btrfs: Call btrfs_pin_reserved_extent only during active transaction

Calling btrfs_pin_reserved_extent makes sense only with a valid
transaction since pinned extents are processed from transaction commit
in btrfs_finish_extent_commit. In case of error it's sufficient to
adjust the reserved counter to account for log tree extents allocated in
the last transaction.

This commit moves btrfs_pin_reserved_extent to be called only with valid
transaction handle and otherwise uses the newly introduced
unaccount_log_buffer to adjust "reserved". If this is not done if a
failure occurs before transaction is committed WARN_ON are going to be
triggered on unmount. This was especially pronounced with generic/475
test.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/tree-log.c

@@ -2695,12 +2695,10 @@ static noinline int walk_down_log_tree(struct btrfs_trans_handle *trans,
 				   struct walk_control *wc)
 {
 	struct btrfs_fs_info *fs_info = root->fs_info;
-	u64 root_owner;
 	u64 bytenr;
 	u64 ptr_gen;
 	struct extent_buffer *next;
 	struct extent_buffer *cur;
-	struct extent_buffer *parent;
 	u32 blocksize;
 	int ret = 0;
 
@@ -2720,9 +2718,6 @@ static noinline int walk_down_log_tree(struct btrfs_trans_handle *trans,
 		btrfs_node_key_to_cpu(cur, &first_key, path->slots[*level]);
 		blocksize = fs_info->nodesize;
 
-		parent = path->nodes[*level];
-		root_owner = btrfs_header_owner(parent);
-
 		next = btrfs_find_create_tree_block(fs_info, bytenr);
 		if (IS_ERR(next))
 			return PTR_ERR(next);
@@ -2750,18 +2745,16 @@ static noinline int walk_down_log_tree(struct btrfs_trans_handle *trans,
 					btrfs_clean_tree_block(next);
 					btrfs_wait_tree_block_writeback(next);
 					btrfs_tree_unlock(next);
+					ret = btrfs_pin_reserved_extent(fs_info,
+							bytenr, blocksize);
+					if (ret) {
+						free_extent_buffer(next);
+						return ret;
+					}
 				} else {
 					if (test_and_clear_bit(EXTENT_BUFFER_DIRTY, &next->bflags))
 						clear_extent_buffer_dirty(next);
-				}
-
-				WARN_ON(root_owner !=
-					BTRFS_TREE_LOG_OBJECTID);
-				ret = btrfs_pin_reserved_extent(fs_info,
-							bytenr, blocksize);
-				if (ret) {
-					free_extent_buffer(next);
-					return ret;
+					unaccount_log_buffer(fs_info, bytenr);
 				}
 			}
 			free_extent_buffer(next);
@@ -2792,7 +2785,6 @@ static noinline int walk_up_log_tree(struct btrfs_trans_handle *trans,
 				 struct walk_control *wc)
 {
 	struct btrfs_fs_info *fs_info = root->fs_info;
-	u64 root_owner;
 	int i;
 	int slot;
 	int ret;
@@ -2805,13 +2797,6 @@ static noinline int walk_up_log_tree(struct btrfs_trans_handle *trans,
 			WARN_ON(*level == 0);
 			return 0;
 		} else {
-			struct extent_buffer *parent;
-			if (path->nodes[*level] == root->node)
-				parent = path->nodes[*level];
-			else
-				parent = path->nodes[*level + 1];
-
-			root_owner = btrfs_header_owner(parent);
 			ret = wc->process_func(root, path->nodes[*level], wc,
 				 btrfs_header_generation(path->nodes[*level]),
 				 *level);
@@ -2829,17 +2814,18 @@ static noinline int walk_up_log_tree(struct btrfs_trans_handle *trans,
 					btrfs_clean_tree_block(next);
 					btrfs_wait_tree_block_writeback(next);
 					btrfs_tree_unlock(next);
+					ret = btrfs_pin_reserved_extent(fs_info,
+						     path->nodes[*level]->start,
+						     path->nodes[*level]->len);
+					if (ret)
+						return ret;
 				} else {
 					if (test_and_clear_bit(EXTENT_BUFFER_DIRTY, &next->bflags))
 						clear_extent_buffer_dirty(next);
-				}
 
-				WARN_ON(root_owner != BTRFS_TREE_LOG_OBJECTID);
-				ret = btrfs_pin_reserved_extent(fs_info,
-						path->nodes[*level]->start,
-						path->nodes[*level]->len);
-				if (ret)
-					return ret;
+					unaccount_log_buffer(fs_info,
+						path->nodes[*level]->start);
+				}
 			}
 			free_extent_buffer(path->nodes[*level]);
 			path->nodes[*level] = NULL;
@@ -2910,15 +2896,15 @@ static int walk_log_tree(struct btrfs_trans_handle *trans,
 				btrfs_clean_tree_block(next);
 				btrfs_wait_tree_block_writeback(next);
 				btrfs_tree_unlock(next);
+				ret = btrfs_pin_reserved_extent(fs_info,
+						next->start, next->len);
+				if (ret)
+					goto out;
 			} else {
 				if (test_and_clear_bit(EXTENT_BUFFER_DIRTY, &next->bflags))
 					clear_extent_buffer_dirty(next);
+				unaccount_log_buffer(fs_info, next->start);
 			}
-
-			ret = btrfs_pin_reserved_extent(fs_info, next->start,
-							next->len);
-			if (ret)
-				goto out;
 		}
 	}