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Date: Mon, 22 Dec 2014 19:28:11 +0200
From: Konstantin Belousov <kostikbel@gmail.com>
To: John Baldwin <jhb@freebsd.org>
Subject: Re: svn commit: r276008 - in head/sys: kern sys
Message-ID: <20141222172810.GY2148@kib.kiev.ua>
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Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org,
 src-committers@freebsd.org, Andriy Gapon <avg@freebsd.org>
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On Mon, Dec 22, 2014 at 09:40:02AM -0500, John Baldwin wrote:
> On Sunday, December 21, 2014 11:21:17 am Andriy Gapon wrote:
> > On 21/12/2014 17:14, Konstantin Belousov wrote:
> > > On Sun, Dec 21, 2014 at 04:45:28PM +0200, Andriy Gapon wrote:
> > >> On 21/12/2014 16:41, Konstantin Belousov wrote:
> > >>> Or, are you asking why caching of the name could be needed for
> > >>> core dump files at all ?
> > >>
> > >> Sort of. Why VN_OPEN_NAMECACHE is useful in the case of core dumps?
> > >> What does it make better?
> > > The vn_fullpath() mostly works for the core files after the change,
> > > comparing with the non-working state at all before.
> > > 
> > 
> > Ah, vn_fullpath(). Thank you.
> 
> Is there something specific to core dumps that makes vn_fullpath() more
> useful to have working before a process tries to open the core?  (As
> compared to other newly-created files)

See other Rui' reply in the thread.  It was done by his request.

Basically, we cannot enable caching for CREATE, since operations like
extracting large archive, would flush the cache.  Doing it rarely
and when needed is acceptable.  The explained use case seems to
be warranted.