From: Dan Magenheimer <dan.magenheimer@oracle.com>
Subject: RE: [PATCH V8 4/8] mm/fs: add hooks to support cleancache
Date: Fri, 15 Apr 2011 08:32:21 -0700 (PDT)
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Cc: Minchan Kim <minchan.kim@gmail.com>, Chris Mason <chris.mason@oracle.com>,
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To: Andrew Morton <akpm@linux-foundation.org>
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> From: Andrew Morton [mailto:akpm@linux-foundation.org]
> On Fri, 15 Apr 2011 07:47:57 -0700 (PDT) Dan Magenheimer
> <dan.magenheimer@oracle.com> wrote:
>=20
> > Hi Minchan --
> >
> > > 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?
>=20
> nope ;)
>=20
> 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.

OK, I guess I am displaying my kernel-newbie-ness... though,
in this case, writeback of a cleancache page to backing store
doesn't make much sense either (since cleancache pages are
by definition "clean").

I'm happy to rename the hooks, though will probably not
repost a V9 unless/until more substantive changes collect...
unless someone considers this an unmergeable offense.

Thanks for the feedback, Minchan and Andrew!
Dan

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