block: remove support for bio remapping from ->make_request

There is very little benefit in allowing to let a ->make_request
instance update the bios device and sector and loop around it in
__generic_make_request when we can archive the same through calling
generic_make_request from the driver and letting the loop in
generic_make_request handle it.

Note that various drivers got the return value from ->make_request and
returned non-zero values for errors.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: NeilBrown <neilb@suse.de>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

1 files changed, 62 insertions, 91 deletions

diff --git a/block/blk-core.c b/block/blk-core.c
index ab673f0..f58e019 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1211,7 +1211,7 @@ void init_request_from_bio(struct request *req, struct bio *bio)
 	blk_rq_bio_prep(req->q, req, bio);
 }
 
-int blk_queue_bio(struct request_queue *q, struct bio *bio)
+void blk_queue_bio(struct request_queue *q, struct bio *bio)
 {
 	const bool sync = !!(bio->bi_rw & REQ_SYNC);
 	struct blk_plug *plug;
@@ -1236,7 +1236,7 @@ int blk_queue_bio(struct request_queue *q, struct bio *bio)
 	 * any locks.
 	 */
 	if (attempt_plug_merge(current, q, bio))
-		goto out;
+		return;
 
 	spin_lock_irq(q->queue_lock);
 
@@ -1312,8 +1312,6 @@ get_rq:
 out_unlock:
 		spin_unlock_irq(q->queue_lock);
 	}
-out:
-	return 0;
 }
 EXPORT_SYMBOL_GPL(blk_queue_bio);	/* for device mapper only */
 
@@ -1441,112 +1439,85 @@ static inline int bio_check_eod(struct bio *bio, unsigned int nr_sectors)
 static inline void __generic_make_request(struct bio *bio)
 {
 	struct request_queue *q;
-	sector_t old_sector;
-	int ret, nr_sectors = bio_sectors(bio);
-	dev_t old_dev;
+	int nr_sectors = bio_sectors(bio);
 	int err = -EIO;
+	char b[BDEVNAME_SIZE];
+	struct hd_struct *part;
 
 	might_sleep();
 
 	if (bio_check_eod(bio, nr_sectors))
 		goto end_io;
 
-	/*
-	 * Resolve the mapping until finished. (drivers are
-	 * still free to implement/resolve their own stacking
-	 * by explicitly returning 0)
-	 *
-	 * NOTE: we don't repeat the blk_size check for each new device.
-	 * Stacking drivers are expected to know what they are doing.
-	 */
-	old_sector = -1;
-	old_dev = 0;
-	do {
-		char b[BDEVNAME_SIZE];
-		struct hd_struct *part;
-
-		q = bdev_get_queue(bio->bi_bdev);
-		if (unlikely(!q)) {
-			printk(KERN_ERR
-			       "generic_make_request: Trying to access "
-				"nonexistent block-device %s (%Lu)\n",
-				bdevname(bio->bi_bdev, b),
-				(long long) bio->bi_sector);
-			goto end_io;
-		}
-
-		if (unlikely(!(bio->bi_rw & REQ_DISCARD) &&
-			     nr_sectors > queue_max_hw_sectors(q))) {
-			printk(KERN_ERR "bio too big device %s (%u > %u)\n",
-			       bdevname(bio->bi_bdev, b),
-			       bio_sectors(bio),
-			       queue_max_hw_sectors(q));
-			goto end_io;
-		}
-
-		if (unlikely(test_bit(QUEUE_FLAG_DEAD, &q->queue_flags)))
-			goto end_io;
-
-		part = bio->bi_bdev->bd_part;
-		if (should_fail_request(part, bio->bi_size) ||
-		    should_fail_request(&part_to_disk(part)->part0,
-					bio->bi_size))
-			goto end_io;
+	q = bdev_get_queue(bio->bi_bdev);
+	if (unlikely(!q)) {
+		printk(KERN_ERR
+		       "generic_make_request: Trying to access "
+			"nonexistent block-device %s (%Lu)\n",
+			bdevname(bio->bi_bdev, b),
+			(long long) bio->bi_sector);
+		goto end_io;
+	}
 
