Btrfs: Record dirty pages tree-log pages in an extent_io tree

This is the same way the transaction code makes sure that all the
other tree blocks are safely on disk.  There's an extent_io tree
for each root, and any blocks allocated to the tree logs are
recorded in that tree.

At tree-log sync, the extent_io tree is walked to flush down the
dirty pages and wait for them.

The main benefit is less time spent walking the tree log and skipping
clean pages, and getting sequential IO down to the drive.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 15 insertions, 14 deletions

diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c
index ae96451..bfa7108 100644
--- a/fs/btrfs/tree-log.c
+++ b/fs/btrfs/tree-log.c
@@ -1954,10 +1954,6 @@ int btrfs_sync_log(struct btrfs_trans_handle *trans,
 	int ret;
 	unsigned long batch;
 	struct btrfs_root *log = root->log_root;
-	struct walk_control wc = {
-		.write = 1,
-		.process_func = process_one_buffer
-	};
 
 	mutex_lock(&log->fs_info->tree_log_mutex);
 	if (atomic_read(&log->fs_info->tree_log_commit)) {
@@ -1985,18 +1981,11 @@ int btrfs_sync_log(struct btrfs_trans_handle *trans,
 		if (batch == log->fs_info->tree_log_batch)
 			break;
 	}
-	ret = walk_log_tree(trans, log, &wc);
-	BUG_ON(ret);
-
-	ret = walk_log_tree(trans, log->fs_info->log_root_tree, &wc);
-	BUG_ON(ret);
-
-	wc.wait = 1;
 
-	ret = walk_log_tree(trans, log, &wc);
+	ret = btrfs_write_and_wait_marked_extents(log, &log->dirty_log_pages);
 	BUG_ON(ret);
-
-	ret = walk_log_tree(trans, log->fs_info->log_root_tree, &wc);
+	ret = btrfs_write_and_wait_marked_extents(root->fs_info->log_root_tree,
+			       &root->fs_info->log_root_tree->dirty_log_pages);
 	BUG_ON(ret);
 
 	btrfs_set_super_log_root(&root->fs_info->super_for_commit,
@@ -2025,6 +2014,8 @@ int btrfs_free_log(struct btrfs_trans_handle *trans, struct btrfs_root *root)
 	int ret;
 	struct btrfs_root *log;
 	struct key;
+	u64 start;
+	u64 end;
 	struct walk_control wc = {
 		.free = 1,
 		.process_func = process_one_buffer
@@ -2037,6 +2028,16 @@ int btrfs_free_log(struct btrfs_trans_handle *trans, struct btrfs_root *root)
 	ret = walk_log_tree(trans, log, &wc);
 	BUG_ON(ret);
 
+	while(1) {
+		ret = find_first_extent_bit(&log->dirty_log_pages,
+				    0, &start, &end, EXTENT_DIRTY);
+		if (ret)
+			break;
+
+		clear_extent_dirty(&log->dirty_log_pages,
+				   start, end, GFP_NOFS);
+	}
+
 	log = root->log_root;
 	ret = btrfs_del_root(trans, root->fs_info->log_root_tree,
 			     &log->root_key);