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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 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: 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 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