[PATCH] Add blk_rq_map_kern()

Add blk_rq_map_kern which takes a kernel buffer and maps it into
a request and bio. This can be used by the dm hw_handlers, old
sg_scsi_ioctl, and one day scsi special requests so all requests
comming into scsi will have bios. All requests having bios
should allow scsi to use scatter lists for all IO and allow it
to use block layer functions.

Signed-off-by: Jens Axboe <axboe@suse.de>

1 files changed, 56 insertions, 0 deletions

diff --git a/drivers/block/ll_rw_blk.c b/drivers/block/ll_rw_blk.c
index f20eba22b14b..e30a3c93b70c 100644
--- a/drivers/block/ll_rw_blk.c
+++ b/drivers/block/ll_rw_blk.c
@@ -281,6 +281,7 @@ static inline void rq_init(request_queue_t *q, struct request *rq)
         rq->special = NULL;
         rq->data_len = 0;
         rq->data = NULL;
+        rq->nr_phys_segments = 0;
         rq->sense = NULL;
         rq->end_io = NULL;
         rq->end_io_data = NULL;
@@ -2176,6 +2177,61 @@ int blk_rq_unmap_user(struct request *rq, struct bio *bio, unsigned int ulen)
 
 EXPORT_SYMBOL(blk_rq_unmap_user);
 
+static int blk_rq_map_kern_endio(struct bio *bio, unsigned int bytes_done,
+                                 int error)
+{
+        if (bio->bi_size)
+                return 1;
+
+        bio_put(bio);
+        return 0;
+}
+
+/**
+ * blk_rq_map_kern - map kernel data to a request, for REQ_BLOCK_PC usage
+ * @q:          request queue where request should be inserted
+ * @rw:         READ or WRITE data
+ * @kbuf:       the kernel buffer
+ * @len:        length of user data
+ */
+struct request *blk_rq_map_kern(request_queue_t *q, int rw, 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);
+
+        bio = bio_map_kern(q, kbuf, len, gfp_mask);
+        if (!IS_ERR(bio)) {
+                if (rw)
+                        bio->bi_rw |= (1 << BIO_RW);
+                bio->bi_end_io = blk_rq_map_kern_endio;
+
+                rq->bio = rq->biotail = bio;
+                blk_rq_bio_prep(q, rq, bio);
+
+                rq->buffer = rq->data = NULL;
+                rq->data_len = len;
+                return rq;
+        }
+
+        /*
+         * bio is the err-ptr
+         */
+        blk_put_request(rq);
+        return (struct request *) bio;
+}
+
+EXPORT_SYMBOL(blk_rq_map_kern);
+
 /**
  * blk_execute_rq - insert a request into queue for execution
  * @q:          queue to insert the request in