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authorShaohua Li <shli@kernel.org>2014-04-09 11:27:42 +0800
committerNeilBrown <neilb@suse.de>2014-04-09 14:42:42 +1000
commite240c1839d11152b0355442f8ac6d2d2d921be36 (patch)
treebb2f80fd9a3be90a710e2e2053c246ff1dedf6f7 /drivers
parent27c0f68f0745218cec70f19ba7560c8c5fc3f817 (diff)
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 <shli@fusionio.com> Signed-off-by: NeilBrown <neilb@suse.de>
Diffstat (limited to 'drivers')
-rw-r--r--drivers/md/raid5.c9
1 files changed, 2 insertions, 7 deletions
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) &&