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AJvYcCUNwgScSPWmrq07K0nO6mxsYVhL/nNrQg85//3G76fSKp6QFnNoDJfOXs6pmJcNKV1XQ1Jt4e4M8Q==@kvack.org X-Gm-Message-State: AOJu0YzvzulGHgZ0wCnbLvm3fbL1LdkKVOHC+RlSjrQMElIXl9Khwt7r bBE97rrkqdLrsGLTEq4LCohM+rlOOu+bwnDYG1TGzew3vnxM33rNIBoMd/wlFR9lZlQHYVR1vru VWNfSLvoqJqIErrcoJEY6RXc5zohpFWk= X-Gm-Gg: ASbGncvap3mdgbJyHV8F7bJDD4KsWy1qgIIoE0OrLboUd3390NnIpNJ1hCxF3/ZS7Ob /YfhShpKVziuXVkoPe4J4m223Gorvrk6BHoq+NGtQMw64Bq1x+tfOwb+iD1bL/y8/o9KqwSFRi9 Ghdib20fGqR4VBCwx3jl4z0mL1wDpsnywDqQnzEYsddx1W8jS2/nBjuedtz+FJQmO1ju0/WMnD3 dme/s0fv3R0w+Zsx2zrgo+5gltZX8MlwsqSrv53ZOHUrhorTxdpJ6YhV79LPyfaIaLfif9wCQ== X-Google-Smtp-Source: AGHT+IH7M+imCkUPIEM0gojaqd/rG3Zx43O7A6mvp4uWZ0+fXegjfowMFGF2jPMC9fA+q+PtLYZiTxzhKO7/x560Dos= X-Received: by 2002:a17:907:25cc:b0:b40:c49b:710 with SMTP id a640c23a62f3a-b6475129316mr2333654966b.47.1761156494265; Wed, 22 Oct 2025 11:08:14 -0700 (PDT) MIME-Version: 1.0 References: <20251022101704.4015055-1-catalin.marinas@arm.com> In-Reply-To: <20251022101704.4015055-1-catalin.marinas@arm.com> From: Yang Shi Date: Wed, 22 Oct 2025 11:08:02 -0700 X-Gm-Features: AS18NWC2FvbWTzA8C7rrkZW5hEdgmLMERlEUwWO1avl88qM2ea0eHvXPjFT8k2c Message-ID: Subject: Re: [PATCH v2] arm64: mte: Do not warn if the page is already tagged in copy_highpage() To: Catalin Marinas Cc: linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, syzbot+d1974fc28545a3e6218b@syzkaller.appspotmail.com, David Hildenbrand , Will Deacon , Kefeng Wang Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Stat-Signature: 6ifg65qk4oc3fgdx91adug78nnrs3yzc X-Rspamd-Queue-Id: 5001240015 X-Rspamd-Server: rspam06 X-Rspam-User: X-HE-Tag: 1761156496-841116 X-HE-Meta: U2FsdGVkX1/LQiczwtCdwZTziM7EJY0+/duzK5/notc/dSFwbA/SUaOXpAxy3osVEGiOkDFoi7jxHgnurKWa6n5MQKqx2VhrnahqNQZzMTTkTjnBgVFoSTjojZhlCBhSqqgAmCkuRyI4mRAx28+/2auoJwLzk/VMhJVIsYCZVaalE8oZU3gH6GQmH0hEWnlXsiNe6XPAvFGAEKfZa0b0pfEusmYjVtYMSBJy8ZVK9zbacWdTfZO1uHRO8sQPIVZQ1JT0J/qOa7dTMC11+a3GWG7U7x5D23LmJOmK15KW0UCYtG3Tpx64NSujKcBuaLPswKFkm1tYpCYquFNCBXnaMsXthfntUh9gjo5e9xd7yMfuX5jVPu87f8tHEeVaw4mYJuGz/AdBnO39Xal+IawRodpU3Ip9vWGEbxQeg8ZC9p0ZGGyPTsUffcl/gy/1GdbZY29NN7XkIGrL7ysixUpu6B2wWDf27UKq9a8VuYP5hWVljbbRL4HZ0xxNXPYarDx33/EPZsAFSRCLIjG4qh8gVe97ALKURAMZGQSk/LqhGKJtIwprWJndWffzjsAF6vqE4wH0eTibTdDaKfnEyqEPkmouhASX+p/pUkFUIQz2MTbFDQv8Jp/q1jBju1vrpUQH+OmsP/snmuwC9fZQJDI9z8+pEhEsvGCKBGTgAzblt+bIuxF+PJ681nqUsadkTWK4aHGygYUBJAcYpzx8QN9TH6e7ULuIU7sqNOfCpIU0o/BfSUzEvp2rut5+vdexj5lZDCuoXCgrnYwRlktbC4OPsZpNrqwbjguE4frgqJQIXwsgci/08rLEyn7KL+73iKccHiijjAZCyC+5iexThCNuho+EndWYSknC7NXfXsJY/68E/b0qZpDMVV5yMoE+WEhLnjx0B48897bCPMfgq2J/bHbIpBtYKNAOc9Yap6MRConZPt6zK6NQ9zZBm/bpzaArJyHYJK6Yj3DyyYnXpT0 hgGaXXyj