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Message-ID: <d19e1033-285f-474b-af1f-ae4c32e32e21@oracle.com>
Date: Fri, 26 Apr 2024 13:33:27 -0700
From: Jane Chu <jane.chu@...cle.com>
To: Matthew Wilcox <willy@...radead.org>,
Sidhartha Kumar <sidhartha.kumar@...cle.com>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org,
akpm@...ux-foundation.org, linmiaohe@...wei.com,
nao.horiguchi@...il.com, osalvador@...e.de
Subject: Re: [PATCH] mm/memory-failure: remove shake_page()
My apology for the gobbled message earlier.
On 4/26/2024 12:52 PM, Jane Chu wrote:
> On 4/26/2024 12:05 PM, Matthew Wilcox wrote:
> [..]
>> That would be unsafe, the safe way would be if we moved page_folio()
>> after
>>> the call to __get_hw_poison() in get_any_page() and there would
>>> still be one
>>> remaining user of shake_page() that we can't convert. A safe version
>>> of this
>>> patch would result in a removal of one use of PageHuge() and two
>>> uses of
>>> put_page(), would that be worth submitting?
>>>
>>> get_any_page()
>>> if(__get_hwpoison_page())
>>> folio = page_folio() /* folio_try_get() returned 1, safe */
>> I think we should convert __get_hwpoison_page() to return either the
>> folio
>> or an ERR_PTR or NULL. Also, I think we should delete the "cannot catch
>> tail" part and just loop in __get_hwpoison_page() until we do catch it.
>> See try_get_folio() in mm/gup.c for inspiration (although you can't use
>> it exactly because that code knows that the page is mapped into a page
>> table, so has a refcount).
>>
>> But that's just an immediate assessment; you might find a reason that
>> doesn't work.
>
Besides, in a possible hugetlb demote scenario, it seems to me that we
should retry
get_hwpoison_hugetlb_folio() instead of falling thru to folio_try_get().
static int __get_hwpoison_page(struct page *page, unsigned long flags)
{
struct folio *folio = page_folio(page);
int ret = 0;
bool hugetlb = false;
ret = get_hwpoison_hugetlb_folio(folio, &hugetlb, false);
if (hugetlb) {
/* Make sure hugetlb demotion did not happen from under
us. */
if (folio == page_folio(page))
return ret;
if (ret > 0) { <===== still hugetlb, don't fall
thru, retry
folio_put(folio);
folio = page_folio(page);
}
}
thanks!
-jane
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