From: Michal Hocko <mhocko@kernel.org>
To: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
linux-mm <linux-mm@kvack.org>,
lkml <linux-kernel@vger.kernel.org>,
Andrea Arcangeli <aarcange@redhat.com>,
"Dr. David Alan Gilbert" <dgilbert@redhat.com>,
Pavel Emelyanov <xemul@virtuozzo.com>,
Mike Kravetz <mike.kravetz@oracle.com>
Subject: Re: [PATCH] userfaultfd: replace ENOSPC with ESRCH in case mm has gone during copy/zeropage
Date: Thu, 10 Aug 2017 11:33:49 +0200 [thread overview]
Message-ID: <20170810093349.GK23863@dhcp22.suse.cz> (raw)
In-Reply-To: <20170808060816.GA31648@rapoport-lnx>
On Tue 08-08-17 09:08:17, Mike Rapoport wrote:
> (adding Michal)
Thanks
> On Mon, Aug 07, 2017 at 04:12:25PM +0300, Mike Rapoport wrote:
> > When the process exit races with outstanding mcopy_atomic, it would be
> > better to return ESRCH error. When such race occurs the process and it's mm
> > are going away and returning "no such process" to the uffd monitor seems
> > better fit than ENOSPC.
Not only the error message would be less confusing I also think that
error handling should be more straightforward. Although I cannot find
any guidelines for ENOSPC handling I've considered this errno as
potentially temporary and retry might be feasible while ESRCH is a
terminal error. I do not expect any userfaultfd users would retry on
error but who knows how the interface will be used in future so better
be prepared.
> > Suggested-by: Michal Hocko <mhocko@suse.com>
> > Cc: Andrea Arcangeli <aarcange@redhat.com>
> > Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> > Cc: Pavel Emelyanov <xemul@virtuozzo.com>
> > Cc: Mike Kravetz <mike.kravetz@oracle.com>
> > Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Acked-by: Michal Hocko <mhocko@suse.com>
> > ---
> > The man-pages update is ready and I'll send it out once the patch is
> > merged.
> >
> > fs/userfaultfd.c | 4 ++--
> > 1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
> > index 06ea26b8c996..b0d5897bc4e6 100644
> > --- a/fs/userfaultfd.c
> > +++ b/fs/userfaultfd.c
> > @@ -1600,7 +1600,7 @@ static int userfaultfd_copy(struct userfaultfd_ctx *ctx,
> > uffdio_copy.len);
> > mmput(ctx->mm);
> > } else {
> > - return -ENOSPC;
> > + return -ESRCH;
> > }
> > if (unlikely(put_user(ret, &user_uffdio_copy->copy)))
> > return -EFAULT;
> > @@ -1647,7 +1647,7 @@ static int userfaultfd_zeropage(struct userfaultfd_ctx *ctx,
> > uffdio_zeropage.range.len);
> > mmput(ctx->mm);
> > } else {
> > - return -ENOSPC;
> > + return -ESRCH;
> > }
> > if (unlikely(put_user(ret, &user_uffdio_zeropage->zeropage)))
> > return -EFAULT;
> > --
> > 2.7.4
> >
>
> --
> Sincerely yours,
> Mike.
>
--
Michal Hocko
SUSE Labs
prev parent reply other threads:[~2017-08-10 9:33 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-08-07 13:12 [PATCH] userfaultfd: replace ENOSPC with ESRCH in case mm has gone during copy/zeropage Mike Rapoport
2017-08-08 6:08 ` Mike Rapoport
2017-08-10 9:33 ` Michal Hocko [this message]
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=20170810093349.GK23863@dhcp22.suse.cz \
--to=mhocko@kernel.org \
--cc=aarcange@redhat.com \
--cc=akpm@linux-foundation.org \
--cc=dgilbert@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mike.kravetz@oracle.com \
--cc=rppt@linux.vnet.ibm.com \
--cc=xemul@virtuozzo.com \
/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).