Date: Wed, 10 Nov 2010 14:02:28 -0800 From: Matthew Jacob <mj@feral.com> To: Oleg Sharoyko <osharoiko@gmail.com> Cc: mjacob@freebsd.org, freebsd-geom@freebsd.org Subject: Re: [patch] [geom_multipath] detached device used as an active path Message-ID: <4CDB1674.1000606@feral.com> In-Reply-To: <AANLkTi=B2Gniv3RDmLexN8Br8W0Q4t=V_0A57XPkQe4g@mail.gmail.com> References: <AANLkTi=B2Gniv3RDmLexN8Br8W0Q4t=V_0A57XPkQe4g@mail.gmail.com>
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It's going to take me a bit to digest this. I have a huge set of diffs I
haven't brought in yet.
On 11/10/2010 12:41 PM, Oleg Sharoyko wrote:
> Hi Matthew,
>
> Please take a look at the patch I'm attaching to this mail. It fixes
> couple of issues with cp->active being left pointing to detached
> device. I have as well tried to remove code duplication a bit by using
> g_multipath_rotate() in g_mpd() and g_multipath_done_error() instead
> of identical loops.
>
> One thing which I'm not 100% sure about is this part (this is within
> g_multipath_access()):
>
> @@ -258,7 +268,7 @@
>
> LIST_FOREACH(cp,&gp->consumer, consumer) {
> error = g_access(cp, dr, dw, de);
> - if (error) {
> + if (error&& error != ENXIO) {
> badcp = cp;
> goto fail;
> }
>
> This change fixes undesired behavior in the following case:
>
> While running
>
> while true; do
> echo
> date
> dd if=/dev/multipath/test of=/dev/null bs=512 count=1
> sleep 1
> done
>
> disconnect currently active path of /dev/multipath/test.
>
> Without "&& error != ENXIO" I have exactly one failed dd. Whith it -
> none of dd fails.
>
> Shouldn't the overall logic of g_multipath_access() be as follows: try
> to do what we're asked to do while there are at least one available
> path, and remove from g_multipath any path for which g_access() call
> has failed? I would suppose that multipath device should try to work
> as long as there is at least one workable path, and any path which has
> failed (no matter if it was a physical failure or, f.e. ENOMEM in
> device driver) should be detached from multipath device.
>
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