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>

1 files changed, 43 insertions, 32 deletions

diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index 2974c4744d5..cf67dc3b7bf 100644
--- 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);