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h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=LJPj6Vqbkc3mTMUAI93C8NbOwBloaliXm1yDvo2pCycXonU39JnmEbEGvRotUsJQs v3buCtsFQPWzwqGa6zUBfB8e5rsaJp3KNo8qcyHZBphFbqSqYPaG89oDANyNyHz3ci AfbaYh0DMEzBATMahNiSDoLVM90p3NKgu7nNs2/Y= Message-ID: Date: Fri, 10 Jul 2026 18:44:32 +0530 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 1/5] mm/rmap: convert page -> folio for hwpoison checks To: "David Hildenbrand (Arm)" , akpm@linux-foundation.org, ljs@kernel.org, muchun.song@linux.dev, osalvador@suse.de Cc: riel@surriel.com, liam@infradead.org, vbabka@kernel.org, harry@kernel.org, jannh@google.com, lance.yang@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, ryan.roberts@arm.com, anshuman.khandual@arm.com References: <20260710055915.638659-1-dev.jain@arm.com> <20260710055915.638659-2-dev.jain@arm.com> <87b94730-7543-487e-8f3e-c13251a00a21@kernel.org> Content-Language: en-US From: Dev Jain In-Reply-To: <87b94730-7543-487e-8f3e-c13251a00a21@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: sn8gsk77ygtt5bawuffdcxwytt8pt9x9 X-Rspamd-Queue-Id: 5C2AE4000C X-Rspam-User: X-Rspamd-Server: rspam07 X-HE-Tag: 1783689280-323783 X-HE-Meta: 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 pzBYYeqQ 9UpgXi8rUNQMstrekuwS921m/bUbuXdAZWzhxcl257UMDYltc86XX1KASQpckd66EN1vhk0xoYg8gqF7LodVwoftJ2tTADOJqc7/e1D3Sae0w3Z703bC6Y3buF4+EFvpUClAVvXfXu0qWRSGVqHAy0YJAlCNbtM7D5exLpvYaQSJssdablBWcWnP+vHLxtsBOXgH0BBR8WEjkCWKo8Yc4t9cWig02wK26FHv2ElmNxq1ITX9REOs6yPp/BY8f0eQ/YpjYdV8A5HyzAQBbbHSmtKs8vPiILBa9L3OnFiIOrGYe+CGzLhG/r69iOsmc2ol9MkSA Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 10/07/26 5:52 pm, David Hildenbrand (Arm) wrote: > On 7/10/26 07:59, Dev Jain wrote: >> try_to_unmap() receives hugetlb folios only from the hwpoison path. >> hugetlb_update_hwpoison() sets the hugetlb folio's head-page >> hwpoison bit, and page_vma_mapped_walk() reports the hugetlb mapping at >> the head PFN, so the previous PageHWPoison(subpage) check happened to >> work for hugetlb. >> >> For non-hugetlb folios, unmap_poisoned_folio() currently rejects large >> folios before calling try_to_unmap(). Hence it is always the case that >> if try_to_unmap_one() handles an hwpoisoned folio, then the head page is >> marked with the poison bit. >> >> Therefore, convert the poisoned subpage checks to folio_test_hwpoison(). >> >> No functional change intended, except that, while at it, >> convert VM_BUG_* to VM_WARN_*. >> >> Acked-by: David Hildenbrand (Arm) >> Signed-off-by: Dev Jain >> --- >> mm/rmap.c | 13 +++++++++---- >> 1 file changed, 9 insertions(+), 4 deletions(-) >> >> diff --git a/mm/rmap.c b/mm/rmap.c >> index 9939400e77c79..dbb077f8443e3 100644 >> --- a/mm/rmap.c >> +++ b/mm/rmap.c >> @@ -2122,10 +2122,11 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma, >> bool anon = folio_test_anon(folio); >> >> /* >> - * The try_to_unmap() is only passed a hugetlb page >> - * in the case where the hugetlb page is poisoned. >> + * The try_to_unmap() is only passed a hugetlb folio >> + * in the case where the hugetlb folio contains a >> + * poisoned page. >> */ >> - VM_BUG_ON_PAGE(!PageHWPoison(subpage), subpage); >> + VM_WARN_ON_FOLIO(!folio_test_hwpoison(folio), folio); >> /* >> * huge_pmd_unshare may unmap an entire PMD page. >> * There is no way of knowing exactly which PMDs may >> @@ -2204,7 +2205,11 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma, >> /* Update high watermark before we lower rss */ >> update_hiwater_rss(mm); >> >> - if (PageHWPoison(subpage) && (flags & TTU_HWPOISON)) { >> + /* >> + * With TTU_HWPOISON, we only expect small folios or hugetlb >> + * folios here for now. >> + */ > > Is this comment helpful given that you change that in patch #2, where you forget > to update the comment? :) Nice spot, let me update this comment in patch 2. >