On 9/5/22 23:27, Kanchan Joshi wrote:
> 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@xxxxxxxxxxx>
> Signed-off-by: Anuj Gupta <anuj20.g@xxxxxxxxxxx>
> ---
> block/blk-map.c | 94 +++++++++++++++++++++++++++++++++++++-----
> include/linux/blk-mq.h | 1 +
> 2 files changed, 85 insertions(+), 10 deletions(-)
>
> diff --git a/block/blk-map.c b/block/blk-map.c
> index f3768876d618..e2f268167342 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];
> @@ -612,6 +623,69 @@ 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;
> +
consider this (untested), it also sets the variable i data type same
as it comparison variable in nr_segs the loop i.e. size_t :-
+ struct bio_vec *bv, *bvec_arr, *bvprvp = NULL;
+ struct request_queue *q = rq->q;
+ struct queue_limits *lim = &q->limits;
+ unsigned int nsegs = 0, bytes = 0;
+ size_t iter_count, nr_segs, i;
+ struct bio *bio;
+ int ret;
> + iter_count = iov_iter_count(iter);
> + nr_segs = iter->nr_segs;
> +
> + if (!iter_count || (iter_count >> 9) > queue_max_hw_sectors(q))
> + return -EINVAL;
can we remove braces for iter_count >> 9 without impacting the intended
functionality?
> + 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 */
> + bvec_arr = (struct bio_vec *)iter->bvec;
> + for (i = 0; i < nr_segs; i++) {
> + bv = &bvec_arr[i];
I'd just call bvecs instead of bvec_arr, just personal preference.
> + /*
> + * 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;
you are only calling goto out_free; from loop with ret = -EINVAL.
you can remove redundant ret = -EINVAL assignment in the loop and
call return -EINVAL from the out_free: label instead return ret.
That will also allow us to remove braces in the loop.
This will also allow us to remove the ret variable on the
since I guess we are in the fast path.
> + }
> + bvprvp = bv;
> + }
> + return 0;
> +out_free:
> + bio_map_put(bio);
> + return ret;
> +}
> +EXPORT_SYMBOL(blk_rq_map_user_bvec);
why not use EXPORT_SYMBOL_GPL() for new addition?
I'm aware that blk-map.c only uses EXPORT_SYMBOL().
> +
> /**
> * 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 *,
