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imf25.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=lst.de; spf=pass (imf25.hostedemail.com: domain of hch@lst.de designates 213.95.11.211 as permitted sender) smtp.mailfrom=hch@lst.de ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1763096656; a=rsa-sha256; cv=none; b=nW1fPdzIO/bT1mbXJIc3jUvcpq+zprhZP2r+lHhSKzatQ+TFWFo7BLuHqVOaaTMBX+eX3e 7/NDo+BTu9GB/jwY6iQg5Ib3iGYotH+9lIG6zDAjKVmb5rTqzV8ugphTOxU6Ef/Tn5fFLv CXTPO7rS89RF4C/a10R1Ria0qH2I4lI= Received: by verein.lst.de (Postfix, from userid 2407) id 37A73227A88; Fri, 14 Nov 2025 06:04:10 +0100 (CET) Date: Fri, 14 Nov 2025 06:04:10 +0100 From: Christoph Hellwig To: Vlastimil Babka Cc: Andrew Morton , Christoph Lameter , David Rientjes , Roman Gushchin , Harry Yoo , Jens Axboe , linux-block@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel test robot , Christoph Hellwig Subject: Re: [PATCH] mm/mempool: fix poisoning order>0 pages with HIGHMEM Message-ID: <20251114050410.GA26404@lst.de> References: <20251113-mempool-poison-v1-1-233b3ef984c3@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251113-mempool-poison-v1-1-233b3ef984c3@suse.cz> User-Agent: Mutt/1.5.17 (2007-11-01) X-Rspamd-Queue-Id: 30B79A000E X-Stat-Signature: xeq7e9en9o9zefzfa17mzrpaj6wtx57i X-Rspamd-Server: rspam02 X-Rspam-User: X-HE-Tag: 1763096655-606507 X-HE-Meta: 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 DZcao9+u dIQTL+HUKetVzxe/L9k/cmKIWOW8FhM9KKpD1uKUdalq81vywCDbJdhZyTB8B+dSyzQ9r87JkOBtPLz2AEJxpFC5OwhU6UhNqO3Tu 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 Thu, Nov 13, 2025 at 07:54:35PM +0100, Vlastimil Babka wrote: > Christoph found out this is due to the poisoning code not dealing > properly with CONFIG_HIGHMEM because only the first page is mapped but > then the whole potentially high-order page is accessed. > > This went unnoticed for years probably because nobody has yet used a > mempool for order>0 pages before the new block code in -next. I did a quick audit: and bcache, dm-integrity (config dependent) and the KASAN unit tests create page based mempools with order > 0. It looks like none of those ever got much testing on highmem systems. The fix looks good: Reviewed-by: Christoph Hellwig