linux-kernel - Re: [PATCH v2] mm/huge_memory: don't unpoison huge_zero

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Message-ID: <ZkXDS9y_cBSzBzeN@localhost.localdomain>
Date: Thu, 16 May 2024 10:26:51 +0200
From: Oscar Salvador <osalvador@...e.de>
To: David Hildenbrand <david@...hat.com>
Cc: Miaohe Lin <linmiaohe@...wei.com>, akpm@...ux-foundation.org,
	shy828301@...il.com, nao.horiguchi@...il.com,
	xuyu@...ux.alibaba.com, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] mm/huge_memory: don't unpoison huge_zero_folio

On Wed, May 15, 2024 at 05:55:39PM +0200, David Hildenbrand wrote:
> > +	if (is_huge_zero_folio(folio)) {
> > +		unpoison_pr_info("Unpoison: huge zero page is not supported %#lx\n",
> > +				 pfn, &unpoison_rs);
> > +		goto unlock_mutex;
> > +	}
> > +

Sorry for spamming your reply David, but for some unknown reason I am not able
to find the original patch in my mailbox, in none of the two accountes I am
subscribed, so I guess I will have to reply here.

Just two things

1) We do not care if someone grabs a refcount for huge_zero_folio,
   because since it is not supported anyway the outcome will not change.
   Also, AFAIK, there is no chance we can unpoison that folio.
   Therefore, I would just lift the check two blocks and place it right after
   the hw_memory_failure check.

2) The whole thing is unsupported, but you will return -EBUSY while you
   should be returning -EOPNOTSUPP AFAICS.

with that you can add:

Reviewed-by: Oscar Salvador <osalvador@...e.de>

-- 
Oscar Salvador
SUSE Labs