Commit 7fb10ed8 authored by Nikolay Borisov's avatar Nikolay Borisov Committed by David Sterba
Browse files

btrfs: introduce btrfs_try_lock_balance 



This function contains the factored out locking sequence of
btrfs_ioctl_balance. Having this piece of code separate helps to
simplify btrfs_ioctl_balance which has too complicated.  This will be
used in the next patch to streamline the logic in btrfs_ioctl_balance.

Signed-off-by: default avatarNikolay Borisov <nborisov@suse.com>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent 1e87770c

fs/btrfs/ioctl.c

+66 −0
Original line number Diff line number Diff line
@@ -4355,6 +4355,72 @@ void btrfs_update_ioctl_balance_args(struct btrfs_fs_info *fs_info, 
	spin_unlock(&fs_info->balance_lock);

}



/**

 * Try to acquire fs_info::balance_mutex as well as set BTRFS_EXLCOP_BALANCE as

 * required.

 *

 * @fs_info:       the filesystem

 * @excl_acquired: ptr to boolean value which is set to false in case balance

 *                 is being resumed

 *

 * Return 0 on success in which case both fs_info::balance is acquired as well

 * as exclusive ops are blocked. In case of failure return an error code.

 */

static int btrfs_try_lock_balance(struct btrfs_fs_info *fs_info, bool *excl_acquired)

{

	int ret;



	/*

	 * Exclusive operation is locked. Three possibilities:

	 *   (1) some other op is running

	 *   (2) balance is running

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

	 */

	while (1) {

		if (btrfs_exclop_start(fs_info, BTRFS_EXCLOP_BALANCE)) {

			*excl_acquired = true;

			mutex_lock(&fs_info->balance_mutex);

			return 0;

		}



		mutex_lock(&fs_info->balance_mutex);

		if (fs_info->balance_ctl) {

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

			if (test_bit(BTRFS_FS_BALANCE_RUNNING, &fs_info->flags)) {

				/* This is (2) */

				ret = -EINPROGRESS;

				goto out_failure;



			} else {

				mutex_unlock(&fs_info->balance_mutex);

				/*

				 * Lock released to allow other waiters to

				 * continue, we'll reexamine the status again.

				 */

				mutex_lock(&fs_info->balance_mutex);



				if (fs_info->balance_ctl &&

				    !test_bit(BTRFS_FS_BALANCE_RUNNING, &fs_info->flags)) {

					/* This is (3) */

					*excl_acquired = false;

					return 0;

				}

			}

		} else {

			/* This is (1) */

			ret = BTRFS_ERROR_DEV_EXCL_RUN_IN_PROGRESS;

			goto out_failure;

		}



		mutex_unlock(&fs_info->balance_mutex);

	}



out_failure:

	mutex_unlock(&fs_info->balance_mutex);

	*excl_acquired = false;

	return ret;

}



static long btrfs_ioctl_balance(struct file *file, void __user *arg)

{

	struct btrfs_root *root = BTRFS_I(file_inode(file))->root;