From: Roger Pau Monne Date: Fri, 7 Dec 2012 18:00:31 +0000 (+0100) Subject: xen-blkfront: handle bvecs with partial data X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=d62f691858252333ff1ddb920e6774d9020734aa;p=linux-beck.git 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 Signed-off-by: Roger Pau Monné Cc: linux-kernel@vger.kernel.org Cc: Konrad Rzeszutek Wilk Signed-off-by: Konrad Rzeszutek Wilk --- diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c index cfdb033c7107..11043c18ac5a 100644 --- a/drivers/block/xen-blkfront.c +++ b/drivers/block/xen-blkfront.c @@ -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 */