From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from digeo-nav01.digeo.com (digeo-nav01.digeo.com [192.168.1.233]) by packet.digeo.com (8.9.3+Sun/8.9.3) with SMTP id MAA00242 for ; Tue, 22 Oct 2002 12:23:43 -0700 (PDT) Message-ID: <3DB5A5BD.D3E00B4A@digeo.com> Date: Tue, 22 Oct 2002 12:23:41 -0700 From: Andrew Morton MIME-Version: 1.0 Subject: Re: [patch] generic nonlinear mappings, 2.5.44-mm2-D0 References: <20021022184938.A2395@infradead.org> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Christoph Hellwig Cc: Ingo Molnar , linux-kernel@vger.kernel.org, linux-mm@kvack.org List-ID: Christoph Hellwig wrote: > > On Tue, Oct 22, 2002 at 07:57:00PM +0200, Ingo Molnar wrote: > > the attached patch (ontop of 2.5.44-mm2) implements generic (swappable!) > > nonlinear mappings and sys_remap_file_pages() support. Ie. no more > > MAP_LOCKED restrictions and strange pagefault semantics. > > > > to implement this i added a new pte concept: "file pte's". This means that > > upon swapout, shared-named mappings do not get cleared but get converted > > into file pte's, which can then be decoded by the pagefault path and can > > be looked up in the pagecache. > > > > the normal linear pagefault path from now on does not assume linearity and > > decodes the offset in the pte. This also tests pte encoding/decoding in > > the pagecache case, and the ->populate functions. > > Ingo, > > what is the reason for that interface? It looks like a gross performance > hack for misdesigned applications to me, kindof windowsish.. > So that evicted pages in non-linear mappings can be reestablished at fault time by the kernel, rather than by delegation to userspace via SIGBUS. We seem to have lost a pte_page_unlock() from fremap.c:zap_pte()? I fixed up the ifdef tangle in there within the shpte-ng patch and then put the pte_page_unlock() back. I also added a page_cache_release() to the error path in filemap_populate(), if install_page() failed. The 2TB file size limit for mmap on non-PAE is a little worrisome. I wonder if we can only instantiate the pte_file() bit if the mapping is using MAP_POPULATE? Seems hard to do. -- 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/