linux-kernel - Re: [RFC v3 PATCH 0/5] Solve silent data loss caused by poisoned page cache (shmem/tmpfs)

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Message-ID: <YWZHOYgFrMYbmNA/@t490s>
Date:   Wed, 13 Oct 2021 10:40:57 +0800
From:   Peter Xu <peterx@...hat.com>
To:     Yang Shi <shy828301@...il.com>
Cc:     naoya.horiguchi@....com, hughd@...gle.com,
        kirill.shutemov@...ux.intel.com, willy@...radead.org,
        osalvador@...e.de, akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC v3 PATCH 0/5] Solve silent data loss caused by poisoned
 page cache (shmem/tmpfs)

On Thu, Sep 30, 2021 at 02:53:06PM -0700, Yang Shi wrote:
> Yang Shi (5):
>       mm: hwpoison: remove the unnecessary THP check
>       mm: filemap: check if THP has hwpoisoned subpage for PMD page fault
>       mm: hwpoison: refactor refcount check handling
>       mm: shmem: don't truncate page if memory failure happens
>       mm: hwpoison: handle non-anonymous THP correctly

Today I just noticed one more thing: unpoison path has (unpoison_memory):

	if (page_mapping(page)) {
		unpoison_pr_info("Unpoison: the hwpoison page has non-NULL mapping %#lx\n",
				 pfn, &unpoison_rs);
		return 0;
	}

I _think_ it was used to make sure we ignore page that was not successfully
poisoned/offlined before (for anonymous), so raising this question up on
whether we should make sure e.g. shmem hwpoisoned pages still can be unpoisoned
for debugging purposes.

-- 
Peter Xu