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Date: Thu, 11 Jan 2024 18:03:57 +0000
From: Matthew Wilcox <willy@infradead.org>
To: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Jiaqi Yan <jiaqiyan@google.com>,
	Muhammad Usama Anjum <usama.anjum@collabora.com>,
	linmiaohe@huawei.com, mike.kravetz@oracle.com,
	naoya.horiguchi@nec.com, akpm@linux-foundation.org,
	songmuchun@bytedance.com, shy828301@gmail.com, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org, jthoughton@google.com,
	"kernel@collabora.com" <kernel@collabora.com>
Subject: Re: [PATCH v4 4/4] selftests/mm: add tests for HWPOISON hugetlbfs
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In-Reply-To: <6bacbd7c-88cb-1399-8bd0-db98c93a1adf@oracle.com>

On Thu, Jan 11, 2024 at 09:51:47AM -0800, Sidhartha Kumar wrote:
> On 1/11/24 9:34 AM, Jiaqi Yan wrote:
> > > -                       if (!folio_test_has_hwpoisoned(folio))
> > > +                       if (!folio_test_hwpoison(folio))
> > 
> > Sidhartha, just curious why this change is needed? Does
> > PageHasHWPoisoned change after commit
> > "a08c7193e4f18dc8508f2d07d0de2c5b94cb39a3"?
> 
> No its not an issue PageHasHWPoisoned(), the original code is testing for
> the wrong flag and I realized that has_hwpoison and hwpoison are two
> different flags. The memory-failure code calls folio_test_set_hwpoison() to
> set the hwpoison flag and does not set the has_hwpoison flag. When
> debugging, I realized this if statement was never true despite the code
> hitting folio_test_set_hwpoison(). Now we are testing the correct flag.
> 
> From page-flags.h
> 
> #ifdef CONFIG_MEMORY_FAILURE
> 	PG_hwpoison,		/* hardware poisoned page. Don't touch */
> #endif
> 
> folio_test_hwpoison() checks this flag ^^^
> 
> /* At least one page in this folio has the hwpoison flag set */
> PG_has_hwpoisoned = PG_error,
> 
> while folio_test_has_hwpoisoned() checks this flag ^^^

So what you're saying is that hugetlb behaves differently from THP
with how memory-failure sets the flags?