All of lore.kernel.org
 help / color / mirror / Atom feed
From: Michal Hocko <mhocko@suse.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Pingfan Liu <kernelfans@gmail.com>,
	linux-mm@kvack.org, David Hildenbrand <david@redhat.com>,
	Dan Williams <dan.j.williams@intel.com>,
	Oscar Salvador <osalvador@suse.de>, Baoquan He <bhe@redhat.com>,
	Qian Cai <cai@lca.pw>,
	kexec@lists.infradead.org, Kazuhito Hagio <k-hagio@ab.jp.nec.com>
Subject: Re: [PATCHv2] mm/sparse: reset section's mem_map when fully deactivated
Date: Fri, 24 Jan 2020 07:49:32 +0100	[thread overview]
Message-ID: <20200124064932.GN29276@dhcp22.suse.cz> (raw)
In-Reply-To: <20200123191047.bc51b301e5ea0aae6eeecbd5@linux-foundation.org>

On Thu 23-01-20 19:10:47, Andrew Morton wrote:
> On Mon, 20 Jan 2020 08:29:39 +0100 Michal Hocko <mhocko@suse.com> wrote:
> 
> > On Mon 20-01-20 10:33:14, Pingfan Liu wrote:
> > > After commit ba72b4c8cf60 ("mm/sparsemem: support sub-section hotplug"),
> > > when a mem section is fully deactivated, section_mem_map still records the
> > > section's start pfn, which is not used any more and will be reassigned
> > > during re-added.
> > > 
> > > In analogy with alloc/free pattern, it is better to clear all fields of
> > > section_mem_map.
> > > 
> > > Beside this, it breaks the user space tool "makedumpfile" [1], which makes
> > > assumption that a hot-removed section has mem_map as NULL, instead of
> > > checking directly against SECTION_MARKED_PRESENT bit. (makedumpfile will be
> > > better to change the assumption, and need a patch)
> > > 
> > > The bug can be reproduced on IBM POWERVM by "drmgr -c mem -r -q 5" ,
> > > trigger a crash, and save vmcore by makedumpfile
> > 
> > While makedumpfile lives very closely to the kernel and occasional
> > breakage is to be expected I still believe that Fixes: ba72b4c8cf60
> > is due.
> 
> But not a cc:stable?

Well, I wouldn't say this is really critical. makedumpfile will get its
fix... But if people think it would be useful in stable I won't oppose. 
-- 
Michal Hocko
SUSE Labs


  reply	other threads:[~2020-01-24  6:49 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-20  2:33 [PATCHv2] mm/sparse: reset section's mem_map when fully deactivated Pingfan Liu
2020-01-20  7:29 ` Michal Hocko
2020-01-20  9:03   ` David Hildenbrand
2020-01-20 10:12     ` Pingfan Liu
2020-01-24  3:10   ` Andrew Morton
2020-01-24  6:49     ` Michal Hocko [this message]
2020-01-25 13:26       ` Pingfan Liu

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=20200124064932.GN29276@dhcp22.suse.cz \
    --to=mhocko@suse.com \
    --cc=akpm@linux-foundation.org \
    --cc=bhe@redhat.com \
    --cc=cai@lca.pw \
    --cc=dan.j.williams@intel.com \
    --cc=david@redhat.com \
    --cc=k-hagio@ab.jp.nec.com \
    --cc=kernelfans@gmail.com \
    --cc=kexec@lists.infradead.org \
    --cc=linux-mm@kvack.org \
    --cc=osalvador@suse.de \
    /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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.