From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Tue, 28 Aug 2007 20:05:10 +0100 From: Christoph Hellwig Subject: Re: [PATCH 4/4] add SGI Altix cross partition memory (XPMEM) driver Message-ID: <20070828190510.GA3256@infradead.org> References: <20070827155622.GA25589@sgi.com> <20070827164112.GF25589@sgi.com> <20070828180235.GB32585@infradead.org> <20070828190043.GB7140@lnx-holt.americas.sgi.com> Mime-Version: 1.0 Content-Type: text/plain; charset=unknown-8bit Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20070828190043.GB7140@lnx-holt.americas.sgi.com> Sender: owner-linux-mm@kvack.org Return-Path: To: Robin Holt Cc: Christoph Hellwig , Dean Nelson , tony.luck@intel.com, linux-ia64@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, jes@sgi.com List-ID: On Tue, Aug 28, 2007 at 02:00:43PM -0500, Robin Holt wrote: > The ioctl is sort of historical. IIRC, in ProPack 3 (RHEL4 based 2.4 > kernel), we added system calls. When the community started making noise > about system calls being bad, we went to a device special file with a > read/write (couldn't get the needed performance from the ioctl() interface > which used to acquire the BKL). Now that the community fixed the ioctl > issues, we went to using an ioctl, but are completely open to change. > > If you want to introduce system calls, we would expect to need, IIRC, 8. > We also pondered an xpmem filesystem today. It really felt wrong, > but we could pursue that as an alternative. The problem is not ioctls per sae, but the kind of operation you export. > What is the correct direction to go with this? get_user_pages() does > currently require the task_struct. Are you proposing we develop a way > to fault pages without the task_struct of the owning process/thread group? Stop trying to mess with vmas and get_user_pages on processes entirely. The only region of virtual memory a driver can deal with is the one it got a mmap request for, or when using get_user_pages the one it's got a read/write request for. You're doing a worse variant of the rdma page pinning scheme we're rejected countless times. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org