xen-blkfront: handle bvecs with partial data
Currently blkfront fails to handle cases in blkif_completion like the
following:
1st loop in rq_for_each_segment
* bv_offset: 3584
* bv_len: 512
* offset += bv_len
* i: 0
2nd loop:
* bv_offset: 0
* bv_len: 512
* i: 0
In the second loop i should be 1, since we assume we only wanted to
read a part of the previous page. This patches fixes this cases where
only a part of the shared page is read, and blkif_completion assumes
that if the bv_offset of a bvec is less than the previous bv_offset
plus the bv_size we have to switch to the next shared page.
Reported-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Cc: linux-kernel@vger.kernel.org
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
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 cfdb033..11043c1 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -836,7 +836,7 @@
static void blkif_completion(struct blk_shadow *s, struct blkfront_info *info,
struct blkif_response *bret)
{
- int i;
+ int i = 0;
struct bio_vec *bvec;
struct req_iterator iter;
unsigned long flags;
@@ -853,7 +853,8 @@
*/
rq_for_each_segment(bvec, s->request, iter) {
BUG_ON((bvec->bv_offset + bvec->bv_len) > PAGE_SIZE);
- i = offset >> PAGE_SHIFT;
+ if (bvec->bv_offset < offset)
+ i++;
BUG_ON(i >= s->req.u.rw.nr_segments);
shared_data = kmap_atomic(
pfn_to_page(s->grants_used[i]->pfn));
@@ -862,7 +863,7 @@
bvec->bv_len);
bvec_kunmap_irq(bvec_data, &flags);
kunmap_atomic(shared_data);
- offset += bvec->bv_len;
+ offset = bvec->bv_offset + bvec->bv_len;
}
}
/* Add the persistent grant into the list of free grants */