GFP_NOIO means we could be getting called recursively - mca_alloc() -> mca_data_alloc() - definitely can't use mutex_lock(bucket_lock) then. Whoops. Signed-off-by: Kent Overstreet <kmo@xxxxxxxxxxxxx> --- On Thu, Aug 29, 2013 at 05:29:54PM -0700, kernel neophyte wrote: > We are evaluating to use bcache on our production systems where the > caching devices are insanely fast, in this scenario under a moderate load > of random 4k writes.. bcache fails miserably :-( > > [ 3588.513638] bcache: bch_cached_dev_attach() Caching sda4 as bcache0 > on set b082ce66-04c6-43d5-8207-ebf39840191d > [ 4442.163661] INFO: task kworker/0:0:4 blocked for more than 120 seconds. > [ 4442.163671] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" > disables this message. > [ 4442.163678] kworker/0:0 D ffffffff81813d40 0 4 2 0x00000000 > [ 4442.163695] Workqueue: bcache bch_data_insert_keys > [ 4442.163699] ffff882fa6ac93c8 0000000000000046 ffff882fa6ac93e8 > 0000000000000151 > [ 4442.163705] ffff882fa6a84cb0 ffff882fa6ac9fd8 ffff882fa6ac9fd8 > ffff882fa6ac9fd8 > [ 4442.163711] ffff882fa6ad6640 ffff882fa6a84cb0 ffff882fa6a84cb0 > ffff8822ca2c0d98 > [ 4442.163716] Call Trace: > [ 4442.163729] [<ffffffff816be299>] schedule+0x29/0x70 > [ 4442.163735] [<ffffffff816be57e>] schedule_preempt_disabled+0xe/0x10 > [ 4442.163741] [<ffffffff816bc862>] __mutex_lock_slowpath+0x112/0x1b0 > [ 4442.163746] [<ffffffff816bc3da>] mutex_lock+0x2a/0x50 > [ 4442.163752] [<ffffffff815112e5>] bch_mca_shrink+0x1b5/0x2f0 > [ 4442.163759] [<ffffffff8117fc32>] ? prune_super+0x162/0x1b0 > [ 4442.163769] [<ffffffff8112ebb4>] shrink_slab+0x154/0x300 > [ 4442.163776] [<ffffffff81076828>] ? resched_task+0x68/0x70 > [ 4442.163782] [<ffffffff81077165>] ? check_preempt_curr+0x75/0xa0 > [ 4442.163788] [<ffffffff8113a379>] ? fragmentation_index+0x19/0x70 > [ 4442.163794] [<ffffffff8113140f>] do_try_to_free_pages+0x20f/0x4b0 > [ 4442.163800] [<ffffffff81131864>] try_to_free_pages+0xe4/0x1a0 > [ 4442.163810] [<ffffffff81126e9c>] __alloc_pages_nodemask+0x60c/0x9b0 > [ 4442.163818] [<ffffffff8116062a>] alloc_pages_current+0xba/0x170 > [ 4442.163824] [<ffffffff8112240e>] __get_free_pages+0xe/0x40 > [ 4442.163829] [<ffffffff8150ebb3>] mca_data_alloc+0x73/0x1d0 > [ 4442.163834] [<ffffffff8150ee5a>] mca_bucket_alloc+0x14a/0x1f0 > [ 4442.163838] [<ffffffff81511020>] mca_alloc+0x360/0x470 > [ 4442.163843] [<ffffffff81511d1c>] bch_btree_node_alloc+0x8c/0x1c0 > [ 4442.163849] [<ffffffff81513020>] btree_split+0x110/0x5c0 Ohhh, that definitely isn't supposed to happen. Wonder why I hadn't seen this before, looking at the backtrace it's pretty obvious what's broken though - try this patch: drivers/md/bcache/btree.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c index 60908de..55e8666 100644 --- a/drivers/md/bcache/btree.c +++ b/drivers/md/bcache/btree.c @@ -617,7 +617,7 @@ static int bch_mca_shrink(struct shrinker *shrink, struct shrink_control *sc) return mca_can_free(c) * c->btree_pages; /* Return -1 if we can't do anything right now */ - if (sc->gfp_mask & __GFP_WAIT) + if (sc->gfp_mask & __GFP_IO) mutex_lock(&c->bucket_lock); else if (!mutex_trylock(&c->bucket_lock)) return -1; -- 1.8.4.rc3 -- To unsubscribe from this list: send the line "unsubscribe linux-bcache" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
