raid5: fix incorrectly counter of conf->empty_inactive_list_nr

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 <liuzhengyuan@kylinos.cn>
Signed-off-by: Shaohua Li <shli@fb.com>

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index d189e894b921700d74fab3fb836f770b23ff14bd..e379b89fd8b18a904cc9fa2e08d6649683e6aeee 100644 (file)
--- 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;
 
        /* Don't cross chunks, so stripe pd_idx/qd_idx is the same */
        tmp_sec = sh->sector;
@@ -779,7 +786,12 @@ 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));
+                       inc_empty_inactive_list_flag = 0;
+                       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;