lgtm
Reviewed-by: Jason Dillaman <dillaman@xxxxxxxxxx>
On Tue, May 23, 2017 at 11:08 AM, Ilya Dryomov <idryomov@xxxxxxxxx> wrote:
> Commit 93c1defedcae ("rbd: remove the discard_zeroes_data flag")
> explicitly didn't implement REQ_OP_WRITE_ZEROES for rbd, while the
> following commit 48920ff2a5a9 ("block: remove the discard_zeroes_data
> flag") dropped ->discard_zeroes_data in favor of REQ_OP_WRITE_ZEROES.
>
> rbd does support efficient zeroing via CEPH_OSD_OP_ZERO opcode and will
> release either some or all blocks depending on whether the zeroing
> request is rbd_obj_bytes() aligned. This is how we currently implement
> discards, so REQ_OP_WRITE_ZEROES can be identical to REQ_OP_DISCARD for
> now. Caveats:
>
> - REQ_NOUNMAP is ignored, but AFAICT that's true of at least two other
> current implementations - nvme and loop
>
> - there is no ->write_zeroes_alignment and blk_bio_write_zeroes_split()
> is hence less helpful than blk_bio_discard_split(), but this can (and
> should) be fixed on the rbd side
>
> In the future we will split these into two code paths to respect
> REQ_NOUNMAP on zeroout and save on zeroing blocks that couldn't be
> released on discard.
>
> Fixes: 93c1defedcae ("rbd: remove the discard_zeroes_data flag")
> Signed-off-by: Ilya Dryomov <idryomov@xxxxxxxxx>
> ---
> drivers/block/rbd.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
> index 454bf9c34882..c16f74547804 100644
> --- a/drivers/block/rbd.c
> +++ b/drivers/block/rbd.c
> @@ -4023,6 +4023,7 @@ static void rbd_queue_workfn(struct work_struct *work)
>
> switch (req_op(rq)) {
> case REQ_OP_DISCARD:
> + case REQ_OP_WRITE_ZEROES:
> op_type = OBJ_OP_DISCARD;
> break;
> case REQ_OP_WRITE:
> @@ -4420,6 +4421,7 @@ static int rbd_init_disk(struct rbd_device *rbd_dev)
> q->limits.discard_granularity = segment_size;
> q->limits.discard_alignment = segment_size;
> blk_queue_max_discard_sectors(q, segment_size / SECTOR_SIZE);
> + blk_queue_max_write_zeroes_sectors(q, segment_size / SECTOR_SIZE);
>
> if (!ceph_test_opt(rbd_dev->rbd_client->client, NOCRC))
> q->backing_dev_info->capabilities |= BDI_CAP_STABLE_WRITES;
> --
> 2.4.3
>
> --
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--
Jason
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