On 07/23/2010 11:07 PM, Dan Magenheimer wrote: >> From: Dan Magenheimer >> Subject: RE: [PATCH V3 0/8] Cleancache: overview >> >>> From: Christoph Hellwig [mailto:hch@xxxxxxxxxxxxx] >>> 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. >> >> Hi Christoph -- >> >> Thanks very much for the quick (instantaneous?) reply! >> >>> 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. >> >> 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). Checks against "known working list" indeed looks horrible. Isn't there any way to identify pagecache -> disk I/O boundaries which every filesystem obeys? I'm not yet sure but if this is doable, then we won't require such hacks. > > 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. > sb->s_magic could also be used, or better if we can somehow get rid of these checks :) > 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. > I will also try making changes to cleancache so it does not touch any fs specific code. Though IMHO one liners to fs-code should really be acceptable but unfortunately this doesn't seem to be the case. Maybe generic cleancache will have better chances. Thanks, Nitin -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>