diff mbox series

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

Message ID 20220927173610.7794-7-joshi.k@samsung.com (mailing list archive)
State New, archived
Headers show
Series [for-next,v10,1/7] io_uring: add io_uring_cmd_import_fixed | expand

Commit Message

Kanchan Joshi Sept. 27, 2022, 5:36 p.m. UTC
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(+)

Comments

Christoph Hellwig Sept. 28, 2022, 5:40 p.m. UTC | #1
On Tue, Sep 27, 2022 at 11:06:09PM +0530, Kanchan Joshi wrote:
> 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.

Can we avoid duplicating some of the checks?  Something like the below
incremental patch.  Note that this now also allows the copy path for
all kinds of iov_iters, but as the copy from/to iter code is safe
and the sanity check was just or the map path that should be fine.
It's best split into a prep patch, though.

---
diff --git a/block/blk-map.c b/block/blk-map.c
index a1aa8dacb02bc..c51de30767403 100644
--- a/block/blk-map.c
+++ b/block/blk-map.c
@@ -549,26 +549,16 @@ 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)
+static int blk_rq_map_user_bvec(struct request *rq, const struct iov_iter *iter)
 {
 	struct request_queue *q = rq->q;
-	size_t nr_iter, nr_segs, i;
-	struct bio *bio = NULL;
-	struct bio_vec *bv, *bvecs, *bvprvp = NULL;
+	size_t nr_iter = iov_iter_count(iter);
+	size_t nr_segs = iter->nr_segs;
+	struct bio_vec *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;
+	struct bio *bio;
+	size_t i;
 
 	if (!nr_iter || (nr_iter >> SECTOR_SHIFT) > queue_max_hw_sectors(q))
 		return -EINVAL;
@@ -586,14 +576,15 @@ static int blk_rq_map_user_bvec(struct request *rq, const struct iov_iter *iter,
 	/* loop to perform a bunch of sanity checks */
 	bvecs = (struct bio_vec *)iter->bvec;
 	for (i = 0; i < nr_segs; i++) {
-		bv = &bvecs[i];
+		struct bio_vec *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;
+			return -EREMOTEIO;
 		}
 		/* check full condition */
 		if (nsegs >= nr_segs || bytes > UINT_MAX - bv->bv_len)
@@ -611,9 +602,6 @@ static int blk_rq_map_user_bvec(struct request *rq, const struct iov_iter *iter,
 put_bio:
 	bio_map_put(bio);
 	return -EINVAL;
-out_copy:
-	*copy = true;
-	return 0;
 }
 
 /**
@@ -635,33 +623,35 @@ int blk_rq_map_user_iov(struct request_queue *q, struct request *rq,
 			struct rq_map_data *map_data,
 			const struct iov_iter *iter, gfp_t gfp_mask)
 {
-	bool copy = false;
+	bool copy = false, map_bvec = false;
 	unsigned long align = q->dma_pad_mask | queue_dma_alignment(q);
 	struct bio *bio = NULL;
 	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;
-
 	if (map_data)
 		copy = true;
 	else if (blk_queue_may_bounce(q))
 		copy = true;
 	else if (iov_iter_alignment(iter) & align)
 		copy = true;
+	else if (iov_iter_is_bvec(iter))
+		map_bvec = true;
+	else if (!iter_is_iovec(iter))
+		copy = true;
 	else if (queue_virt_boundary(q))
 		copy = queue_virt_boundary(q) & iov_iter_gap_alignment(iter);
 
-do_copy:
+	if (map_bvec) {
+		ret = blk_rq_map_user_bvec(rq, iter);
+		if (!ret)
+			return 0;
+		if (ret != -EREMOTEIO)
+			goto fail;
+		/* fall back to copying the data on limits mismatches */
+		copy = true;
+	}
+
 	i = *iter;
 	do {
 		if (copy)
Anuj Gupta Sept. 29, 2022, 11:33 a.m. UTC | #2
On Wed, Sep 28, 2022 at 07:40:39PM +0200, Christoph Hellwig wrote:
> On Tue, Sep 27, 2022 at 11:06:09PM +0530, Kanchan Joshi wrote:
> > 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.
> 
> Can we avoid duplicating some of the checks?  Something like the below
> incremental patch.  Note that this now also allows the copy path for
> all kinds of iov_iters, but as the copy from/to iter code is safe
> and the sanity check was just or the map path that should be fine.
> It's best split into a prep patch, though.

