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Message-ID: <f80e7b54-b897-4df2-a49d-bc6012640a8a@linux.dev>
Date: Sat, 2 Nov 2024 08:39:35 +0100
From: Zhu Yanjun <yanjun.zhu@...ux.dev>
To: Leon Romanovsky <leon@...nel.org>, Jens Axboe <axboe@...nel.dk>,
Jason Gunthorpe <jgg@...pe.ca>, Robin Murphy <robin.murphy@....com>,
Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
Christoph Hellwig <hch@....de>, Sagi Grimberg <sagi@...mberg.me>
Cc: Keith Busch <kbusch@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>,
Logan Gunthorpe <logang@...tatee.com>, Yishai Hadas <yishaih@...dia.com>,
Shameer Kolothum <shameerali.kolothum.thodi@...wei.com>,
Kevin Tian <kevin.tian@...el.com>,
Alex Williamson <alex.williamson@...hat.com>,
Marek Szyprowski <m.szyprowski@...sung.com>,
Jérôme Glisse <jglisse@...hat.com>,
Andrew Morton <akpm@...ux-foundation.org>, Jonathan Corbet <corbet@....net>,
linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-block@...r.kernel.org, linux-rdma@...r.kernel.org,
iommu@...ts.linux.dev, linux-nvme@...ts.infradead.org,
linux-pci@...r.kernel.org, kvm@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [RFC PATCH 2/7] block: don't merge different kinds of P2P
transfers in a single bio
在 2024/10/27 15:21, Leon Romanovsky 写道:
> From: Christoph Hellwig <hch@....de>
>
> To get out of the dma mapping helpers having to check every segment for
> it's P2P status, ensure that bios either contain P2P transfers or non-P2P
> transfers, and that a P2P bio only contains ranges from a single device.
>
> This means we do the page zone access in the bio add path where it should
> be still page hot, and will only have do the fairly expensive P2P topology
> lookup once per bio down in the dma mapping path, and only for already
> marked bios.
>
> Signed-off-by: Christoph Hellwig <hch@....de>
> Signed-off-by: Leon Romanovsky <leonro@...dia.com>
> ---
> block/bio.c | 36 +++++++++++++++++++++++++++++-------
> block/blk-map.c | 32 ++++++++++++++++++++++++--------
> include/linux/blk_types.h | 2 ++
> 3 files changed, 55 insertions(+), 15 deletions(-)
>
> diff --git a/block/bio.c b/block/bio.c
> index 2d3bc8bfb071..943a6d78cb3e 100644
> --- a/block/bio.c
> +++ b/block/bio.c
> @@ -928,8 +928,6 @@ static bool bvec_try_merge_page(struct bio_vec *bv, struct page *page,
> return false;
> if (xen_domain() && !xen_biovec_phys_mergeable(bv, page))
> return false;
> - if (!zone_device_pages_have_same_pgmap(bv->bv_page, page))
> - return false;
>
> *same_page = ((vec_end_addr & PAGE_MASK) == ((page_addr + off) &
> PAGE_MASK));
> @@ -993,6 +991,14 @@ int bio_add_hw_page(struct request_queue *q, struct bio *bio,
> if (bio->bi_vcnt > 0) {
> struct bio_vec *bv = &bio->bi_io_vec[bio->bi_vcnt - 1];
>
> + /*
> + * When doing ZONE_DEVICE-based P2P transfers, all pages in a
> + * bio must be P2P pages from the same device.
> + */
> + if ((bio->bi_opf & REQ_P2PDMA) &&
> + !zone_device_pages_have_same_pgmap(bv->bv_page, page))
> + return 0;
> +
> if (bvec_try_merge_hw_page(q, bv, page, len, offset,
> same_page)) {
> bio->bi_iter.bi_size += len;
> @@ -1009,6 +1015,9 @@ int bio_add_hw_page(struct request_queue *q, struct bio *bio,
> */
> if (bvec_gap_to_prev(&q->limits, bv, offset))
> return 0;
> + } else {
> + if (is_pci_p2pdma_page(page))
> + bio->bi_opf |= REQ_P2PDMA | REQ_NOMERGE;
> }
>
> bvec_set_page(&bio->bi_io_vec[bio->bi_vcnt], page, len, offset);
> @@ -1133,11 +1142,24 @@ static int bio_add_page_int(struct bio *bio, struct page *page,
> if (bio->bi_iter.bi_size > UINT_MAX - len)
> return 0;
>
> - if (bio->bi_vcnt > 0 &&
> - bvec_try_merge_page(&bio->bi_io_vec[bio->bi_vcnt - 1],
> - page, len, offset, same_page)) {
> - bio->bi_iter.bi_size += len;
> - return len;
> + if (bio->bi_vcnt > 0) {
> + struct bio_vec *bv = &bio->bi_io_vec[bio->bi_vcnt - 1];
> +
> + /*
> + * When doing ZONE_DEVICE-based P2P transfers, all pages in a
> + * bio must be P2P pages from the same device.
