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Mon, 19 Apr 2021 06:34:56 +0000 Received: by verein.lst.de (Postfix, from userid 2407) id A92C068B05; Mon, 19 Apr 2021 08:34:41 +0200 (CEST) Date: Mon, 19 Apr 2021 08:34:41 +0200 From: Christoph Hellwig To: Matthew Wilcox Cc: Jesper Dangaard Brouer , David Laight , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , "netdev@vger.kernel.org" , "linuxppc-dev@lists.ozlabs.org" , "linux-arm-kernel@lists.infradead.org" , "linux-mips@vger.kernel.org" , Ilias Apalodimas , Matteo Croce , Grygorii Strashko , Arnd Bergmann , Christoph Hellwig Subject: Re: [PATCH 1/1] mm: Fix struct page layout on 32-bit systems Message-ID: <20210419063441.GA18787@lst.de> References: <20210411114307.5087f958@carbon> <20210411103318.GC2531743@casper.infradead.org> <20210412011532.GG2531743@casper.infradead.org> <20210414101044.19da09df@carbon> <20210414115052.GS2531743@casper.infradead.org> <20210414211322.3799afd4@carbon> <20210414213556.GY2531743@casper.infradead.org> <20210415200832.32796445@carbon> <20210416152755.GL2531743@casper.infradead.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20210416152755.GL2531743@casper.infradead.org> User-Agent: Mutt/1.5.17 (2007-11-01) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210418_233451_605655_F76BC555 X-CRM114-Status: GOOD ( 16.44 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, Apr 16, 2021 at 04:27:55PM +0100, Matthew Wilcox wrote: > On Thu, Apr 15, 2021 at 08:08:32PM +0200, Jesper Dangaard Brouer wrote: > > See below patch. Where I swap32 the dma address to satisfy > > page->compound having bit zero cleared. (It is the simplest fix I could > > come up with). > > I think this is slightly simpler, and as a bonus code that assumes the > old layout won't compile. So, why do we even do this crappy overlay of a dma address? This just all seems like a giant hack. Random subsystems should not just steal a few struct page fields as that just turns into the desasters like the one we've seen here or probably something worse next time. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel