From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail191.messagelabs.com (mail191.messagelabs.com [216.82.242.19]) by kanga.kvack.org (Postfix) with SMTP id 6D5AF6B005A for ; Tue, 29 Sep 2009 23:10:39 -0400 (EDT) Received: by ywh28 with SMTP id 28so8173018ywh.11 for ; Tue, 29 Sep 2009 20:23:55 -0700 (PDT) Message-ID: <4AC2CF46.5070600@gmail.com> Date: Wed, 30 Sep 2009 11:23:50 +0800 From: Huang Shijie MIME-Version: 1.0 Subject: Re: [PATCH] filemap : fix the wrong offset References: <1254215185-29841-1-git-send-email-shijie8@gmail.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Hugh Dickins Cc: akpm@linux-foundation.org, linux-mm@kvack.org List-ID: Hugh Dickins wrote: > I really think this issue is better ignored. There was a time, > seven years ago, when I cared about it, and made such corrections > in mm/shmem.c. But we're chipping away at the tip of the iceberg > here, and it's just a waste of everybody's time for so long as > PAGE_CACHE_SIZE == PAGE_SIZE. > > There have been patches experimenting with PAGE_CACHE_SIZE multiple > of PAGE_SIZE (and probably not PAGE_SIZE multiple of PAGE_CACHE_SIZE); > and I've come to the conclusion that the only sensible place for these > PAGE_CACHE_SHIFT - PAGE_SHIFT patches is in a patch which really makes > that difference. > > I wish PAGE_CACHE_SIZE had never been added in the first place, > long before it was needed; but ripping it out doesn't seem quite > the right thing to do either; and likewise I leave a smattering of > PAGE_CACHE_SHIFT - PAGE_SHIFT lines in, just to remind us from time > to time that there might one day be a difference. > > Ok. I get it. But the filemap_fault() looks strange. Some functions such as do_sync_mmap_readahead() treat offset in the PAGE_CAHE_SHIFT unit,though offset is actually in the PAGE_SHIFT unit. > I know this is a very unsatisfying response: but you and I > and everyone else have better things to spend our time on. > Thinking about the difference between two things that are > always the same is rather a waste of mental energy. > Thanks a lot for your explanation. -- 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