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([2a02:6b67:d751:7400:c2b:f323:d172:e42a]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-37ee0a5b98asm9646228f8f.61.2024.10.23.12.59.16 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 23 Oct 2024 12:59:17 -0700 (PDT) Message-ID: <71c0c05b-d731-48c2-8023-5c7cda3518a1@gmail.com> Date: Wed, 23 Oct 2024 20:59:16 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm: avoid VM_BUG_ON when try to map an anon large folio to zero page. To: Zi Yan , linux-mm@kvack.org, Andrew Morton Cc: baohua@kernel.org, cerasuolodomenico@gmail.com, corbet@lwn.net, david@redhat.com, hannes@cmpxchg.org, kernel-team@meta.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, npache@redhat.com, riel@surriel.com, roman.gushchin@linux.dev, rppt@kernel.org, ryan.roberts@arm.com, ryncsn@gmail.com, shakeel.butt@linux.dev, willy@infradead.org, yuzhao@google.com References: <20241023171236.1122535-1-ziy@nvidia.com> Content-Language: en-US From: Usama Arif In-Reply-To: <20241023171236.1122535-1-ziy@nvidia.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: D61881C0012 X-Stat-Signature: 9ppcizbiyf1nm794f5miz87aihugooer X-Rspam-User: X-HE-Tag: 1729713525-146306 X-HE-Meta: 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 Y1NpNsxj 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 23/10/2024 18:12, Zi Yan wrote: > An anonymous large folio can be split into non order-0 folios, > try_to_map_unused_to_zeropage() should not VM_BUG_ON compound pages but > just return false. This fixes the crash when splitting anonymous large > folios to non order-0 folios. > > Fixes: b1f202060afe ("mm: remap unused subpages to shared zeropage when splitting isolated thp") > Signed-off-by: Zi Yan > --- > mm/migrate.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/mm/migrate.c b/mm/migrate.c > index e950fd62607f..7ffdbe078aa7 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -206,7 +206,8 @@ static bool try_to_map_unused_to_zeropage(struct page_vma_mapped_walk *pvmw, > pte_t newpte; > void *addr; > > - VM_BUG_ON_PAGE(PageCompound(page), page); > + if (PageCompound(page)) > + return false; > VM_BUG_ON_PAGE(!PageAnon(page), page); > VM_BUG_ON_PAGE(!PageLocked(page), page); > VM_BUG_ON_PAGE(pte_present(*pvmw->pte), page); Thanks for fixing it! Acked-by: Usama Arif