block: restore the meaning of rq->data_len to the true data length

The meaning of rq->data_len was changed to the length of an allocated
buffer from the true data length. It breaks SG_IO friends and
bsg. This patch restores the meaning of rq->data_len to the true data
length and adds rq->extra_len to store an extended length (due to
drain buffer and padding).

This patch also removes the code to update bio in blk_rq_map_user
introduced by the commit 40b01b9b.
The commit adjusts bio according to memory alignment
(queue_dma_alignment). However, memory alignment is NOT padding
alignment. This adjustment also breaks SG_IO friends and bsg. Padding
alignment needs to be fixed in a proper way (by a separate patch).
Signed-off-by: NFUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: NJens Axboe <axboe@carl.home.kernel.dk>

block/blk-core.c

@@ -127,7 +127,6 @@ void rq_init(struct request_queue *q, struct request *rq)
 	rq->nr_hw_segments = 0;
 	rq->ioprio = 0;
 	rq->special = NULL;
-	rq->raw_data_len = 0;
 	rq->buffer = NULL;
 	rq->tag = -1;
 	rq->errors = 0;
@@ -135,6 +134,7 @@ void rq_init(struct request_queue *q, struct request *rq)
 	rq->cmd_len = 0;
 	memset(rq->cmd, 0, sizeof(rq->cmd));
 	rq->data_len = 0;
+	rq->extra_len = 0;
 	rq->sense_len = 0;
 	rq->data = NULL;
 	rq->sense = NULL;
@@ -2018,7 +2018,6 @@ void blk_rq_bio_prep(struct request_queue *q, struct request *rq,
 	rq->hard_cur_sectors = rq->current_nr_sectors;
 	rq->hard_nr_sectors = rq->nr_sectors = bio_sectors(bio);
 	rq->buffer = bio_data(bio);
-	rq->raw_data_len = bio->bi_size;
 	rq->data_len = bio->bi_size;
 
 	rq->bio = rq->biotail = bio;

block/blk-map.c

@@ -19,7 +19,6 @@ int blk_rq_append_bio(struct request_queue *q, struct request *rq,
 		rq->biotail->bi_next = bio;
 		rq->biotail = bio;
 
-		rq->raw_data_len += bio->bi_size;
 		rq->data_len += bio->bi_size;
 	}
 	return 0;
@@ -151,11 +150,8 @@ int blk_rq_map_user(struct request_queue *q, struct request *rq,
 	 */
 	if (len & queue_dma_alignment(q)) {
 		unsigned int pad_len = (queue_dma_alignment(q) & ~len) + 1;
-		struct bio *bio = rq->biotail;
 
-		bio->bi_io_vec[bio->bi_vcnt - 1].bv_len += pad_len;
-		bio->bi_size += pad_len;
-		rq->data_len += pad_len;
+		rq->extra_len += pad_len;
 	}
 
 	rq->buffer = rq->data = NULL;

block/blk-merge.c

@@ -231,7 +231,7 @@ int blk_rq_map_sg(struct request_queue *q, struct request *rq,
 			    ((unsigned long)q->dma_drain_buffer) &
 			    (PAGE_SIZE - 1));
 		nsegs++;
-		rq->data_len += q->dma_drain_size;
+		rq->extra_len += q->dma_drain_size;
 	}
 
 	if (sg)

block/bsg.c

@@ -437,14 +437,14 @@ static int blk_complete_sgv4_hdr_rq(struct request *rq, struct sg_io_v4 *hdr,
 	}
 
 	if (rq->next_rq) {
-		hdr->dout_resid = rq->raw_data_len;
-		hdr->din_resid = rq->next_rq->raw_data_len;
+		hdr->dout_resid = rq->data_len;
+		hdr->din_resid = rq->next_rq->data_len;
 		blk_rq_unmap_user(bidi_bio);
 		blk_put_request(rq->next_rq);
 	} else if (rq_data_dir(rq) == READ)
-		hdr->din_resid = rq->raw_data_len;
+		hdr->din_resid = rq->data_len;
 	else
-		hdr->dout_resid = rq->raw_data_len;
+		hdr->dout_resid = rq->data_len;
 
 	/*
 	 * If the request generated a negative error number, return it

block/scsi_ioctl.c

@@ -266,7 +266,7 @@ static int blk_complete_sghdr_rq(struct request *rq, struct sg_io_hdr *hdr,
 	hdr->info = 0;
 	if (hdr->masked_status || hdr->host_status || hdr->driver_status)
 		hdr->info |= SG_INFO_CHECK;
-	hdr->resid = rq->raw_data_len;
+	hdr->resid = rq->data_len;
 	hdr->sb_len_wr = 0;
 
 	if (rq->sense_len && hdr->sbp) {
@@ -528,8 +528,8 @@ static int __blk_send_generic(struct request_queue *q, struct gendisk *bd_disk,
 	rq = blk_get_request(q, WRITE, __GFP_WAIT);
 	rq->cmd_type = REQ_TYPE_BLOCK_PC;
 	rq->data = NULL;
-	rq->raw_data_len = 0;
 	rq->data_len = 0;
+	rq->extra_len = 0;
 	rq->timeout = BLK_DEFAULT_SG_TIMEOUT;
 	memset(rq->cmd, 0, sizeof(rq->cmd));
 	rq->cmd[0] = cmd;

drivers/ata/libata-scsi.c

@@ -2538,7 +2538,7 @@ static unsigned int atapi_xlat(struct ata_queued_cmd *qc)
 	}
 
 	qc->tf.command = ATA_CMD_PACKET;
-	qc->nbytes = scsi_bufflen(scmd);
+	qc->nbytes = scsi_bufflen(scmd) + scmd->request->extra_len;
 
 	/* check whether ATAPI DMA is safe */
 	if (!using_pio && ata_check_atapi_dma(qc))
@@ -2549,7 +2549,7 @@ static unsigned int atapi_xlat(struct ata_queued_cmd *qc)
 	 * want to set it properly, and for DMA where it is
 	 * effectively meaningless.
 	 */
-	nbytes = min(scmd->request->raw_data_len, (unsigned int)63 * 1024);
+	nbytes = min(scmd->request->data_len, (unsigned int)63 * 1024);
 
 	/* Most ATAPI devices which honor transfer chunk size don't
 	 * behave according to the spec when odd chunk size which
@@ -2875,7 +2875,7 @@ static unsigned int ata_scsi_pass_thru(struct ata_queued_cmd *qc)
 	 * TODO: find out if we need to do more here to
 	 *       cover scatter/gather case.
 	 */
-	qc->nbytes = scsi_bufflen(scmd);
+	qc->nbytes = scsi_bufflen(scmd) + scmd->request->extra_len;
 
 	/* request result TF and be quiet about device error */
 	qc->flags |= ATA_QCFLAG_RESULT_TF | ATA_QCFLAG_QUIET;

include/linux/blkdev.h

@@ -216,8 +216,8 @@ struct request {
 	unsigned int cmd_len;
 	unsigned char cmd[BLK_MAX_CDB];
 
-	unsigned int raw_data_len;
 	unsigned int data_len;
+	unsigned int extra_len;	/* length of alignment and padding */
 	unsigned int sense_len;
 	void *data;
 	void *sense;