Btrfs: Fix cache_block_group to catch holes at the start of the group

Cache block group was overly complex and missed free blocks at the very start
of the group.  This patch simplifies things significantly.

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

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index b074ad1416ddca63329543e0d2c96f1c4437aa4a..9151850266b0bb7ae85cec3703d1bc4780f1bdb8 100644 (file)
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -39,6 +39,7 @@ static int cache_block_group(struct btrfs_root *root,
        u64 i;
        u64 last = 0;
        u64 hole_size;
+       u64 first_free;
        int found = 0;
 
        root = root->fs_info->extent_root;
@@ -51,16 +52,22 @@ static int cache_block_group(struct btrfs_root *root,
        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;
+
        path->reada = 2;
+       first_free = block_group->key.objectid;
        key.objectid = block_group->key.objectid;
        key.flags = 0;
        key.offset = 0;
+
        btrfs_set_key_type(&key, BTRFS_EXTENT_ITEM_KEY);
        ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
+
        if (ret < 0)
                return ret;
+
        if (ret && path->slots[0] > 0)
                path->slots[0]--;
+
        while(1) {
                leaf = btrfs_buffer_leaf(path->nodes[0]);
                slot = path->slots[0];
@@ -71,50 +78,48 @@ static int cache_block_group(struct btrfs_root *root,
                        if (ret == 0) {
                                continue;
                        } else {
-                               if (found) {
-                                       hole_size = block_group->key.objectid +
-                                               block_group->key.offset - last;
-                               } else {
-                                       last = block_group->key.objectid;
-                                       hole_size = block_group->key.offset;
-                               }
-                               for (i = 0; i < hole_size; i++) {
-                                       set_radix_bit(extent_radix,
-                                                     last + i);
-                               }
                                break;
                        }
                }
+
                btrfs_disk_key_to_cpu(&key, &leaf->items[slot].key);
+               if (key.objectid < block_group->key.objectid) {
+                       if (key.objectid + key.offset > first_free)
+                               first_free = key.objectid + key.offset;
+                       goto next;
+               }
+
                if (key.objectid >= block_group->key.objectid +
                    block_group->key.offset) {
-                       if (found) {
-                               hole_size = block_group->key.objectid +
-                                       block_group->key.offset - last;
-                       } else {
-                               last = block_group->key.objectid;
-                               hole_size = block_group->key.offset;
-                       }
-                       for (i = 0; i < hole_size; i++) {
-                               set_radix_bit(extent_radix, last + i);
-                       }
                        break;
                }
+
                if (btrfs_key_type(&key) == BTRFS_EXTENT_ITEM_KEY) {
                        if (!found) {
-                               last = key.objectid + key.offset;
+                               last = first_free;
                                found = 1;
-                       } else {
-                               hole_size = key.objectid - last;
-                               for (i = 0; i < hole_size; i++) {
-                                       set_radix_bit(extent_radix, last + i);
-                               }
-                               last = key.objectid + key.offset;
                        }
+                       hole_size = key.objectid - last;
+                       for (i = 0; i < hole_size; i++) {
+                               set_radix_bit(extent_radix, last + i);
+                       }
+                       last = key.objectid + key.offset;
                }
+next:
                path->slots[0]++;
        }
 
+       if (!found)
+               last = first_free;
+       if (block_group->key.objectid +
+           block_group->key.offset > last) {
+               hole_size = block_group->key.objectid +
+                       block_group->key.offset - last;
+               for (i = 0; i < hole_size; i++) {
+                       set_radix_bit(extent_radix,
+                                       last + i);
+               }
+       }
        block_group->cached = 1;
 err:
        btrfs_free_path(path);