = kzalloc(sizeof(*bctl), GFP_NOFS);

	if (!bctl) {
@@ -3504,11 +3548,17 @@ static long btrfs_ioctl_balance(struct file *file, void __user *arg) 
	}



do_balance:

	ret = btrfs_balance(bctl, bargs);

	/*

	 * bctl is freed in __cancel_balance or in free_fs_info if

	 * restriper was paused all the way until unmount

	 * Ownership of bctl and mutually_exclusive_operation_running

	 * goes to to btrfs_balance.  bctl is freed in __cancel_balance,

	 * or, if restriper was paused all the way until unmount, in

	 * free_fs_info.  mutually_exclusive_operation_running is

	 * cleared in __cancel_balance.

	 */

	need_unlock = false;



	ret = btrfs_balance(bctl, bargs);



	if (arg) {

		if (copy_to_user(arg, bargs, sizeof(*bargs)))

			ret = -EFAULT;
@@ -3516,12 +3566,12 @@ do_balance: 


out_bargs:

	kfree(bargs);

out:

	if (need_to_clear_lock)

		atomic_set(&root->fs_info->mutually_exclusive_operation_running,

			   0);

out_unlock:

	mutex_unlock(&fs_info->balance_mutex);

	mutex_unlock(&fs_info->volume_mutex);

	if (need_unlock)

		atomic_set(&fs_info->mutually_exclusive_operation_running, 0);

out:

	mnt_drop_write_file(file);

	return ret;

}

fs/btrfs/volumes.c

+7 −3
Original line number Diff line number Diff line
@@ -2959,6 +2959,8 @@ static void __cancel_balance(struct btrfs_fs_info *fs_info) 
	unset_balance_control(fs_info);

	ret = del_balance_item(fs_info->tree_root);

	BUG_ON(ret);



	atomic_set(&fs_info->mutually_exclusive_operation_running, 0);

}



void update_ioctl_balance_args(struct btrfs_fs_info *fs_info, int lock,
@@ -3138,8 +3140,10 @@ int btrfs_balance(struct btrfs_balance_control *bctl, 
out:

	if (bctl->flags & BTRFS_BALANCE_RESUME)

		__cancel_balance(fs_info);

	else

	else {

		kfree(bctl);

		atomic_set(&fs_info->mutually_exclusive_operation_running, 0);

	}

	return ret;

}
@@ -3156,7 +3160,6 @@ static int balance_kthread(void *data) 
		ret = btrfs_balance(fs_info->balance_ctl, NULL);

	}



	atomic_set(&fs_info->mutually_exclusive_operation_running, 0);

	mutex_unlock(&fs_info->balance_mutex);

	mutex_unlock(&fs_info->volume_mutex);
@@ -3179,7 +3182,6 @@ int btrfs_resume_balance_async(struct btrfs_fs_info *fs_info) 
		return 0;

	}



	WARN_ON(atomic_xchg(&fs_info->mutually_exclusive_operation_running, 1));

	tsk = kthread_run(balance_kthread, fs_info, "btrfs-balance");

	if (IS_ERR(tsk))

		return PTR_ERR(tsk);
@@ -3233,6 +3235,8 @@ int btrfs_recover_balance(struct btrfs_fs_info *fs_info) 
	btrfs_balance_sys(leaf, item, &disk_bargs);

	btrfs_disk_balance_args_to_cpu(&bctl->sys, &disk_bargs);



	WARN_ON(atomic_xchg(&fs_info->mutually_exclusive_operation_running, 1));



	mutex_lock(&fs_info->volume_mutex);

	mutex_lock(&fs_info->balance_mutex);

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