From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755693AbcCUMp1 (ORCPT ); Mon, 21 Mar 2016 08:45:27 -0400 Received: from mail-wm0-f67.google.com ([74.125.82.67]:32823 "EHLO mail-wm0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755425AbcCUMpY (ORCPT ); Mon, 21 Mar 2016 08:45:24 -0400 Date: Mon, 21 Mar 2016 13:45:22 +0100 From: Michal Hocko To: "Kirill A. Shutemov" Cc: Andrew Morton , Alexander Viro , Linus Torvalds , Christoph Lameter , Matthew Wilcox , Hugh Dickins , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH 1/3] mm, fs: get rid of PAGE_CACHE_* and page_cache_{get,release} macros Message-ID: <20160321124522.GC23066@dhcp22.suse.cz> References: <1458561998-126622-1-git-send-email-kirill.shutemov@linux.intel.com> <1458561998-126622-2-git-send-email-kirill.shutemov@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1458561998-126622-2-git-send-email-kirill.shutemov@linux.intel.com> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon 21-03-16 15:06:36, Kirill A. Shutemov wrote: > PAGE_CACHE_{SIZE,SHIFT,MASK,ALIGN} macros were introduced *long* time ago > with promise that one day it will be possible to implement page cache with > bigger chunks than PAGE_SIZE. > > This promise never materialized. And unlikely will. > > We have many places where PAGE_CACHE_SIZE assumed to be equal to > PAGE_SIZE. And it's constant source of confusion on whether PAGE_CACHE_* > or PAGE_* constant should be used in a particular case, especially on the > border between fs and mm. > > Global switching to PAGE_CACHE_SIZE != PAGE_SIZE would cause to much > breakage to be doable. > > Let's stop pretending that pages in page cache are special. They are not. > > The changes are pretty straight-forward: > > - << (PAGE_CACHE_SHIFT - PAGE_SHIFT) -> ; > > - >> (PAGE_CACHE_SHIFT - PAGE_SHIFT) -> ; > > - PAGE_CACHE_{SIZE,SHIFT,MASK,ALIGN} -> PAGE_{SIZE,SHIFT,MASK,ALIGN}; > > - page_cache_get() -> get_page(); > > - page_cache_release() -> put_page(); > > This patch contains automated changes generated with coccinelle using > script below. For some reason, coccinelle doesn't patch header files. > I've called spatch for them manually. > > The only adjustment after coccinelle is revert of changes to > PAGE_CAHCE_ALIGN definition: we are going to drop it later. > > There are few places in the code where coccinelle didn't reach. > I'll fix them manually in a separate patch. Comments and documentation > also will be addressed with the separate patch. > > virtual patch > > @@ > expression E; > @@ > - E << (PAGE_CACHE_SHIFT - PAGE_SHIFT) > + E > > @@ > expression E; > @@ > - E >> (PAGE_CACHE_SHIFT - PAGE_SHIFT) > + E > > @@ > @@ > - PAGE_CACHE_SHIFT > + PAGE_SHIFT > > @@ > @@ > - PAGE_CACHE_SIZE > + PAGE_SIZE > > @@ > @@ > - PAGE_CACHE_MASK > + PAGE_MASK > > @@ > expression E; > @@ > - PAGE_CACHE_ALIGN(E) > + PAGE_ALIGN(E) > > @@ > expression E; > @@ > - page_cache_get(E) > + get_page(E) > > @@ > expression E; > @@ > - page_cache_release(E) > + put_page(E) > > Signed-off-by: Kirill A. Shutemov It is great to see PAGE_CACHE_* going away finally. It is even better that a large part of the removal could be automated. The semantic patch makes sense to me. Acked-by: Michal Hocko Thanks! [...] -- Michal Hocko SUSE Labs