block: introduce struct rq_map_data to use reserved pages

This patch introduces struct rq_map_data to enable bio_copy_use_iov()
use reserved pages.

Currently, bio_copy_user_iov allocates bounce pages but
drivers/scsi/sg.c wants to allocate pages by itself and use
them. struct rq_map_data can be used to pass allocated pages to
bio_copy_user_iov.

The current users of bio_copy_user_iov simply passes NULL (they don't
want to use pre-allocated pages).

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: Jens Axboe <jens.axboe@oracle.com>
Cc: Douglas Gilbert <dougg@torque.net>
Cc: Mike Christie <michaelc@cs.wisc.edu>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

3 files changed, 22 insertions, 15 deletions

diff --git a/block/blk-map.c b/block/blk-map.c
index ac21b7397e15..dad6a2907835 100644
--- a/block/blk-map.c
+++ b/block/blk-map.c
@@ -41,8 +41,8 @@ static int __blk_rq_unmap_user(struct bio *bio)
 }
 
 static int __blk_rq_map_user(struct request_queue *q, struct request *rq,
-			     void __user *ubuf, unsigned int len,
-			     gfp_t gfp_mask)
+			     struct rq_map_data *map_data, void __user *ubuf,
+			     unsigned int len, gfp_t gfp_mask)
 {
 	unsigned long uaddr;
 	unsigned int alignment;
@@ -57,10 +57,10 @@ static int __blk_rq_map_user(struct request_queue *q, struct request *rq,
 	 */
 	uaddr = (unsigned long) ubuf;
 	alignment = queue_dma_alignment(q) | q->dma_pad_mask;
-	if (!(uaddr & alignment) && !(len & alignment))
+	if (!(uaddr & alignment) && !(len & alignment) && !map_data)
 		bio = bio_map_user(q, NULL, uaddr, len, reading, gfp_mask);
 	else
-		bio = bio_copy_user(q, uaddr, len, reading, gfp_mask);
+		bio = bio_copy_user(q, map_data, uaddr, len, reading, gfp_mask);
 
 	if (IS_ERR(bio))
 		return PTR_ERR(bio);
@@ -89,6 +89,7 @@ static int __blk_rq_map_user(struct request_queue *q, struct request *rq,
  * blk_rq_map_user - map user data to a request, for REQ_TYPE_BLOCK_PC usage
  * @q:		request queue where request should be inserted
  * @rq:		request structure to fill
+ * @map_data:   pointer to the rq_map_data holding pages (if necessary)
  * @ubuf:	the user buffer
  * @len:	length of user data
  * @gfp_mask:	memory allocation flags
@@ -107,7 +108,8 @@ static int __blk_rq_map_user(struct request_queue *q, struct request *rq,
  *    unmapping.
  */
 int blk_rq_map_user(struct request_queue *q, struct request *rq,
-		    void __user *ubuf, unsigned long len, gfp_t gfp_mask)
+		    struct rq_map_data *map_data, void __user *ubuf,
+		    unsigned long len, gfp_t gfp_mask)
 {
 	unsigned long bytes_read = 0;
 	struct bio *bio = NULL;
@@ -134,7 +136,8 @@ int blk_rq_map_user(struct request_queue *q, struct request *rq,
 		if (end - start > BIO_MAX_PAGES)
 			map_len -= PAGE_SIZE;
 
