[PATCH for-next v3 3/4] block: add helper to map bvec iterator for passthrough

Kanchan Joshi
2022-09-02T15:27:52Z

Add blk_rq_map_user_bvec which maps the bvec iterator into a bio and
places that into the request.
This helper is to be used in nvme for uring-passthrough with
fixed-buffer.

Signed-off-by: Kanchan Joshi <joshi.k@samsung.com>
Signed-off-by: Anuj Gupta <anuj20.g@samsung.com>
---
block/blk-map.c | 71 ++++++++++++++++++++++++++++++++++++++++++
include/linux/blk-mq.h | 1 +
2 files changed, 72 insertions(+)

diff --git a/block/blk-map.c b/block/blk-map.c
index f3768876d618..0f7dc568e34b 100644
--- a/block/blk-map.c
+++ b/block/blk-map.c
@@ -612,6 +612,77 @@ int blk_rq_map_user(struct request_queue *q, struct request *rq,
}
EXPORT_SYMBOL(blk_rq_map_user);

+/* Prepare bio for passthrough IO given an existing bvec iter */
+int blk_rq_map_user_bvec(struct request *rq, struct iov_iter *iter)
+{
+ struct request_queue *q = rq->q;
+ size_t iter_count, nr_segs;
+ struct bio *bio;
+ struct bio_vec *bv, *bvec_arr, *bvprvp = NULL;
+ struct queue_limits *lim = &q->limits;
+ unsigned int nsegs = 0, bytes = 0;
+ int ret, i;
+
+ iter_count = iov_iter_count(iter);
+ nr_segs = iter->nr_segs;
+
+ if (!iter_count || (iter_count >> 9) > queue_max_hw_sectors(q))
+ return -EINVAL;
+ if (nr_segs > queue_max_segments(q))
+ return -EINVAL;
+ if (rq->cmd_flags & REQ_POLLED) {
+ blk_opf_t opf = rq->cmd_flags | REQ_ALLOC_CACHE;
+
+ /* no iovecs to alloc, as we already have a BVEC iterator */
+ bio = bio_alloc_bioset(NULL, 0, opf, GFP_KERNEL,
+ &fs_bio_set);
+ if (!bio)
+ return -ENOMEM;
+ } else {
+ bio = bio_kmalloc(0, GFP_KERNEL);
+ if (!bio)
+ return -ENOMEM;
+ bio_init(bio, NULL, bio->bi_inline_vecs, 0, req_op(rq));
+ }
+ bio_iov_bvec_set(bio, iter);
+ blk_rq_bio_prep(rq, bio, nr_segs);
+
+ /* loop to perform a bunch of sanity checks */
+ bvec_arr = (struct bio_vec *)iter->bvec;
+ for (i = 0; i < nr_segs; i++) {
+ bv = &bvec_arr[i];
+ /*
+ * If the queue doesn't support SG gaps and adding this
+ * offset would create a gap, disallow it.
+ */
+ if (bvprvp && bvec_gap_to_prev(lim, bvprvp, bv->bv_offset)) {
+ ret = -EINVAL;
+ goto out_free;
+ }
+
+ /* check full condition */
+ if (nsegs >= nr_segs || bytes > UINT_MAX - bv->bv_len) {
+ ret = -EINVAL;
+ goto out_free;
+ }
+
+ if (bytes + bv->bv_len <= iter_count &&
+ bv->bv_offset + bv->bv_len <= PAGE_SIZE) {
+ nsegs++;
+ bytes += bv->bv_len;
+ } else {
+ ret = -EINVAL;
+ goto out_free;
+ }
+ bvprvp = bv;
+ }
+ return 0;
+out_free:
+ bio_map_put(bio);
+ return ret;
+}
+EXPORT_SYMBOL(blk_rq_map_user_bvec);
+
/**
* blk_rq_unmap_user - unmap a request with user data
* @bio: start of bio list
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index b43c81d91892..83bef362f0f9 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -970,6 +970,7 @@ struct rq_map_data {
bool from_user;
};

+int blk_rq_map_user_bvec(struct request *rq, struct iov_iter *iter);
int blk_rq_map_user(struct request_queue *, struct request *,
struct rq_map_data *, void __user *, unsigned long, gfp_t);
int blk_rq_map_user_iov(struct request_queue *, struct request *,
--
2.25.1