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block: use bio_add_page in bio_iov_iter_get_pages
Replace a nasty hack with a different nasty hack to prepare for multipage bio_vecs. By moving the temporary page array as far up as possible in the space allocated for the bio_vec array we can iterate forward over it and thus use bio_add_page. Using bio_add_page means we'll be able to merge physically contiguous pages once support for multipath bio_vecs is merged. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
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parent
c8765de0ad
commit
576ed91354
1 changed files with 20 additions and 21 deletions
41
block/bio.c
41
block/bio.c
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@ -827,6 +827,8 @@ int bio_add_page(struct bio *bio, struct page *page,
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}
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}
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EXPORT_SYMBOL(bio_add_page);
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EXPORT_SYMBOL(bio_add_page);
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#define PAGE_PTRS_PER_BVEC (sizeof(struct bio_vec) / sizeof(struct page *))
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/**
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/**
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* __bio_iov_iter_get_pages - pin user or kernel pages and add them to a bio
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* __bio_iov_iter_get_pages - pin user or kernel pages and add them to a bio
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* @bio: bio to add pages to
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* @bio: bio to add pages to
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@ -839,38 +841,35 @@ EXPORT_SYMBOL(bio_add_page);
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*/
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*/
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static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
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static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
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{
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{
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unsigned short nr_pages = bio->bi_max_vecs - bio->bi_vcnt, idx;
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unsigned short nr_pages = bio->bi_max_vecs - bio->bi_vcnt;
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unsigned short entries_left = bio->bi_max_vecs - bio->bi_vcnt;
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struct bio_vec *bv = bio->bi_io_vec + bio->bi_vcnt;
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struct bio_vec *bv = bio->bi_io_vec + bio->bi_vcnt;
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struct page **pages = (struct page **)bv;
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struct page **pages = (struct page **)bv;
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ssize_t size, left;
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unsigned len, i;
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size_t offset;
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size_t offset;
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ssize_t size;
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/*
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* Move page array up in the allocated memory for the bio vecs as far as
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* possible so that we can start filling biovecs from the beginning
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* without overwriting the temporary page array.
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*/
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BUILD_BUG_ON(PAGE_PTRS_PER_BVEC < 2);
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pages += entries_left * (PAGE_PTRS_PER_BVEC - 1);
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size = iov_iter_get_pages(iter, pages, LONG_MAX, nr_pages, &offset);
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size = iov_iter_get_pages(iter, pages, LONG_MAX, nr_pages, &offset);
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if (unlikely(size <= 0))
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if (unlikely(size <= 0))
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return size ? size : -EFAULT;
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return size ? size : -EFAULT;
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idx = nr_pages = (size + offset + PAGE_SIZE - 1) / PAGE_SIZE;
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/*
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for (left = size, i = 0; left > 0; left -= len, i++) {
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* Deep magic below: We need to walk the pinned pages backwards
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struct page *page = pages[i];
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* because we are abusing the space allocated for the bio_vecs
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* for the page array. Because the bio_vecs are larger than the
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* page pointers by definition this will always work. But it also
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* means we can't use bio_add_page, so any changes to it's semantics
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* need to be reflected here as well.
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*/
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bio->bi_iter.bi_size += size;
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bio->bi_vcnt += nr_pages;
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while (idx--) {
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len = min_t(size_t, PAGE_SIZE - offset, left);
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bv[idx].bv_page = pages[idx];
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if (WARN_ON_ONCE(bio_add_page(bio, page, len, offset) != len))
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bv[idx].bv_len = PAGE_SIZE;
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return -EINVAL;
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bv[idx].bv_offset = 0;
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offset = 0;
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}
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}
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bv[0].bv_offset += offset;
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bv[0].bv_len -= offset;
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bv[nr_pages - 1].bv_len -= nr_pages * PAGE_SIZE - offset - size;
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iov_iter_advance(iter, size);
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iov_iter_advance(iter, size);
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return 0;
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return 0;
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}
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}
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