From: Shaohua Li Date: Wed, 9 Apr 2014 03:27:42 +0000 (+0800) Subject: raid5: get_active_stripe avoids device_lock X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=e240c1839d11152b0355442;p=GitHub%2Fexynos8895%2Fandroid_kernel_samsung_universal8895.git raid5: get_active_stripe avoids device_lock For sequential workload (or request size big workload), get_active_stripe can find cached stripe. In this case, we always hold device_lock, which exposes a lot of lock contention for such workload. If stripe count isn't 0, we don't need hold the lock actually, since we just increase its count. And this is the hot code path for such workload. Unfortunately we must delete the BUG_ON. Signed-off-by: Shaohua Li Signed-off-by: NeilBrown --- diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c index a904a2c80fc8..25247a852912 100644 --- a/drivers/md/raid5.c +++ b/drivers/md/raid5.c @@ -679,14 +679,9 @@ get_active_stripe(struct r5conf *conf, sector_t sector, init_stripe(sh, sector, previous); atomic_inc(&sh->count); } - } else { + } else if (!atomic_inc_not_zero(&sh->count)) { spin_lock(&conf->device_lock); - if (atomic_read(&sh->count)) { - BUG_ON(!list_empty(&sh->lru) - && !test_bit(STRIPE_EXPANDING, &sh->state) - && !test_bit(STRIPE_ON_UNPLUG_LIST, &sh->state) - ); - } else { + if (!atomic_read(&sh->count)) { if (!test_bit(STRIPE_HANDLE, &sh->state)) atomic_inc(&conf->active_stripes); BUG_ON(list_empty(&sh->lru) &&