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, 304 insertions, 14 deletions

diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
index 1fb7d8da3084..da8458357b57 100644
--- a/fs/btrfs/qgroup.c
+++ b/fs/btrfs/qgroup.c
@@ -31,13 +31,13 @@
 #include "locking.h"
 #include "ulist.h"
 #include "backref.h"
+#include "extent_io.h"
 
 /* TODO XXX FIXME
  *  - subvol delete -> delete when ref goes to 0? delete limits also?
  *  - reorganize keys
  *  - compressed
  *  - sync
- *  - rescan
  *  - copy also limits on subvol creation
  *  - limit
  *  - caches fuer ulists
@@ -98,6 +98,14 @@ struct btrfs_qgroup_list {
 	struct btrfs_qgroup *member;
 };
 
+struct qgroup_rescan {
+	struct btrfs_work	work;
+	struct btrfs_fs_info	*fs_info;
+};
+
+static void qgroup_rescan_start(struct btrfs_fs_info *fs_info,
+				struct qgroup_rescan *qscan);
+
 /* must be called with qgroup_ioctl_lock held */
 static struct btrfs_qgroup *find_qgroup_rb(struct btrfs_fs_info *fs_info,
 					   u64 qgroupid)
@@ -298,7 +306,20 @@ int btrfs_read_qgroup_config(struct btrfs_fs_info *fs_info)
 			}
 			fs_info->qgroup_flags = btrfs_qgroup_status_flags(l,
 									  ptr);
-			/* FIXME read scan element */
+			fs_info->qgroup_rescan_progress.objectid =
+					btrfs_qgroup_status_rescan(l, ptr);
+			if (fs_info->qgroup_flags &
+			    BTRFS_QGROUP_STATUS_FLAG_RESCAN) {
+				struct qgroup_rescan *qscan =
+					kmalloc(sizeof(*qscan), GFP_NOFS);
+				if (!qscan) {
+					ret = -ENOMEM;
+					goto out;
+				}
+				fs_info->qgroup_rescan_progress.type = 0;
+				fs_info->qgroup_rescan_progress.offset = 0;
+				qgroup_rescan_start(fs_info, qscan);
+			}
 			goto next1;
 		}
 
@@ -719,7 +740,8 @@ static int update_qgroup_status_item(struct btrfs_trans_handle *trans,
 	ptr = btrfs_item_ptr(l, slot, struct btrfs_qgroup_status_item);
 	btrfs_set_qgroup_status_flags(l, ptr, fs_info->qgroup_flags);
 	btrfs_set_qgroup_status_generation(l, ptr, trans->transid);
-	/* XXX scan */
+	btrfs_set_qgroup_status_rescan(l, ptr,
+				fs_info->qgroup_rescan_progress.objectid);
 
 	btrfs_mark_buffer_dirty(l);
 
@@ -830,7 +852,7 @@ int btrfs_quota_enable(struct btrfs_trans_handle *trans,
 	fs_info->qgroup_flags = BTRFS_QGROUP_STATUS_FLAG_ON |
 				BTRFS_QGROUP_STATUS_FLAG_INCONSISTENT;
 	btrfs_set_qgroup_status_flags(leaf, ptr, fs_info->qgroup_flags);
-	btrfs_set_qgroup_status_scan(leaf, ptr, 0);
+	btrfs_set_qgroup_status_rescan(leaf, ptr, 0);
 
 	btrfs_mark_buffer_dirty(leaf);
 
@@ -944,10 +966,11 @@ out:
 	return ret;
 }
 
-int btrfs_quota_rescan(struct btrfs_fs_info *fs_info)
+static void qgroup_dirty(struct btrfs_fs_info *fs_info,
+			 struct btrfs_qgroup *qgroup)
 {
-	/* FIXME */
-	return 0;
+	if (list_empty(&qgroup->dirty))
+		list_add(&qgroup->dirty, &fs_info->dirty_qgroups);
 }
 
 int btrfs_add_qgroup_relation(struct btrfs_trans_handle *trans,
@@ -1155,13 +1178,6 @@ out:
 	return ret;
 }
 
-static void qgroup_dirty(struct btrfs_fs_info *fs_info,
-			 struct btrfs_qgroup *qgroup)
-{
-	if (list_empty(&qgroup->dirty))
-		list_add(&qgroup->dirty, &fs_info->dirty_qgroups);
-}
-
 /*
  * btrfs_qgroup_record_ref is called when the ref is added or deleted. it puts
  * the modification into a list that's later used by btrfs_end_transaction to
@@ -1390,6 +1406,15 @@ int btrfs_qgroup_account_ref(struct btrfs_trans_handle *trans,
 		BUG();
 	}
 
+	mutex_lock(&fs_info->qgroup_rescan_lock);
+	if (fs_info->qgroup_flags & BTRFS_QGROUP_STATUS_FLAG_RESCAN) {
+		if (fs_info->qgroup_rescan_progress.objectid <= node->bytenr) {
+			mutex_unlock(&fs_info->qgroup_rescan_lock);
+			return 0;
+		}
+	}
+	mutex_unlock(&fs_info->qgroup_rescan_lock);
+
 	/*
 	 * the delayed ref sequence number we pass depends on the direction of
 	 * the operation. for add operations, we pass
@@ -1403,7 +1428,15 @@ int btrfs_qgroup_account_ref(struct btrfs_trans_handle *trans,
 	if (ret < 0)
 		return ret;
 
+	mutex_lock(&fs_info->qgroup_rescan_lock);
 	spin_lock(&fs_info->qgroup_lock);
+	if (fs_info->qgroup_flags & BTRFS_QGROUP_STATUS_FLAG_RESCAN) {
+		if (fs_info->qgroup_rescan_progress.objectid <= node->bytenr) {
+			ret = 0;
+			goto unlock;
+		}
+	}
+
 	quota_root = fs_info->quota_root;
 	if (!quota_root)
 		goto unlock;
@@ -1445,6 +1478,7 @@ int btrfs_qgroup_account_ref(struct btrfs_trans_handle *trans,
 
 unlock:
 	spin_unlock(&fs_info->qgroup_lock);
+	mutex_unlock(&fs_info->qgroup_rescan_lock);
 	ulist_free(roots);
 	ulist_free(tmp);
 
@@ -1823,3 +1857,259 @@ void assert_qgroups_uptodate(struct btrfs_trans_handle *trans)
 		(u32)trans->delayed_ref_elem.seq);
 	BUG();
 }
+
+/*
+ * returns < 0 on error, 0 when more leafs are to be scanned.
+ * returns 1 when done, 2 when done and FLAG_INCONSISTENT was cleared.
+ */
+static int
+qgroup_rescan_leaf(struct qgroup_rescan *qscan, struct btrfs_path *path,
+		   struct btrfs_trans_handle *trans, struct ulist *tmp,
+		   struct extent_buffer *scratch_leaf)
+{
+	struct btrfs_key found;
+	struct btrfs_fs_info *fs_info = qscan->fs_info;
+	struct ulist *roots = NULL;
+	struct ulist_node *unode;
+	struct ulist_iterator uiter;
+	struct seq_list tree_mod_seq_elem = {};
+	u64 seq;
+	int slot;
+	int ret;
+
+	path->leave_spinning = 1;
+	mutex_lock(&fs_info->qgroup_rescan_lock);
+	ret = btrfs_search_slot_for_read(fs_info->extent_root,
+					 &fs_info->qgroup_rescan_progress,
+					 path, 1, 0);
+
+	pr_debug("current progress key (%llu %u %llu), search_slot ret %d\n",
+		 (unsigned long long)fs_info->qgroup_rescan_progress.objectid,
+		 fs_info->qgroup_rescan_progress.type,
+		 (unsigned long long)fs_info->qgroup_rescan_progress.offset,
+		 ret);
+
+	if (ret) {
+		/*
+		 * The rescan is about to end, we will not be scanning any
+		 * further blocks. We cannot unset the RESCAN flag here, because
+		 * we want to commit the transaction if everything went well.
+		 * To make the live accounting work in this phase, we set our
+		 * scan progress pointer such that every real extent objectid
+		 * will be smaller.
+		 */
+		fs_info->qgroup_rescan_progress.objectid = (u64)-1;
+		btrfs_release_path(path);
+		mutex_unlock(&fs_info->qgroup_rescan_lock);
+		return ret;
+	}
+
+	btrfs_item_key_to_cpu(path->nodes[0], &found,
+			      btrfs_header_nritems(path->nodes[0]) - 1);
+	fs_info->qgroup_rescan_progress.objectid = found.objectid + 1;
+
+	btrfs_get_tree_mod_seq(fs_info, &tree_mod_seq_elem);
+	memcpy(scratch_leaf, path->nodes[0], sizeof(*scratch_leaf));
+	slot = path->slots[0];
+	btrfs_release_path(path);
+	mutex_unlock(&fs_info->qgroup_rescan_lock);
+
+	for (; slot < btrfs_header_nritems(scratch_leaf); ++slot) {
+		btrfs_item_key_to_cpu(scratch_leaf, &found, slot);
+		if (found.type != BTRFS_EXTENT_ITEM_KEY)
+			continue;
+		ret = btrfs_find_all_roots(trans, fs_info, found.objectid,
+					   tree_mod_seq_elem.seq, &roots);
+		if (ret < 0)
+			goto out;
+		spin_lock(&fs_info->qgroup_lock);
+		seq = fs_info->qgroup_seq;
+		fs_info->qgroup_seq += roots->nnodes + 1; /* max refcnt */
+
+		ret = qgroup_account_ref_step1(fs_info, roots, tmp, seq);
+		if (ret) {
+			spin_unlock(&fs_info->qgroup_lock);
+			ulist_free(roots);
+			goto out;
+		}
+
+		/*
+		 * step2 of btrfs_qgroup_account_ref works from a single root,
+		 * we're doing all at once here.
+		 */
+		ulist_reinit(tmp);
+		ULIST_ITER_INIT(&uiter);
+		while ((unode = ulist_next(roots, &uiter))) {
+			struct btrfs_qgroup *qg;
+
+			qg = find_qgroup_rb(fs_info, unode->val);
+			if (!qg)
+				continue;
+
+			ret = ulist_add(tmp, qg->qgroupid, (uintptr_t)qg,
+					GFP_ATOMIC);
+			if (ret < 0) {
+				spin_unlock(&fs_info->qgroup_lock);
+				ulist_free(roots);
+				goto out;
+			}
+		}
+
+		/* this loop is similar to step 2 of btrfs_qgroup_account_ref */
+		ULIST_ITER_INIT(&uiter);
+		while ((unode = ulist_next(tmp, &uiter))) {
+			struct btrfs_qgroup *qg;
+			struct btrfs_qgroup_list *glist;
+
+			qg = (struct btrfs_qgroup *)(uintptr_t) unode->aux;
+			qg->rfer += found.offset;
+			qg->rfer_cmpr += found.offset;
+			WARN_ON(qg->tag >= seq);
+			if (qg->refcnt - seq == roots->nnodes) {
+				qg->excl += found.offset;
+				qg->excl_cmpr += found.offset;
+			}
+			qgroup_dirty(fs_info, qg);
