The counter conf->empty_inactive_list_nr is only used for determine if the raid5 is congested which is deal with in function raid5_congested(). It was increased in get_free_stripe() when conf->inactive_list got to be empty and decreased in release_inactive_stripe_list() when splice temp_inactive_list to conf->inactive_list. However, this may have a problem when raid5_get_active_stripe or stripe_add_to_batch_list was called, because these two functions may call list_del_init(&sh->lru) to delete sh from "conf->inactive_list + hash" which may cause "conf->inactive_list + hash" to be empty when atomic_inc_not_zero(&sh->count) got false. So a check should be done at these two point and increase empty_inactive_list_nr accordingly. Otherwise the counter may get to be negative number which would influence async readahead from VFS.
Signed-off-by: ZhengYuan Liu <[email protected]> --- drivers/md/raid5.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c index 7c53861..1656c44 100644 --- a/drivers/md/raid5.c +++ b/drivers/md/raid5.c @@ -659,6 +659,7 @@ raid5_get_active_stripe(struct r5conf *conf, sector_t sector, { struct stripe_head *sh; int hash = stripe_hash_locks_hash(sector); + int inc_empty_inactive_list_flag; pr_debug("get_stripe, sector %llu\n", (unsigned long long)sector); @@ -703,7 +704,12 @@ raid5_get_active_stripe(struct r5conf *conf, sector_t sector, atomic_inc(&conf->active_stripes); BUG_ON(list_empty(&sh->lru) && !test_bit(STRIPE_EXPANDING, &sh->state)); + inc_empty_inactive_list_flag = 0; + if (!list_empty(conf->inactive_list + hash)) + inc_empty_inactive_list_flag = 1; list_del_init(&sh->lru); + if (list_empty(conf->inactive_list + hash) && inc_empty_inactive_list_flag) + atomic_inc(&conf->empty_inactive_list_nr); if (sh->group) { sh->group->stripes_cnt--; sh->group = NULL; @@ -762,6 +768,7 @@ static void stripe_add_to_batch_list(struct r5conf *conf, struct stripe_head *sh sector_t head_sector, tmp_sec; int hash; int dd_idx; + int inc_empty_inactive_list_flag; if (!stripe_can_batch(sh)) return; @@ -781,7 +788,11 @@ static void stripe_add_to_batch_list(struct r5conf *conf, struct stripe_head *sh atomic_inc(&conf->active_stripes); BUG_ON(list_empty(&head->lru) && !test_bit(STRIPE_EXPANDING, &head->state)); + if (!list_empty(conf->inactive_list + hash)) + inc_empty_inactive_list_flag = 1; list_del_init(&head->lru); + if (list_empty(conf->inactive_list + hash) && inc_empty_inactive_list_flag) + atomic_inc(&conf->empty_inactive_list_nr); if (head->group) { head->group->stripes_cnt--; head->group = NULL; -- 1.9.1