-		ret = __blk_rq_map_user(q, rq, ubuf, map_len, gfp_mask);
+		ret = __blk_rq_map_user(q, rq, map_data, ubuf, map_len,
+					gfp_mask);
 		if (ret < 0)
 			goto unmap_rq;
 		if (!bio)
@@ -159,6 +162,7 @@ EXPORT_SYMBOL(blk_rq_map_user);
  * blk_rq_map_user_iov - map user data to a request, for REQ_TYPE_BLOCK_PC usage
  * @q:		request queue where request should be inserted
  * @rq:		request to map data to
+ * @map_data:   pointer to the rq_map_data holding pages (if necessary)
  * @iov:	pointer to the iovec
  * @iov_count:	number of elements in the iovec
  * @len:	I/O byte count
@@ -178,8 +182,8 @@ EXPORT_SYMBOL(blk_rq_map_user);
  *    unmapping.
  */
 int blk_rq_map_user_iov(struct request_queue *q, struct request *rq,
-			struct sg_iovec *iov, int iov_count, unsigned int len,
-			gfp_t gfp_mask)
+			struct rq_map_data *map_data, struct sg_iovec *iov,
+			int iov_count, unsigned int len, gfp_t gfp_mask)
 {
 	struct bio *bio;
 	int i, read = rq_data_dir(rq) == READ;
@@ -197,8 +201,9 @@ int blk_rq_map_user_iov(struct request_queue *q, struct request *rq,
 		}
 	}
 
-	if (unaligned || (q->dma_pad_mask & len))
-		bio = bio_copy_user_iov(q, iov, iov_count, read, gfp_mask);
+	if (unaligned || (q->dma_pad_mask & len) || map_data)
+		bio = bio_copy_user_iov(q, map_data, iov, iov_count, read,
+					gfp_mask);
 	else
 		bio = bio_map_user_iov(q, NULL, iov, iov_count, read, gfp_mask);
 
@@ -220,6 +225,7 @@ int blk_rq_map_user_iov(struct request_queue *q, struct request *rq,
 	rq->buffer = rq->data = NULL;
 	return 0;
 }
+EXPORT_SYMBOL(blk_rq_map_user_iov);
 
 /**
  * blk_rq_unmap_user - unmap a request with user data
diff --git a/block/bsg.c b/block/bsg.c
index e7a142e9916c..56cb343c76d8 100644
--- a/block/bsg.c
+++ b/block/bsg.c
@@ -283,8 +283,8 @@ bsg_map_hdr(struct bsg_device *bd, struct sg_io_v4 *hdr, int has_write_perm)
 		next_rq->cmd_type = rq->cmd_type;
 
 		dxferp = (void*)(unsigned long)hdr->din_xferp;
-		ret =  blk_rq_map_user(q, next_rq, dxferp, hdr->din_xfer_len,
-				       GFP_KERNEL);
+		ret =  blk_rq_map_user(q, next_rq, NULL, dxferp,
+				       hdr->din_xfer_len, GFP_KERNEL);
 		if (ret)
 			goto out;
 	}
@@ -299,7 +299,8 @@ bsg_map_hdr(struct bsg_device *bd, struct sg_io_v4 *hdr, int has_write_perm)
 		dxfer_len = 0;
 
 	if (dxfer_len) {
-		ret = blk_rq_map_user(q, rq, dxferp, dxfer_len, GFP_KERNEL);
+		ret = blk_rq_map_user(q, rq, NULL, dxferp, dxfer_len,
+				      GFP_KERNEL);
 		if (ret)
 			goto out;
 	}
diff --git a/block/scsi_ioctl.c b/block/scsi_ioctl.c
index f49d6a11a69e..c34272a348fe 100644
--- a/block/scsi_ioctl.c
+++ b/block/scsi_ioctl.c
@@ -314,11 +314,11 @@ static int sg_io(struct file *file, struct request_queue *q,
 			goto out;
 		}
 
-		ret = blk_rq_map_user_iov(q, rq, iov, hdr->iovec_count,
+		ret = blk_rq_map_user_iov(q, rq, NULL, iov, hdr->iovec_count,
 					  hdr->dxfer_len, GFP_KERNEL);
 		kfree(iov);
 	} else if (hdr->dxfer_len)
-		ret = blk_rq_map_user(q, rq, hdr->dxferp, hdr->dxfer_len,
+		ret = blk_rq_map_user(q, rq, NULL, hdr->dxferp, hdr->dxfer_len,
 				      GFP_KERNEL);
 
 	if (ret)