Re: [PATCH AUTOSEL 4.14 71/95] Revert "mm, memory_hotplug: initialize struct pages for the full memory section"

From: Alexander Duyck <alexander.duyck@gmail.com>
To: Sasha Levin <sashal@kernel.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
	stable@vger.kernel.org,  Michal Hocko <mhocko@suse.com>,
	Robert Shteynfeld <robert.shteynfeld@gmail.com>,
	stable@kernel.org,
	 Linus Torvalds <torvalds@linux-foundation.org>,
	Sasha Levin <alexander.levin@microsoft.com>,
	 linux-mm <linux-mm@kvack.org>
Subject: Re: [PATCH AUTOSEL 4.14 71/95] Revert "mm, memory_hotplug: initialize struct pages for the full memory section"
Date: Tue, 7 May 2019 10:25:40 -0700	[thread overview]
Message-ID: <CAKgT0Uf89zkZDU5d5GO-i4B4igASXWqUioWCpoTsY92V4gEWjg@mail.gmail.com> (raw)
In-Reply-To: <20190507053826.31622-71-sashal@kernel.org>

On Mon, May 6, 2019 at 10:40 PM Sasha Levin <sashal@kernel.org> wrote:
>
> From: Michal Hocko <mhocko@suse.com>
>
> [ Upstream commit 4aa9fc2a435abe95a1e8d7f8c7b3d6356514b37a ]
>
> This reverts commit 2830bf6f05fb3e05bc4743274b806c821807a684.
>
> The underlying assumption that one sparse section belongs into a single
> numa node doesn't hold really. Robert Shteynfeld has reported a boot
> failure. The boot log was not captured but his memory layout is as
> follows:
>
>   Early memory node ranges
>     node   1: [mem 0x0000000000001000-0x0000000000090fff]
>     node   1: [mem 0x0000000000100000-0x00000000dbdf8fff]
>     node   1: [mem 0x0000000100000000-0x0000001423ffffff]
>     node   0: [mem 0x0000001424000000-0x0000002023ffffff]
>
> This means that node0 starts in the middle of a memory section which is
> also in node1.  memmap_init_zone tries to initialize padding of a
> section even when it is outside of the given pfn range because there are
> code paths (e.g.  memory hotplug) which assume that the full worth of
> memory section is always initialized.
>
> In this particular case, though, such a range is already intialized and
> most likely already managed by the page allocator.  Scribbling over
> those pages corrupts the internal state and likely blows up when any of
> those pages gets used.
>
> Reported-by: Robert Shteynfeld <robert.shteynfeld@gmail.com>
> Fixes: 2830bf6f05fb ("mm, memory_hotplug: initialize struct pages for the full memory section")
> Cc: stable@kernel.org
> Signed-off-by: Michal Hocko <mhocko@suse.com>
> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
> Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
> ---
>  mm/page_alloc.c | 12 ------------
>  1 file changed, 12 deletions(-)

So it looks like you already had the revert of the earlier patch I
pointed out enqueued as well. So you can probably at a minimum just
drop this patch and the earlier patch that this reverts.

Thanks.

- Alex