From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7F9E9263F34; Sat, 25 Apr 2026 05:51:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777096278; cv=none; b=IbTMCCNXUfCmCh6C6mLKb999cjAj91LaBwXZcUPNm41h+Pfe85CGBy8mYylLg/0odRT8KGar8+xhRMTkJGm9tojQHjbdtyGI1ySO5CXICeSTfzaV1w2D9PQ9xxmg9ZHRlqk5Z8313WoI+BbE7+VHdckbjvJ0A/yXmdlgJgvDCfI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777096278; c=relaxed/simple; bh=1TX6ihQk3kucuVDvqFiea8KYgGnEz+xLRlMxsOzGOA4=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=rL7nSA+6aBpGavq/knyBoTZKHs5zXqskuLr1Hkpvdl+JVu4P8A31SRNTgGz09ZmrVB4RZZo5wUVBHBquq/zhkdtyahc58vboc4+WTKVdR+fR0/Ln2n5SZEJCjmiwDdTqXEX/6b8Sup94W54zcyGK1Wn29fWiEQlJMoAYJtd1D9c= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=n4kzHdFk; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="n4kzHdFk" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 43358C2BCB0; Sat, 25 Apr 2026 05:51:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1777096278; bh=1TX6ihQk3kucuVDvqFiea8KYgGnEz+xLRlMxsOzGOA4=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=n4kzHdFkS93dzBf/0sB8LNKsZ13c/FMalJ7qio3iOrsEsZ7KoSTLEFgzargeBcq+d 91GPSZFDSYKszIoGvVWUcz4DBGBcNf/fGVAheD01TE6yF3/oM/FF2HA4YprwGHF8YC HmX2P/Ex08ZqCO8bd/tQoXuXA6iN8Z2uBkWM69wbTQhDPR3Q0Nmfh4pfyzsuEO9W1f Lp/Fnq+oVLRj8WQ1OBEpzbF5vmN6zREJhq3cBavYShrRFJiYGAYG+hxtZAiRVGG9dA Za/4kBiS4LglmJRU758hdOa5ybFwfbSnO3RsKBwcDgP/VN9eQX/4DO3RF9ii8tmYSd 2szB50df5VyvQ== Message-ID: Date: Sat, 25 Apr 2026 07:51:10 +0200 Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC 0/7] mm: dual-bitmap page allocator consistency checker To: Sasha Levin , "Vlastimil Babka (SUSE)" Cc: akpm@linux-foundation.org, corbet@lwn.net, ljs@kernel.org, Liam.Howlett@oracle.com, rppt@kernel.org, surenb@google.com, mhocko@suse.com, skhan@linuxfoundation.org, jackmanb@google.com, hannes@cmpxchg.org, ziy@nvidia.com, linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260424140056.2094777-1-sashal@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 4/24/26 18:25, Sasha Levin wrote: > On Fri, Apr 24, 2026 at 05:42:53PM +0200, Vlastimil Babka (SUSE) wrote: >> On 4/24/26 16:00, Sasha Levin wrote: >>> Existing memory debugging tools - KASAN, KFENCE, page_poisoning - detect >>> access violations and content corruption, but none of them can detect >>> silent corruption in the page allocator's own metadata. If a hardware >>> bit flip corrupts an allocation bitmap, the allocator hands out a page >> >> An allocation what? The page allocator is a buddy allocator, it has no >> bitmap to track free/allocated state of pages? > > You're right, the cover letter is misleading there. Buddy doesn't use a bitmap: > PageBuddy lives in page_type, the free list is a list, and page->private holds > the order. The dual-bitmap is new metadata the feature adds, maintained from > the alloc/free hooks. Given that you have PageBuddy (first "bit"), could we use a second bit in page_ext? -- Cheers, David