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

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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@lst.de>
Reviewed-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
Reviewed-by: Leon Romanovsky <leonro@nvidia.com>
Link: https://lore.kernel.org/r/20250625113531.522027-2-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Christoph Hellwig 2025-06-25 13:34:58 +02:00 • committed by Jens Axboe
parent 409f9287da
commit 3844601464
3 changed files with 18 additions and 7 deletions
Download patch file Download diff file Expand all files Collapse all files

3
block/bio-integrity.c
View file

@ -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;

20
block/bio.c
View file

@ -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++;
@ -1022,11 +1023,16 @@ 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)) {
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];
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)

2
include/linux/blk_types.h
View file

@ -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)