Commit 38446014 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Jens Axboe
Browse files

block: don't merge different kinds of P2P transfers in a single bio 



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: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarKeith Busch <kbusch@kernel.org>
Reviewed-by: default avatarLogan Gunthorpe <logang@deltatee.com>
Reviewed-by: default avatarLeon Romanovsky <leonro@nvidia.com>
Link: https://lore.kernel.org/r/20250625113531.522027-2-hch@lst.de


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 409f9287

block/bio-integrity.c

+3 −0
Original line number Diff line number Diff line
@@ -128,6 +128,9 @@ int bio_integrity_add_page(struct bio *bio, struct page *page, 
	if (bip->bip_vcnt > 0) {

		struct bio_vec *bv = &bip->bip_vec[bip->bip_vcnt - 1];



		if (!zone_device_pages_have_same_pgmap(bv->bv_page, page))

			return 0;



		if (bvec_try_merge_hw_page(q, bv, page, len, offset)) {

			bip->bip_iter.bi_size += len;

			return len;

block/bio.c

+13 −7
Original line number Diff line number Diff line
@@ -930,8 +930,6 @@ 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;



	if ((vec_end_addr & PAGE_MASK) != ((page_addr + off) & PAGE_MASK)) {

		if (IS_ENABLED(CONFIG_KMSAN))
@@ -982,6 +980,9 @@ void __bio_add_page(struct bio *bio, struct page *page, 
	WARN_ON_ONCE(bio_flagged(bio, BIO_CLONED));

	WARN_ON_ONCE(bio_full(bio, len));



	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, off);

	bio->bi_iter.bi_size += len;

	bio->bi_vcnt++;
@@ -1022,12 +1023,17 @@ int bio_add_page(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)) {

	if (bio->bi_vcnt > 0) {

		struct bio_vec *bv = &bio->bi_io_vec[bio->bi_vcnt - 1];



		if (!zone_device_pages_have_same_pgmap(bv->bv_page, page))

			return 0;



		if (bvec_try_merge_page(bv, page, len, offset)) {

			bio->bi_iter.bi_size += len;

			return len;

		}

	}



	if (bio->bi_vcnt >= bio->bi_max_vecs)

		return 0;

include/linux/blk_types.h

+2 −0
Original line number Diff line number Diff line
@@ -386,6 +386,7 @@ 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:

	 */
@@ -418,6 +419,7 @@ 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_NOUNMAP	(__force blk_opf_t)(1ULL << __REQ_NOUNMAP)