linux-kernel - Re: [PATCH v4 04/10] userfaultfd/shmem: support minor fault registration for shmem

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Date:   Tue, 27 Apr 2021 11:57:13 -0400
From:   Peter Xu <peterx@...hat.com>
To:     Hugh Dickins <hughd@...gle.com>
Cc:     Axel Rasmussen <axelrasmussen@...gle.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jerome Glisse <jglisse@...hat.com>,
        Joe Perches <joe@...ches.com>,
        Lokesh Gidra <lokeshgidra@...gle.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>,
        Shaohua Li <shli@...com>, Shuah Khan <shuah@...nel.org>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Wang Qing <wangqing@...o.com>, linux-api@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-kselftest@...r.kernel.org, linux-mm@...ck.org,
        Brian Geffon <bgeffon@...gle.com>,
        "Dr . David Alan Gilbert" <dgilbert@...hat.com>,
        Mina Almasry <almasrymina@...gle.com>,
        Oliver Upton <oupton@...gle.com>
Subject: Re: [PATCH v4 04/10] userfaultfd/shmem: support minor fault
 registration for shmem

On Mon, Apr 26, 2021 at 07:23:57PM -0700, Hugh Dickins wrote:
> On Tue, 20 Apr 2021, Axel Rasmussen wrote:
> 
> > This patch allows shmem-backed VMAs to be registered for minor faults.
> > Minor faults are appropriately relayed to userspace in the fault path,
> > for VMAs with the relevant flag.
> > 
> > This commit doesn't hook up the UFFDIO_CONTINUE ioctl for shmem-backed
> > minor faults, though, so userspace doesn't yet have a way to resolve
> > such faults.
> > 
> > Acked-by: Peter Xu <peterx@...hat.com>
> > Signed-off-by: Axel Rasmussen <axelrasmussen@...gle.com>
> 
> And if this "04/10" had been numbered 03/10, I would have said
> Acked-by: Hugh Dickins <hughd@...gle.com>
> 
> Just read the comment above: "so userspace doesn't yet have a way to
> resolve such faults" - if it doesn't by this stage, we're in trouble.

Right, so merging the two patches might be easier.  Even if we don't merge
them, we'll need to touch up the commit message since at least above paragraph
is not true anymore as we've already have UFFDIO_CONTINUE.  Thanks,

-- 
Peter Xu