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Commit a1b83ac5 authored by Anand Jain's avatar Anand Jain Committed by Chris Mason
Browse files

btrfs: fix get set label blocking against balance 



btrfs_ioctl_get_fslabel() and btrfs_ioctl_set_fslabel()
used root->fs_info->volume_mutex mutex which caused operations
like balance to block set/get label operation until its
completion and generally balance operation takes a long
time to complete, so it will be annoying to the user when
cli appears hung

also this patch will add a bit of optimization within
the btrfs_ioctl_get_falabel() function.

v1->v2:
   use fs_info->super_lock instead of uuid_mutex

Signed-off-by: default avatarAnand Jain <anand.jain@oracle.com>
Signed-off-by: default avatarJosef Bacik <jbacik@fusionio.com>
Signed-off-by: default avatarChris Mason <chris.mason@fusionio.com>
parent d4c34f6b

fs/btrfs/ioctl.c

+10 −6
Original line number Diff line number Diff line
@@ -4042,18 +4042,22 @@ static long btrfs_ioctl_set_received_subvol(struct file *file, 
static int btrfs_ioctl_get_fslabel(struct file *file, void __user *arg)

{

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

	const char *label = root->fs_info->super_copy->label;

	size_t len = strnlen(label, BTRFS_LABEL_SIZE);

	size_t len;

	int ret;

	char label[BTRFS_LABEL_SIZE];



	spin_lock(&root->fs_info->super_lock);

	memcpy(label, root->fs_info->super_copy->label, BTRFS_LABEL_SIZE);

	spin_unlock(&root->fs_info->super_lock);



	len = strnlen(label, BTRFS_LABEL_SIZE);



	if (len == BTRFS_LABEL_SIZE) {

		pr_warn("btrfs: label is too long, return the first %zu bytes\n",

			--len);

	}



	mutex_lock(&root->fs_info->volume_mutex);

	ret = copy_to_user(arg, label, len);

	mutex_unlock(&root->fs_info->volume_mutex);



	return ret ? -EFAULT : 0;

}
@@ -4082,18 +4086,18 @@ static int btrfs_ioctl_set_fslabel(struct file *file, void __user *arg) 
	if (ret)

		return ret;



	mutex_lock(&root->fs_info->volume_mutex);

	trans = btrfs_start_transaction(root, 0);

	if (IS_ERR(trans)) {

		ret = PTR_ERR(trans);

		goto out_unlock;

	}



	spin_lock(&root->fs_info->super_lock);

	strcpy(super_block->label, label);

	spin_unlock(&root->fs_info->super_lock);

	ret = btrfs_end_transaction(trans, root);



out_unlock:

	mutex_unlock(&root->fs_info->volume_mutex);

	mnt_drop_write_file(file);

	return ret;

}