From mboxrd@z Thu Jan  1 00:00:00 1970
From: Theodore Ts'o <tytso@mit.edu>
Subject: Re: Refreshing after OOB file update?
Date: Thu, 28 Aug 2014 19:32:37 -0400
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To: Rob Harris <rob.harris@gmail.com>
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On Thu, Aug 28, 2014 at 10:37:04AM -0400, Rob Harris wrote:
> 
> This tells me (probably naively) that the kernel is caching the old file
> contents.

Yes, that's what the page cache is all about.

> Is there a way for me to tell the file system that something out-of-band
> change a file contents and to force a re-read from the disk?

Have your userspace program do an O_DIRECT read.  That will discard
the page cache and do a direct read from the disk.

Cheers,

							- Ted