On Mon, Oct 15, 2018 at 10:40:06AM +0200, Richard Weinberger wrote: > hm, this breaks UML. > Every filesystem fails to mount. > > I did some very rough tests, it seems that the driver fails to read > data correctly as soon the upper layer tries to get more than 4096 bytes > at once out of the block device. > > IOW: > dd if=/dev/ubda bs=4096 count=1 skip=0 2>/dev/null| md5sum - > is good. > As soon I set bs to something greater it returns garbage. > > Later this day I might have some cycles left to debug further.
It probably needs this on top: diff --git a/arch/um/drivers/ubd_kern.c b/arch/um/drivers/ubd_kern.c index aafe9c467fdc..5adce80a7ee3 100644 --- a/arch/um/drivers/ubd_kern.c +++ b/arch/um/drivers/ubd_kern.c @@ -1290,7 +1290,7 @@ static void cowify_req(struct io_thread_req *req, unsigned long *bitmap, } static int ubd_queue_one_vec(struct blk_mq_hw_ctx *hctx, struct request *req, - sector_t pos, struct bio_vec *bvec) + u64 off, struct bio_vec *bvec) { struct ubd *dev = hctx->queue->queuedata; struct io_thread_req *io_req; @@ -1311,7 +1311,7 @@ static int ubd_queue_one_vec(struct blk_mq_hw_ctx *hctx, struct request *req, } else { io_req->fds[1] = dev->fd; io_req->cow_offset = -1; - io_req->offset = (unsigned long long)pos << 9; + io_req->offset = off; io_req->length = bvec->bv_len; io_req->error = 0; io_req->sector_mask = 0; @@ -1346,17 +1346,17 @@ static blk_status_t ubd_queue_rq(struct blk_mq_hw_ctx *hctx, struct bio *bio = req->bio; struct bvec_iter iter; struct bio_vec bvec; - sector_t pos = blk_rq_pos(req); + u64 off = (u64)blk_rq_pos(req) << 9; blk_mq_start_request(req); for_each_bio(bio) { bio_for_each_segment(bvec, bio, iter) { - if (ubd_queue_one_vec(hctx, req, pos, &bvec) < 0) { + if (ubd_queue_one_vec(hctx, req, off, &bvec) < 0) { blk_mq_requeue_request(req, true); return BLK_STS_OK; } - pos += bvec.bv_len; + off += bvec.bv_len; } }