From: Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH V8 4/8] mm/fs: add hooks to support cleancache
Date: Fri, 15 Apr 2011 08:10:54 -0700
Message-ID: <20110415081054.79a164d3.akpm@linux-foundation.org>
References: <20110414211732.GA27761@ca-server1.us.oracle.com
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Cc: Minchan Kim <minchan.kim@gmail.com>, Chris Mason
 <chris.mason@oracle.com>,
        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 <kurt.hackel@oracle.com>, npiggin@kernel.dk,
        Dave Mccracken
 <dave.mccracken@oracle.com>, riel@redhat.com,
        avi@redhat.com, Konrad Wilk
 <konrad.wilk@oracle.com>, mel@csn.ul.ie,
        yinghan@google.com, gthelen@google.com, torvalds@linux-foundation.org
To: Dan Magenheimer <dan.magenheimer@oracle.com>
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On Fri, 15 Apr 2011 07:47:57 -0700 (PDT) Dan Magenheimer <dan.magenheimer@oracle.com> wrote:

> Hi Minchan --
> 
> > First of all, thanks for resolving conflict with my patch.
> 
> You're welcome!  As I pointed out offlist, yours was the first
> change in MM that caused any semantic changes to the cleancache
> core hooks patch since before 2.6.18.
>  
> > 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.  

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