linux-ext4 - Re: Refreshing after OOB file update?

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Message-ID: <20140828233237.GA31174@thunk.org>
Date:	Thu, 28 Aug 2014 19:32:37 -0400
From:	Theodore Ts'o <tytso@....edu>
To:	Rob Harris <rob.harris@...il.com>
Cc:	linux-ext4@...r.kernel.org
Subject: Re: Refreshing after OOB file update?

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
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