linux-kernel - Re: [PATCH] drivers/virt: use get_user_pages

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Message-ID: <20170103213653.GB18167@dhcp22.suse.cz>
Date:   Tue, 3 Jan 2017 22:36:53 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Lorenzo Stoakes <lstoakes@...il.com>
Cc:     linux-mm <linux-mm@...ck.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Kumar Gala <galak@...nel.crashing.org>,
        Mihai Caraman <mihai.caraman@...escale.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] drivers/virt: use get_user_pages_unlocked()

On Tue 03-01-17 21:14:20, Lorenzo Stoakes wrote:
> Just a gentle ping on this :) I think this might be a slightly
> abandoned corner of the kernel so not sure who else to ping to get
> this moving.

Maybe Andrew can pick it up?
http://lkml.kernel.org/r/20161101194332.23961-1-lstoakes@gmail.com

> On 1 November 2016 at 19:43, Lorenzo Stoakes <lstoakes@...il.com> wrote:
> > Moving from get_user_pages() to get_user_pages_unlocked() simplifies the code
> > and takes advantage of VM_FAULT_RETRY functionality when faulting in pages.
> >
> > Signed-off-by: Lorenzo Stoakes <lstoakes@...il.com>
> > ---
> >  drivers/virt/fsl_hypervisor.c | 7 ++-----
> >  1 file changed, 2 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/virt/fsl_hypervisor.c b/drivers/virt/fsl_hypervisor.c
> > index 150ce2a..d3eca87 100644
> > --- a/drivers/virt/fsl_hypervisor.c
> > +++ b/drivers/virt/fsl_hypervisor.c
> > @@ -243,11 +243,8 @@ static long ioctl_memcpy(struct fsl_hv_ioctl_memcpy __user *p)
> >         sg_list = PTR_ALIGN(sg_list_unaligned, sizeof(struct fh_sg_list));
> >
> >         /* Get the physical addresses of the source buffer */
> > -       down_read(&current->mm->mmap_sem);
> > -       num_pinned = get_user_pages(param.local_vaddr - lb_offset,
> > -               num_pages, (param.source == -1) ? 0 : FOLL_WRITE,
> > -               pages, NULL);
> > -       up_read(&current->mm->mmap_sem);
> > +       num_pinned = get_user_pages_unlocked(param.local_vaddr - lb_offset,
> > +               num_pages, pages, (param.source == -1) ? 0 : FOLL_WRITE);
> >
> >         if (num_pinned != num_pages) {
> >                 /* get_user_pages() failed */
> > --
> > 2.10.2
> >
> 
> 
> 
> -- 
> Lorenzo Stoakes
> https://ljs.io

-- 
Michal Hocko
SUSE Labs