On Thu, Sep 01, 2011 at 06:39:09PM +0800, Li Dongyang wrote:
> The blkfront driver now will read discard related nodes from xenstore,
> and set up the request queue, then we can forward the
> discard requests to backend driver.
A better description is as follow:
xen-blkfront: Handle discard requests.
If the backend advertises 'feature-discard', then interrogate
the backend for alignment, granularity, and max discard block size.
Setup the request queue with the appropiate values and send the
discard operation as required.
>
> 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..86e2c63 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_discard;
> + 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_DISCARD;
> + ring_req->nr_segments = 0;
> + ring_req->u.discard.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_discard) {
> + queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, rq);
> + blk_queue_max_discard_sectors(rq, get_capacity(gd));
This is not correct. I took a look at the SCSI support for this
('sd_config_discard') and if you look there carefully you will see that
the value can be 64KB for example.
You need to provide a mechanism similar to 'discard-*' to fetch that data
from the backend.
> + rq->limits.discard_granularity = info->discard_granularity;
> + rq->limits.discard_alignment = info->discard_alignment;
> + }
> +
> /* Hard sector size and max sectors impersonate the equiv. hardware. */
> blk_queue_logical_block_size(rq, sector_size);
> blk_queue_max_hw_sectors(rq, 512);
> @@ -722,6 +740,19 @@ static irqreturn_t blkif_interrupt(int irq, void *dev_id)
>
> error = (bret->status == BLKIF_RSP_OKAY) ? 0 : -EIO;
> switch (bret->operation) {
> + case BLKIF_OP_DISCARD:
> + if (unlikely(bret->status == BLKIF_RSP_EOPNOTSUPP)) {
> + struct request_queue *rq = info->rq;
> + printk(KERN_WARNING "blkfront: %s: discard op
> failed\n",
> + info->gd->disk_name);
> + error = -EOPNOTSUPP;
> + info->feature_discard = 0;
> + spin_lock(rq->queue_lock);
> + queue_flag_clear(QUEUE_FLAG_DISCARD, rq);
> + spin_unlock(rq->queue_lock);
> + }
> + __blk_end_request_all(req, error);
> + break;
> case BLKIF_OP_FLUSH_DISKCACHE:
> case BLKIF_OP_WRITE_BARRIER:
> if (unlikely(bret->status == BLKIF_RSP_EOPNOTSUPP)) {
> @@ -1098,6 +1129,33 @@ blkfront_closing(struct blkfront_info *info)
> bdput(bdev);
> }
>
> +static void blkfront_setup_discard(struct blkfront_info *info)
> +{
> + int err;
> + char *type;
> + unsigned int discard_granularity;
> + unsigned int discard_alignment;
> +
> + type = xenbus_read(XBT_NIL, info->xbdev->otherend, "type", NULL);
> + if (IS_ERR(type))
> + return;
> +
> + if (strncmp(type, "phy", 3) == 0) {
> + err = xenbus_gather(XBT_NIL, info->xbdev->otherend,
> + "discard-granularity", "%u", &discard_granularity,
> + "discard-alignment", "%u", &discard_alignment,
> + NULL);
> + if (!err) {
> + info->feature_discard = 1;
> + info->discard_granularity = discard_granularity;
> + info->discard_alignment = discard_alignment;
> + }
> + } else if (strncmp(type, "file", 4) == 0)
> + info->feature_discard = 1;
> +
> + kfree(type);
> +}
> +
> /*
> * Invoked when the backend is finally 'ready' (and has told produced
> * the details about the physical device - #sectors, size, etc).
> @@ -1108,7 +1166,7 @@ static void blkfront_connect(struct blkfront_info *info)
> unsigned long sector_size;
> unsigned int binfo;
> int err;
> - int barrier, flush;
> + int barrier, flush, discard;
>
> switch (info->connected) {
> case BLKIF_STATE_CONNECTED:
> @@ -1178,7 +1236,14 @@ static void blkfront_connect(struct blkfront_info
> *info)
> info->feature_flush = REQ_FLUSH;
> info->flush_op = BLKIF_OP_FLUSH_DISKCACHE;
> }
> -
> +
> + err = xenbus_gather(XBT_NIL, info->xbdev->otherend,
> + "feature-discard", "%d", &discard,
> + NULL);
> +
> + if (!err && discard)
> + blkfront_setup_discard(info);
> +
> err = xlvbd_alloc_gendisk(sectors, info, binfo, sector_size);
> if (err) {
> xenbus_dev_fatal(info->xbdev, err, "xlvbd_add at %s",
> --
> 1.7.6
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