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smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=R7xKMfQW; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id BCF84606A326; Sat, 7 Nov 2026 19:41:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=R7xKMfQW Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8C4C31F0089F; Sat, 7 Nov 2026 19:41:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794080488; bh=qrayV5HgmTcSMMMhveHmxbWzQ03GCDulO+jtmHjEwSs=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=R7xKMfQWAmEBP+7jr8m/rTZ0qcf3cHfKaGgUQmL4AL+Jj4Q2KlaWLJPKn2wxc/iKK w9lZQcb/W0uS33hvwpHeyja1a1AQGSExELOIHIA+c/XPHnmuVxQ56RTUbkNWaePdN+ SB78P3uixsTGMMZNrngsUP4hm6/kMzANIxudL81PFPRxkj4MztpEE7T1Kn7dxsTZmz PhkVPpKh/5AYLInaD/Ev+Y+vUawgIT+MO67PN3fHo5eAvvaSeA2gbcEXbMlKgwbKUS MozNuMr9XlaQ1OoA7p69wSmY1N6ilueUU+3XjSJknb7Y7qum6Wb/FLvYPYvJ3s1Wzf Ll0jmq/T6D4tw== Message-ID: Date: Sat, 7 Nov 2026 20:41:20 +0100 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/memory_hotplug: don't offline a hwpoisoned page still in the page cache To: Mani Tofigh , Oscar Salvador , Andrew Morton Cc: Miaohe Lin , Naoya Horiguchi , Vlastimil Babka , Gregory Price , linux-mm@kvack.org, linux-cxl@vger.kernel.org, linux-kernel@vger.kernel.org, tz2294@columbia.edu, stable@vger.kernel.org References: <20261101-memhp-hwpoison-pagecache-v1-1-ed8785ca44eb@columbia.edu> <1b6a6d13-8a01-414b-9bbe-cd194af1f539@kernel.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 11/3/26 20:59, Mani Tofigh wrote: > On 11/2/26 1:56 AM, David Hildenbrand (Arm) wrote: >> >> What if we still have the page pinned somehow? (vmscplice etc). >> >> Wouldn't it be better to make sure that poisoning code holds exactly one >> reference (whoever set hwpoison) and check here that the refcount is 1 ? >> >> Pagecache references would turn it > 1. > > > Yes right, a pin isn't covered (neither before nor with this patch). > > I don't think refcount == 1 can replace the mapping check though. In the > race from the changelog memory_failure() has set PG_hwpoison but is > still waiting in get_hwpoison_page(), so it doesn't hold its reference > yet, and a clean page-cache folio then has just the one reference from > the page cache. memory_failure() also doesn't take a reference on the > kernel pages it ignores, and a poisoned page that gets freed later sits > at 0. So the right fix is to fix that then. We'd need to sync memory_failure() with memory offlining, correct? -- Cheers, David