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Date: Thu, 14 Aug 2008 02:17:03 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: "Trevor Woollacott [ MTN - Innovation Centre ]" <Woolla_T@mtn.co.za>
Cc: <linux-kernel@vger.kernel.org>
Subject: Re: POSIX_FADV_DONTNEED
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On Fri, 1 Aug 2008 17:05:39 +0200 "Trevor Woollacott [ MTN - Innovation Centre ]" <Woolla_T@mtn.co.za> wrote:

> 
> Hi all
> 
> Does anyone know if posix_fadvise() with POSIX_FADV_DONTNEED is
> blocking/unblocking?

It tries to be nonblocking and will mostly succeed in that.  It might
occasionally block on a metadata read or journal congestion or
something, so it isn't guaranteed.