Josef Bacik wrote:
> 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 <l...@cn.fujitsu.com>
>> ---
>> 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,
>
In try_merge_free_space() we try to merge the left and right entry into
@entry, and then the caller has to insert the @entry into the tree by
itself.
Similarly, In btrfs_add_free_space() we call link_free_space() no matter
try_merge_free_space() returns success or not.
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