Btrfs: Avoid superfluous tree-log writeout
We allow two log transactions at a time, but use same flag
to mark dirty tree-log btree blocks. So we may flush dirty
blocks belonging to newer log transaction when committing a
log transaction. This patch fixes the issue by using two
flags to mark dirty tree-log btree blocks.
Signed-off-by: Yan Zheng <zheng.yan@oracle.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c
index 741666a..31da000 100644
--- a/fs/btrfs/tree-log.c
+++ b/fs/btrfs/tree-log.c
@@ -1977,10 +1977,11 @@
{
int index1;
int index2;
+ int mark;
int ret;
struct btrfs_root *log = root->log_root;
struct btrfs_root *log_root_tree = root->fs_info->log_root_tree;
- u64 log_transid = 0;
+ unsigned long log_transid = 0;
mutex_lock(&root->log_mutex);
index1 = root->log_transid % 2;
@@ -2014,24 +2015,29 @@
goto out;
}
+ log_transid = root->log_transid;
+ if (log_transid % 2 == 0)
+ mark = EXTENT_DIRTY;
+ else
+ mark = EXTENT_NEW;
+
/* we start IO on all the marked extents here, but we don't actually
* wait for them until later.
*/
- ret = btrfs_write_marked_extents(log, &log->dirty_log_pages);
+ ret = btrfs_write_marked_extents(log, &log->dirty_log_pages, mark);
BUG_ON(ret);
btrfs_set_root_node(&log->root_item, log->node);
root->log_batch = 0;
- log_transid = root->log_transid;
root->log_transid++;
log->log_transid = root->log_transid;
root->log_start_pid = 0;
smp_mb();
/*
- * log tree has been flushed to disk, new modifications of
- * the log will be written to new positions. so it's safe to
- * allow log writers to go in.
+ * IO has been started, blocks of the log tree have WRITTEN flag set
+ * in their headers. new modifications of the log will be written to
+ * new positions. so it's safe to allow log writers to go in.
*/
mutex_unlock(&root->log_mutex);
@@ -2052,7 +2058,7 @@
index2 = log_root_tree->log_transid % 2;
if (atomic_read(&log_root_tree->log_commit[index2])) {
- btrfs_wait_marked_extents(log, &log->dirty_log_pages);
+ btrfs_wait_marked_extents(log, &log->dirty_log_pages, mark);
wait_log_commit(trans, log_root_tree,
log_root_tree->log_transid);
mutex_unlock(&log_root_tree->log_mutex);
@@ -2072,16 +2078,17 @@
* check the full commit flag again
*/
if (root->fs_info->last_trans_log_full_commit == trans->transid) {
- btrfs_wait_marked_extents(log, &log->dirty_log_pages);
+ btrfs_wait_marked_extents(log, &log->dirty_log_pages, mark);
mutex_unlock(&log_root_tree->log_mutex);
ret = -EAGAIN;
goto out_wake_log_root;
}
ret = btrfs_write_and_wait_marked_extents(log_root_tree,
- &log_root_tree->dirty_log_pages);
+ &log_root_tree->dirty_log_pages,
+ EXTENT_DIRTY | EXTENT_NEW);
BUG_ON(ret);
- btrfs_wait_marked_extents(log, &log->dirty_log_pages);
+ btrfs_wait_marked_extents(log, &log->dirty_log_pages, mark);
btrfs_set_super_log_root(&root->fs_info->super_for_commit,
log_root_tree->node->start);
@@ -2147,12 +2154,12 @@
while (1) {
ret = find_first_extent_bit(&log->dirty_log_pages,
- 0, &start, &end, EXTENT_DIRTY);
+ 0, &start, &end, EXTENT_DIRTY | EXTENT_NEW);
if (ret)
break;
- clear_extent_dirty(&log->dirty_log_pages,
- start, end, GFP_NOFS);
+ clear_extent_bits(&log->dirty_log_pages, start, end,
+ EXTENT_DIRTY | EXTENT_NEW, GFP_NOFS);
}
if (log->log_transid > 0) {
