From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from pizda.ninka.net (pizda.ninka.net [216.101.162.242]) by dsl2.external.hp.com (Postfix) with ESMTP id 07D7648D8 for ; Fri, 22 Aug 2003 10:46:29 -0600 (MDT) Date: Fri, 22 Aug 2003 09:39:00 -0700 From: "David S. Miller" To: Matthew Wilcox Cc: James.Bottomley@SteelEye.com, linux-kernel@vger.kernel.org, parisc-linux@lists.parisc-linux.org, drepper@redhat.com Subject: Re: [parisc-linux] Re: Problems with kernel mmap (failing tst-mmap-eofsync in glibc on parisc) Message-Id: <20030822093900.4468c012.davem@redhat.com> In-Reply-To: <20030822163429.GH18834@parcelfarce.linux.theplanet.co.uk> References: <1061563239.2090.25.camel@mulgrave> <20030822091447.6ecea6ca.davem@redhat.com> <20030822163429.GH18834@parcelfarce.linux.theplanet.co.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: parisc-linux-admin@lists.parisc-linux.org Errors-To: parisc-linux-admin@lists.parisc-linux.org List-Help: List-Post: List-Subscribe: , List-Id: parisc-linux developers list List-Unsubscribe: , List-Archive: On Fri, 22 Aug 2003 17:34:29 +0100 Matthew Wilcox wrote: > On Fri, Aug 22, 2003 at 09:14:47AM -0700, David S. Miller wrote: > > On 22 Aug 2003 09:40:37 -0500 > > flush_dcache_page() checks both the shared and non-shared mmap lists, > > so if it is on _either_ list it is flushed. It does not check only > > the shared list. > > Gah, that's going to get really inefficient. I still think we want to > split flush_dcache_page() into two operations -- flush_dcache_user() and > flush_dcache_kernel(). flush_dcache_user() would flush this specific > user mapping back to ram and flush_dcache_kernel() would flush the > kernel mapping. Obviously we'd still want to have flush_dcache_page() > as there are instances when you want to flush all user mappings and the > kernel mapping back to ram. flush_dcache_page() works only on kernel pages. It is defined to execute when the kernel executes store instructions into a page. Therefore splitting it into a "user" part makes absolutely no sense. > > The VM_SHARED change you are proposing is definitely wrong. > > Why is it wrong? Why should whether-or-not a mapping is read-only affect > whether it's mapped shared? I can't see anything in SuS v3 that suggests > we should do this. MAP_SHARED has no meaning if the mapping isn't writable.