[PATCH 5.13 011/113] blk-iocost: fix lockdep warning on blkcg->lock

From: Greg Kroah-Hartman
Date: Wed Sep 01 2021 - 08:45:51 EST


From: Ming Lei <ming.lei@xxxxxxxxxx>

[ Upstream commit 11431e26c9c43fa26f6b33ee1a90989f57b86024 ]

blkcg->lock depends on q->queue_lock which may depend on another driver
lock required in irq context, one example is dm-thin:

Chain exists of:
&pool->lock#3 --> &q->queue_lock --> &blkcg->lock

Possible interrupt unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&blkcg->lock);
local_irq_disable();
lock(&pool->lock#3);
lock(&q->queue_lock);
<Interrupt>
lock(&pool->lock#3);

Fix the issue by using spin_lock_irq(&blkcg->lock) in ioc_weight_write().

Cc: Tejun Heo <tj@xxxxxxxxxx>
Reported-by: Bruno Goncalves <bgoncalv@xxxxxxxxxx>
Link: https://lore.kernel.org/linux-block/CA+QYu4rzz6079ighEanS3Qq_Dmnczcf45ZoJoHKVLVATTo1e4Q@xxxxxxxxxxxxxx/T/#u
Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
Acked-by: Tejun Heo <tj@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20210803070608.1766400-1-ming.lei@xxxxxxxxxx
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
block/blk-iocost.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/block/blk-iocost.c b/block/blk-iocost.c
index 5fac3757e6e0..0e56557cacf2 100644
--- a/block/blk-iocost.c
+++ b/block/blk-iocost.c
@@ -3061,19 +3061,19 @@ static ssize_t ioc_weight_write(struct kernfs_open_file *of, char *buf,
if (v < CGROUP_WEIGHT_MIN || v > CGROUP_WEIGHT_MAX)
return -EINVAL;

- spin_lock(&blkcg->lock);
+ spin_lock_irq(&blkcg->lock);
iocc->dfl_weight = v * WEIGHT_ONE;
hlist_for_each_entry(blkg, &blkcg->blkg_list, blkcg_node) {
struct ioc_gq *iocg = blkg_to_iocg(blkg);

if (iocg) {
- spin_lock_irq(&iocg->ioc->lock);
+ spin_lock(&iocg->ioc->lock);
ioc_now(iocg->ioc, &now);
weight_updated(iocg, &now);
- spin_unlock_irq(&iocg->ioc->lock);
+ spin_unlock(&iocg->ioc->lock);
}
}
- spin_unlock(&blkcg->lock);
+ spin_unlock_irq(&blkcg->lock);

return nbytes;
}
--
2.30.2