On Mon, 17 Oct 2016 09:27:31 +0800
Qu Wenruo <quwen...@cn.fujitsu.com> wrote:
> For READ, caller normally hopes to get what they request, other than
> full stripe map.
>
> In this case, we should remove unrelated stripe map, just like the
> following case:
> 32K 96K
> |<-request range->|
> 0 64k 128K
> RAID0: | Data 1 | Data 2 |
> disk1 disk2
> Before this patch, we return the full stripe:
> Stripe 0: Logical 0, Physical X, Len 64K, Dev disk1
> Stripe 1: Logical 64k, Physical Y, Len 64K, Dev disk2
>
> After this patch, we limit the stripe result to the request range:
> Stripe 0: Logical 32K, Physical X+32K, Len 32K, Dev disk1
> Stripe 1: Logical 64k, Physical Y, Len 32K, Dev disk2
>
> And if it's a RAID5/6 stripe, we just handle it like RAID0, ignoring
> parities.
>
> This should make caller easier to use.
>
> Signed-off-by: Qu Wenruo <quwen...@cn.fujitsu.com>
> ---
> volumes.c | 103
> +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 102 insertions(+), 1 deletion(-)
>
> diff --git a/volumes.c b/volumes.c
> index 94f3e42..ba16d19 100644
> --- a/volumes.c
> +++ b/volumes.c
> @@ -1682,6 +1682,107 @@ static int fill_full_map_block(struct map_lookup
> *map, u64 start, u64 length,
> return 0;
> }
>
> +static void del_one_stripe(struct btrfs_map_block *map_block, int i)
> +{
> + int cur_nr = map_block->num_stripes;
> + int size_left = (cur_nr - 1 - i) * sizeof(struct btrfs_map_stripe);
> +
> + memmove(&map_block->stripes[i], &map_block->stripes[i + 1], size_left);
> + map_block->num_stripes--;
> +}
> +
> +static void remove_unrelated_stripes(struct map_lookup *map,
> + int rw, u64 start, u64 length,
> + struct btrfs_map_block *map_block)
> +{
> + int i = 0;
> + /*
> + * RAID5/6 write must use full stripe.
> + * No need to do anything.
> + */
> + if (map->type & (BTRFS_BLOCK_GROUP_RAID5 | BTRFS_BLOCK_GROUP_RAID6) &&
> + rw == WRITE)
> + return;
I believe it should be an "or" operation in the loop condition, rather than a
single pipe.
Sanidhya
> + /*
> + * For RAID0/1/10/DUP, whatever read/write, we can remove unrelated
> + * stripes without causing anything wrong.
> + * RAID5/6 READ is just like RAID0, we don't care parity unless we need
> + * to recovery.
> + * For recovery, rw should be set to WRITE.
> + */
> + while (i < map_block->num_stripes) {
> + struct btrfs_map_stripe *stripe;
> + u64 orig_logical; /* Original stripe logical start */
> + u64 orig_end; /* Original stripe logical end */
> +
> + stripe = &map_block->stripes[i];
> +
> + /*
> + * For READ, we don't really care parity
> + */
> + if (stripe->logical == BTRFS_RAID5_P_STRIPE ||
> + stripe->logical == BTRFS_RAID6_Q_STRIPE) {
> + del_one_stripe(map_block, i);
> + continue;
> + }
> + /* Completely unrelated stripe */
> + if (stripe->logical >= start + length ||
> + stripe->logical + stripe->length <= start) {
> + del_one_stripe(map_block, i);
> + continue;
> + }
> + /* Covered stripe, modify its logical and physical */
> + orig_logical = stripe->logical;
> + orig_end = stripe->logical + stripe->length;
> + if (start + length <= orig_end) {
> + /*
> + * |<--range-->|
> + * | stripe |
> + * Or
> + * |<range>|
> + * | stripe |
> + */
> + stripe->logical = max(orig_logical, start);
> + stripe->length = start + length;
> + stripe->physical += stripe->logical - orig_logical;
> + } else if (start >= orig_logical) {
> + /*
> + * |<-range--->|
> + * | stripe |
> + * Or
> + * |<range>|
> + * | stripe |
> + */
> + stripe->logical = start;
> + stripe->length = min(orig_end, start + length);
> + stripe->physical += stripe->logical - orig_logical;
> + }
> + /*
> + * Remaining case:
> + * |<----range----->|
> + * | stripe |
> + * No need to do any modification
> + */
> + i++;
> + }
> +
> + /* Recaculate map_block size */
> + map_block->start = 0;
> + map_block->length = 0;
> + for (i = 0; i < map_block->num_stripes; i++) {
> + struct btrfs_map_stripe *stripe;
> +
> + stripe = &map_block->stripes[i];
> + if (stripe->logical > map_block->start)
> + map_block->start = stripe->logical;
> + if (stripe->logical + stripe->length >
> + map_block->start + map_block->length)
> + map_block->length = stripe->logical + stripe->length -
> + map_block->start;
> + }
> +}
> +
> int __btrfs_map_block_v2(struct btrfs_fs_info *fs_info, int rw, u64 logical,
> u64 length, struct btrfs_map_block **map_ret)
> {
> @@ -1717,7 +1818,7 @@ int __btrfs_map_block_v2(struct btrfs_fs_info *fs_info,
> int rw, u64 logical,
> free(map_block);
> return ret;
> }
> - /* TODO: Remove unrelated map_stripes for READ operation */
> + remove_unrelated_stripes(map, rw, logical, length, map_block);
>
> *map_ret = map_block;
> return 0;
--
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