block: remove the write_hint field from struct request

The write_hint is only used for read/write requests, which must have a
bio attached to them. Just use the bio field instead.

Signed-off-by: Christoph Hellwig <[e-mail]>
Reviewed-by: Bart Van Assche <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jens Axboe <[e-mail]>

block/blk-merge.c

···
 	if (rq_data_dir(req) != rq_data_dir(next))
 		return NULL;
 
-	/* Don't merge requests with different write hints. */
-	if (req->write_hint != next->write_hint)
-		return NULL;
+	if (req->bio && next->bio) {
+		/* Don't merge requests with different write hints. */
+		if (req->bio->bi_write_hint != next->bio->bi_write_hint)
+			return NULL;
+	}
 
 	if (req->ioprio != next->ioprio)
 		return NULL;
···
 	if (!bio_crypt_rq_ctx_compatible(rq, bio))
 		return false;
 
-	/* Don't merge requests with different write hints. */
-	if (rq->write_hint != bio->bi_write_hint)
-		return false;
+	if (rq->bio) {
+		/* Don't merge requests with different write hints. */
+		if (rq->bio->bi_write_hint != bio->bi_write_hint)
+			return false;
+	}
 
 	if (rq->ioprio != bio_prio(bio))
 		return false;

block/blk-mq.c

···
 		rq->cmd_flags |= REQ_FAILFAST_MASK;
 
 	rq->__sector = bio->bi_iter.bi_sector;
-	rq->write_hint = bio->bi_write_hint;
 	blk_rq_bio_prep(rq, bio, nr_segs);
 	if (bio_integrity(bio))
 		rq->nr_integrity_segments = blk_rq_count_integrity_sg(rq->q,
···
 	}
 	rq->nr_phys_segments = rq_src->nr_phys_segments;
 	rq->ioprio = rq_src->ioprio;
-	rq->write_hint = rq_src->write_hint;
 
 	if (rq->bio && blk_crypto_rq_bio_prep(rq, rq->bio, gfp_mask) < 0)
 		goto free_and_out;

drivers/scsi/sd.c

···
 	if (!sdkp->rscs)
 		return 0;
 
-	return min3((u32)rq->write_hint, (u32)sdkp->permanent_stream_count,
-		    0x3fu);
+	return min3((u32)rq->bio->bi_write_hint,
+		    (u32)sdkp->permanent_stream_count, 0x3fu);
 }
 
 static blk_status_t sd_setup_rw32_cmnd(struct scsi_cmnd *cmd, bool write,
···
 		ret = sd_setup_rw16_cmnd(cmd, write, lba, nr_blocks,
 					 protect | fua, dld);
 	} else if ((nr_blocks > 0xff) || (lba > 0x1fffff) ||
-		   sdp->use_10_for_rw || protect || rq->write_hint) {
+		   sdp->use_10_for_rw || protect || rq->bio->bi_write_hint) {
 		ret = sd_setup_rw10_cmnd(cmd, write, lba, nr_blocks,
 					 protect | fua);
 	} else {

include/linux/blk-mq.h

···
 	struct blk_crypto_keyslot *crypt_keyslot;
 #endif
 
-	enum rw_hint write_hint;
 	unsigned short ioprio;
 
 	enum mq_rq_state state;