Sven Köhler wrote:
Hi,
below is the output of the kernel just before it goes down and
crashes. I have to use "xm destroy" to kill it.
I have tried the enable/disable the "Optimize for Size" setting in the
kernel. I hopes that it's some kind of compiler bug because of the
"invalid opcode" thing. But actually I don't a clue what this might be
caused by.
Do you have any idea?
The crash is very reproducable.
Looks like the crash fixed by the change below
(c7241227f61ca6606a7fa3555391360d92bd8d9b in linux-2.6.git)
J
From c7241227f61ca6606a7fa3555391360d92bd8d9b Mon Sep 17 00:00:00 2001
From: Jens Axboe <jens.axboe@xxxxxxxxxx>
Date: Mon, 16 Feb 2009 13:18:28 -0800
Subject: [PATCH] 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@xxxxxxxxxx>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>
diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index 918ef72..b6c8ce2 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);
_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel
|
Home