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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>
This commit is contained in:
Roger Pau Monne 2012-12-07 19:00:31 +01:00 committed by Konrad Rzeszutek Wilk
parent ebb351cf78
commit d62f691858
1 changed files with 4 additions and 3 deletions
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7
drivers/block/xen-blkfront.c
View File

@ -836,7 +836,7 @@ static void blkif_free(struct blkfront_info *info, int suspend)
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 @@ static void blkif_completion(struct blk_shadow *s, struct blkfront_info *info,
*/
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 @@ static void blkif_completion(struct blk_shadow *s, struct blkfront_info *info,
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 */