Re: [BUG] at drivers/md/raid5.c:291! kernel 3.13-rc8

[NeilBrown <neilb@suse.de>]

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On Mon, 20 Jan 2014 01:49:17 +0100 Ian Kumlien <ian.kumlien@gmail.com> wrote:

> On mån, 2014-01-20 at 11:38 +1100, NeilBrown wrote:
> > On Sun, 19 Jan 2014 23:00:23 +0100 Ian Kumlien <ian.kumlien@gmail.com> wrote:
> > 
> > > Ok, so third try to actually email this... 
> > > ---
> > > 
> > > Hi,
> > > 
> > > I started testing 3.13-rc8 on another machine since the first one seemed
> > > to be working fine...
> > > 
> > > One spontaneous reboot later i'm not so sure ;)
> > > 
> > > Right now i captured a kernel oops in the raid code it seems...
> > > 
> > > (Also attached to avoid mangling)
> > > 
> > > [33411.934672] ------------[ cut here ]------------
> > > [33411.934685] kernel BUG at drivers/md/raid5.c:291!
> > > [33411.934690] invalid opcode: 0000 [#1] PREEMPT SMP 
> > > [33411.934696] Modules linked in: bonding btrfs microcode
> > > [33411.934705] CPU: 4 PID: 2319 Comm: md2_raid6 Not tainted 3.13.0-rc8 #83
> > > [33411.934709] Hardware name: System manufacturer System Product Name/Crosshair IV Formula, BIOS 3029    10/09/2012
> > > [33411.934716] task: ffff880326265880 ti: ffff880320472000 task.ti: ffff880320472000
> > > [33411.934720] RIP: 0010:[<ffffffff81a3a5be>]  [<ffffffff81a3a5be>] do_release_stripe+0x18e/0x1a0
> > > [33411.934731] RSP: 0018:ffff880320473d28  EFLAGS: 00010087
> > > [33411.934735] RAX: ffff8802f0875a60 RBX: 0000000000000001 RCX: ffff8800b0d816b0
> > > [33411.934739] RDX: ffff880324eeee98 RSI: ffff8802f0875a40 RDI: ffff880324eeec00
> > > [33411.934743] RBP: ffff8802f0875a50 R08: 0000000000000000 R09: 0000000000000001
> > > [33411.934747] R10: 0000000000000000 R11: 0000000000000000 R12: ffff880324eeec00
> > > [33411.934752] R13: ffff880324eeee58 R14: ffff880320473e88 R15: 0000000000000000
> > > [33411.934756] FS:  00007fc38654d700(0000) GS:ffff880337d00000(0000) knlGS:0000000000000000
> > > [33411.934761] CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
> > > [33411.934765] CR2: 00007f0cb28bd000 CR3: 00000002ebcf6000 CR4: 00000000000407e0
> > > [33411.934769] Stack:
> > > [33411.934771]  ffff8800bba09690 ffff8800b4f16588 ffff880303005a40 0000000000000001
> > > [33411.934779]  ffff8800b33e43d0 ffffffff81a3a62d ffff880324eeee58 0000000000000000
> > > [33411.934786]  ffff880324eeee58 ffff880326660670 ffff880326265880 ffffffff81a41692
> > > [33411.934794] Call Trace:
> > > [33411.934798]  [<ffffffff81a3a62d>] ? release_stripe_list+0x4d/0x70
> > > [33411.934803]  [<ffffffff81a41692>] ? raid5d+0xa2/0x4d0
> > > [33411.934808]  [<ffffffff81a65ed6>] ? md_thread+0xe6/0x120
> > > [33411.934814]  [<ffffffff81122060>] ? finish_wait+0x90/0x90
> > > [33411.934818]  [<ffffffff81a65df0>] ? md_rdev_init+0x100/0x100
> > > [33411.934823]  [<ffffffff8110958c>] ? kthread+0xbc/0xe0
> > > [33411.934828]  [<ffffffff81110000>] ? smpboot_park_threads+0x70/0x70Hi,
> > 
> > Thanks for the report.
> > Can you provide any more context about the details of the array in question?
> > I see it was RAID6.  Was it degraded?  Was it resyncing?  Was it being
> > reshaped?
> > Was there any way that it was different from the array one the machine where
> > it seemed to work?
> 
> Yes, it's a raid6 and no, there is no reshaping or syncing going on... 
> 
> Basically everything worked fine before:
> reboot   system boot  3.13.0-rc8       Sun Jan 19 21:47 - 01:42  (03:55)    
> reboot   system boot  3.13.0-rc8       Sun Jan 19 21:38 - 01:42  (04:04)    
> reboot   system boot  3.13.0-rc8       Sun Jan 19 12:13 - 01:42  (13:29)    
> reboot   system boot  3.13.0-rc8       Sat Jan 18 21:23 - 01:42 (1+04:19)   
> reboot   system boot  3.12.6           Mon Dec 30 16:27 - 22:21 (19+05:53)  
> 
> As in, no problems before the 3.13.0-rc8 upgrade...
> 
> cat /proc/mdstat:
> Personalities : [linear] [raid0] [raid1] [raid10] [raid6] [raid5] [raid4] [multipath] 
> md2 : active raid6 sdf1[2] sdd1[9] sdj1[8] sdg1[4] sde1[5] sdi1[11] sdc1[0] sdh1[10]
>       11721074304 blocks super 1.2 level 6, 64k chunk, algorithm 2 [8/8] [UUUUUUUU]
>       bitmap: 0/15 pages [0KB], 65536KB chunk
> 
> What i do do is:
> echo 32768 > /sys/block/*/md/stripe_cache_size
> 
> Which has caused no problems during intense write operations before... 
> 
> I find it quite surprising since it only requires ~3 gigabytes of writes
> to die and almost assume that it's related to the stripe_cache_size.
> (Since all memory is ECC and i doubt it would break, quite literally,
> over night i haven't run extensive memory tests)
> 
> I don't quite know what other information you might need...

Thanks - that extra info is quite useful.  Knowing that nothing else unusual
is happening can be quite valuable (and I don't like to assume).

I haven't found anything that would clearly cause your crash, but I have
found something that looks wrong and conceivably could.

Could you please try this patch on top of what you are currently using?  By
the look of it you get a crash at least every day, often more often.  So if
this produces a day with no crashes, that would be promising.

The important aspect of the patch is that it moves the "atomic_inc" of
"sh->count" back under the protection of ->device_lock in the case when some
other thread might be using the same 'sh'.

Thanks,
NeilBrown


diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 3088d3af5a89..03f82ab87d9e 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -675,8 +675,10 @@ get_active_stripe(struct r5conf *conf, sector_t sector,
 					 || !conf->inactive_blocked),
 					*(conf->hash_locks + hash));
 				conf->inactive_blocked = 0;
-			} else
+			} else {
 				init_stripe(sh, sector, previous);
+				atomic_inc(&sh->count);
+			}
 		} else {
 			spin_lock(&conf->device_lock);
 			if (atomic_read(&sh->count)) {
@@ -695,13 +697,11 @@ get_active_stripe(struct r5conf *conf, sector_t sector,
 					sh->group = NULL;
 				}
 			}
+			atomic_inc(&sh->count);
 			spin_unlock(&conf->device_lock);
 		}
 	} while (sh == NULL);
 
-	if (sh)
-		atomic_inc(&sh->count);
-
 	spin_unlock_irq(conf->hash_locks + hash);
 	return sh;
 }

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