From mboxrd@z Thu Jan 1 00:00:00 1970 From: Juha Aatrokoski Subject: Re: bcache hangs on writes, recovers after disabling discard on cache device Date: Tue, 16 Jul 2013 21:14:09 +0300 (EEST) Message-ID: References: <51C891C9.4060809@modelnine.org> <20130712011554.GA17799@kmo-pixel> Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Return-path: In-Reply-To: Sender: linux-bcache-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Kent Overstreet Cc: Heiko Wundram , linux-bcache-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-bcache@vger.kernel.org On Fri, 12 Jul 2013, Juha Aatrokoski wrote: > On Thu, 11 Jul 2013, Kent Overstreet wrote: > >> On Thu, Jul 11, 2013 at 05:58:17PM +0300, Juha Aatrokoski wrote: >>> On Mon, 24 Jun 2013, Heiko Wundram wrote: >>> >>>> In a rather old thread of mine (514C4FC1.6090804-EqIAFqbRPK3NLxjTenLetw@public.gmane.org), I >>>> already stated a problem I was seeing back at the time, namely >>>> that bcache seems to hang on writes to the SSD device after some >>>> time, writing 50 MB/s continuously to the output device. >>> ... >>>> Disabling discard on the SSD device (by echo 0 > >>>> /sys/fs/bcache/.../cache0/discard) makes the bcache device become >>>> responsive again. >>> >>> I can confirm this. On Monday I booted into kernel 3.8.13-gentoo >>> with the current "bcache" branch patched onto it. Discard was on for >>> the cache device, and today this 50MB/s hang occured. Disabling >>> discard did indeed fix it. >>> >>> I had CONFIG_BCACHE_CLOSURES_DEBUG=y in the kernel, and the contents >>> of /sys/kernel/debug/bcache/bcache-UUID and >>> /sys/kernel/debug/closures both before and after disabling discard >>> can be found at the address below, in case they can help in >>> determining where exactly the hang happens. >> >> Can you give this patch a try? It's on top of the current >> bcache-for-3.11 branch > > OK, now running the same kernel with this patch applied and discard enabled. > However, it has previously taken my system 2-4 days to trigger this bug, so > I'd say at least two weeks before I can say the patch (may have) fixed the > issue. No such luck, hit the bug after four days of uptime. Disabling discard fixed the problem so at least it's not any worse than before.