diff options
| -rw-r--r-- | block/blk-cgroup.c | 40 |
1 files changed, 21 insertions, 19 deletions
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c index 5e2723f2c6a3..2ff74ffcbb27 100644 --- a/block/blk-cgroup.c +++ b/block/blk-cgroup.c @@ -29,6 +29,14 @@ #define MAX_KEY_LEN 100 +/* + * blkcg_pol_mutex protects blkcg_policy[] and policy [de]activation. + * blkcg_pol_register_mutex nests outside of it and synchronizes entire + * policy [un]register operations including cgroup file additions / + * removals. Putting cgroup file registration outside blkcg_pol_mutex + * allows grabbing it from cgroup callbacks. + */ +static DEFINE_MUTEX(blkcg_pol_register_mutex); static DEFINE_MUTEX(blkcg_pol_mutex); struct blkcg blkcg_root; @@ -453,20 +461,7 @@ static int blkcg_reset_stats(struct cgroup_subsys_state *css, struct blkcg_gq *blkg; int i; - /* - * XXX: We invoke cgroup_add/rm_cftypes() under blkcg_pol_mutex - * which ends up putting cgroup's internal cgroup_tree_mutex under - * it; however, cgroup_tree_mutex is nested above cgroup file - * active protection and grabbing blkcg_pol_mutex from a cgroup - * file operation creates a possible circular dependency. cgroup - * internal locking is planned to go through further simplification - * and this issue should go away soon. For now, let's trylock - * blkcg_pol_mutex and restart the write on failure. - * - * http://lkml.kernel.org/g/5363C04B.4010400@oracle.com - */ - if (!mutex_trylock(&blkcg_pol_mutex)) - return restart_syscall(); + mutex_lock(&blkcg_pol_mutex); spin_lock_irq(&blkcg->lock); /* @@ -1190,6 +1185,7 @@ int blkcg_policy_register(struct blkcg_policy *pol) if (WARN_ON(pol->pd_size < sizeof(struct blkg_policy_data))) return -EINVAL; + mutex_lock(&blkcg_pol_register_mutex); mutex_lock(&blkcg_pol_mutex); /* find an empty slot */ @@ -1198,19 +1194,23 @@ int blkcg_policy_register(struct blkcg_policy *pol) if (!blkcg_policy[i]) break; if (i >= BLKCG_MAX_POLS) - goto out_unlock; + goto err_unlock; /* register and update blkgs */ pol->plid = i; blkcg_policy[i] = pol; + mutex_unlock(&blkcg_pol_mutex); /* everything is in place, add intf files for the new policy */ if (pol->cftypes) WARN_ON(cgroup_add_legacy_cftypes(&blkio_cgrp_subsys, pol->cftypes)); - ret = 0; -out_unlock: + mutex_unlock(&blkcg_pol_register_mutex); + return 0; + +err_unlock: mutex_unlock(&blkcg_pol_mutex); + mutex_unlock(&blkcg_pol_register_mutex); return ret; } EXPORT_SYMBOL_GPL(blkcg_policy_register); @@ -1223,7 +1223,7 @@ EXPORT_SYMBOL_GPL(blkcg_policy_register); */ void blkcg_policy_unregister(struct blkcg_policy *pol) { - mutex_lock(&blkcg_pol_mutex); + mutex_lock(&blkcg_pol_register_mutex); if (WARN_ON(blkcg_policy[pol->plid] != pol)) goto out_unlock; @@ -1233,8 +1233,10 @@ void blkcg_policy_unregister(struct blkcg_policy *pol) cgroup_rm_cftypes(pol->cftypes); /* unregister and update blkgs */ + mutex_lock(&blkcg_pol_mutex); blkcg_policy[pol->plid] = NULL; -out_unlock: mutex_unlock(&blkcg_pol_mutex); +out_unlock: + mutex_unlock(&blkcg_pol_register_mutex); } EXPORT_SYMBOL_GPL(blkcg_policy_unregister); |