>>> On 25.08.11 at 08:37, Li Dongyang <lidongyang@xxxxxxxxxx> wrote:
> On Wed, Aug 24, 2011 at 6:42 PM, Jan Beulich <JBeulich@xxxxxxxxxx> wrote:
>>>>> On 24.08.11 at 11:23, Li Dongyang <lidongyang@xxxxxxxxxx> wrote:
>>> The blkfront driver now will read feature-trim from xenstore,
>>> and set up the request queue with trim params, then we can forward the
>>> discard requests to backend driver.
>>>
>>> Signed-off-by: Li Dongyang <lidongyang@xxxxxxxxxx>
>>> ---
>>> drivers/block/xen-blkfront.c | 111
>>> +++++++++++++++++++++++++++++++++---------
>>> 1 files changed, 88 insertions(+), 23 deletions(-)
>>>
>>> diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
>>> index 9ea8c25..aa3cede 100644
>>> --- a/drivers/block/xen-blkfront.c
>>> +++ b/drivers/block/xen-blkfront.c
>>> @@ -98,6 +98,9 @@ struct blkfront_info
>>> unsigned long shadow_free;
>>> unsigned int feature_flush;
>>> unsigned int flush_op;
>>> + unsigned int feature_trim;
>>> + unsigned int discard_granularity;
>>> + unsigned int discard_alignment;
>>> int is_ready;
>>> };
>>>
>>> @@ -302,29 +305,36 @@ static int blkif_queue_request(struct request *req)
>>> ring_req->operation = info->flush_op;
>>> }
>>>
>>> - ring_req->nr_segments = blk_rq_map_sg(req->q, req, info->sg);
>>> - BUG_ON(ring_req->nr_segments > BLKIF_MAX_SEGMENTS_PER_REQUEST);
>>> + if (unlikely(req->cmd_flags & REQ_DISCARD)) {
>>> + /* id, sector_number and handle are set above. */
>>> + ring_req->operation = BLKIF_OP_TRIM;
>>> + ring_req->nr_segments = 0;
>>> + ring_req->u.trim.nr_sectors = blk_rq_sectors(req);
>>> + } else {
>>> + ring_req->nr_segments = blk_rq_map_sg(req->q, req, info->sg);
>>> + BUG_ON(ring_req->nr_segments >
>>> BLKIF_MAX_SEGMENTS_PER_REQUEST);
>>>
>>> - for_each_sg(info->sg, sg, ring_req->nr_segments, i) {
>>> - buffer_mfn = pfn_to_mfn(page_to_pfn(sg_page(sg)));
>>> - fsect = sg->offset >> 9;
>>> - lsect = fsect + (sg->length >> 9) - 1;
>>> - /* install a grant reference. */
>>> - ref = gnttab_claim_grant_reference(&gref_head);
>>> - BUG_ON(ref == -ENOSPC);
>>> + for_each_sg(info->sg, sg, ring_req->nr_segments, i) {
>>> + buffer_mfn = pfn_to_mfn(page_to_pfn(sg_page(sg)));
>>> + fsect = sg->offset >> 9;
>>> + lsect = fsect + (sg->length >> 9) - 1;
>>> + /* install a grant reference. */
>>> + ref = gnttab_claim_grant_reference(&gref_head);
>>> + BUG_ON(ref == -ENOSPC);
>>>
>>> - gnttab_grant_foreign_access_ref(
>>> - ref,
>>> - info->xbdev->otherend_id,
>>> - buffer_mfn,
>>> - rq_data_dir(req) );
>>> -
>>> - info->shadow[id].frame[i] = mfn_to_pfn(buffer_mfn);
>>> - ring_req->u.rw.seg[i] =
>>> - (struct blkif_request_segment) {
>>> - .gref = ref,
>>> - .first_sect = fsect,
>>> - .last_sect = lsect };
>>> + gnttab_grant_foreign_access_ref(
>>> + ref,
>>> + info->xbdev->otherend_id,
>>> + buffer_mfn,
>>> + rq_data_dir(req));
>>> +
>>> + info->shadow[id].frame[i] = mfn_to_pfn(buffer_mfn);
>>> + ring_req->u.rw.seg[i] =
>>> + (struct blkif_request_segment) {
>>> + .gref = ref,
>>> + .first_sect = fsect,
>>> + .last_sect = lsect };
>>> + }
>>> }
>>>
>>> info->ring.req_prod_pvt++;
>>> @@ -399,6 +409,7 @@ wait:
>>> static int xlvbd_init_blk_queue(struct gendisk *gd, u16 sector_size)
>>> {
>>> struct request_queue *rq;
>>> + struct blkfront_info *info = gd->private_data;
>>>
>>> rq = blk_init_queue(do_blkif_request, &blkif_io_lock);
>>> if (rq == NULL)
>>> @@ -406,6 +417,13 @@ static int xlvbd_init_blk_queue(struct gendisk *gd, u16
>>> sector_size)
>>>
>>> queue_flag_set_unlocked(QUEUE_FLAG_VIRT, rq);
>>>
>>> + if (info->feature_trim) {
>>> + queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, rq);
>>> + blk_queue_max_discard_sectors(rq, get_capacity(gd));
>>> + rq->limits.discard_granularity = info->discard_granularity;
>>> + rq->limits.discard_alignment = info->discard_alignment;
>>
>> Don't you also need to set rq->limits.max_discard_sectors here (since
>> when zero blkdev_issue_discard() doesn't do anything)? And wouldn't
>> that need to be propagated from the backend, too?
> the max_discard_sectors are set by blk_queue_max_discard_sectors() above ;-)
Oh, silly me to overlook that.
> rq->limits.max_discard_sectors is the full phy device size, and if we
> only assign
> a partition to guest, the number is incorrect for guest, so the
> max_discard_sectors should
> be the capacity the guest will see, Thanks
Using the capacity seems right only for the file: case; I'd still think
the backend should pass the underlying disk's setting for the phy:
one.
Jan
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