btrfs: divide btrfs_update_reserved_bytes() into two functions

This patch divides btrfs_update_reserved_bytes() into
btrfs_add_reserved_bytes() and btrfs_free_reserved_bytes(), and
next patch will extend btrfs_add_reserved_bytes（）to fix some
false ENOSPC error, please see later patch for detailed info.
Signed-off-by: Wang Xiaoguang <wangxg.fnst@cn.fujitsu.com>
Reviewed-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Chris Mason <clm@fb.com>

fs/btrfs/extent-tree.c

@@ -104,9 +104,10 @@ static int find_next_key(struct btrfs_path *path, int level,
 			 struct btrfs_key *key);
 static void dump_space_info(struct btrfs_space_info *info, u64 bytes,
 			    int dump_block_groups);
-static int btrfs_update_reserved_bytes(struct btrfs_block_group_cache *cache,
-				       u64 num_bytes, int reserve,
-				       int delalloc);
+static int btrfs_add_reserved_bytes(struct btrfs_block_group_cache *cache,
+				    u64 num_bytes, int reserve, int delalloc);
+static int btrfs_free_reserved_bytes(struct btrfs_block_group_cache *cache,
+				     u64 num_bytes, int delalloc);
 static int block_rsv_use_bytes(struct btrfs_block_rsv *block_rsv,
 			       u64 num_bytes);
 int btrfs_pin_extent(struct btrfs_root *root,
@@ -6497,19 +6498,14 @@ void btrfs_wait_block_group_reservations(struct btrfs_block_group_cache *bg)
 }
 
 /**
- * btrfs_update_reserved_bytes - update the block_group and space info counters
+ * btrfs_add_reserved_bytes - update the block_group and space info counters
  * @cache:	The cache we are manipulating
  * @num_bytes:	The number of bytes in question
  * @reserve:	One of the reservation enums
  * @delalloc:   The blocks are allocated for the delalloc write
  *
- * This is called by the allocator when it reserves space, or by somebody who is
- * freeing space that was never actually used on disk.  For example if you
- * reserve some space for a new leaf in transaction A and before transaction A
- * commits you free that leaf, you call this with reserve set to 0 in order to
- * clear the reservation.
- *
- * Metadata reservations should be called with RESERVE_ALLOC so we do the proper
+ * This is called by the allocator when it reserves space. Metadata
+ * reservations should be called with RESERVE_ALLOC so we do the proper
  * ENOSPC accounting.  For data we handle the reservation through clearing the
  * delalloc bits in the io_tree.  We have to do this since we could end up
  * allocating less disk space for the amount of data we have reserved in the
@@ -6519,7 +6515,7 @@ void btrfs_wait_block_group_reservations(struct btrfs_block_group_cache *bg)
  * make the reservation and return -EAGAIN, otherwise this function always
  * succeeds.
  */
-static int btrfs_update_reserved_bytes(struct btrfs_block_group_cache *cache,
+static int btrfs_add_reserved_bytes(struct btrfs_block_group_cache *cache,
 				    u64 num_bytes, int reserve, int delalloc)
 {
 	struct btrfs_space_info *space_info = cache->space_info;
@@ -6527,7 +6523,6 @@ static int btrfs_update_reserved_bytes(struct btrfs_block_group_cache *cache,
 
 	spin_lock(&space_info->lock);
 	spin_lock(&cache->lock);
-	if (reserve != RESERVE_FREE) {
 	if (cache->ro) {
 		ret = -EAGAIN;
 	} else {
@@ -6543,7 +6538,31 @@ static int btrfs_update_reserved_bytes(struct btrfs_block_group_cache *cache,
 		if (delalloc)
 			cache->delalloc_bytes += num_bytes;
 	}
-	} else {
+	spin_unlock(&cache->lock);
+	spin_unlock(&space_info->lock);
+	return ret;
+}
+
+/**
+ * btrfs_free_reserved_bytes - update the block_group and space info counters
+ * @cache:      The cache we are manipulating
+ * @num_bytes:  The number of bytes in question
+ * @delalloc:   The blocks are allocated for the delalloc write
+ *
+ * This is called by somebody who is freeing space that was never actually used
+ * on disk.  For example if you reserve some space for a new leaf in transaction
+ * A and before transaction A commits you free that leaf, you call this with
+ * reserve set to 0 in order to clear the reservation.
+ */
+
+static int btrfs_free_reserved_bytes(struct btrfs_block_group_cache *cache,
+				     u64 num_bytes, int delalloc)
+{
+	struct btrfs_space_info *space_info = cache->space_info;
+	int ret = 0;
+
+	spin_lock(&space_info->lock);
+	spin_lock(&cache->lock);
 	if (cache->ro)
 		space_info->bytes_readonly += num_bytes;
 	cache->reserved -= num_bytes;
@@ -6551,12 +6570,10 @@ static int btrfs_update_reserved_bytes(struct btrfs_block_group_cache *cache,
 
 	if (delalloc)
 		cache->delalloc_bytes -= num_bytes;
-	}
 	spin_unlock(&cache->lock);
 	spin_unlock(&space_info->lock);
 	return ret;
 }
-
 void btrfs_prepare_extent_commit(struct btrfs_trans_handle *trans,
 				struct btrfs_root *root)
 {
@@ -7191,7 +7208,7 @@ void btrfs_free_tree_block(struct btrfs_trans_handle *trans,
 		WARN_ON(test_bit(EXTENT_BUFFER_DIRTY, &buf->bflags));
 
 		btrfs_add_free_space(cache, buf->start, buf->len);
-		btrfs_update_reserved_bytes(cache, buf->len, RESERVE_FREE, 0);
+		btrfs_free_reserved_bytes(cache, buf->len, 0);
 		btrfs_put_block_group(cache);
 		trace_btrfs_reserved_extent_free(root, buf->start, buf->len);
 		pin = 0;
@@ -7763,7 +7780,7 @@ static noinline int find_free_extent(struct btrfs_root *orig_root,
 					     search_start - offset);
 		BUG_ON(offset > search_start);
 
-		ret = btrfs_update_reserved_bytes(block_group, num_bytes,
+		ret = btrfs_add_reserved_bytes(block_group, num_bytes,
 				alloc_type, delalloc);
 		if (ret == -EAGAIN) {
 			btrfs_add_free_space(block_group, offset, num_bytes);
@@ -7995,7 +8012,7 @@ static int __btrfs_free_reserved_extent(struct btrfs_root *root,
 		if (btrfs_test_opt(root->fs_info, DISCARD))
 			ret = btrfs_discard_extent(root, start, len, NULL);
 		btrfs_add_free_space(cache, start, len);
-		btrfs_update_reserved_bytes(cache, len, RESERVE_FREE, delalloc);
+		btrfs_free_reserved_bytes(cache, len, delalloc);
 		trace_btrfs_reserved_extent_free(root, start, len);
 	}
 
@@ -8223,7 +8240,7 @@ int btrfs_alloc_logged_file_extent(struct btrfs_trans_handle *trans,
 	if (!block_group)
 		return -EINVAL;
 
-	ret = btrfs_update_reserved_bytes(block_group, ins->offset,
+	ret = btrfs_add_reserved_bytes(block_group, ins->offset,
 			RESERVE_ALLOC_NO_ACCOUNT, 0);
 	BUG_ON(ret); /* logic error */
 	ret = alloc_reserved_file_extent(trans, root, 0, root_objectid,