Btrfs: Limit btree writeback to prevent seeks
Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 3e16cca..28e9ef8 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -210,6 +210,15 @@
{
struct extent_map_tree *tree;
tree = &BTRFS_I(mapping->host)->extent_tree;
+ if (wbc->sync_mode == WB_SYNC_NONE) {
+ u64 num_dirty;
+ u64 start = 0;
+ unsigned long thresh = 96 * 1024 * 1024;
+ num_dirty = count_range_bits(tree, &start, thresh, EXTENT_DIRTY);
+ if (num_dirty < thresh) {
+ return 0;
+ }
+ }
return extent_writepages(tree, mapping, btree_get_extent, wbc);
}