> + */
> + if ((bio->bi_opf & REQ_P2PDMA) &&
> + !zone_device_pages_have_same_pgmap(bv->bv_page, page))
> + return 0;
> +
> + if (bvec_try_merge_page(bv, page, len, offset, same_page)) {
> + bio->bi_iter.bi_size += len;
> + return len;
> + }
> + } else {
> + if (is_pci_p2pdma_page(page))
> + bio->bi_opf |= REQ_P2PDMA | REQ_NOMERGE;
> }
>
> if (bio->bi_vcnt >= bio->bi_max_vecs)
> diff --git a/block/blk-map.c b/block/blk-map.c
> index 0e1167b23934..03192b1ca6ea 100644
> --- a/block/blk-map.c
> +++ b/block/blk-map.c
> @@ -568,6 +568,7 @@ static int blk_rq_map_user_bvec(struct request *rq, const struct iov_iter *iter)
> const struct queue_limits *lim = &q->limits;
> unsigned int nsegs = 0, bytes = 0;
> struct bio *bio;
> + int error;
> size_t i;
>
> if (!nr_iter || (nr_iter >> SECTOR_SHIFT) > queue_max_hw_sectors(q))
> @@ -588,15 +589,30 @@ static int blk_rq_map_user_bvec(struct request *rq, const struct iov_iter *iter)
> for (i = 0; i < nr_segs; 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)) {
> - blk_mq_map_bio_put(bio);
> - return -EREMOTEIO;
> + error = -EREMOTEIO;
> + if (bvprvp) {
> + /*
> + * If the queue doesn't support SG gaps and adding this
> + * offset would create a gap, fallback to copy.
> + */
> + if (bvec_gap_to_prev(lim, bvprvp, bv->bv_offset))
> + goto put_bio;
> +
> + /*
> + * When doing ZONE_DEVICE-based P2P transfers, all pages
> + * in a bio must be P2P pages, and from the same device.
> + */
> + if ((bio->bi_opf & REQ_P2PDMA) &&
> + zone_device_pages_have_same_pgmap(bvprvp->bv_page,
> + bv->bv_page))
> + goto put_bio;
> + } else {
> + if (is_pci_p2pdma_page(bv->bv_page))
> + bio->bi_opf |= REQ_P2PDMA | REQ_NOMERGE;
> }
> +
> /* check full condition */
> + error = -EINVAL;
> if (nsegs >= nr_segs || bytes > UINT_MAX - bv->bv_len)
> goto put_bio;
> if (bytes + bv->bv_len > nr_iter)
> @@ -611,7 +627,7 @@ static int blk_rq_map_user_bvec(struct request *rq, const struct iov_iter *iter)
> return 0;
> put_bio:
> blk_mq_map_bio_put(bio);
> - return -EINVAL;
> + return error;
> }
>
> /**
> diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
> index dce7615c35e7..94cf146e8ce6 100644
> --- a/include/linux/blk_types.h
> +++ b/include/linux/blk_types.h
> @@ -378,6 +378,7 @@ enum req_flag_bits {
> __REQ_DRV, /* for driver use */
> __REQ_FS_PRIVATE, /* for file system (submitter) use */
> __REQ_ATOMIC, /* for atomic write operations */
> + __REQ_P2PDMA, /* contains P2P DMA pages */
> /*
> * Command specific flags, keep last:
> */
> @@ -410,6 +411,7 @@ enum req_flag_bits {
> #define REQ_DRV (__force blk_opf_t)(1ULL << __REQ_DRV)
> #define REQ_FS_PRIVATE (__force blk_opf_t)(1ULL << __REQ_FS_PRIVATE)
> #define REQ_ATOMIC (__force blk_opf_t)(1ULL << __REQ_ATOMIC)
> +#define REQ_P2PDMA (__force blk_opf_t)(1ULL << __REQ_P2PDMA)
#define REQ_P2PDMA (__force blk_opf_t)BIT_ULL(__REQ_P2PDMA)
Use BIT_ULL instead of direct left shit.
Zhu Yanjun
>
> #define REQ_NOUNMAP (__force blk_opf_t)(1ULL << __REQ_NOUNMAP)
>
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