linux-kernel - Re: [PATCH v1 15/15] ceph: use put_user_pages() instead of ceph_put_page

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Message-ID: <df4da184-fe8b-c189-43e5-fac58adb3ed9@redhat.com>
Date:   Mon, 15 Apr 2019 15:46:59 +0800
From:   "Yan, Zheng" <zyan@...hat.com>
To:     jglisse@...hat.com, linux-kernel@...r.kernel.org
Cc:     linux-fsdevel@...r.kernel.org, linux-block@...r.kernel.org,
        linux-mm@...ck.org, John Hubbard <jhubbard@...dia.com>,
        Jan Kara <jack@...e.cz>,
        Dan Williams <dan.j.williams@...el.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Johannes Thumshirn <jthumshirn@...e.de>,
        Christoph Hellwig <hch@....de>, Jens Axboe <axboe@...nel.dk>,
        Ming Lei <ming.lei@...hat.com>,
        Dave Chinner <david@...morbit.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Matthew Wilcox <willy@...radead.org>,
        Sage Weil <sage@...hat.com>, Ilya Dryomov <idryomov@...il.com>,
        ceph-devel@...r.kernel.org
Subject: Re: [PATCH v1 15/15] ceph: use put_user_pages() instead of
 ceph_put_page_vector()

On 4/12/19 5:08 AM, jglisse@...hat.com wrote:
> From: Jérôme Glisse <jglisse@...hat.com>
> 
> When page reference were taken through GUP (get_user_page*()) we need
> to drop them with put_user_pages().
> 
> Signed-off-by: Jérôme Glisse <jglisse@...hat.com>
> Cc: linux-fsdevel@...r.kernel.org
> Cc: linux-block@...r.kernel.org
> Cc: linux-mm@...ck.org
> Cc: John Hubbard <jhubbard@...dia.com>
> Cc: Jan Kara <jack@...e.cz>
> Cc: Dan Williams <dan.j.williams@...el.com>
> Cc: Alexander Viro <viro@...iv.linux.org.uk>
> Cc: Johannes Thumshirn <jthumshirn@...e.de>
> Cc: Christoph Hellwig <hch@....de>
> Cc: Jens Axboe <axboe@...nel.dk>
> Cc: Ming Lei <ming.lei@...hat.com>
> Cc: Dave Chinner <david@...morbit.com>
> Cc: Jason Gunthorpe <jgg@...pe.ca>
> Cc: Matthew Wilcox <willy@...radead.org>
> Cc: Yan Zheng <zyan@...hat.com>
> Cc: Sage Weil <sage@...hat.com>
> Cc: Ilya Dryomov <idryomov@...il.com>
> Cc: ceph-devel@...r.kernel.org
> ---
>   fs/ceph/file.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/ceph/file.c b/fs/ceph/file.c
> index 6c5b85f01721..5842ad3a4218 100644
> --- a/fs/ceph/file.c
> +++ b/fs/ceph/file.c
> @@ -667,7 +667,8 @@ static ssize_t ceph_sync_read(struct kiocb *iocb, struct iov_iter *to,
>   			} else {
>   				iov_iter_advance(to, 0);
>   			}
> -			ceph_put_page_vector(pages, num_pages, false);
> +			/* iov_iter_get_pages_alloc() did call GUP */
> +			put_user_pages(pages, num_pages);

pages in pipe were not from get_user_pages(). Am I missing anything?

Regards
Yan, Zheng

>   		} else {
>   			int idx = 0;
>   			size_t left = ret > 0 ? ret : 0;
>