On Fri, Aug 02, 2013 at 06:40:27PM +0200, Roger Pau Monne wrote: > In blkif_queue_request blkfront iterates over the scatterlist in order > to set the segments of the request, and in blkif_completion blkfront > iterates over the raw request, which makes it hard to know the exact > position of the source and destination memory positions. > > This can be solved by allocating a scatterlist for each request, that > will be keep until the request is finished, allowing us to copy the > data back to the original memory without having to iterate over the > raw request. > > This is a backport of b7649158a0d241f8d53d13ff7441858539e16656 to > apply against the 3.10-stable tree.
Thank you! > > Oracle-Bug: 16660413 - LARGE ASYNCHRONOUS READS APPEAR BROKEN ON 2.6.39-400 > CC: [email protected] > Signed-off-by: Roger Pau Monné <[email protected]> > Reported-by: Anne Milicia <[email protected]> > Cc: Konrad Rzeszutek Wilk <[email protected]> > Cc: Anne Milicia <[email protected]> > --- > drivers/block/xen-blkfront.c | 36 +++++++++++++++++------------------- > 1 files changed, 17 insertions(+), 19 deletions(-) > > diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c > index d89ef86..69b45fc 100644 > --- a/drivers/block/xen-blkfront.c > +++ b/drivers/block/xen-blkfront.c > @@ -75,6 +75,7 @@ struct blk_shadow { > struct blkif_request req; > struct request *request; > struct grant *grants_used[BLKIF_MAX_SEGMENTS_PER_REQUEST]; > + struct scatterlist sg[BLKIF_MAX_SEGMENTS_PER_REQUEST]; > }; > > static DEFINE_MUTEX(blkfront_mutex); > @@ -98,7 +99,6 @@ 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; > @@ -422,11 +422,11 @@ static int blkif_queue_request(struct request *req) > ring_req->u.discard.flag = 0; > } else { > ring_req->u.rw.nr_segments = blk_rq_map_sg(req->q, req, > - info->sg); > + info->shadow[id].sg); > BUG_ON(ring_req->u.rw.nr_segments > > BLKIF_MAX_SEGMENTS_PER_REQUEST); > > - for_each_sg(info->sg, sg, ring_req->u.rw.nr_segments, i) { > + for_each_sg(info->shadow[id].sg, sg, > ring_req->u.rw.nr_segments, i) { > fsect = sg->offset >> 9; > lsect = fsect + (sg->length >> 9) - 1; > > @@ -867,12 +867,12 @@ static void blkif_completion(struct blk_shadow *s, > struct blkfront_info *info, > struct blkif_response *bret) > { > int i = 0; > - struct bio_vec *bvec; > - struct req_iterator iter; > - unsigned long flags; > + struct scatterlist *sg; > char *bvec_data; > void *shared_data; > - unsigned int offset = 0; > + int nseg; > + > + nseg = s->req.u.rw.nr_segments; > > if (bret->operation == BLKIF_OP_READ) { > /* > @@ -881,19 +881,16 @@ static void blkif_completion(struct blk_shadow *s, > struct blkfront_info *info, > * than PAGE_SIZE, we have to keep track of the current offset, > * to be sure we are copying the data from the right shared > page. > */ > - rq_for_each_segment(bvec, s->request, iter) { > - BUG_ON((bvec->bv_offset + bvec->bv_len) > PAGE_SIZE); > - if (bvec->bv_offset < offset) > - i++; > - BUG_ON(i >= s->req.u.rw.nr_segments); > + for_each_sg(s->sg, sg, nseg, i) { > + BUG_ON(sg->offset + sg->length > PAGE_SIZE); > shared_data = kmap_atomic( > pfn_to_page(s->grants_used[i]->pfn)); > - bvec_data = bvec_kmap_irq(bvec, &flags); > - memcpy(bvec_data, shared_data + bvec->bv_offset, > - bvec->bv_len); > - bvec_kunmap_irq(bvec_data, &flags); > + bvec_data = kmap_atomic(sg_page(sg)); > + memcpy(bvec_data + sg->offset, > + shared_data + sg->offset, > + sg->length); > + kunmap_atomic(bvec_data); > kunmap_atomic(shared_data); > - offset = bvec->bv_offset + bvec->bv_len; > } > } > /* Add the persistent grant into the list of free grants */ > @@ -1022,7 +1019,7 @@ static int setup_blkring(struct xenbus_device *dev, > struct blkfront_info *info) > { > struct blkif_sring *sring; > - int err; > + int err, i; > > info->ring_ref = GRANT_INVALID_REF; > > @@ -1034,7 +1031,8 @@ 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); > + for (i = 0; i < BLK_RING_SIZE; i++) > + sg_init_table(info->shadow[i].sg, > BLKIF_MAX_SEGMENTS_PER_REQUEST); > > /* Allocate memory for grants */ > err = fill_grant_buffer(info, BLK_RING_SIZE * > -- > 1.7.7.5 (Apple Git-26) > -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
