From: OGAWA Hirofumi Subject: Re: [PATCH V8 4/8] mm/fs: add hooks to support cleancache Date: Sat, 16 Apr 2011 00:37:36 +0900 Message-ID: <871v135xvj.fsf@devron.myhome.or.jp> References: <83ef8b69-f041-43e6-a5a9-880ff3da26f2@default> <20110415081054.79a164d3.akpm@linux-foundation.org> Mime-Version: 1.0 Content-Type: text/plain Cc: Dan Magenheimer , Minchan Kim , Chris Mason , viro@zeniv.linux.org.uk, adilger.kernel@dilger.ca, tytso@mit.edu, mfasheh@suse.com, jlbec@evilplan.org, matthew@wil.cx, linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, ocfs2-devel@oss.oracle.com, linux-mm@kvack.org, hch@infradead.org, ngupta@vflare.org, jeremy@goop.org, JBeulich@novell.com, Kurt Hackel , npiggin@kernel.dk, Dave Mccracken , riel@redhat.com, avi@redhat.com, Konrad Wilk , mel@csn.ul.ie, yinghan@google.com, gthelen@google.com, torvalds@linux-foundation.org To: Andrew Morton Return-path: Received: from mail.parknet.co.jp ([210.171.160.6]:35410 "EHLO mail.parknet.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754151Ab1DOPh7 (ORCPT ); Fri, 15 Apr 2011 11:37:59 -0400 In-Reply-To: <20110415081054.79a164d3.akpm@linux-foundation.org> (Andrew Morton's message of "Fri, 15 Apr 2011 08:10:54 -0700") Sender: linux-ext4-owner@vger.kernel.org List-ID: Andrew Morton writes: >> > Before I suggested a thing about cleancache_flush_page, >> > cleancache_flush_inode. >> > >> > what's the meaning of flush's semantic? >> > I thought it means invalidation. >> > AFAIC, how about change flush with invalidate? >> >> I'm not sure the words "flush" and "invalidate" are defined >> precisely or used consistently everywhere in computer >> science, but I think that "invalidate" is to destroy >> a "pointer" to some data, but not necessarily destroy the >> data itself. And "flush" means to actually remove >> the data. So one would "invalidate a mapping" but one >> would "flush a cache". >> >> Since cleancache_flush_page and cleancache_flush_inode >> semantically remove data from cleancache, I think flush >> is a better name than invalidate. >> >> Does that make sense? >> > > nope ;) > > Kernel code freely uses "flush" to refer to both invalidation and to > writeback, sometimes in confusing ways. In this case, > cleancache_flush_inode and cleancache_flush_page rather sound like they > might write those things to backing store. I'd like to mention about *_{get,put}_page too. In linux get/put is not meaning read/write. There is {get,put}_page those are refcount stuff (Yeah, and I felt those methods does refcount by quick read. But it seems to be false. There is no xen codes, so I don't know actually though.). And I agree, I also think the needing thing is consistency on the linux codes (term). Thanks. -- OGAWA Hirofumi