Btrfs: rescan for qgroups

If qgroup tracking is out of sync, a rescan operation can be started. It
iterates the complete extent tree and recalculates all qgroup tracking data.
This is an expensive operation and should not be used unless required.

A filesystem under rescan can still be umounted. The rescan continues on the
next mount.  Status information is provided with a separate ioctl while a
rescan operation is in progress.

Signed-off-by: Jan Schmidt <list.btrfs@jan-o-sch.net>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>

1 files changed, 69 insertions, 14 deletions

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index a74edc79753..f5f6af338b5 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -3701,12 +3701,10 @@ static long btrfs_ioctl_quota_ctl(struct file *file, void __user *arg)
 	}
 
 	down_write(&root->fs_info->subvol_sem);
-	if (sa->cmd != BTRFS_QUOTA_CTL_RESCAN) {
-		trans = btrfs_start_transaction(root->fs_info->tree_root, 2);
-		if (IS_ERR(trans)) {
-			ret = PTR_ERR(trans);
-			goto out;
-		}
+	trans = btrfs_start_transaction(root->fs_info->tree_root, 2);
+	if (IS_ERR(trans)) {
+		ret = PTR_ERR(trans);
+		goto out;
 	}
 
 	switch (sa->cmd) {
@@ -3716,9 +3714,6 @@ static long btrfs_ioctl_quota_ctl(struct file *file, void __user *arg)
 	case BTRFS_QUOTA_CTL_DISABLE:
 		ret = btrfs_quota_disable(trans, root->fs_info);
 		break;
-	case BTRFS_QUOTA_CTL_RESCAN:
-		ret = btrfs_quota_rescan(root->fs_info);
-		break;
 	default:
 		ret = -EINVAL;
 		break;
@@ -3727,11 +3722,9 @@ static long btrfs_ioctl_quota_ctl(struct file *file, void __user *arg)
 	if (copy_to_user(arg, sa, sizeof(*sa)))
 		ret = -EFAULT;
 
-	if (trans) {
-		err = btrfs_commit_transaction(trans, root->fs_info->tree_root);
-		if (err && !ret)
-			ret = err;
-	}
+	err = btrfs_commit_transaction(trans, root->fs_info->tree_root);
+	if (err && !ret)
+		ret = err;
 out:
 	kfree(sa);
 	up_write(&root->fs_info->subvol_sem);
@@ -3886,6 +3879,64 @@ drop_write:
 	return ret;
 }
 
+static long btrfs_ioctl_quota_rescan(struct file *file, void __user *arg)
+{
+	struct btrfs_root *root = BTRFS_I(fdentry(file)->d_inode)->root;
+	struct btrfs_ioctl_quota_rescan_args *qsa;
+	int ret;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	ret = mnt_want_write_file(file);
+	if (ret)
+		return ret;
+
+	qsa = memdup_user(arg, sizeof(*qsa));
+	if (IS_ERR(qsa)) {
+		ret = PTR_ERR(qsa);
+		goto drop_write;
+	}
+
+	if (qsa->flags) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	ret = btrfs_qgroup_rescan(root->fs_info);
+
+out:
+	kfree(qsa);
+drop_write:
+	mnt_drop_write_file(file);
+	return ret;
+}
+
+static long btrfs_ioctl_quota_rescan_status(struct file *file, void __user *arg)
+{
+	struct btrfs_root *root = BTRFS_I(fdentry(file)->d_inode)->root;
+	struct btrfs_ioctl_quota_rescan_args *qsa;
+	int ret = 0;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	qsa = kzalloc(sizeof(*qsa), GFP_NOFS);
+	if (!qsa)
+		return -ENOMEM;
+
+	if (root->fs_info->qgroup_flags & BTRFS_QGROUP_STATUS_FLAG_RESCAN) {
+		qsa->flags = 1;
+		qsa->progress = root->fs_info->qgroup_rescan_progress.objectid;
+	}
+
+	if (copy_to_user(arg, qsa, sizeof(*qsa)))
+		ret = -EFAULT;
+
+	kfree(qsa);
+	return ret;
+}
+
 static long btrfs_ioctl_set_received_subvol(struct file *file,
 					    void __user *arg)
 {
@@ -4124,6 +4175,10 @@ long btrfs_ioctl(struct file *file, unsigned int
 		return btrfs_ioctl_qgroup_create(file, argp);
 	case BTRFS_IOC_QGROUP_LIMIT:
 		return btrfs_ioctl_qgroup_limit(file, argp);
+	case BTRFS_IOC_QUOTA_RESCAN:
+		return btrfs_ioctl_quota_rescan(file, argp);
+	case BTRFS_IOC_QUOTA_RESCAN_STATUS:
+		return btrfs_ioctl_quota_rescan_status(file, argp);
 	case BTRFS_IOC_DEV_REPLACE:
 		return btrfs_ioctl_dev_replace(root, argp);
 	case BTRFS_IOC_GET_FSLABEL: