[PATCH 1/3] btrfs: qgroup: Refactor btrfs_qgroup_insert_dirty_extent()

[Qu Wenruo <quwenruo@cn.fujitsu.com>]

Refactor btrfs_qgroup_insert_dirty_extent() function, to two functions:
1. _btrfs_qgroup_insert_dirty_extent()
   Almost the same with original code.
   For delayed_ref usage, which has delayed refs locked.

   Change the return value type to int, since caller never needs the
   pointer, but only needs to know if they need to free the allocated
   memory.

2. btrfs_qgroup_record_dirty_extent()
   The more encapsulated version.

   Will do the delayed_refs lock, memory allocation, quota enabled check
   and other misc things.

The original design is to keep exported functions to minimal, but since
more btrfs hacks exposed, like replacing path in balance, needs us to
record dirty extents manually, so we have to add such functions.

Also, add comment for both functions, to info developers how to keep
qgroup correct when doing hacks.

Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
---
 fs/btrfs/delayed-ref.c |  5 +----
 fs/btrfs/extent-tree.c | 36 +++++-------------------------------
 fs/btrfs/qgroup.c      | 39 ++++++++++++++++++++++++++++++++++-----
 fs/btrfs/qgroup.h      | 44 +++++++++++++++++++++++++++++++++++++++++---
 4 files changed, 81 insertions(+), 43 deletions(-)

diff --git a/fs/btrfs/delayed-ref.c b/fs/btrfs/delayed-ref.c
index 430b368..5eed597 100644
--- a/fs/btrfs/delayed-ref.c
+++ b/fs/btrfs/delayed-ref.c
@@ -541,7 +541,6 @@ add_delayed_ref_head(struct btrfs_fs_info *fs_info,
 	struct btrfs_delayed_ref_head *existing;
 	struct btrfs_delayed_ref_head *head_ref = NULL;
 	struct btrfs_delayed_ref_root *delayed_refs;
-	struct btrfs_qgroup_extent_record *qexisting;
 	int count_mod = 1;
 	int must_insert_reserved = 0;
 
@@ -606,9 +605,7 @@ add_delayed_ref_head(struct btrfs_fs_info *fs_info,
 		qrecord->num_bytes = num_bytes;
 		qrecord->old_roots = NULL;
 
-		qexisting = btrfs_qgroup_insert_dirty_extent(delayed_refs,
-							     qrecord);
-		if (qexisting)
+		if(_btrfs_qgroup_insert_dirty_extent(delayed_refs, qrecord))
 			kfree(qrecord);
 	}
 
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 82b912a..cf63150 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -8307,34 +8307,6 @@ reada:
 	wc->reada_slot = slot;
 }
 
-/*
- * These may not be seen by the usual inc/dec ref code so we have to
- * add them here.
- */
-static int record_one_subtree_extent(struct btrfs_trans_handle *trans,
-				     struct btrfs_root *root, u64 bytenr,
-				     u64 num_bytes)
-{
-	struct btrfs_qgroup_extent_record *qrecord;
-	struct btrfs_delayed_ref_root *delayed_refs;
-
-	qrecord = kmalloc(sizeof(*qrecord), GFP_NOFS);
-	if (!qrecord)
-		return -ENOMEM;
-
-	qrecord->bytenr = bytenr;
-	qrecord->num_bytes = num_bytes;
-	qrecord->old_roots = NULL;
-
-	delayed_refs = &trans->transaction->delayed_refs;
-	spin_lock(&delayed_refs->lock);
-	if (btrfs_qgroup_insert_dirty_extent(delayed_refs, qrecord))
-		kfree(qrecord);
-	spin_unlock(&delayed_refs->lock);
-
-	return 0;
-}
-
 static int account_leaf_items(struct btrfs_trans_handle *trans,
 			      struct btrfs_root *root,
 			      struct extent_buffer *eb)
@@ -8368,7 +8340,8 @@ static int account_leaf_items(struct btrfs_trans_handle *trans,
 
 		num_bytes = btrfs_file_extent_disk_num_bytes(eb, fi);
 
-		ret = record_one_subtree_extent(trans, root, bytenr, num_bytes);
+		ret = btrfs_qgroup_record_dirty_extent(trans, root->fs_info,
+				bytenr, num_bytes, GFP_NOFS);
 		if (ret)
 			return ret;
 	}
@@ -8517,8 +8490,9 @@ walk_down:
 			btrfs_set_lock_blocking_rw(eb, BTRFS_READ_LOCK);
 			path->locks[level] = BTRFS_READ_LOCK_BLOCKING;
 
-			ret = record_one_subtree_extent(trans, root, child_bytenr,
-							root->nodesize);
+			ret = btrfs_qgroup_record_dirty_extent(trans,
+					root->fs_info, child_bytenr,
+					root->nodesize, GFP_NOFS);
 			if (ret)
 				goto out;
 		}
diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
index 9d4c05b..76d4f67 100644
--- a/fs/btrfs/qgroup.c
+++ b/fs/btrfs/qgroup.c
@@ -1453,9 +1453,9 @@ int btrfs_qgroup_prepare_account_extents(struct btrfs_trans_handle *trans,
 	return ret;
 }
 