-		/*
-		 * If this device has partitions, remap block n
-		 * of partition p to block n+start(p) of the disk.
-		 */
-		blk_partition_remap(bio);
+	if (unlikely(!(bio->bi_rw & REQ_DISCARD) &&
+		     nr_sectors > queue_max_hw_sectors(q))) {
+		printk(KERN_ERR "bio too big device %s (%u > %u)\n",
+		       bdevname(bio->bi_bdev, b),
+		       bio_sectors(bio),
+		       queue_max_hw_sectors(q));
+		goto end_io;
+	}
 
-		if (bio_integrity_enabled(bio) && bio_integrity_prep(bio))
-			goto end_io;
+	if (unlikely(test_bit(QUEUE_FLAG_DEAD, &q->queue_flags)))
+		goto end_io;
 
-		if (old_sector != -1)
-			trace_block_bio_remap(q, bio, old_dev, old_sector);
+	part = bio->bi_bdev->bd_part;
+	if (should_fail_request(part, bio->bi_size) ||
+	    should_fail_request(&part_to_disk(part)->part0,
+				bio->bi_size))
+		goto end_io;
 
-		old_sector = bio->bi_sector;
-		old_dev = bio->bi_bdev->bd_dev;
+	/*
+	 * If this device has partitions, remap block n
+	 * of partition p to block n+start(p) of the disk.
+	 */
+	blk_partition_remap(bio);
 
-		if (bio_check_eod(bio, nr_sectors))
-			goto end_io;
+	if (bio_integrity_enabled(bio) && bio_integrity_prep(bio))
+		goto end_io;
 
-		/*
-		 * Filter flush bio's early so that make_request based
-		 * drivers without flush support don't have to worry
-		 * about them.
-		 */
-		if ((bio->bi_rw & (REQ_FLUSH | REQ_FUA)) && !q->flush_flags) {
-			bio->bi_rw &= ~(REQ_FLUSH | REQ_FUA);
-			if (!nr_sectors) {
-				err = 0;
-				goto end_io;
-			}
-		}
+	if (bio_check_eod(bio, nr_sectors))
+		goto end_io;
 
-		if ((bio->bi_rw & REQ_DISCARD) &&
-		    (!blk_queue_discard(q) ||
-		     ((bio->bi_rw & REQ_SECURE) &&
-		      !blk_queue_secdiscard(q)))) {
-			err = -EOPNOTSUPP;
+	/*
+	 * Filter flush bio's early so that make_request based
+	 * drivers without flush support don't have to worry
+	 * about them.
+	 */
+	if ((bio->bi_rw & (REQ_FLUSH | REQ_FUA)) && !q->flush_flags) {
+		bio->bi_rw &= ~(REQ_FLUSH | REQ_FUA);
+		if (!nr_sectors) {
+			err = 0;
 			goto end_io;
 		}
+	}
 
-		if (blk_throtl_bio(q, &bio))
-			goto end_io;
-
-		/*
-		 * If bio = NULL, bio has been throttled and will be submitted
-		 * later.
-		 */
-		if (!bio)
-			break;
-
-		trace_block_bio_queue(q, bio);
+	if ((bio->bi_rw & REQ_DISCARD) &&
+	    (!blk_queue_discard(q) ||
+	     ((bio->bi_rw & REQ_SECURE) &&
+	      !blk_queue_secdiscard(q)))) {
+		err = -EOPNOTSUPP;
+		goto end_io;
+	}
 
-		ret = q->make_request_fn(q, bio);
-	} while (ret);
+	if (blk_throtl_bio(q, &bio))
+		goto end_io;
 
+	/* if bio = NULL, bio has been throttled and will be submitted later. */
+	if (!bio)
+		return;
+	trace_block_bio_queue(q, bio);
+	q->make_request_fn(q, bio);
 	return;
 
 end_io: