From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Andrew Morton <akpm@linux-foundation.org>,
Linux-MM <linux-mm@kvack.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Naresh Kamboju <naresh.kamboju@linaro.org>,
Joel Fernandes <joel@joelfernandes.org>,
William Kucharski <william.kucharski@oracle.com>
Subject: Re: [PATCHv2] mm: Fix warning in move_normal_pmd()
Date: Wed, 15 Jul 2020 23:55:08 +0300 [thread overview]
Message-ID: <20200715205508.3rzrkhulruzpy6iv@box> (raw)
In-Reply-To: <CAHk-=wh4pB-jRngOjcGxpc8=NPds3jWqJwDMUWC3-OEo4dRiKg@mail.gmail.com>
On Wed, Jul 15, 2020 at 11:36:59AM -0700, Linus Torvalds wrote:
> On Wed, Jul 15, 2020 at 6:50 AM Kirill A. Shutemov
> <kirill.shutemov@linux.intel.com> wrote:
> >
> > mremap(2) does not allow source and destination regions to overlap, but
> > shift_arg_pages() calls move_page_tables() directly and in this case the
> > source and destination overlap often. It
>
> Actually, before we do this patch (which I think is a good idea), I'd
> like Naresh to test the attached patch.
>
> And Kirill, Joel, mind looking it over too.
I don't understand 'len' calculation in try_to_align_end().
IIUC, it increases 'len' by PMD_SIZE if 'new_addr+len' is not aligned to
PMD_SIZE. It doesn't make sense to me.
Maybe
*len = roundup_up(*new_addr + *len, PMD_SIZE) - *new_addr;
or something?
BUT
I *think* there's a bigger problem with the patch:
For stack relocation case both VMAs are the same and always(?) the only
VMA around at the time. It means none of ADDR_BEFORE_PREV and
ADDR_AFTER_NEXT are going to stop us.
Consider the following case, before and after try_to_align_start():
before after
old_addr: 0x0123000 0x0000000
new_addr: 0x1123000 0x1000000
len: 0x1000000 0x1123000
(4k PAGE_SIZE, 2M PMD_SIZE)
On the first iteration we would attempt to move 0x0-0x200000 to
0x1000000-0x1200000 and step onto the same WARN(), no?
--
Kirill A. Shutemov
next prev parent reply other threads:[~2020-07-15 20:55 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-15 13:50 [PATCHv2] mm: Fix warning in move_normal_pmd() Kirill A. Shutemov
2020-07-15 18:36 ` Linus Torvalds
2020-07-15 20:54 ` Joel Fernandes
2020-07-15 21:13 ` Kirill A. Shutemov
2020-07-15 21:31 ` Linus Torvalds
2020-07-15 21:43 ` Linus Torvalds
2020-07-15 22:22 ` Kirill A. Shutemov
2020-07-15 22:36 ` Linus Torvalds
2020-07-15 22:57 ` Linus Torvalds
2020-07-15 23:04 ` Linus Torvalds
2020-07-15 23:18 ` Linus Torvalds
2020-07-16 6:37 ` Naresh Kamboju
2020-07-16 7:23 ` Naresh Kamboju
2020-07-16 8:46 ` Kirill A. Shutemov
2020-07-16 8:32 ` Naresh Kamboju
2020-07-16 13:16 ` Kirill A. Shutemov
2020-07-16 17:54 ` Linus Torvalds
2020-07-16 18:47 ` Joel Fernandes
2020-07-15 20:55 ` Kirill A. Shutemov [this message]
2020-07-15 21:35 ` Linus Torvalds
2020-07-15 21:51 ` Linus Torvalds
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=20200715205508.3rzrkhulruzpy6iv@box \
--to=kirill@shutemov.name \
--cc=akpm@linux-foundation.org \
--cc=joel@joelfernandes.org \
--cc=kirill.shutemov@linux.intel.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=naresh.kamboju@linaro.org \
--cc=torvalds@linux-foundation.org \
--cc=william.kucharski@oracle.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).