dbb1ed6d87
reproducer: https://www.spinics.net/lists/linux-block/msg28507.html ubuntu bugreport: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1796542 Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
78 lines
2.7 KiB
Diff
78 lines
2.7 KiB
Diff
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Martin Wilck <mwilck@suse.com>
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Date: Tue, 9 Oct 2018 17:04:40 +0100
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Subject: [PATCH] block: bio_iov_iter_get_pages: fix size of last iovec
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Buglink: https://bugs.launchpad.net/bugs/1796542
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If the last page of the bio is not "full", the length of the last
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vector slot needs to be corrected. This slot has the index
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(bio->bi_vcnt - 1), but only in bio->bi_io_vec. In the "bv" helper
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array, which is shifted by the value of bio->bi_vcnt at function
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invocation, the correct index is (nr_pages - 1).
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v2: improved readability following suggestions from Ming Lei.
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v3: followed a formatting suggestion from Christoph Hellwig.
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Fixes: 2cefe4dbaadf ("block: add bio_iov_iter_get_pages()")
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Reviewed-by: Hannes Reinecke <hare@suse.com>
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Reviewed-by: Ming Lei <ming.lei@redhat.com>
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Reviewed-by: Jan Kara <jack@suse.cz>
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Reviewed-by: Christoph Hellwig <hch@lst.de>
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Signed-off-by: Martin Wilck <mwilck@suse.com>
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Signed-off-by: Jens Axboe <axboe@kernel.dk>
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(cherry picked from commit b403ea2404889e1227812fa9657667a1deb9c694)
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Signed-off-by: Colin Ian King <colin.king@canonical.com>
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Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
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---
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block/bio.c | 18 ++++++++----------
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1 file changed, 8 insertions(+), 10 deletions(-)
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diff --git a/block/bio.c b/block/bio.c
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index 2636d15af979..d76372a6a5fe 100644
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--- a/block/bio.c
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+++ b/block/bio.c
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@@ -911,16 +911,16 @@ 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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@@ -933,17 +933,15 @@ 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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