From 77fd359b6dfdba58f476d5c17097bab024af9467 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Mon, 12 May 2025 06:23:54 +0200 Subject: [PATCH] block: remove the same_page output argument to bvec_try_merge_page 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 Link: https://lore.kernel.org/r/20250512042354.514329-1-hch@lst.de Signed-off-by: Jens Axboe --- block/bio-integrity.c | 4 +--- block/bio.c | 55 ++++++++++++++++++------------------------- block/blk.h | 3 +-- 3 files changed, 25 insertions(+), 37 deletions(-) diff --git a/block/bio-integrity.c b/block/bio-integrity.c index 43ef6bd06c85..cb94e9be26dc 100644 --- a/block/bio-integrity.c +++ b/block/bio-integrity.c @@ -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; } diff --git a/block/bio.c b/block/bio.c index 988f5de3c02c..56ae38ce006e 100644 --- a/block/bio.c +++ b/block/bio.c @@ -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; } diff --git a/block/blk.h b/block/blk.h index 21af4f0c4c00..4f9d64bf1f0e 100644 --- a/block/blk.h +++ b/block/blk.h @@ -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) -- 2.25.1