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block: bio_iov_iter_get_pages: fix size of last iovec
commitb403ea2404
upstream. If the last page of the bio is not "full", the length of the last vector slot needs to be corrected. This slot has the index (bio->bi_vcnt - 1), but only in bio->bi_io_vec. In the "bv" helper array, which is shifted by the value of bio->bi_vcnt at function invocation, the correct index is (nr_pages - 1). v2: improved readability following suggestions from Ming Lei. v3: followed a formatting suggestion from Christoph Hellwig. Fixes:2cefe4dbaa
("block: add bio_iov_iter_get_pages()") Reviewed-by: Hannes Reinecke <hare@suse.com> Reviewed-by: Ming Lei <ming.lei@redhat.com> Reviewed-by: Jan Kara <jack@suse.cz> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Martin Wilck <mwilck@suse.com> Signed-off-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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1 changed files with 8 additions and 10 deletions
18
block/bio.c
18
block/bio.c
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@ -881,16 +881,16 @@ EXPORT_SYMBOL(bio_add_page);
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*/
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int bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
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{
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unsigned short nr_pages = bio->bi_max_vecs - bio->bi_vcnt;
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unsigned short nr_pages = bio->bi_max_vecs - bio->bi_vcnt, idx;
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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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size_t offset, diff;
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size_t offset;
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ssize_t size;
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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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return size ? size : -EFAULT;
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nr_pages = (size + offset + PAGE_SIZE - 1) / PAGE_SIZE;
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idx = nr_pages = (size + offset + PAGE_SIZE - 1) / PAGE_SIZE;
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/*
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* Deep magic below: We need to walk the pinned pages backwards
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@ -903,17 +903,15 @@ int bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
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bio->bi_iter.bi_size += size;
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bio->bi_vcnt += nr_pages;
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diff = (nr_pages * PAGE_SIZE - offset) - size;
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while (nr_pages--) {
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bv[nr_pages].bv_page = pages[nr_pages];
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bv[nr_pages].bv_len = PAGE_SIZE;
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bv[nr_pages].bv_offset = 0;
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while (idx--) {
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bv[idx].bv_page = pages[idx];
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bv[idx].bv_len = PAGE_SIZE;
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bv[idx].bv_offset = 0;
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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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if (diff)
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bv[bio->bi_vcnt - 1].bv_len -= diff;
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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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return 0;
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