[PATCH for-next v7 4/5] block: add helper to map bvec iterator for passthrough

Kanchan Joshi
2022-09-09T10:32:28Z

Add blk_rq_map_user_bvec which maps the bvec iterator into a bio and
places that into the request. This helper will be used in nvme for
uring-passthrough with fixed-buffer.
While at it, create another helper bio_map_get to reduce the code
duplication.

Signed-off-by: Kanchan Joshi <joshi.k@samsung.com>
Signed-off-by: Anuj Gupta <anuj20.g@samsung.com>
---
block/blk-map.c | 87 +++++++++++++++++++++++++++++++++++++-----
include/linux/blk-mq.h | 1 +
2 files changed, 78 insertions(+), 10 deletions(-)

diff --git a/block/blk-map.c b/block/blk-map.c
index 7693f8e3c454..5dcfa112f240 100644
--- a/block/blk-map.c
+++ b/block/blk-map.c
@@ -241,17 +241,10 @@ static void bio_map_put(struct bio *bio)
}
}

-static int bio_map_user_iov(struct request *rq, struct iov_iter *iter,
+static struct bio *bio_map_get(struct request *rq, unsigned int nr_vecs,
gfp_t gfp_mask)
{
- unsigned int max_sectors = queue_max_hw_sectors(rq->q);
- unsigned int nr_vecs = iov_iter_npages(iter, BIO_MAX_VECS);
struct bio *bio;
- int ret;
- int j;
-
- if (!iov_iter_count(iter))
- return -EINVAL;

if (rq->cmd_flags & REQ_POLLED) {
blk_opf_t opf = rq->cmd_flags | REQ_ALLOC_CACHE;
@@ -259,13 +252,31 @@ static int bio_map_user_iov(struct request *rq, struct iov_iter *iter,
bio = bio_alloc_bioset(NULL, nr_vecs, opf, gfp_mask,
&fs_bio_set);
if (!bio)
- return -ENOMEM;
+ return NULL;
} else {
bio = bio_kmalloc(nr_vecs, gfp_mask);
if (!bio)
- return -ENOMEM;
+ return NULL;
bio_init(bio, NULL, bio->bi_inline_vecs, nr_vecs, req_op(rq));
}
+ return bio;
+}
+
+static int bio_map_user_iov(struct request *rq, struct iov_iter *iter,
+ gfp_t gfp_mask)
+{
+ unsigned int max_sectors = queue_max_hw_sectors(rq->q);
+ unsigned int nr_vecs = iov_iter_npages(iter, BIO_MAX_VECS);
+ struct bio *bio;
+ int ret;
+ int j;
+
+ if (!iov_iter_count(iter))
+ return -EINVAL;
+
+ bio = bio_map_get(rq, nr_vecs, gfp_mask);
+ if (bio == NULL)
+ return -ENOMEM;

while (iov_iter_count(iter)) {
struct page **pages, *stack_pages[UIO_FASTIOV];
@@ -611,6 +622,62 @@ 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 nr_iter, nr_segs, i;
+ struct bio *bio;
+ struct bio_vec *bv, *bvecs, *bvprvp = NULL;
+ struct queue_limits *lim = &q->limits;
+ unsigned int nsegs = 0, bytes = 0;
+
+ 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, 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, disallow it.
+ */
+ if (bvprvp && bvec_gap_to_prev(lim, bvprvp, bv->bv_offset))
+ goto out_err;
+
+ /* check full condition */
+ if (nsegs >= nr_segs || bytes > UINT_MAX - bv->bv_len)
+ goto out_err;
+
+ if (bytes + bv->bv_len <= nr_iter &&
+ bv->bv_offset + bv->bv_len <= PAGE_SIZE) {
+ nsegs++;
+ bytes += bv->bv_len;
+ } else
+ goto out_err;
+ bvprvp = bv;
+ }
+ return 0;
+out_err:
+ bio_map_put(bio);
+ return -EINVAL;
+}
+EXPORT_SYMBOL_GPL(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