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authorJens Axboe <jens.axboe@oracle.com>2009-02-24 08:10:09 +0100
committerJens Axboe <jens.axboe@oracle.com>2009-02-26 10:45:48 +0100
commit9e973e64ac6dc504e6447d52193d4fff1a670156 (patch)
tree518cb0f34f9229f7faa81754733ce3926b84625c /drivers
parent1e42807918d17e8c93bf14fbb74be84b141334c1 (diff)
xen/blkfront: use blk_rq_map_sg to generate ring entries
On occasion, the request will apparently have more segments than we fit into the ring. Jens says: > The second problem is that the block layer then appears to create one > too many segments, but from the dump it has rq->nr_phys_segments == > BLKIF_MAX_SEGMENTS_PER_REQUEST. I suspect the latter is due to > xen-blkfront not handling the merging on its own. It should check that > the new page doesn't form part of the previous page. The > rq_for_each_segment() iterates all single bits in the request, not dma > segments. The "easiest" way to do this is to call blk_rq_map_sg() and > then iterate the mapped sg list. That will give you what you are > looking for. > Here's a test patch, compiles but otherwise untested. I spent more > time figuring out how to enable XEN than to code it up, so YMMV! > Probably the sg list wants to be put inside the ring and only > initialized on allocation, then you can get rid of the sg on stack and > sg_init_table() loop call in the function. I'll leave that, and the > testing, to you. [Moved sg array into info structure, and initialize once. -J] Signed-off-by: Jens Axboe <jens.axboe@oracle.com> Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Diffstat (limited to 'drivers')
-rw-r--r--drivers/block/xen-blkfront.c30
1 files changed, 15 insertions, 15 deletions
diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index 918ef725de4..b6c8ce25435 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -40,6 +40,7 @@
#include <linux/hdreg.h>
#include <linux/cdrom.h>
#include <linux/module.h>
+#include <linux/scatterlist.h>
#include <xen/xenbus.h>
#include <xen/grant_table.h>
@@ -82,6 +83,7 @@ struct blkfront_info
enum blkif_state connected;
int ring_ref;
struct blkif_front_ring ring;
+ struct scatterlist sg[BLKIF_MAX_SEGMENTS_PER_REQUEST];
unsigned int evtchn, irq;
struct request_queue *rq;
struct work_struct work;
@@ -204,12 +206,11 @@ static int blkif_queue_request(struct request *req)
struct blkfront_info *info = req->rq_disk->private_data;
unsigned long buffer_mfn;
struct blkif_request *ring_req;
- struct req_iterator iter;
- struct bio_vec *bvec;
unsigned long id;
unsigned int fsect, lsect;
- int ref;
+ int i, ref;
grant_ref_t gref_head;
+ struct scatterlist *sg;
if (unlikely(info->connected != BLKIF_STATE_CONNECTED))
return 1;
@@ -238,12 +239,13 @@ static int blkif_queue_request(struct request *req)
if (blk_barrier_rq(req))
ring_req->operation = BLKIF_OP_WRITE_BARRIER;
- ring_req->nr_segments = 0;
- rq_for_each_segment(bvec, req, iter) {
- BUG_ON(ring_req->nr_segments == BLKIF_MAX_SEGMENTS_PER_REQUEST);
- buffer_mfn = pfn_to_mfn(page_to_pfn(bvec->bv_page));
- fsect = bvec->bv_offset >> 9;
- lsect = fsect + (bvec->bv_len >> 9) - 1;
+ 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);
@@ -254,16 +256,12 @@ static int blkif_queue_request(struct request *req)
buffer_mfn,
rq_data_dir(req) );
- info->shadow[id].frame[ring_req->nr_segments] =
- mfn_to_pfn(buffer_mfn);
-
- ring_req->seg[ring_req->nr_segments] =
+ info->shadow[id].frame[i] = mfn_to_pfn(buffer_mfn);
+ ring_req->seg[i] =
(struct blkif_request_segment) {
.gref = ref,
.first_sect = fsect,
.last_sect = lsect };
-
- ring_req->nr_segments++;
}
info->ring.req_prod_pvt++;
@@ -622,6 +620,8 @@ static int setup_blkring(struct xenbus_device *dev,
SHARED_RING_INIT(sring);
FRONT_RING_INIT(&info->ring, sring, PAGE_SIZE);
+ sg_init_table(info->sg, BLKIF_MAX_SEGMENTS_PER_REQUEST);
+
err = xenbus_grant_ring(dev, virt_to_mfn(info->ring.sring));
if (err < 0) {
free_page((unsigned long)sring);