Btrfs: avoid unnecessary bitmap search for cluster setup

setup_cluster_no_bitmap() searches all the extents and bitmaps starting
from offset. Therefore if it returns -ENOSPC, all the bitmaps starting
from offset are in the bitmaps list, so it's sufficient to search from
this list in setup_cluser_bitmap().

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index 8f792f41feabd3419c865c918cf7c24b5557945c..8c32434da2cbbba1c07087092aeac50f9d427f2b 100644 (file)
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -2451,7 +2451,6 @@ setup_cluster_bitmap(struct btrfs_block_group_cache *block_group,
 {
        struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
        struct btrfs_free_space *entry;
-       struct rb_node *node;
        int ret = -ENOSPC;
        u64 bitmap_offset = offset_to_bitmap(ctl, offset);
 
@@ -2469,10 +2468,6 @@ setup_cluster_bitmap(struct btrfs_block_group_cache *block_group,
                        list_add(&entry->list, bitmaps);
        }
 
-       /*
-        * First check our cached list of bitmaps and see if there is an entry
-        * here that will work.
-        */
        list_for_each_entry(entry, bitmaps, list) {
                if (entry->bytes < min_bytes)
                        continue;
@@ -2483,38 +2478,10 @@ setup_cluster_bitmap(struct btrfs_block_group_cache *block_group,
        }
 
        /*
-        * If we do have entries on our list and we are here then we didn't find
-        * anything, so go ahead and get the next entry after the last entry in
-        * this list and start the search from there.
+        * The bitmaps list has all the bitmaps that record free space
+        * starting after offset, so no more search is required.
         */
-       if (!list_empty(bitmaps)) {
-               entry = list_entry(bitmaps->prev, struct btrfs_free_space,
-                                  list);
-               node = rb_next(&entry->offset_index);
-               if (!node)
-                       return -ENOSPC;
-               entry = rb_entry(node, struct btrfs_free_space, offset_index);
-               goto search;
-       }
-
-       entry = tree_search_offset(ctl, offset_to_bitmap(ctl, offset), 0, 1);
-       if (!entry)
-               return -ENOSPC;
-
-search:
-       node = &entry->offset_index;
-       do {
-               entry = rb_entry(node, struct btrfs_free_space, offset_index);
-               node = rb_next(&entry->offset_index);
-               if (!entry->bitmap)
-                       continue;
-               if (entry->bytes < min_bytes)
-                       continue;
-               ret = btrfs_bitmap_cluster(block_group, entry, cluster, offset,
-                                          bytes, min_bytes);
-       } while (ret && node);
-
-       return ret;
+       return -ENOSPC;
 }
 
 /*
@@ -2532,8 +2499,8 @@ int btrfs_find_space_cluster(struct btrfs_trans_handle *trans,
                             u64 offset, u64 bytes, u64 empty_size)
 {
        struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
-       struct list_head bitmaps;
        struct btrfs_free_space *entry, *tmp;
+       LIST_HEAD(bitmaps);
        u64 min_bytes;
        int ret;
 
@@ -2572,7 +2539,6 @@ int btrfs_find_space_cluster(struct btrfs_trans_handle *trans,
                goto out;
        }
 
-       INIT_LIST_HEAD(&bitmaps);
        ret = setup_cluster_no_bitmap(block_group, cluster, &bitmaps, offset,
                                      bytes, min_bytes);
        if (ret)