On Mon, Aug 23, 2010 at 09:24:07AM +0800, Li Zefan wrote:
> After returing extents from a cluster to the block group, some
> extents in the block group may be mergeable.
>
> Signed-off-by: Li Zefan <lizf@xxxxxxxxxxxxxx>
> ---
> fs/btrfs/free-space-cache.c | 26 ++++++++++++++++++++------
> 1 files changed, 20 insertions(+), 6 deletions(-)
>
> diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
> index faeec8f..c11f4f7 100644
> --- a/fs/btrfs/free-space-cache.c
> +++ b/fs/btrfs/free-space-cache.c
> @@ -234,11 +234,18 @@ tree_search_offset(struct btrfs_block_group_cache *block_group,
> return entry;
> }
>
> -static void unlink_free_space(struct btrfs_block_group_cache *block_group,
> - struct btrfs_free_space *info)
> +static inline void
> +__unlink_free_space(struct btrfs_block_group_cache *block_group,
> + struct btrfs_free_space *info)
> {
> rb_erase(&info->offset_index, &block_group->free_space_offset);
> block_group->free_extents--;
> +}
> +
> +static void unlink_free_space(struct btrfs_block_group_cache *block_group,
> + struct btrfs_free_space *info)
> +{
> + __unlink_free_space(block_group, info);
> block_group->free_space -= info->bytes;
> }
>
> @@ -611,7 +618,7 @@ out:
> }
>
> bool try_merge_free_space(struct btrfs_block_group_cache *block_group,
> - struct btrfs_free_space *info)
> + struct btrfs_free_space *info, bool update_stat)
> {
> struct btrfs_free_space *left_info;
> struct btrfs_free_space *right_info;
> @@ -632,7 +639,10 @@ bool try_merge_free_space(struct btrfs_block_group_cache *block_group,
> left_info = tree_search_offset(block_group, offset - 1, 0, 0);
>
> if (right_info && !right_info->bitmap) {
> - unlink_free_space(block_group, right_info);
> + if (update_stat)
> + unlink_free_space(block_group, right_info);
> + else
> + __unlink_free_space(block_group, right_info);
> info->bytes += right_info->bytes;
> kfree(right_info);
> merged = true;
> @@ -640,7 +650,10 @@ bool try_merge_free_space(struct btrfs_block_group_cache *block_group,
>
> if (left_info && !left_info->bitmap &&
> left_info->offset + left_info->bytes == offset) {
> - unlink_free_space(block_group, left_info);
> + if (update_stat)
> + unlink_free_space(block_group, left_info);
> + else
> + __unlink_free_space(block_group, left_info);
> info->offset = left_info->offset;
> info->bytes += left_info->bytes;
> kfree(left_info);
> @@ -665,7 +678,7 @@ int btrfs_add_free_space(struct btrfs_block_group_cache *block_group,
>
> spin_lock(&block_group->tree_lock);
>
> - if (try_merge_free_space(block_group, info))
> + if (try_merge_free_space(block_group, info, true))
> goto link;
>
> /*
> @@ -883,6 +896,7 @@ __btrfs_return_cluster_to_free_space(
> node = rb_next(&entry->offset_index);
> rb_erase(&entry->offset_index, &cluster->root);
> BUG_ON(entry->bitmap);
> + try_merge_free_space(block_group, entry, false);
> tree_insert_offset(&block_group->free_space_offset,
> entry->offset, &entry->offset_index, 0);
It's early in the morning here, so forgive me if I'm missing something obvious,
but if try_merge_free_space() succeeds here, then won't tree_insert_offset()
then add an entry that overlaps the same spot? Should we do something like
merged = try_merge_free_space();
if (!merged)
tree_insert_offset();
? Thanks,
Josef
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