+
+			list_for_each_entry(glist, &qg->groups, next_group) {
+				ret = ulist_add(tmp, glist->group->qgroupid,
+						(uintptr_t)glist->group,
+						GFP_ATOMIC);
+				if (ret < 0) {
+					spin_unlock(&fs_info->qgroup_lock);
+					ulist_free(roots);
+					goto out;
+				}
+			}
+		}
+
+		spin_unlock(&fs_info->qgroup_lock);
+		ulist_free(roots);
+		ret = 0;
+	}
+
+out:
+	btrfs_put_tree_mod_seq(fs_info, &tree_mod_seq_elem);
+
+	return ret;
+}
+
+static void btrfs_qgroup_rescan_worker(struct btrfs_work *work)
+{
+	struct qgroup_rescan *qscan = container_of(work, struct qgroup_rescan,
+						   work);
+	struct btrfs_path *path;
+	struct btrfs_trans_handle *trans = NULL;
+	struct btrfs_fs_info *fs_info = qscan->fs_info;
+	struct ulist *tmp = NULL;
+	struct extent_buffer *scratch_leaf = NULL;
+	int err = -ENOMEM;
+
+	path = btrfs_alloc_path();
+	if (!path)
+		goto out;
+	tmp = ulist_alloc(GFP_NOFS);
+	if (!tmp)
+		goto out;
+	scratch_leaf = kmalloc(sizeof(*scratch_leaf), GFP_NOFS);
+	if (!scratch_leaf)
+		goto out;
+
+	err = 0;
+	while (!err) {
+		trans = btrfs_start_transaction(fs_info->fs_root, 0);
+		if (IS_ERR(trans)) {
+			err = PTR_ERR(trans);
+			break;
+		}
+		if (!fs_info->quota_enabled) {
+			err = -EINTR;
+		} else {
+			err = qgroup_rescan_leaf(qscan, path, trans,
+						 tmp, scratch_leaf);
+		}
+		if (err > 0)
+			btrfs_commit_transaction(trans, fs_info->fs_root);
+		else
+			btrfs_end_transaction(trans, fs_info->fs_root);
+	}
+
+out:
+	kfree(scratch_leaf);
+	ulist_free(tmp);
+	btrfs_free_path(path);
+	kfree(qscan);
+
+	mutex_lock(&fs_info->qgroup_rescan_lock);
+	fs_info->qgroup_flags &= ~BTRFS_QGROUP_STATUS_FLAG_RESCAN;
+
+	if (err == 2 &&
+	    fs_info->qgroup_flags & BTRFS_QGROUP_STATUS_FLAG_INCONSISTENT) {
+		fs_info->qgroup_flags &= ~BTRFS_QGROUP_STATUS_FLAG_INCONSISTENT;
+	} else if (err < 0) {
+		fs_info->qgroup_flags |= BTRFS_QGROUP_STATUS_FLAG_INCONSISTENT;
+	}
+	mutex_unlock(&fs_info->qgroup_rescan_lock);
+
+	if (err >= 0) {
+		pr_info("btrfs: qgroup scan completed%s\n",
+			err == 2 ? " (inconsistency flag cleared)" : "");
+	} else {
+		pr_err("btrfs: qgroup scan failed with %d\n", err);
+	}
+}
+
+static void
+qgroup_rescan_start(struct btrfs_fs_info *fs_info, struct qgroup_rescan *qscan)
+{
+	memset(&qscan->work, 0, sizeof(qscan->work));
+	qscan->work.func = btrfs_qgroup_rescan_worker;
+	qscan->fs_info = fs_info;
+
+	pr_info("btrfs: qgroup scan started\n");
+	btrfs_queue_worker(&fs_info->qgroup_rescan_workers, &qscan->work);
+}
+
+int
+btrfs_qgroup_rescan(struct btrfs_fs_info *fs_info)
+{
+	int ret = 0;
+	struct rb_node *n;
+	struct btrfs_qgroup *qgroup;
+	struct qgroup_rescan *qscan = kmalloc(sizeof(*qscan), GFP_NOFS);
+
+	if (!qscan)
+		return -ENOMEM;
+
+	mutex_lock(&fs_info->qgroup_rescan_lock);
+	spin_lock(&fs_info->qgroup_lock);
+	if (fs_info->qgroup_flags & BTRFS_QGROUP_STATUS_FLAG_RESCAN)
+		ret = -EINPROGRESS;
+	else if (!(fs_info->qgroup_flags & BTRFS_QGROUP_STATUS_FLAG_ON))
+		ret = -EINVAL;
+	if (ret) {
+		spin_unlock(&fs_info->qgroup_lock);
+		mutex_unlock(&fs_info->qgroup_rescan_lock);
+		kfree(qscan);
+		return ret;
+	}
+
+	fs_info->qgroup_flags |= BTRFS_QGROUP_STATUS_FLAG_RESCAN;
+	memset(&fs_info->qgroup_rescan_progress, 0,
+		sizeof(fs_info->qgroup_rescan_progress));
+
+	/* clear all current qgroup tracking information */
+	for (n = rb_first(&fs_info->qgroup_tree); n; n = rb_next(n)) {
+		qgroup = rb_entry(n, struct btrfs_qgroup, node);
+		qgroup->rfer = 0;
+		qgroup->rfer_cmpr = 0;
+		qgroup->excl = 0;
+		qgroup->excl_cmpr = 0;
+	}
+	spin_unlock(&fs_info->qgroup_lock);
+	mutex_unlock(&fs_info->qgroup_rescan_lock);
+
+	qgroup_rescan_start(fs_info, qscan);
+
+	return 0;
+}