linux-kernel - Re: [PATCH v2 1/3] xen/privcmd: Corrected error handling path

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Date:   Tue, 7 Jul 2020 17:10:08 +0530
From:   Souptick Joarder <jrdr.linux@...il.com>
To:     Jürgen Groß <jgross@...e.com>
Cc:     Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        sstabellini@...nel.org, xen-devel@...ts.xenproject.org,
        linux-kernel@...r.kernel.org, John Hubbard <jhubbard@...dia.com>,
        Paul Durrant <xadimgnik@...il.com>
Subject: Re: [PATCH v2 1/3] xen/privcmd: Corrected error handling path

On Tue, Jul 7, 2020 at 3:05 PM Jürgen Groß <jgross@...e.com> wrote:
>
> On 06.07.20 20:16, Souptick Joarder wrote:
> > Previously, if lock_pages() end up partially mapping pages, it used
> > to return -ERRNO due to which unlock_pages() have to go through
> > each pages[i] till *nr_pages* to validate them. This can be avoided
> > by passing correct number of partially mapped pages & -ERRNO separately,
> > while returning from lock_pages() due to error.
> >
> > With this fix unlock_pages() doesn't need to validate pages[i] till
> > *nr_pages* for error scenario and few condition checks can be ignored.
> >
> > Signed-off-by: Souptick Joarder <jrdr.linux@...il.com>
> > Cc: John Hubbard <jhubbard@...dia.com>
> > Cc: Boris Ostrovsky <boris.ostrovsky@...cle.com>
> > Cc: Paul Durrant <xadimgnik@...il.com>
> > ---
> >   drivers/xen/privcmd.c | 31 +++++++++++++++----------------
> >   1 file changed, 15 insertions(+), 16 deletions(-)
> >
> > diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c
> > index a250d11..33677ea 100644
> > --- a/drivers/xen/privcmd.c
> > +++ b/drivers/xen/privcmd.c
> > @@ -580,13 +580,13 @@ static long privcmd_ioctl_mmap_batch(
> >
> >   static int lock_pages(
> >       struct privcmd_dm_op_buf kbufs[], unsigned int num,
> > -     struct page *pages[], unsigned int nr_pages)
> > +     struct page *pages[], unsigned int nr_pages, unsigned int *pinned)
> >   {
> >       unsigned int i;
> > +     int page_count = 0;
>
> Initial value shouldn't be needed, and ...
>
> >
> >       for (i = 0; i < num; i++) {
> >               unsigned int requested;
> > -             int pinned;
>
> ... you could move the declaration here.
>
> With that done you can add my
>
> Reviewed-by: Juergen Gross <jgross@...e.com>

Ok. But does it going make any difference other than limiting scope ?

>
>
> Juergen