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b=lwL9r7Hh7relOof30oLbXNAQGciP0LI00Mjhi1C6Yz+HE94rQfdQ6sui104q6tvyA 8/iNYuHx5QsBpvHGRjb2xpPUb7DNBCMkSkcLbQwRSgAs4r1mDN8HpQsduhO0wxRQOB QPZDQWIj2jkjYkVfI8IKID5O5/yr+LDE0RgYfyzqpI+hkl7LFZW8blwU19kUBBW7db 00MfvbTPlK8tZZ8JmPHQeaX1lqfRjTNrVKT8V1MNHB4lu/p6xghOBgnsSLxXQZyEQE 5lsdI6kINwdr55RvMd2VGFcXMAcbeB5mtGaUPbJ8Rt1uAxbnWajJL2y6dzmFCZWCcG rLPim2PrhWj6w== Date: Fri, 24 Jul 2026 10:20:22 +0100 From: "Lorenzo Stoakes (ARM)" To: Dev Jain Cc: akpm@linux-foundation.org, david@kernel.org, muchun.song@linux.dev, osalvador@suse.de, 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 Subject: Re: [PATCH v3 1/5] mm/rmap: convert page -> folio for hwpoison checks Message-ID: References: <20260713050050.1017741-1-dev.jain@arm.com> <20260713050050.1017741-2-dev.jain@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260713050050.1017741-2-dev.jain@arm.com> X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 15A8320006 X-Rspam-User: X-Stat-Signature: 1e6pmqq3c68oao9r4jxaeqg6icer67fw X-HE-Tag: 1784884840-438778 X-HE-Meta: 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 K/2+eAv8 vaRSklCBBlY2bnDyXLniaERiDAbAMygLRkCCJebX/t5SEtnO4T84WyITfZjKFIVZzx6nPLoSgDO0MzhjcOkRf2y6EDQw5IkSDC+5QCyyS+QYjRMU2p2EurXk+gZyh7RPcz2ktaAv4GQjPNUFU6pNg9pkfQoLq26Ne7Uf1Zm5CjMLZNimp+MUCzmrtDZhmfGxcDpl1KKSi9eH3sq0IXVgR4oHJuYbEt9XvCgSkM/Wf/fdppKvs9PY1PZ3KMrADXfa5/JS3xADDdq5+FhqsazTigcKt5QRjmS3xsovpaZgi+FtpBXwLIU4Xt84djQvmnf2XB2r6PvOpG+A+eCNY/okKr8DsFA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Jul 13, 2026 at 05:00:44AM +0000, 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 Oops reviewed v2 by mistake. This LGTM so: Reviewed-by: Lorenzo Stoakes (ARM) > --- > mm/rmap.c | 13 +++++++++---- > 1 file changed, 9 insertions(+), 4 deletions(-) > > diff --git a/mm/rmap.c b/mm/rmap.c > index 26166a6b8cb9b..2b74668f356d6 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); Thanks for converting this also! > /* > * 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. > + */ > + if (folio_test_hwpoison(folio) && (flags & TTU_HWPOISON)) { As per v2 discussion, I feel this could be tightened up, maybe something like: /* unmap_poisoned_folio() only refs order-0 or hugetlb folios */ > pteval = swp_entry_to_pte(make_hwpoison_entry(subpage)); > if (folio_test_hugetlb(folio)) { > hugetlb_count_sub(folio_nr_pages(folio), mm); > -- > 2.43.0 > Cheers, Lorenzo