From: Dan Williams <dan.j.williams@intel.com>
To: Pingfan Liu <kernelfans@gmail.com>
Cc: Michal Hocko <mhocko@suse.com>, Linux-MM <linux-mm@kvack.org>,
Andrew Morton <akpm@linux-foundation.org>,
David Hildenbrand <david@redhat.com>,
Oscar Salvador <osalvador@suse.de>,
Kexec Mailing List <kexec@lists.infradead.org>,
Kazuhito Hagio <k-hagio@ab.jp.nec.com>
Subject: Re: [PATCH] mm/sparse: reset section's mem_map when fully deactivated
Date: Thu, 16 Jan 2020 23:14:02 -0800 [thread overview]
Message-ID: <CAPcyv4iOQHrZ1c13vNN_UqVyKu5O5zqrMvdMHbLHmCjPW6a=Pw@mail.gmail.com> (raw)
In-Reply-To: <CAFgQCTuG6K3nbKDjp3SJFLNqsx2gaC_TGWcgL0vzDcD_Gv7VdA@mail.gmail.com>
On Thu, Jan 16, 2020 at 10:23 PM Pingfan Liu <kernelfans@gmail.com> wrote:
>
> On Thu, Jan 16, 2020 at 3:50 PM Michal Hocko <mhocko@suse.com> wrote:
> >
> > On Thu 16-01-20 11:01:08, Pingfan Liu wrote:
> > > When fully deactivated, it is meaningless to keep the value of a section's
> > > mem_map. And its mem_map will be reassigned during re-added.
> > >
> > > Beside this, it breaks the user space tool "makedumpfile", which makes
> > > assumption that a hot-removed section having mem_map as NULL.
> >
> > We used to do that before ba72b4c8cf60 ("mm/sparsemem: support
> > sub-section hotplug"). Dan was this an intentional change?
> I do not know the purpose of this. But the change just leave section
> start pfn in fully deactivated section_mem_map, and not used any more.
Not intentional, IIRC at the time I had convinced myself that the
value would always be translated by sparse_decode_mem_map(), so I
thought it could be hiding NULL de-references. I don't see any harm
in the patch.
next prev parent reply other threads:[~2020-01-17 7:14 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-16 3:01 Pingfan Liu
2020-01-16 3:18 ` Qian Cai
2020-01-16 3:34 ` Pingfan Liu
2020-01-16 7:50 ` Michal Hocko
2020-01-17 6:22 ` Pingfan Liu
2020-01-17 7:14 ` Dan Williams [this message]
2020-01-17 7:47 ` Michal Hocko
2020-01-17 9:49 ` Pingfan Liu
2020-01-17 9:52 ` David Hildenbrand
2020-01-20 2:31 ` Pingfan Liu
2020-01-16 8:06 ` David Hildenbrand
2020-01-16 8:14 ` David Hildenbrand
2020-01-16 8:24 ` Baoquan He
2020-01-16 8:57 ` David Hildenbrand
2020-01-17 6:20 ` Pingfan Liu
2020-01-17 6:18 ` Pingfan Liu
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