linux-kernel - Re: [PATCH] Ceph: Avoid data inconsistency due to d-cache aliasing in readpage()

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Message-ID: <CAAM7YA=1DXyW+tr8CcAidOw_Hqmq=2o7QhcKGQO93n8jY5qAdg@mail.gmail.com>
Date:	Wed, 13 Nov 2013 21:19:12 +0800
From:	"Yan, Zheng" <ukernel@...il.com>
To:	Li Wang <liwang@...ntukylin.com>
Cc:	ceph-devel <ceph-devel@...r.kernel.org>,
	Sage Weil <sage@...tank.com>, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Ceph: Avoid data inconsistency due to d-cache aliasing in readpage()

On Wed, Nov 13, 2013 at 3:22 PM, Li Wang <liwang@...ntukylin.com> wrote:
> If the length of data to be read in readpage() is exactly
> PAGE_CACHE_SIZE, the original code does not flush d-cache
> for data consistency after finishing reading. This patches fixes
> this.
>
> Signed-off-by: Li Wang <liwang@...ntukylin.com>
> ---
>  fs/ceph/addr.c |    8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c
> index 6df8bd4..7b0000a 100644
> --- a/fs/ceph/addr.c
> +++ b/fs/ceph/addr.c
> @@ -210,9 +210,13 @@ static int readpage_nounlock(struct file *filp, struct page *page)
>         if (err < 0) {
>                 SetPageError(page);
>                 goto out;
> -       } else if (err < PAGE_CACHE_SIZE) {
> +       } else {
> +               if (err < PAGE_CACHE_SIZE) {
>                 /* zero fill remainder of page */
> -               zero_user_segment(page, err, PAGE_CACHE_SIZE);
> +                       zero_user_segment(page, err, PAGE_CACHE_SIZE);
> +               } else {
> +                       flush_dcache_page(page);
> +               }

this doesn't make sense for me. why not call flush_dcache_page unconditionally?

Regards
Yan, Zheng
>         }
>         SetPageUptodate(page);
>
> --
> 1.7.9.5
>
> --
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