Re: [RESEND][PATCH v2] btrfs-progs: add dev stats returncode option

From: David Sterba <dsterba@suse.cz>
To: "Austin S. Hemmelgarn" <ahferroin7@gmail.com>
Cc: dsterba@suse.cz, linux-btrfs@vger.kernel.org
Subject: Re: [RESEND][PATCH v2] btrfs-progs: add dev stats returncode option
Date: Thu, 8 Dec 2016 18:20:30 +0100	[thread overview]
Message-ID: <20161208172030.GJ12522@twin.jikos.cz> (raw)
In-Reply-To: <20161205183520.67039-1-ahferroin7@gmail.com>

On Mon, Dec 05, 2016 at 01:35:20PM -0500, Austin S. Hemmelgarn wrote:
> Currently, `btrfs device stats` returns non-zero only when there was an
> error getting the counter values.  This is fine for when it gets run by a
> user directly, but is a serious pain when trying to use it in a script or
> for monitoring since you need to parse the (not at all machine friendly)
> output to check the counter values.
> 
> This patch adds an option ('-s') which causes `btrfs device stats`
> to set bit 6 in the return code if any of the counters are non-zero.
> This greatly simplifies checking from a script or monitoring software if
> any errors have been recorded.  In the event that this switch is passed
> and an error occurs reading the stats, the return code will have bit
> 0 set (so if there are errors reading counters, and the counters which
> were read were non-zero, the return value will be 65).

So a typical check in a script would look for either 64 or 65 returned
from the command, I don't think we can do it simpler. The option naming
is a bit confusing to me, as it duplicates the 'stats' from the command
itself. I'd suggest to use '--check' instead, does it sound OK to you?

I'll apply the patch as-is for now (and maybe do some cleanups in the
surrounding code).