Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965196AbWH2SA5 (ORCPT ); Tue, 29 Aug 2006 14:00:57 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S965197AbWH2SA5 (ORCPT ); Tue, 29 Aug 2006 14:00:57 -0400 Received: from smtp.osdl.org ([65.172.181.4]:52642 "EHLO smtp.osdl.org") by vger.kernel.org with ESMTP id S965196AbWH2SA5 (ORCPT ); Tue, 29 Aug 2006 14:00:57 -0400 Date: Tue, 29 Aug 2006 11:00:48 -0700 From: Andrew Morton To: Jan Engelhardt Cc: Linux Kernel Mailing List , OGAWA Hirofumi Subject: Re: Drop cache has no effect? Message-Id: <20060829110048.20e23e75.akpm@osdl.org> In-Reply-To: References: X-Mailer: Sylpheed version 2.2.7 (GTK+ 2.8.6; i686-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1630 Lines: 42 On Tue, 29 Aug 2006 14:53:34 +0200 (MEST) Jan Engelhardt wrote: > Hello, > > > recently I picked up knowledge of /proc/sys/vm/drop_caches > (http://lkml.org/lkml/2006/8/4/95) > > It does not always work right away: > > (/U is a vfat, that is, permissions are back to 755 as soon as the caches > are gone) > 14:51 gwdg-wb04A:/U # chmod 644 * > 14:51 gwdg-wb04A:/U # sync > 14:51 gwdg-wb04A:/U # echo 2 >/proc/sys/vm/drop_caches > 14:51 gwdg-wb04A:/U # l > total 50713 > drwxr-xr-x 3 jengelh users 2048 2006-08-29 14:48 . > drwxr-xr-x 22 root root 4096 2006-08-25 14:00 .. > drw-r--r-- 2 jengelh users 2048 2006-08-29 13:55 as > -rw-r--r-- 1 jengelh users 13806629 2006-08-29 14:00 all-20060611.tar.bz2 > -rw-r--r-- 1 jengelh users 37816633 2006-07-28 19:25 > inkscape-0.44-2.guru.suse101.i686.rpm > -rw-r--r-- 1 jengelh users 297243 2006-08-15 01:13 > vmware-any-any-update104.tar.gz > > Remains 644. > That would be a vfat problem - the changed permission bits weren't written back to disk, so when you re-read them from disk (or, more likely, from blockdev pagecache) they came back with the original values. Does vfat even have the ability to store the seven bits? Don't think so? If not, permitting the user to change them in icache but not being to write them out to permanent store seems rather bad behaviour. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/