From: Matthew Wilcox <willy@infradead.org>
To: Matthew Garrett <mjg59@google.com>
Cc: linux-mm@kvack.org,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] mm: Allow userland to request that the kernel clear memory on release
Date: Wed, 24 Apr 2019 13:20:06 -0700 [thread overview]
Message-ID: <20190424202006.GH19031@bombadil.infradead.org> (raw)
In-Reply-To: <CACdnJutj4K1kQj7yXcCNVWM_hmrUwMfZ-JBi=FHkBvYFfbJNZA@mail.gmail.com>
On Wed, Apr 24, 2019 at 12:33:11PM -0700, Matthew Garrett wrote:
> On Wed, Apr 24, 2019 at 12:28 PM Matthew Wilcox <willy@infradead.org> wrote:
> > But you can't have a new PageFlag. Can you instead zero the memory in
> > unmap_single_vma() where we call uprobe_munmap() and untrack_pfn() today?
>
> Is there any way the page could be referenced by something other than
> a VMA at this point? If so we probably don't want to zero it here, but
> we do want to zero it when the page is finally released (which is why
> I went with a page flag)
It could be the target/source of direct I/O, or userspace could have
registered it with an RDMA device, or ...
It depends on the semantics you want. There's no legacy code to
worry about here. I was seeing this as the equivalent of an atexit()
handler; userspace is saying "When this page is unmapped, zero it".
So it doesn't matter that somebody else might be able to reference it --
userspace could have zeroed it themselves.
next prev parent reply other threads:[~2019-04-24 20:20 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-24 19:14 [PATCH] mm: Allow userland to request that the kernel clear memory on release Matthew Garrett
2019-04-24 19:28 ` Matthew Wilcox
2019-04-24 19:33 ` Matthew Garrett
2019-04-24 20:20 ` Matthew Wilcox [this message]
2019-04-24 20:22 ` Matthew Garrett
2019-04-24 21:10 ` [PATCH V2] " Matthew Garrett
2019-04-25 12:14 ` Michal Hocko
2019-04-25 12:37 ` Michal Hocko
2019-04-25 20:39 ` Matthew Garrett
2019-04-26 5:25 ` Michal Hocko
2019-04-26 18:08 ` Matthew Garrett
2019-04-29 21:44 ` Michal Hocko
2019-04-25 12:40 ` Vlastimil Babka
2019-04-25 20:45 ` Matthew Garrett
2019-04-25 12:42 ` Jann Horn
2019-04-25 20:43 ` Matthew Garrett
2019-04-26 5:31 ` Michal Hocko
2019-04-26 13:33 ` Jann Horn
2019-04-26 13:47 ` Michal Hocko
2019-04-26 14:03 ` Jann Horn
2019-04-26 14:08 ` Michal Hocko
2019-04-25 22:58 ` [PATCH V3] " Matthew Garrett
2019-04-26 7:45 ` Vlastimil Babka
2019-04-26 18:10 ` Matthew Garrett
2019-04-29 19:36 ` [PATCH V4] " Matthew Garrett
2019-06-05 18:26 ` Matthew Garrett
2019-06-06 22:45 ` Kees Cook
2019-04-25 15:32 ` [PATCH] " Christopher Lameter
2019-04-25 20:29 ` Matthew Garrett
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=20190424202006.GH19031@bombadil.infradead.org \
--to=willy@infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mjg59@google.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).