Re: [PATCH] Ceph: Avoid data inconsistency due to d-cache aliasingin readpage()

[Li Wang]

Hi Yan,
  zero_user_segment() has invoked flush_dcache_page() for us, we donnot 
wanna flush d-cache twice.

Cheers,
Li Wang

On 11/13/2013 09:19 PM, Yan, Zheng wrote:
> On Wed, Nov 13, 2013 at 3:22 PM, Li Wang <liwang@xxxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxxx>
> > ---
> >   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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