[PATCH] Cleanup blk_rq_map_* interfaces

Change the blk_rq_map_user() and blk_rq_map_kern() interface to require
a previously allocated request to be passed in. This is both more efficient
for multiple iterations of mapping data to the same request, and it is also
a much nicer API.
Signed-off-by: Jens Axboe <axboe@suse.de>

drivers/block/ll_rw_blk.c

@@ -2107,21 +2107,19 @@ EXPORT_SYMBOL(blk_insert_request);
  *    original bio must be passed back in to blk_rq_unmap_user() for proper
  *    unmapping.
  */
-struct request *blk_rq_map_user(request_queue_t *q, int rw, void __user *ubuf,
+int blk_rq_map_user(request_queue_t *q, struct request *rq, void __user *ubuf,
 		    unsigned int len)
 {
 	unsigned long uaddr;
-	struct request *rq;
 	struct bio *bio;
+	int reading;
 
 	if (len > (q->max_sectors << 9))
-		return ERR_PTR(-EINVAL);
-	if ((!len && ubuf) || (len && !ubuf))
-		return ERR_PTR(-EINVAL);
+		return -EINVAL;
+	if (!len || !ubuf)
+		return -EINVAL;
 
-	rq = blk_get_request(q, rw, __GFP_WAIT);
-	if (!rq)
-		return ERR_PTR(-ENOMEM);
+	reading = rq_data_dir(rq) == READ;
 
 	/*
 	 * if alignment requirement is satisfied, map in user pages for
@@ -2129,9 +2127,9 @@ struct request *blk_rq_map_user(request_queue_t *q, int rw, void __user *ubuf,
 	 */
 	uaddr = (unsigned long) ubuf;
 	if (!(uaddr & queue_dma_alignment(q)) && !(len & queue_dma_alignment(q)))
-		bio = bio_map_user(q, NULL, uaddr, len, rw == READ);
+		bio = bio_map_user(q, NULL, uaddr, len, reading);
 	else
-		bio = bio_copy_user(q, uaddr, len, rw == READ);
+		bio = bio_copy_user(q, uaddr, len, reading);
 
 	if (!IS_ERR(bio)) {
 		rq->bio = rq->biotail = bio;
@@ -2139,14 +2137,13 @@ struct request *blk_rq_map_user(request_queue_t *q, int rw, void __user *ubuf,
 
 		rq->buffer = rq->data = NULL;
 		rq->data_len = len;
-		return rq;
+		return 0;
 	}
 
 	/*
 	 * bio is the err-ptr
 	 */
-	blk_put_request(rq);
-	return (struct request *) bio;
+	return PTR_ERR(bio);
 }
 
 EXPORT_SYMBOL(blk_rq_map_user);
@@ -2160,7 +2157,7 @@ EXPORT_SYMBOL(blk_rq_map_user);
  * Description:
  *    Unmap a request previously mapped by blk_rq_map_user().
  */
-int blk_rq_unmap_user(struct request *rq, struct bio *bio, unsigned int ulen)
+int blk_rq_unmap_user(struct bio *bio, unsigned int ulen)
 {
 	int ret = 0;
 
@@ -2171,8 +2168,7 @@ int blk_rq_unmap_user(struct request *rq, struct bio *bio, unsigned int ulen)
 			ret = bio_uncopy_user(bio);
 	}
 
-	blk_put_request(rq);
-	return ret;
+	return 0;
 }
 
 EXPORT_SYMBOL(blk_rq_unmap_user);
@@ -2184,24 +2180,21 @@ EXPORT_SYMBOL(blk_rq_unmap_user);
  * @kbuf:	the kernel buffer
  * @len:	length of user data
  */
-struct request *blk_rq_map_kern(request_queue_t *q, int rw, void *kbuf,
+int blk_rq_map_kern(request_queue_t *q, struct request *rq, void *kbuf,
 		    unsigned int len, unsigned int gfp_mask)
 {
-	struct request *rq;
 	struct bio *bio;
 
 	if (len > (q->max_sectors << 9))
-		return ERR_PTR(-EINVAL);
-	if ((!len && kbuf) || (len && !kbuf))
-		return ERR_PTR(-EINVAL);
-
-	rq = blk_get_request(q, rw, gfp_mask);
-	if (!rq)
-		return ERR_PTR(-ENOMEM);
+		return -EINVAL;
+	if (!len || !kbuf)
+		return -EINVAL;
 
 	bio = bio_map_kern(q, kbuf, len, gfp_mask);
-	if (!IS_ERR(bio)) {
-		if (rw)
+	if (IS_ERR(bio))
+		return PTR_ERR(bio);
+
+	if (rq_data_dir(rq) == WRITE)
 		bio->bi_rw |= (1 << BIO_RW);
 
 	rq->bio = rq->biotail = bio;
@@ -2209,14 +2202,7 @@ struct request *blk_rq_map_kern(request_queue_t *q, int rw, void *kbuf,
 
 	rq->buffer = rq->data = NULL;
 	rq->data_len = len;
-		return rq;
-	}
-
-	/*
-	 * bio is the err-ptr
-	 */
-	blk_put_request(rq);
-	return (struct request *) bio;
+	return 0;
 }
 