uXhCR4bl3RvscaybIU6cOgcbsTrK+Oitl7MTNLbo4Z/fAhyX3mA2gZ0xyy2P8Vnb7UTjGZQP6iQATAhDsMS9qUt9cE7C4zn2sMiWxO9D+Y8zhH+Rm9n2h0sUaE6x70SogXanoR8kVisQ9e2mFWuv7WBsp+cAHqkv3J9HTHpXROwtfK571Duc7kMdrPmgdeXXl/Qe+BiAwIbvekfOaAxhCLOOtpgvK7PTowJoAAWPfXUv6W5qJbZj8gAakqK6VrPUk0bfAG/kTimM3uXyLiQffvGW3F+xWS8V6pPK3uE6iMpn2ndclwTX2BSLkhL9C6iN38DA21w3azfBzYJwJh24UtV5J8wcnuVg/ToDDeBCDDi0rMdKtip5A+w1C8pl9wKZm5wd7A2O8XI/b4/ouiMCFxi9ZM/hoXfW2vSaJGAl6z/AoFL58tBldUxLxbK21KE03xPJjSvH2Tm5V7c3Cjd/OxSNDTpj3U0l6ldX6sFquyIqfXP+B69i7pzI0j7MzAkLd7Mn4J/oWMkL9zUJqnGepoNJRmjfg4z4wQC5BYUD55xVmEsCNknThZW8/lux6TAJfwyduEt7GvcpEqyZaJHqQl8bBLnOypp0rZei93hDBPpPCZ4XANdxXdavFcBWqlI0Z4UtGLLeQ9vm+jEw0V89X/A/9UiV9vOyRmdWXRhRUWXEX7E8BWcsDTXBzORzUYa8Yms8Q96PZgsg7hpcmJELXDX5aqZ4+UMirsfCND7R3qPL1Ut6DIvK9cqTXWdFfte0nPMOQznWXgEhfNELi14bb5+hI7CMZKzPqteIdpA4T+a2S0ak= 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 Wed, Oct 22, 2025 at 3:20=E2=80=AFAM Catalin Marinas wrote: > > The arm64 copy_highpage() assumes that the destination page is newly > allocated and not MTE-tagged (PG_mte_tagged unset) and warns > accordingly. However, following commit 060913999d7a ("mm: migrate: > support poisoned recover from migrate folio"), folio_mc_copy() is called > before __folio_migrate_mapping(). If the latter fails (-EAGAIN), the > copy will be done again to the same destination page. Since > copy_highpage() already set the PG_mte_tagged flag, this second copy > will warn. > > Replace the WARN_ON_ONCE(page already tagged) in the arm64 > copy_highpage() with a comment. > > Signed-off-by: Catalin Marinas > Reported-by: syzbot+d1974fc28545a3e6218b@syzkaller.appspotmail.com > Link: https://lore.kernel.org/r/68dda1ae.a00a0220.102ee.0065.GAE@google.c= om > Reviewed-by: David Hildenbrand > Cc: Will Deacon > Cc: Kefeng Wang > Cc: # 6.12.x > --- > > v2: > - Also remove the WARN_ON_ONCE for hugetlb pages > - Drop a double-underscore in the commit log Reviewed-by: Yang Shi > > arch/arm64/mm/copypage.c | 11 ++++++++--- > 1 file changed, 8 insertions(+), 3 deletions(-) > > diff --git a/arch/arm64/mm/copypage.c b/arch/arm64/mm/copypage.c > index a86c897017df..cd5912ba617b 100644 > --- a/arch/arm64/mm/copypage.c > +++ b/arch/arm64/mm/copypage.c > @@ -35,7 +35,7 @@ void copy_highpage(struct page *to, struct page *from) > from !=3D folio_page(src, 0)) > return; > > - WARN_ON_ONCE(!folio_try_hugetlb_mte_tagging(dst)); > + folio_try_hugetlb_mte_tagging(dst); > > /* > * Populate tags for all subpages. > @@ -51,8 +51,13 @@ void copy_highpage(struct page *to, struct page *from) > } > folio_set_hugetlb_mte_tagged(dst); > } else if (page_mte_tagged(from)) { > - /* It's a new page, shouldn't have been tagged yet */ > - WARN_ON_ONCE(!try_page_mte_tagging(to)); > + /* > + * Most of the time it's a new page that shouldn't have b= een > + * tagged yet. However, folio migration can end up reusin= g the > + * same page without untagging it. Ignore the warning if = the > + * page is already tagged. > + */ > + try_page_mte_tagging(to); > > mte_copy_page_tags(kto, kfrom); > set_page_mte_tagged(to); >