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Message-ID: <531BDD77.5020809@kernel.dk> Date: Sat, 08 Mar 2014 20:18:15 -0700 From: Jens Axboe <axboe@...nel.dk> To: Mike Snitzer <snitzer@...hat.com> CC: Hannes Reinecke <hare@...e.de>, Mike Snitzer <snitzer@...il.com>, Christoph Hellwig <hch@...radead.org>, Jeff Moyer <jmoyer@...hat.com>, Shaohua Li <shli@...ionio.com>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org> Subject: Re: block: fix q->flush_rq NULL pointer crash on dm-mpath flush On 2014-03-08 17:57, Mike Snitzer wrote: > On Sat, Mar 08 2014 at 7:24pm -0500, > Jens Axboe <axboe@...nel.dk> wrote: > >> On 2014-03-08 15:09, Mike Snitzer wrote: >>> On Sat, Mar 08 2014 at 4:33pm -0500, >>> Hannes Reinecke <hare@...e.de> wrote: >>> >>>> On 03/08/2014 07:13 PM, Mike Snitzer wrote: >>>>> >>>>> I'm calm.. was just a bit frustrated. But this isn't a big deal. >>>>> I'll make an effort to reach out to relevant people sooner when >>>>> similar stuff is reported against recently upstreamed code. Would be >>>>> cool if you did the same. I can relate to needing to have the distro >>>>> vendor hat on (first needing to determine/answer "is this issue >>>>> specific to our hacked distro kernel?", etc). >>>>> >>>> The patch I made wasn't in the context of 'recently upstreamed >>>> code', it was due to a backport Jan Kara did for our next distro >>>> kernels (3.12-based). >>> >>> "3.12-based" means nothing given all the backporting for SLES, much like >>> "3.10-based" means nothing in the context of RHEL7. >>> >>> The only way this fix is applicable is in the context of "recently >>> upstreamed code", commit 1874198 ("blk-mq: rework flush sequencing >>> logic") went upstream for v3.14-rc3. >>> >>> Jens, please feel free to queue this tested fix for 3.14-rc: >> >> Thanks Mike, queued up. > > Thanks. > >> Also queued up the list addition reversal change. > > I had a look at what you queued, thing is commit 1874198 replaced code > in blk_kick_flush() that did use list_add_tail(). So getting back to > the way the original code was (before 1874198) would need something > like the following patch. > > But it isn't clear to me why we'd have the duality of front vs tail > additions for flushes. Maybe Christoph knows? Not sure it'd even make a difference with the use case, but always tail would be broken. But the flushing in general is a bit of a nightmare, so I'd be inclined to add your full fix too, at least this late in -rc. -- Jens Axboe -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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