On 10/18/2012 04:18 PM, Miao Xie wrote:
> When we find a bitmap free space entry, we may check the previous extent
> entry covers the offset or not. But if we find this entry is also a bitmap
> entry, we will continue to check the previous entry of the current one by
> a while loop. It is unnecessary because it is impossible that the extent
> entry which is in front of a bitmap entry can cover the offset of the entry
> after that bitmap entry.
>
Looks good to me.
Reviewed-by: Liu Bo <bo.li.liu@xxxxxxxxxx>
> Signed-off-by: Miao Xie <miaox@xxxxxxxxxxxxxx>
> ---
> Changelog v1 -> v2:
> - fix the same problem in the other place
> ---
> fs/btrfs/free-space-cache.c | 30 ++++++++++--------------------
> 1 files changed, 10 insertions(+), 20 deletions(-)
>
> diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
> index 1027b85..557502c 100644
> --- a/fs/btrfs/free-space-cache.c
> +++ b/fs/btrfs/free-space-cache.c
> @@ -1250,18 +1250,13 @@ tree_search_offset(struct btrfs_free_space_ctl *ctl,
> * if previous extent entry covers the offset,
> * we should return it instead of the bitmap entry
> */
> - n = &entry->offset_index;
> - while (1) {
> - n = rb_prev(n);
> - if (!n)
> - break;
> + n = rb_prev(&entry->offset_index);
> + if (n) {
> prev = rb_entry(n, struct btrfs_free_space,
> offset_index);
> - if (!prev->bitmap) {
> - if (prev->offset + prev->bytes > offset)
> - entry = prev;
> - break;
> - }
> + if (!prev->bitmap &&
> + prev->offset + prev->bytes > offset)
> + entry = prev;
> }
> }
> return entry;
> @@ -1287,18 +1282,13 @@ tree_search_offset(struct btrfs_free_space_ctl *ctl,
> }
>
> if (entry->bitmap) {
> - n = &entry->offset_index;
> - while (1) {
> - n = rb_prev(n);
> - if (!n)
> - break;
> + n = rb_prev(&entry->offset_index);
> + if (n) {
> prev = rb_entry(n, struct btrfs_free_space,
> offset_index);
> - if (!prev->bitmap) {
> - if (prev->offset + prev->bytes > offset)
> - return prev;
> - break;
> - }
> + if (!prev->bitmap &&
> + prev->offset + prev->bytes > offset)
> + return prev;
> }
> if (entry->offset + BITS_PER_BITMAP * ctl->unit > offset)
> return entry;
>
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