From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752411AbZHNIdu (ORCPT ); Fri, 14 Aug 2009 04:33:50 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750916AbZHNIdt (ORCPT ); Fri, 14 Aug 2009 04:33:49 -0400 Received: from viefep11-int.chello.at ([62.179.121.31]:34988 "EHLO viefep11-int.chello.at" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750728AbZHNIds (ORCPT ); Fri, 14 Aug 2009 04:33:48 -0400 X-SourceIP: 213.93.53.227 Subject: Re: Does perf_counter need to make mmap pages uptodate? From: Peter Zijlstra To: Paul Mackerras Cc: Ingo Molnar , linux-kernel@vger.kernel.org In-Reply-To: <19076.64899.915246.955189@drongo.ozlabs.ibm.com> References: <19076.64899.915246.955189@drongo.ozlabs.ibm.com> Content-Type: text/plain Date: Fri, 14 Aug 2009 10:33:19 +0200 Message-Id: <1250238799.5241.1167.camel@twins> Mime-Version: 1.0 X-Mailer: Evolution 2.26.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2009-08-14 at 16:00 +1000, Paul Mackerras wrote: > At a colleague's request, I did a backport of the perf_counter code to > 2.6.30.3. When I tried "perf record ls" I hit the WARN_ON_ONCE in > __set_page_dirty (fs/buffer.c line 669): > > WARN_ON_ONCE(warn && !PageUptodate(page)); > > and indeed we never mark the pages that we let userspace mmap as being > uptodate. To get around the problem I added > > SetPageUptodate(vmf->page); > > after the get_page call in perf_mmap_fault, but I can't see any > relevant changes between 2.6.30 and current upstream that would cause > this to be necessary for 2.6.30 but not for current upstream. > > Should we in fact be marking the pages uptodate, or is there some > reason why we should never get to that WARN_ON_ONCE? commit d3a9262e59f7fb83c6d44df3b2b1460ed57d3ea1 Author: Peter Zijlstra Date: Thu Jun 18 12:54:00 2009 +0200 fs: Provide empty .set_page_dirty() aop for anon inodes .set_page_dirty() is one of those a_ops that defaults to the buffer implementation when not set. Therefore provide a dummy function to make it do nothing. (Uncovered by perfcounters fd's which can now be writable-mmap-ed.) Signed-off-by: Peter Zijlstra Cc: Al Viro Cc: Davide Libenzi LKML-Reference: Signed-off-by: Ingo Molnar diff --git a/fs/anon_inodes.c b/fs/anon_inodes.c index 1dd96d4..47d4a01 100644 --- a/fs/anon_inodes.c +++ b/fs/anon_inodes.c @@ -52,6 +52,19 @@ static const struct dentry_operations anon_inodefs_dentry_operations = { .d_delete = anon_inodefs_delete_dentry, }; +/* + * nop .set_page_dirty method so that people can use .page_mkwrite on + * anon inodes. + */ +static int anon_set_page_dirty(struct page *page) +{ + return 0; +}; + +static const struct address_space_operations anon_aops = { + .set_page_dirty = anon_set_page_dirty, +}; + /** * anon_inode_getfd - creates a new file instance by hooking it up to an * anonymous inode, and a dentry that describe the "class" @@ -151,6 +164,8 @@ static struct inode *anon_inode_mkinode(void) inode->i_fop = &anon_inode_fops; + inode->i_mapping->a_ops = &anon_aops; + /* * Mark the inode dirty from the very beginning, * that way it will never be moved to the dirty