Right, this one looks way better. Will fold this in a separate prep patch.

> 
> ---
> diff --git a/block/blk-map.c b/block/blk-map.c
> index a1aa8dacb02bc..c51de30767403 100644
> --- a/block/blk-map.c
> +++ b/block/blk-map.c
> @@ -549,26 +549,16 @@ 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)
> +static int blk_rq_map_user_bvec(struct request *rq, const struct iov_iter *iter)
>  {
>  	struct request_queue *q = rq->q;
> -	size_t nr_iter, nr_segs, i;
> -	struct bio *bio = NULL;
> -	struct bio_vec *bv, *bvecs, *bvprvp = NULL;
> +	size_t nr_iter = iov_iter_count(iter);
> +	size_t nr_segs = iter->nr_segs;
> +	struct bio_vec *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;
> +	struct bio *bio;
> +	size_t i;
>  
>  	if (!nr_iter || (nr_iter >> SECTOR_SHIFT) > queue_max_hw_sectors(q))
>  		return -EINVAL;
> @@ -586,14 +576,15 @@ static int blk_rq_map_user_bvec(struct request *rq, const struct iov_iter *iter,
>  	/* loop to perform a bunch of sanity checks */
>  	bvecs = (struct bio_vec *)iter->bvec;
>  	for (i = 0; i < nr_segs; i++) {
> -		bv = &bvecs[i];
> +		struct bio_vec *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;
> +			return -EREMOTEIO;
>  		}
>  		/* check full condition */
>  		if (nsegs >= nr_segs || bytes > UINT_MAX - bv->bv_len)
> @@ -611,9 +602,6 @@ static int blk_rq_map_user_bvec(struct request *rq, const struct iov_iter *iter,
>  put_bio:
>  	bio_map_put(bio);
>  	return -EINVAL;
> -out_copy:
> -	*copy = true;
> -	return 0;
>  }
>  
>  /**
> @@ -635,33 +623,35 @@ int blk_rq_map_user_iov(struct request_queue *q, struct request *rq,
>  			struct rq_map_data *map_data,
>  			const struct iov_iter *iter, gfp_t gfp_mask)
>  {
> -	bool copy = false;
> +	bool copy = false, map_bvec = false;
>  	unsigned long align = q->dma_pad_mask | queue_dma_alignment(q);
>  	struct bio *bio = NULL;
>  	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;
> -
>  	if (map_data)
>  		copy = true;
>  	else if (blk_queue_may_bounce(q))
>  		copy = true;
>  	else if (iov_iter_alignment(iter) & align)
>  		copy = true;
> +	else if (iov_iter_is_bvec(iter))
> +		map_bvec = true;
> +	else if (!iter_is_iovec(iter))
> +		copy = true;
>  	else if (queue_virt_boundary(q))
>  		copy = queue_virt_boundary(q) & iov_iter_gap_alignment(iter);
>  
> -do_copy:
> +	if (map_bvec) {
> +		ret = blk_rq_map_user_bvec(rq, iter);
> +		if (!ret)
> +			return 0;
> +		if (ret != -EREMOTEIO)
> +			goto fail;
> +		/* fall back to copying the data on limits mismatches */
> +		copy = true;
> +	}
> +
>  	i = *iter;
>  	do {
>  		if (copy)
> 

--
Anuj Gupta
diff mbox series

Patch

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)