[PATCH for-next v10 6/7] block: extend functionality to map bvec iterator

Kanchan Joshi
2022-09-27T17:47:25Z

Extend blk_rq_map_user_iov so that it can handle bvec iterator.
It maps the pages from bvec iterator into a bio and place the bio into
request.

This helper will be used by nvme for uring-passthrough path when IO is
done using pre-mapped buffers.

Signed-off-by: Kanchan Joshi <joshi.k@samsung.com>
Signed-off-by: Anuj Gupta <anuj20.g@samsung.com>
---
block/blk-map.c | 77 +++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 77 insertions(+)

diff --git a/block/blk-map.c b/block/blk-map.c
index a7838879e28e..a1aa8dacb02b 100644
--- a/block/blk-map.c
+++ b/block/blk-map.c
@@ -548,6 +548,74 @@ int blk_rq_append_bio(struct request *rq, struct bio *bio)
}
EXPORT_SYMBOL(blk_rq_append_bio);

+/* Prepare bio for passthrough IO given ITER_BVEC iter */
+static int blk_rq_map_user_bvec(struct request *rq, const struct iov_iter *iter,
+ bool *copy)
+{
+ struct request_queue *q = rq->q;
+ size_t nr_iter, nr_segs, i;
+ struct bio *bio = NULL;
+ struct bio_vec *bv, *bvecs, *bvprvp = NULL;
+ struct queue_limits *lim = &q->limits;
+ unsigned int nsegs = 0, bytes = 0;
+ unsigned long align = q->dma_pad_mask | queue_dma_alignment(q);
+
+ /* see if we need to copy pages due to any weird situation */
+ if (blk_queue_may_bounce(q))
+ goto out_copy;
+ else if (iov_iter_alignment(iter) & align)
+ goto out_copy;
+ /* virt-alignment gap is checked anyway down, so avoid extra loop here */
+
+ nr_iter = iov_iter_count(iter);
+ nr_segs = iter->nr_segs;
+
+ if (!nr_iter || (nr_iter >> SECTOR_SHIFT) > queue_max_hw_sectors(q))
+ return -EINVAL;
+ if (nr_segs > queue_max_segments(q))
+ return -EINVAL;
+
+ /* no iovecs to alloc, as we already have a BVEC iterator */
+ bio = bio_map_get(rq, 0, GFP_KERNEL);
+ if (bio == NULL)
+ return -ENOMEM;
+
+ bio_iov_bvec_set(bio, (struct iov_iter *)iter);
+ blk_rq_bio_prep(rq, bio, nr_segs);
+
+ /* loop to perform a bunch of sanity checks */
+ bvecs = (struct bio_vec *)iter->bvec;
+ for (i = 0; i < nr_segs; i++) {
+ bv = &bvecs[i];
+ /*
+ * If the queue doesn't support SG gaps and adding this
+ * offset would create a gap, fallback to copy.
+ */
+ if (bvprvp && bvec_gap_to_prev(lim, bvprvp, bv->bv_offset)) {
+ bio_map_put(bio);
+ goto out_copy;
+ }
+ /* check full condition */
+ if (nsegs >= nr_segs || bytes > UINT_MAX - bv->bv_len)
+ goto put_bio;
+ if (bytes + bv->bv_len > nr_iter)
+ goto put_bio;
+ if (bv->bv_offset + bv->bv_len > PAGE_SIZE)
+ goto put_bio;
+
+ nsegs++;
+ bytes += bv->bv_len;
+ bvprvp = bv;
+ }
+ return 0;
+put_bio:
+ bio_map_put(bio);
+ return -EINVAL;
+out_copy:
+ *copy = true;
+ return 0;
+}
+
/**
* blk_rq_map_user_iov - map user data to a request, for passthrough requests
* @q: request queue where request should be inserted
@@ -573,6 +641,14 @@ int blk_rq_map_user_iov(struct request_queue *q, struct request *rq,
struct iov_iter i;
int ret = -EINVAL;

+ if (iov_iter_is_bvec(iter)) {
+ ret = blk_rq_map_user_bvec(rq, iter, &copy);
+ if (ret != 0)
+ goto fail;
+ if (copy)
+ goto do_copy;
+ return ret;
+ }
if (!iter_is_iovec(iter))
goto fail;

@@ -585,6 +661,7 @@ int blk_rq_map_user_iov(struct request_queue *q, struct request *rq,
else if (queue_virt_boundary(q))
copy = queue_virt_boundary(q) & iov_iter_gap_alignment(iter);

+do_copy:
i = *iter;
do {
if (copy)
--
2.25.1