Btrfs: Limit btree writeback to prevent seeks

[deliverable/linux.git] / fs / btrfs / disk-io.c

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 3e16cca72b4962d04d82308b1c2cd28caa65c13d..28e9ef8a3253db0e8443d26cb0c752577b380625 100644 (file)
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -210,6 +210,15 @@ static int btree_writepages(struct address_space *mapping,
 {
        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);
 }