btrfs: Add a helper try_merge_free_space()

When adding a new extent, we'll firstly see if we can merge
this extent to the left or/and right extent. Extract this as
a helper try_merge_free_space().

As a side effect, we fix a small bug that if the new extent
has non-bitmap left entry but is unmergeble, we'll directly
link the extent without trying to drop it into bitmap.

This also prepares for the next patch.

Reviewed-by: Josef Bacik <josef@redhat.com>
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>

diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index 2974c47..cf67dc3 100644 (file)
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -1363,22 +1363,14 @@ out:
        return ret;
 }
 
-int btrfs_add_free_space(struct btrfs_block_group_cache *block_group,
-                        u64 offset, u64 bytes)
+bool try_merge_free_space(struct btrfs_block_group_cache *block_group,
+                         struct btrfs_free_space *info)
 {
-       struct btrfs_free_space *right_info = NULL;
-       struct btrfs_free_space *left_info = NULL;
-       struct btrfs_free_space *info = NULL;
-       int ret = 0;
-
-       info = kzalloc(sizeof(struct btrfs_free_space), GFP_NOFS);
-       if (!info)
-               return -ENOMEM;
-
-       info->offset = offset;
-       info->bytes = bytes;
-
-       spin_lock(&block_group->tree_lock);
+       struct btrfs_free_space *left_info;
+       struct btrfs_free_space *right_info;
+       bool merged = false;
+       u64 offset = info->offset;
+       u64 bytes = info->bytes;
 
        /*
         * first we want to see if there is free space adjacent to the range we
@@ -1392,27 +1384,11 @@ int btrfs_add_free_space(struct btrfs_block_group_cache *block_group,
        else
                left_info = tree_search_offset(block_group, offset - 1, 0, 0);
 
-       /*
-        * If there was no extent directly to the left or right of this new
-        * extent then we know we're going to have to allocate a new extent, so
-        * before we do that see if we need to drop this into a bitmap
-        */
-       if ((!left_info || left_info->bitmap) &&
-           (!right_info || right_info->bitmap)) {
-               ret = insert_into_bitmap(block_group, info);
-
-               if (ret < 0) {
-                       goto out;
-               } else if (ret) {
-                       ret = 0;
-                       goto out;
-               }
-       }
-
        if (right_info && !right_info->bitmap) {
                unlink_free_space(block_group, right_info);
                info->bytes += right_info->bytes;
                kfree(right_info);
+               merged = true;
        }
 
        if (left_info && !left_info->bitmap &&
@@ -1421,8 +1397,43 @@ int btrfs_add_free_space(struct btrfs_block_group_cache *block_group,
                info->offset = left_info->offset;
                info->bytes += left_info->bytes;
                kfree(left_info);
+               merged = true;
        }
 
+       return merged;
+}
+
+int btrfs_add_free_space(struct btrfs_block_group_cache *block_group,
+                        u64 offset, u64 bytes)
+{
+       struct btrfs_free_space *info;
+       int ret = 0;
+
+       info = kzalloc(sizeof(struct btrfs_free_space), GFP_NOFS);
+       if (!info)
+               return -ENOMEM;
+
+       info->offset = offset;
+       info->bytes = bytes;
+
+       spin_lock(&block_group->tree_lock);
+
+       if (try_merge_free_space(block_group, info))
+               goto link;
+
+       /*
+        * There was no extent directly to the left or right of this new
+        * extent then we know we're going to have to allocate a new extent, so
+        * before we do that see if we need to drop this into a bitmap
+        */
+       ret = insert_into_bitmap(block_group, info);
+       if (ret < 0) {
+               goto out;
+       } else if (ret) {
+               ret = 0;
+               goto out;
+       }
+link:
        ret = link_free_space(block_group, info);
        if (ret)
                kfree(info);