-struct btrfs_qgroup_extent_record
-*btrfs_qgroup_insert_dirty_extent(struct btrfs_delayed_ref_root *delayed_refs,
-				  struct btrfs_qgroup_extent_record *record)
+int _btrfs_qgroup_insert_dirty_extent(
+		struct btrfs_delayed_ref_root *delayed_refs,
+		struct btrfs_qgroup_extent_record *record)
 {
 	struct rb_node **p = &delayed_refs->dirty_extent_root.rb_node;
 	struct rb_node *parent_node = NULL;
@@ -1474,12 +1474,41 @@ struct btrfs_qgroup_extent_record
 		else if (bytenr > entry->bytenr)
 			p = &(*p)->rb_right;
 		else
-			return entry;
+			return 1;
 	}
 
 	rb_link_node(&record->node, parent_node, p);
 	rb_insert_color(&record->node, &delayed_refs->dirty_extent_root);
-	return NULL;
+	return 0;
+}
+
+int btrfs_qgroup_record_dirty_extent(struct btrfs_trans_handle *trans,
+		struct btrfs_fs_info *fs_info, u64 bytenr, u64 num_bytes,
+		gfp_t gfp_flag)
+{
+	struct btrfs_qgroup_extent_record *record;
+	struct btrfs_delayed_ref_root *delayed_refs;
+	int ret;
+
+	if (!fs_info->quota_enabled || bytenr == 0 || num_bytes == 0)
+		return 0;
+	if (WARN_ON(trans == NULL))
+		return -EINVAL;
+	record = kmalloc(sizeof(*record), gfp_flag);
+	if (!record)
+		return -ENOMEM;
+
+	delayed_refs = &trans->transaction->delayed_refs;
+	record->bytenr = bytenr;
+	record->num_bytes = num_bytes;
+	record->old_roots = NULL;
+
+	spin_lock(&delayed_refs->lock);
+	ret = _btrfs_qgroup_insert_dirty_extent(delayed_refs, record);
+	spin_unlock(&delayed_refs->lock);
+	if (ret > 0)
+		kfree(record);
+	return 0;
 }
 
 #define UPDATE_NEW	0
diff --git a/fs/btrfs/qgroup.h b/fs/btrfs/qgroup.h
index ecb2c14..f6691e3 100644
--- a/fs/btrfs/qgroup.h
+++ b/fs/btrfs/qgroup.h
@@ -63,9 +63,47 @@ void btrfs_free_qgroup_config(struct btrfs_fs_info *fs_info);
 struct btrfs_delayed_extent_op;
 int btrfs_qgroup_prepare_account_extents(struct btrfs_trans_handle *trans,
 					 struct btrfs_fs_info *fs_info);
-struct btrfs_qgroup_extent_record
-*btrfs_qgroup_insert_dirty_extent(struct btrfs_delayed_ref_root *delayed_refs,
-				  struct btrfs_qgroup_extent_record *record);
+
+/*
+ * Insert one dirty extent record into delayed_refs for qgroup.
+ * Caller must ensure the delayed_refs are already locked and quota is enabled.
+ *
+ * Return 0 if there is no existing dirty extent record for that bytenr, and
+ * insert that record into delayed_refs.
+ * Return > 0 if there is already existing dirty extent record for that bytenr.
+ * Caller then can free the record structure.
+ * Error is not possible
+ *
+ * For caller needs better encapsulated interface, call
+ * btrfs_qgroup_record_dirty_extent(), which will handle locks and memory
+ * allocation.
+ */
+int _btrfs_qgroup_insert_dirty_extent(
+		struct btrfs_delayed_ref_root *delayed_refs,
+		struct btrfs_qgroup_extent_record *record);
+
+/*
+ * Info qgroup to track one extent, so at trans commit time qgroup can
+ * update qgroup accounts for that extent.
+ *
+ * That extent can be either meta or data.
+ * This function can be called several times for any extent and won't cause
+ * any qgroup incorrectness.
+ * As long as dirty extent is recorded, qgroup can hardly go wrong.
+ *
+ * This function should be called when owner of extent is changed and the
+ * code uses hack to avoid normal inc/dev_extent_ref().
+ * For example, swapping two tree blocks in balance or modifying file extent
+ * disk bytenr manually.
+ *
+ * Return 0 if the operation is done.
+ * Return <0 for error, like memory allocation failure or invalid parameter
+ * (NULL trans)
+ */
+int btrfs_qgroup_record_dirty_extent(struct btrfs_trans_handle *trans,
+		struct btrfs_fs_info *fs_info, u64 bytenr, u64 num_bytes,
+		gfp_t gfp_flag);
+
 int
 btrfs_qgroup_account_extent(struct btrfs_trans_handle *trans,
 			    struct btrfs_fs_info *fs_info,
-- 
2.9.0