From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: [patch 2/2] only allow nonlinear vmas for ram backed filesystems From: Peter Zijlstra In-Reply-To: References: <1175765760.6483.93.camel@twins> Content-Type: text/plain Date: Thu, 05 Apr 2007 11:50:00 +0200 Message-Id: <1175766600.6483.100.camel@twins> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Miklos Szeredi Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org List-ID: On Thu, 2007-04-05 at 11:39 +0200, Miklos Szeredi wrote: > > > + /* > > > + * page_mkclean doesn't work on nonlinear vmas, so if dirty > > > + * pages need to be accounted, emulate with linear vmas. > > > + */ > > > + if (mapping_cap_account_dirty(mapping)) { > > > > Perhaps this should read: > > > > if (vma_wants_writenotify(vma)) { > > > > I looked at that, but IIRC vma_wants_writenotify() doesn't work after > mmap(), because of the updated protection bits. Right, bother, that again. I fudged it in mprotect by setting the pgprot bits to what was expected although I had a parametrised version earlier. But that was disliked. > > That way we would even allow read only non-linear mappings of 'real' > > filesystem files. > > Well, we could do that, but is it really worth the hassle? The real > question is whether anyone would want to use non-linear > shared-read-only mappings or not. Hmm, yeah, I thought that was the case with that code snippet Andrew pulled of the interweb, but on second inspection they do map it writable too. I was led astray by the fact that they map the same file twice. Oh well, lets just keep the patch as is then. -- 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