From: zhong jiang <zhongjiang@huawei.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
akpm@linux-foundation.org, qiuxishi@huawei.com, vbabka@suse.cz,
mm-commits@vger.kernel.org,
Mike Kravetz <mike.kravetz@oracle.com>,
Mel Gorman <mgorman@suse.de>,
linux-mm@kvack.org
Subject: Re: + mm-hugetlb-fix-race-when-migrate-pages.patch added to -mm tree
Date: Thu, 21 Jul 2016 21:58:23 +0800 [thread overview]
Message-ID: <5790D4FF.8070907@huawei.com> (raw)
In-Reply-To: <20160721134044.GL26379@dhcp22.suse.cz>
On 2016/7/21 21:40, Michal Hocko wrote:
> On Thu 21-07-16 21:25:38, zhong jiang wrote:
>> On 2016/7/21 20:55, Michal Hocko wrote:
> [...]
>>> OK, now I understand what you mean. So you mean that a different process
>>> initiates the migration while this path copies to pte. That is certainly
>>> possible but I still fail to see what is the problem about that.
>>> huge_pte_alloc will return the identical pte whether it is regular or
>>> migration one. So what exactly is the problem?
>>>
>> copy_hugetlb_page_range obtain the shared dst_pte, it may be not equal
>> to the src_pte. The dst_pte can come from other process sharing the
>> mapping.
> So you mean that the parent doesn't have the shared pte while the child
> would get one?
>
no, parent must have the shared pte because the the child copy the parent. but parent is
not the only source pte we can get. when we scan the maping->i_mmap, firstly ,it can obtain
a shared pte from other process. but I am not sure.
>> /* If the pagetables are shared don't copy or take references */
>> if (dst_pte == src_pte)
>> continue;
>>
>> Even it do the fork path, we scan the i_mmap to find same pte. I think
>> that dst_pte may come from other process. It is not the parent. it
>> will lead to the dst_pte is not equal to the src_pte from the parent.
> Let's say this would be possible (I am not really sure but for the sake
> of argumentation), if the src is not shared while dst is shared and the
> page is under migration then all the page table should be marked as
> swap migrate entries no? If they are not and copy_hugetlb_page_range
> cannot handle with that then it is a bug in copy_hugetlb_page_range
> which doesn't have anything to do with the BUG_ON in huge_pte_alloc.
> So I would argue that if the problem exists at all it is a separate
> issue IMHO.
yes, it is a separate issule.
> Naoya, could you comment on that please?
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2016-07-21 14:00 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <578eb28b.YbRUDGz5RloTVlrE%akpm@linux-foundation.org>
2016-07-21 7:43 ` + mm-hugetlb-fix-race-when-migrate-pages.patch added to -mm tree Michal Hocko
2016-07-21 8:13 ` Naoya Horiguchi
2016-07-21 10:29 ` Michal Hocko
2016-07-21 10:54 ` zhong jiang
2016-07-21 11:27 ` Michal Hocko
2016-07-21 12:14 ` zhong jiang
2016-07-21 12:30 ` Michal Hocko
2016-07-21 12:45 ` zhong jiang
2016-07-21 12:55 ` Michal Hocko
2016-07-21 13:25 ` zhong jiang
2016-07-21 13:40 ` Michal Hocko
2016-07-21 13:58 ` zhong jiang [this message]
2016-07-21 14:01 ` Michal Hocko
2016-07-21 14:13 ` zhong jiang
2016-07-21 14:27 ` Michal Hocko
2016-07-21 14:33 ` zhong jiang
2016-07-22 7:17 ` Naoya Horiguchi
2016-07-26 7:58 ` Michal Hocko
2016-07-26 14:04 ` zhong jiang
2016-07-27 14:44 ` Michal Hocko
2016-07-29 11:27 ` Michal Hocko
2016-07-30 6:33 ` zhong jiang
2016-08-01 11:02 ` Michal Hocko
2016-08-01 15:04 ` zhong jiang
2016-08-01 15:31 ` Michal Hocko
[not found] <003701d1e328$202ca9d0$6085fd70$@alibaba-inc.com>
2016-07-21 8:19 ` Hillf Danton
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=5790D4FF.8070907@huawei.com \
--to=zhongjiang@huawei.com \
--cc=akpm@linux-foundation.org \
--cc=linux-mm@kvack.org \
--cc=mgorman@suse.de \
--cc=mhocko@kernel.org \
--cc=mike.kravetz@oracle.com \
--cc=mm-commits@vger.kernel.org \
--cc=n-horiguchi@ah.jp.nec.com \
--cc=qiuxishi@huawei.com \
--cc=vbabka@suse.cz \
/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).