linux-kernel - Re: [PATCH v7 00/14] HWPOISON: soft offline rework

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Message-ID: <20200923132911.GF17169@cathedrallabs.org>
Date:   Wed, 23 Sep 2020 09:29:12 -0400
From:   Aristeu Rozanski <aris@...vo.org>
To:     Oscar Salvador <osalvador@...e.de>
Cc:     akpm@...ux-foundation.org, naoya.horiguchi@....com,
        mhocko@...nel.org, tony.luck@...el.com, cai@....pw,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH v7 00/14] HWPOISON: soft offline rework

Hi Oscar,

On Tue, Sep 22, 2020 at 03:56:36PM +0200, Oscar Salvador wrote:
> This patchset is the latest version of soft offline rework patchset
> targetted for v5.9.
> 
> This patchset fixes a couple of issues that the patchset Naoya
> sent [1] contained due to rebasing problems and a misunterdansting.
> 
> Main focus of this series is to stabilize soft offline.  Historically soft
> offlined pages have suffered from racy conditions because PageHWPoison is
> used to a little too aggressively, which (directly or indirectly) invades
> other mm code which cares little about hwpoison.  This results in unexpected
> behavior or kernel panic, which is very far from soft offline's "do not
> disturb userspace or other kernel component" policy.
> An example of this can be found here [2].
> 
> Along with several cleanups, this code refactors and changes the way soft
> offline work.
> Main point of this change set is to contain target page "via buddy allocator"
> or in migrating path.
> For ther former we first free the target page as we do for normal pages, and
> once it has reached buddy and it has been taken off the freelists, we flag it
> as HWpoison.
> For the latter we never get to release the page in unmap_and_move, so
> the page is under our control and we can handle it in hwpoison code.
> 
> [1] https://patchwork.kernel.org/cover/11704083/
> [2] https://lore.kernel.org/linux-mm/20190826104144.GA7849@linux/T/#u

FWIW, tested again with these patches in the ppc64 box and they work.
I see that you added my Tested-by in the last patch but in any case:

Tested-by: Aristeu Rozanski <aris@...vo.org>

-- 
Aristeu