From: Dan Magenheimer Subject: RE: [PATCH V3 0/8] Cleancache: overview Date: Fri, 23 Jul 2010 10:37:51 -0700 (PDT) Message-ID: References: <20100621231809.GA11111@ca-server1.us.oracle.com4C49468B.40307@vflare.org> <840b32ff-a303-468e-9d4e-30fc92f629f8@default 20100723140440.GA12423@infradead.org 364c83bd-ccb2-48cc-920d-ffcf9ca7df19@default> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable Cc: akpm@linux-foundation.org, Chris Mason , viro@zeniv.linux.org.uk, adilger@sun.com, tytso@mit.edu, mfasheh@suse.com, Joel Becker , 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, jeremy@goop.org, JBeulich@novell.com, Kurt Hackel , npiggin@suse.de, Dave Mccracken , riel@redhat.com, avi@redhat.com, Konrad Wilk To: Christoph Hellwig , ngupta@vflare.org Return-path: In-Reply-To: <364c83bd-ccb2-48cc-920d-ffcf9ca7df19@default> Sender: owner-linux-mm@kvack.org List-Id: linux-ext4.vger.kernel.org > From: Dan Magenheimer > Subject: RE: [PATCH V3 0/8] Cleancache: overview >=20 > > From: Christoph Hellwig [mailto:hch@infradead.org] > > Subject: Re: [PATCH V3 0/8] Cleancache: overview > > > > On Fri, Jul 23, 2010 at 06:58:03AM -0700, Dan Magenheimer wrote: > > > CHRISTOPH AND ANDREW, if you disagree and your concerns have > > > not been resolved, please speak up. >=20 > Hi Christoph -- >=20 > Thanks very much for the quick (instantaneous?) reply! >=20 > > Anything that need modification of a normal non-shared fs is utterly > > broken and you'll get a clear NAK, so the propsal before is a good > > one. >=20 > Unless/until all filesystems are 100% built on top of VFS, > I have to disagree. Abstractions (e.g. VFS) are never perfect. After thinking about this some more, I can see a way to enforce "opt-in" in the cleancache backend without any changes to non-generic fs code. I think it's a horrible hack and we can try it, but I expect fs maintainers would prefer the explicit one-line-patch opt-in. 1) Cleancache backend maintains a list of "known working" filesystems (those that have been tested). 2) Nitin's proposed changes pass the *sb as a parameter. The string name of the filesystem type is available via sb->s_type->name. This can be compared against the "known working" list. Using the sb pointer as a "handle" requires an extra table search on every cleancache get/put/flush, and fs/super.c changes are required for fs unmount notification anyway (e.g. to call cleancache_flush_fs) so I'd prefer to keep the cleancache_poolid addition to the sb. I'll assume this is OK since this is in generic fs code. Dan -- 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