xen-blkfront: Handle discard requests.

If the backend advertises 'feature-discard', then interrogate
the backend for alignment and granularity. Setup the request
queue with the appropiate values and send the discard operation
as required.

Signed-off-by: Li Dongyang <lidongyang@novell.com>
[v1: Amended commit description]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index 9ea8c2576c70e768f22ad8ea2cc423337611fb4f..86e2c6377f9a4cd1e96cf4328d65854a6f4421a5 100644 (file)
--- 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));
+               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",