linux-kernel - Re: [PATCH v3 1/9] mm: Introduce new vm_insert

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Message-ID: <CAFqt6zbuT3mhLCSas=EO38NW+M4KAARKeBpMqDz6xwkVbw=FGA@mail.gmail.com>
Date:   Sat, 8 Dec 2018 03:18:49 +0530
From:   Souptick Joarder <jrdr.linux@...il.com>
To:     robin.murphy@....com
Cc:     Matthew Wilcox <willy@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...e.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        vbabka@...e.cz, Rik van Riel <riel@...riel.com>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        rppt@...ux.vnet.ibm.com, Peter Zijlstra <peterz@...radead.org>,
        Russell King - ARM Linux <linux@...linux.org.uk>,
        iamjoonsoo.kim@....com, treding@...dia.com,
        Kees Cook <keescook@...omium.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        stefanr@...6.in-berlin.de, hjc@...k-chips.com,
        Heiko Stuebner <heiko@...ech.de>, airlied@...ux.ie,
        oleksandr_andrushchenko@...m.com, joro@...tes.org,
        pawel@...iak.com, Kyungmin Park <kyungmin.park@...sung.com>,
        mchehab@...nel.org, Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>, linux-kernel@...r.kernel.org,
        Linux-MM <linux-mm@...ck.org>,
        linux-arm-kernel@...ts.infradead.org,
        linux1394-devel@...ts.sourceforge.net,
        dri-devel@...ts.freedesktop.org,
        linux-rockchip@...ts.infradead.org, xen-devel@...ts.xen.org,
        iommu@...ts.linux-foundation.org, linux-media@...r.kernel.org
Subject: Re: [PATCH v3 1/9] mm: Introduce new vm_insert_range API

On Sat, Dec 8, 2018 at 2:40 AM Robin Murphy <robin.murphy@....com> wrote:
>
> On 2018-12-07 7:28 pm, Souptick Joarder wrote:
> > On Fri, Dec 7, 2018 at 10:41 PM Matthew Wilcox <willy@...radead.org> wrote:
> >>
> >> On Fri, Dec 07, 2018 at 03:34:56PM +0000, Robin Murphy wrote:
> >>>> +int vm_insert_range(struct vm_area_struct *vma, unsigned long addr,
> >>>> +                   struct page **pages, unsigned long page_count)
> >>>> +{
> >>>> +   unsigned long uaddr = addr;
> >>>> +   int ret = 0, i;
> >>>
> >>> Some of the sites being replaced were effectively ensuring that vma and
> >>> pages were mutually compatible as an initial condition - would it be worth
> >>> adding something here for robustness, e.g.:
> >>>
> >>> +     if (page_count != vma_pages(vma))
> >>> +             return -ENXIO;
> >>
> >> I think we want to allow this to be used to populate part of a VMA.
> >> So perhaps:
> >>
> >>          if (page_count > vma_pages(vma))
> >>                  return -ENXIO;
> >
> > Ok, This can be added.
> >
> > I think Patch [2/9] is the only leftover place where this
> > check could be removed.
>
> Right, 9/9 could also have relied on my stricter check here, but since
> it's really testing whether it actually managed to allocate vma_pages()
> worth of pages earlier, Matthew's more lenient version won't help for
> that one.


(Why privcmd_buf_mmap() doesn't clean up and return an error
> as soon as that allocation loop fails, without taking the mutex under
> which it still does a bunch more pointless work to only undo it again,
> is a mind-boggling mystery, but that's not our problem here...)

I think some clean up can be done here in a separate patch.