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block: remove the same_page output argument to bvec_try_merge_page

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bvec_try_merge_page currently returns if the added page fragment is
within the same page as the last page in the last current bio_vec.

This information is used by __bio_iov_iter_get_pages so that we always
have a single folio pin per page even when the page is split over
multiple __bio_iov_iter_get_pages calls.

Threading this through the entire lowlevel add page to bio logic is
annoying and inefficient and leads to less code sharing than otherwise
possible.  Instead add code to __bio_iov_iter_get_pages that checks if
the bio_vecs did not change and thus a merge into the last segment must
have happened, and if there is an offset into the page for the currently
added fragment, because if yes we must have already had a previous
fragment of the same page in the last bio_vec.  While this is still a bit
ugly, it keeps the logic in the one place that needs it and allows for
more code sharing.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20250512042354.514329-1-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Christoph Hellwig 2025-05-12 06:23:54 +02:00 committed by Jens Axboe
parent d1ba22ab2b
commit 77fd359b6d
3 changed files with 25 additions and 37 deletions
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4
block/bio-integrity.c
View File

@ -127,10 +127,8 @@ 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];
bool same_page = false;
if (bvec_try_merge_hw_page(q, bv, page, len, offset,
&same_page)) {
if (bvec_try_merge_hw_page(q, bv, page, len, offset)) {
bip->bip_iter.bi_size += len;
return len;
}

55
block/bio.c
View File

@ -920,7 +920,7 @@ static inline bool bio_full(struct bio *bio, unsigned len)
}
static bool bvec_try_merge_page(struct bio_vec *bv, struct page *page,
unsigned int len, unsigned int off, bool *same_page)
unsigned int len, unsigned int off)
{
size_t bv_end = bv->bv_offset + bv->bv_len;
phys_addr_t vec_end_addr = page_to_phys(bv->bv_page) + bv_end - 1;
@ -933,9 +933,7 @@ static bool bvec_try_merge_page(struct bio_vec *bv, struct page *page,
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));
if (!*same_page) {
if ((vec_end_addr & PAGE_MASK) != ((page_addr + off) & PAGE_MASK)) {
if (IS_ENABLED(CONFIG_KMSAN))
return false;
if (bv->bv_page + bv_end / PAGE_SIZE != page + off / PAGE_SIZE)
@ -955,8 +953,7 @@ static bool bvec_try_merge_page(struct bio_vec *bv, struct page *page,
* helpers to split. Hopefully this will go away soon.
*/
bool bvec_try_merge_hw_page(struct request_queue *q, struct bio_vec *bv,
struct page *page, unsigned len, unsigned offset,
bool *same_page)
struct page *page, unsigned len, unsigned offset)
{
unsigned long mask = queue_segment_boundary(q);
phys_addr_t addr1 = bvec_phys(bv);
@ -966,7 +963,7 @@ bool bvec_try_merge_hw_page(struct request_queue *q, struct bio_vec *bv,
return false;
if (len > queue_max_segment_size(q) - bv->bv_len)
return false;
return bvec_try_merge_page(bv, page, len, offset, same_page);
return bvec_try_merge_page(bv, page, len, offset);
}
/**
@ -1020,8 +1017,6 @@ EXPORT_SYMBOL_GPL(bio_add_virt_nofail);
int bio_add_page(struct bio *bio, struct page *page,
unsigned int len, unsigned int offset)
{
bool same_page = false;
if (WARN_ON_ONCE(bio_flagged(bio, BIO_CLONED)))
return 0;
if (bio->bi_iter.bi_size > UINT_MAX - len)
@ -1029,7 +1024,7 @@ int bio_add_page(struct bio *bio, struct page *page,
if (bio->bi_vcnt > 0 &&
bvec_try_merge_page(&bio->bi_io_vec[bio->bi_vcnt - 1],
page, len, offset, &same_page)) {
page, len, offset)) {
bio->bi_iter.bi_size += len;
return len;
}
@ -1161,27 +1156,6 @@ void bio_iov_bvec_set(struct bio *bio, const struct iov_iter *iter)
bio_set_flag(bio, BIO_CLONED);
}
static int bio_iov_add_folio(struct bio *bio, struct folio *folio, size_t len,
size_t offset)
{
bool same_page = false;
if (WARN_ON_ONCE(bio->bi_iter.bi_size > UINT_MAX - len))
return -EIO;
if (bio->bi_vcnt > 0 &&
bvec_try_merge_page(&bio->bi_io_vec[bio->bi_vcnt - 1],
folio_page(folio, 0), len, offset,
&same_page)) {
bio->bi_iter.bi_size += len;
if (same_page && bio_flagged(bio, BIO_PAGE_PINNED))
unpin_user_folio(folio, 1);
return 0;
}
bio_add_folio_nofail(bio, folio, len, offset);
return 0;
}
static unsigned int get_contig_folio_len(unsigned int *num_pages,
struct page **pages, unsigned int i,
struct folio *folio, size_t left,
@ -1276,6 +1250,7 @@ static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
for (left = size, i = 0; left > 0; left -= len, i += num_pages) {
struct page *page = pages[i];
struct folio *folio = page_folio(page);
unsigned int old_vcnt = bio->bi_vcnt;
folio_offset = ((size_t)folio_page_idx(folio, page) <<
PAGE_SHIFT) + offset;
@ -1288,7 +1263,23 @@ static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
len = get_contig_folio_len(&num_pages, pages, i,
folio, left, offset);
bio_iov_add_folio(bio, folio, len, folio_offset);
if (!bio_add_folio(bio, folio, len, folio_offset)) {
WARN_ON_ONCE(1);
ret = -EINVAL;
goto out;
}
if (bio_flagged(bio, BIO_PAGE_PINNED)) {
/*
* We're adding another fragment of a page that already
* was part of the last segment. Undo our pin as the
* page was pinned when an earlier fragment of it was
* added to the bio and __bio_release_pages expects a
* single pin per page.
*/
if (offset && bio->bi_vcnt == old_vcnt)
unpin_user_folio(folio, 1);
}
offset = 0;
}

3
block/blk.h
View File

@ -103,8 +103,7 @@ struct bio_vec *bvec_alloc(mempool_t *pool, unsigned short *nr_vecs,
void bvec_free(mempool_t *pool, struct bio_vec *bv, unsigned short nr_vecs);
bool bvec_try_merge_hw_page(struct request_queue *q, struct bio_vec *bv,
struct page *page, unsigned len, unsigned offset,
bool *same_page);
struct page *page, unsigned len, unsigned offset);
static inline bool biovec_phys_mergeable(struct request_queue *q,
struct bio_vec *vec1, struct bio_vec *vec2)