From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx186.postini.com [74.125.245.186]) by kanga.kvack.org (Postfix) with SMTP id CAFBD6B004D for ; Tue, 26 Jun 2012 18:30:48 -0400 (EDT) Received: by dakp5 with SMTP id p5so592869dak.14 for ; Tue, 26 Jun 2012 15:30:48 -0700 (PDT) Date: Tue, 26 Jun 2012 15:30:43 -0700 From: Tejun Heo Subject: Re: [PATCH 1/2] fix bad behavior in use_hierarchy file Message-ID: <20120626223043.GC15811@google.com> References: <1340725634-9017-1-git-send-email-glommer@parallels.com> <1340725634-9017-2-git-send-email-glommer@parallels.com> <20120626152522.c7161b5a.akpm@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120626152522.c7161b5a.akpm@linux-foundation.org> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Glauber Costa , cgroups@vger.kernel.org, linux-mm@kvack.org, kamezawa.hiroyu@jp.fujitsu.com, Michal Hocko , Johannes Weiner , Dhaval Giani , Li Zefan (cc'ing Li) Hello, Andrew. On Tue, Jun 26, 2012 at 03:25:22PM -0700, Andrew Morton wrote: > hm. The various .write_u64() implementations go and return zero on > success and cgroup_write_X64() sees this and rewrites the return value > to `nbytes'. > > That was a bit naughty of us - it prevents a .write_u64() instance from > being able to fully implement a partial write. We can *partially* > implement a partial write, by returning a value between 1 and nbytes-1, > but we can't return zero. It's a weird interface, it's a surprising > interface and it was quite unnecessary to do it this way. Someone > please slap Paul. > > It's hardly a big problem I, but that's why the unix write() interface > was designed the way it is. The whole file interface is severely over-designed like a lot of other things in cgorup. I'm thinking about consolidating all the different read/write methods into one generic pair, likely based on seq_file and make all others helpers. Thanks. -- tejun -- 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