From: Jan Kara <jack@suse.cz>
To: Martin Wilck <mwilck@suse.com>
Cc: Jens Axboe <axboe@kernel.dk>, Ming Lei <ming.lei@redhat.com>,
Jan Kara <jack@suse.com>, Hannes Reinecke <hare@suse.de>,
Johannes Thumshirn <jthumshirn@suse.de>,
Kent Overstreet <kent.overstreet@gmail.com>,
Christoph Hellwig <hch@lst.de>,
linux-block@vger.kernel.org
Subject: Re: [PATCH 1/2] block: bio_iov_iter_get_pages: fix size of last iovec
Date: Thu, 19 Jul 2018 12:20:00 +0200 [thread overview]
Message-ID: <20180719102000.ev3mvvmiaa27wv65@quack2.suse.cz> (raw)
In-Reply-To: <20180719093918.28876-2-mwilck@suse.com>
On Thu 19-07-18 11:39:17, Martin Wilck wrote:
> 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.
>
> Fixes: 2cefe4dbaadf ("block: add bio_iov_iter_get_pages()")
> Signed-off-by: Martin Wilck <mwilck@suse.com>
Looks good to me. You can add:
Reviewed-by: Jan Kara <jack@suse.cz>
BTW, explicit CC: stable@vger.kernel.org would be good. But Jens can add it
I guess.
Honza
> ---
> block/bio.c | 18 ++++++++----------
> 1 file changed, 8 insertions(+), 10 deletions(-)
>
> diff --git a/block/bio.c b/block/bio.c
> index 67eff5e..0964328 100644
> --- a/block/bio.c
> +++ b/block/bio.c
> @@ -912,16 +912,16 @@ EXPORT_SYMBOL(bio_add_page);
> */
> int bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
> {
> - unsigned short nr_pages = bio->bi_max_vecs - bio->bi_vcnt;
> + unsigned short idx, nr_pages = bio->bi_max_vecs - bio->bi_vcnt;
> struct bio_vec *bv = bio->bi_io_vec + bio->bi_vcnt;
> struct page **pages = (struct page **)bv;
> - size_t offset, diff;
> + size_t offset;
> ssize_t size;
>
> size = iov_iter_get_pages(iter, pages, LONG_MAX, nr_pages, &offset);
> if (unlikely(size <= 0))
> return size ? size : -EFAULT;
> - nr_pages = (size + offset + PAGE_SIZE - 1) / PAGE_SIZE;
> + idx = nr_pages = (size + offset + PAGE_SIZE - 1) / PAGE_SIZE;
>
> /*
> * Deep magic below: We need to walk the pinned pages backwards
> @@ -934,17 +934,15 @@ int bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
> bio->bi_iter.bi_size += size;
> bio->bi_vcnt += nr_pages;
>
> - diff = (nr_pages * PAGE_SIZE - offset) - size;
> - while (nr_pages--) {
> - bv[nr_pages].bv_page = pages[nr_pages];
> - bv[nr_pages].bv_len = PAGE_SIZE;
> - bv[nr_pages].bv_offset = 0;
> + while (idx--) {
> + bv[idx].bv_page = pages[idx];
> + bv[idx].bv_len = PAGE_SIZE;
> + bv[idx].bv_offset = 0;
> }
>
> bv[0].bv_offset += offset;
> bv[0].bv_len -= offset;
> - if (diff)
> - bv[bio->bi_vcnt - 1].bv_len -= diff;
> + bv[nr_pages - 1].bv_len -= nr_pages * PAGE_SIZE - offset - size;
>
> iov_iter_advance(iter, size);
> return 0;
> --
> 2.17.1
>
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
next prev parent reply other threads:[~2018-07-19 10:20 UTC|newest]
Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-12 14:36 Silent data corruption in blkdev_direct_IO() Hannes Reinecke
2018-07-12 15:08 ` Jens Axboe
2018-07-12 16:11 ` Martin Wilck
2018-07-12 16:14 ` Hannes Reinecke
2018-07-12 16:20 ` Jens Axboe
2018-07-12 16:42 ` Jens Axboe
2018-07-13 6:47 ` Martin Wilck
2018-07-13 16:56 ` Martin Wilck
2018-07-13 18:00 ` Jens Axboe
2018-07-13 18:50 ` Jens Axboe
2018-07-13 22:21 ` Martin Wilck
2018-07-13 20:48 ` Martin Wilck
2018-07-13 20:52 ` Jens Axboe
2018-07-16 19:05 ` Martin Wilck
2018-07-12 23:29 ` Ming Lei
2018-07-13 18:54 ` Jens Axboe
2018-07-13 22:29 ` Martin Wilck
2018-07-16 11:45 ` Ming Lei
2018-07-18 0:07 ` Martin Wilck
2018-07-18 2:48 ` Ming Lei
2018-07-18 7:32 ` Martin Wilck
2018-07-18 7:54 ` Ming Lei
2018-07-18 9:20 ` Johannes Thumshirn
2018-07-18 11:40 ` Jan Kara
2018-07-18 11:57 ` Jan Kara
2018-07-19 9:39 ` [PATCH 0/2] Fix silent " Martin Wilck
2018-07-19 9:39 ` [PATCH 1/2] block: bio_iov_iter_get_pages: fix size of last iovec Martin Wilck
2018-07-19 10:05 ` Hannes Reinecke
2018-07-19 10:09 ` Ming Lei
2018-07-19 10:20 ` Jan Kara [this message]
2018-07-19 14:52 ` Christoph Hellwig
2018-07-19 9:39 ` [PATCH 2/2] blkdev: __blkdev_direct_IO_simple: make sure to fill up the bio Martin Wilck
2018-07-19 10:06 ` Hannes Reinecke
2018-07-19 10:21 ` Ming Lei
2018-07-19 10:37 ` Jan Kara
2018-07-19 10:46 ` Ming Lei
2018-07-19 11:08 ` Al Viro
2018-07-19 14:53 ` Christoph Hellwig
2018-07-19 15:06 ` Jan Kara
2018-07-19 15:11 ` Christoph Hellwig
2018-07-19 19:21 ` Martin Wilck
2018-07-19 19:34 ` Martin Wilck
2018-07-19 10:45 ` Jan Kara
2018-07-19 12:23 ` Martin Wilck
2018-07-19 15:15 ` Jan Kara
2018-07-19 20:01 ` Martin Wilck
2018-07-19 11:04 ` Ming Lei
2018-07-19 11:56 ` Jan Kara
2018-07-19 12:20 ` Ming Lei
2018-07-19 15:21 ` Jan Kara
2018-07-19 19:06 ` Martin Wilck
2018-07-19 12:25 ` Martin Wilck
2018-07-19 10:08 ` [PATCH 0/2] Fix silent data corruption in blkdev_direct_IO() Hannes Reinecke
2018-07-19 14:50 ` Christoph Hellwig
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