linux-kernel - Re: [PATCH v2] fs/hugetlbfs/inode.c: mm/memory-failure.c: fix hugetlbfs hwpoison handling

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Date: Tue, 16 Jan 2024 10:43:00 +0800
From: Muchun Song <muchun.song@...ux.dev>
To: Sidhartha Kumar <sidhartha.kumar@...cle.com>
Cc: LKML <linux-kernel@...r.kernel.org>,
 Linux-MM <linux-mm@...ck.org>,
 Andrew Morton <akpm@...ux-foundation.org>,
 usama.anjum@...labora.com,
 Jiaqi Yan <jiaqiyan@...gle.com>,
 "Matthew Wilcox (Oracle)" <willy@...radead.org>,
 Miaohe Lin <linmiaohe@...wei.com>,
 Naoya Horiguchi <naoya.horiguchi@....com>,
 Yang Shi <shy828301@...il.com>,
 James Houghton <jthoughton@...gle.com>,
 jane.chu@...cle.com,
 stable@...r.kernel.org
Subject: Re: [PATCH v2] fs/hugetlbfs/inode.c: mm/memory-failure.c: fix
 hugetlbfs hwpoison handling



> On Jan 13, 2024, at 02:08, Sidhartha Kumar <sidhartha.kumar@...cle.com> wrote:
> 
> has_extra_refcount() makes the assumption that the page cache adds a ref
> count of 1 and subtracts this in the extra_pins case. Commit a08c7193e4f1
> (mm/filemap: remove hugetlb special casing in filemap.c) modifies
> __filemap_add_folio() by calling folio_ref_add(folio, nr); for all cases
> (including hugtetlb) where nr is the number of pages in the folio. We
> should adjust the number of references coming from the page cache by
> subtracing the number of pages rather than 1.
> 
> In hugetlbfs_read_iter(), folio_test_has_hwpoisoned() is testing the wrong
> flag as, in the hugetlb case, memory-failure code calls
> folio_test_set_hwpoison() to indicate poison. folio_test_hwpoison() is the
> correct function to test for that flag.
> 
> After these fixes, the hugetlb hwpoison read selftest passes all cases.
> 
> Fixes: a08c7193e4f1 ("mm/filemap: remove hugetlb special casing in filemap.c")
> Closes: https://lore.kernel.org/linux-mm/20230713001833.3778937-1-jiaqiyan@google.com/T/#m8e1469119e5b831bbd05d495f96b842e4a1c5519
> Cc: <stable@...r.kernel.org> # 6.7+
> Signed-off-by: Sidhartha Kumar <sidhartha.kumar@...cle.com>
> Reported-by: Muhammad Usama Anjum <usama.anjum@...labora.com>

Acked-by: Muchun Song <muchun.song@...ux.dev>

Thanks.