From: Yu Kuai <yukuai3@huawei.com>
Date: Thu, 19 Jan 2023 19:03:49 +0800
Subject: blk-cgroup: support to track if policy is online
Git-commit: dfd6200a095440b663099d8d42f1efb0175a1ce3
Patch-mainline: v6.3-rc1
References: bsc#1216062
A new field 'online' is added to blkg_policy_data to fix following
2 problem:
1) In blkcg_activate_policy(), if pd_alloc_fn() with 'GFP_NOWAIT'
failed, 'queue_lock' will be dropped and pd_alloc_fn() will try again
without 'GFP_NOWAIT'. In the meantime, remove cgroup can race with
it, and pd_offline_fn() will be called without pd_init_fn() and
pd_online_fn(). This way null-ptr-deference can be triggered.
2) In order to synchronize pd_free_fn() from blkg_free_workfn() and
blkcg_deactivate_policy(), 'list_del_init(&blkg->q_node)' will be
delayed to blkg_free_workfn(), hence pd_offline_fn() can be called
first in blkg_destroy(), and then blkcg_deactivate_policy() will
call it again, we must prevent it.
The new field 'online' will be set after pd_online_fn() and will be
cleared after pd_offline_fn(), in the meantime pd_offline_fn() will only
be called if 'online' is set.
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Acked-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20230119110350.2287325-3-yukuai1@huaweicloud.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
[mkoutny: KABI note blkg_policy_data.online should fit into 4B padding at the end of struct]
Acked-by: Michal Koutný <mkoutny@suse.com>
---
block/blk-cgroup.c | 24 +++++++++++++++++-------
block/blk-cgroup.h | 1 +
2 files changed, 18 insertions(+), 7 deletions(-)
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index c6d7d1fce65a..75f3c4460715 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -288,6 +288,7 @@ static struct blkcg_gq *blkg_alloc(struct blkcg *blkcg, struct gendisk *disk,
blkg->pd[i] = pd;
pd->blkg = blkg;
pd->plid = i;
+ pd->online = false;
}
return blkg;
@@ -359,8 +360,11 @@ static struct blkcg_gq *blkg_create(struct blkcg *blkcg, struct gendisk *disk,
for (i = 0; i < BLKCG_MAX_POLS; i++) {
struct blkcg_policy *pol = blkcg_policy[i];
- if (blkg->pd[i] && pol->pd_online_fn)
- pol->pd_online_fn(blkg->pd[i]);
+ if (blkg->pd[i]) {
+ if (pol->pd_online_fn)
+ pol->pd_online_fn(blkg->pd[i]);
+ blkg->pd[i]->online = true;
+ }
}
}
blkg->online = true;
@@ -465,8 +469,11 @@ static void blkg_destroy(struct blkcg_gq *blkg)
for (i = 0; i < BLKCG_MAX_POLS; i++) {
struct blkcg_policy *pol = blkcg_policy[i];
- if (blkg->pd[i] && pol->pd_offline_fn)
- pol->pd_offline_fn(blkg->pd[i]);
+ if (blkg->pd[i] && blkg->pd[i]->online) {
+ if (pol->pd_offline_fn)
+ pol->pd_offline_fn(blkg->pd[i]);
+ blkg->pd[i]->online = false;
+ }
}
blkg->online = false;
@@ -1448,6 +1455,7 @@ int blkcg_activate_policy(struct request_queue *q,
blkg->pd[pol->plid] = pd;
pd->blkg = blkg;
pd->plid = pol->plid;
+ pd->online = false;
}
/* all allocated, init in the same order */
@@ -1455,9 +1463,11 @@ int blkcg_activate_policy(struct request_queue *q,
list_for_each_entry_reverse(blkg, &q->blkg_list, q_node)
pol->pd_init_fn(blkg->pd[pol->plid]);
- if (pol->pd_online_fn)
- list_for_each_entry_reverse(blkg, &q->blkg_list, q_node)
+ list_for_each_entry_reverse(blkg, &q->blkg_list, q_node) {
+ if (pol->pd_online_fn)
pol->pd_online_fn(blkg->pd[pol->plid]);
+ blkg->pd[pol->plid]->online = true;
+ }
__set_bit(pol->plid, q->blkcg_pols);
ret = 0;
@@ -1519,7 +1529,7 @@ void blkcg_deactivate_policy(struct request_queue *q,
spin_lock(&blkcg->lock);
if (blkg->pd[pol->plid]) {
- if (pol->pd_offline_fn)
+ if (blkg->pd[pol->plid]->online && pol->pd_offline_fn)
pol->pd_offline_fn(blkg->pd[pol->plid]);
pol->pd_free_fn(blkg->pd[pol->plid]);
blkg->pd[pol->plid] = NULL;
diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index 1e94e404eaa8..b13ee84f358e 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -135,6 +135,7 @@ struct blkg_policy_data {
/* the blkg and policy id this per-policy data belongs to */
struct blkcg_gq *blkg;
int plid;
+ bool online;
};
/*
--
2.35.3