 EXPORT_SYMBOL(blk_rq_map_kern);

drivers/block/scsi_ioctl.c

@@ -216,7 +216,7 @@ static int sg_io(struct file *file, request_queue_t *q,
 		struct gendisk *bd_disk, struct sg_io_hdr *hdr)
 {
 	unsigned long start_time;
-	int reading, writing;
+	int reading, writing, ret;
 	struct request *rq;
 	struct bio *bio;
 	char sense[SCSI_SENSE_BUFFERSIZE];
@@ -255,14 +255,17 @@ static int sg_io(struct file *file, request_queue_t *q,
 			reading = 1;
 			break;
 		}
+	}
 
-		rq = blk_rq_map_user(q, writing ? WRITE : READ, hdr->dxferp,
-				     hdr->dxfer_len);
+	rq = blk_get_request(q, writing ? WRITE : READ, GFP_KERNEL);
+	if (!rq)
+		return -ENOMEM;
 
-		if (IS_ERR(rq))
-			return PTR_ERR(rq);
-	} else
-		rq = blk_get_request(q, READ, __GFP_WAIT);
+	if (reading || writing) {
+		ret = blk_rq_map_user(q, rq, hdr->dxferp, hdr->dxfer_len);
+		if (ret)
+			goto out;
+	}
 
 	/*
 	 * fill in request structure
@@ -321,11 +324,13 @@ static int sg_io(struct file *file, request_queue_t *q,
 	}
 
 	if (blk_rq_unmap_user(rq, bio, hdr->dxfer_len))
-		return -EFAULT;
+		ret = -EFAULT;
 
 	/* may not have succeeded, but output values written to control
 	 * structure (struct sg_io_hdr).  */
-	return 0;
+out:
+	blk_put_request(rq);
+	return ret;
 }
 
 #define OMAX_SB_LEN 16          /* For backward compatibility */

drivers/cdrom/cdrom.c

@@ -2097,6 +2097,10 @@ static int cdrom_read_cdda_bpc(struct cdrom_device_info *cdi, __u8 __user *ubuf,
 	if (!q)
 		return -ENXIO;
 
+	rq = blk_get_request(q, READ, GFP_KERNEL);
+	if (!rq)
+		return -ENOMEM;
+
 	cdi->last_sense = 0;
 
 	while (nframes) {
@@ -2108,9 +2112,9 @@ static int cdrom_read_cdda_bpc(struct cdrom_device_info *cdi, __u8 __user *ubuf,
 
 		len = nr * CD_FRAMESIZE_RAW;
 
-		rq = blk_rq_map_user(q, READ, ubuf, len);
-		if (IS_ERR(rq))
-			return PTR_ERR(rq);
+		ret = blk_rq_map_user(q, rq, ubuf, len);
+		if (ret)
+			break;
 
 		memset(rq->cmd, 0, sizeof(rq->cmd));
 		rq->cmd[0] = GPCMD_READ_CD;
@@ -2138,7 +2142,7 @@ static int cdrom_read_cdda_bpc(struct cdrom_device_info *cdi, __u8 __user *ubuf,
 			cdi->last_sense = s->sense_key;
 		}
 
-		if (blk_rq_unmap_user(rq, bio, len))
+		if (blk_rq_unmap_user(bio, len))
 			ret = -EFAULT;
 
 		if (ret)
@@ -2149,6 +2153,7 @@ static int cdrom_read_cdda_bpc(struct cdrom_device_info *cdi, __u8 __user *ubuf,
 		ubuf += len;
 	}
 
+	blk_put_request(rq);
 	return ret;
 }
 

include/linux/blkdev.h

@@ -558,10 +558,9 @@ extern void blk_sync_queue(struct request_queue *q);
 extern void __blk_stop_queue(request_queue_t *q);
 extern void blk_run_queue(request_queue_t *);
 extern void blk_queue_activity_fn(request_queue_t *, activity_fn *, void *);
-extern struct request *blk_rq_map_user(request_queue_t *, int, void __user *, unsigned int);
-extern int blk_rq_unmap_user(struct request *, struct bio *, unsigned int);
-extern struct request *blk_rq_map_kern(request_queue_t *, int, void *,
-					unsigned int, unsigned int);
+extern int blk_rq_map_user(request_queue_t *, struct request *, void __user *, unsigned int);
+extern int blk_rq_unmap_user(struct bio *, unsigned int);
+extern int blk_rq_map_kern(request_queue_t *, struct request *, void *, unsigned int, unsigned int);
 extern int blk_execute_rq(request_queue_t *, struct gendisk *, struct request *);
 
 static inline request_queue_t *bdev_get_queue(struct block_device *bdev)