From: Peter Xu <peterx@redhat.com>
To: Li Wang <liwang@redhat.com>
Cc: Nadav Amit <nadav.amit@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
linux-kernel <linux-kernel@vger.kernel.org>,
Linux-MM <linux-mm@kvack.org>,
linux-fsdevel@vger.kernel.org, Nadav Amit <namit@vmware.com>,
Andrea Arcangeli <aarcange@redhat.com>,
stable@vger.kernel.org
Subject: Re: [PATCH] userfaultfd: fix a race between writeprotect and exit_mmap()
Date: Thu, 23 Sep 2021 20:16:19 -0400 [thread overview]
Message-ID: <YU0Y045lHEpdIu3X@t490s> (raw)
In-Reply-To: <CAEemH2d++nJmTkMYzNsJ-KsfdoQ=WHSFpY=EfBZn2jqVauBGAw@mail.gmail.com>
On Wed, Sep 22, 2021 at 05:06:53PM +0800, Li Wang wrote:
> Hi,
Li,
>
> I confirmed this patch (applied on 5.14) gets rid of the below userfaultfd
> test failure.
>
> # ./userfaultfd anon 16 2
> nr_pages: 4096, nr_pages_per_cpu: 256
> bounces: 1, mode: rnd read, userfaults: 313 missing
> (51+34+37+26+41+28+15+20+16+12+13+7+10+2+0+1) 995 wp
> (121+79+96+53+90+104+48+61+56+82+56+41+49+26+11+22)
> bounces: 0, mode: read, userfaults: 64 missing
> (15+8+10+6+5+2+4+3+3+1+4+0+0+2+0+1) 2157 wp
> (223+274+189+141+116+132+203+153+143+126+110+114+101+66+42+24)
> testing uffd-wp with pagemap (pgsize=4096): done
> testing uffd-wp with pagemap (pgsize=2097152): done
> testing UFFDIO_ZEROPAGE: done.
> testing signal delivery: done.
> testing events (fork, remap, remove): ERROR: nr 3933 memory corruption 0 1
> (errno=0, line=963)
> ERROR: faulting process failed (errno=0, line=1117)
Just to keep a record within this thread - my understanding is above issue is a
separate issue from what Nadav has fixed. The other fix could be:
https://lore.kernel.org/lkml/20210923232512.210092-1-peterx@redhat.com/
When verify with Nadav's patch, please check whether you have thp enabled
globally:
# echo always > /sys/kernel/mm/transparent_hugepage/enabled
Thanks,
--
Peter Xu
next prev parent reply other threads:[~2021-09-24 0:16 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-21 20:02 [PATCH] userfaultfd: fix a race between writeprotect and exit_mmap() Nadav Amit
2021-09-22 9:06 ` Li Wang
2021-09-24 0:16 ` Peter Xu [this message]
2021-09-22 14:30 ` Peter Xu
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=YU0Y045lHEpdIu3X@t490s \
--to=peterx@redhat.com \
--cc=aarcange@redhat.com \
--cc=akpm@linux-foundation.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=liwang@redhat.com \
--cc=nadav.amit@gmail.com \
--cc=namit@vmware.com \
--cc=stable@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).