From: Tao Su <tao1.su@linux.intel.com>
Date: Fri, 28 Apr 2023 12:51:49 +0800
Subject: [PATCH] block: Skip destroyed blkg when restart in blkg_destroy_all()
References: bsc#1012628
Patch-mainline: 6.3.3
Git-commit: 8176080d59e6d4ff9fc97ae534063073b4f7a715

[ Upstream commit 8176080d59e6d4ff9fc97ae534063073b4f7a715 ]

Kernel hang in blkg_destroy_all() when total blkg greater than
BLKG_DESTROY_BATCH_SIZE, because of not removing destroyed blkg in
blkg_list. So the size of blkg_list is same after destroying a
batch of blkg, and the infinite 'restart' occurs.

Since blkg should stay on the queue list until blkg_free_workfn(),
skip destroyed blkg when restart a new round, which will solve this
kernel hang issue and satisfy the previous will to restart.

Reported-by: Xiangfei Ma <xiangfeix.ma@intel.com>
Tested-by: Xiangfei Ma <xiangfeix.ma@intel.com>
Tested-by: Farrah Chen <farrah.chen@intel.com>
Signed-off-by: Tao Su <tao1.su@linux.intel.com>
Fixes: f1c006f1c685 ("blk-cgroup: synchronize pd_free_fn() from blkg_free_workfn() and blkcg_deactivate_policy()")
Suggested-and-reviewed-by: Yu Kuai <yukuai3@huawei.com>
Link: https://lore.kernel.org/r/20230428045149.1310073-1-tao1.su@linux.intel.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 block/blk-cgroup.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index bd50b55b..75bad5d6 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -528,6 +528,9 @@ static void blkg_destroy_all(struct gendisk *disk)
 	list_for_each_entry_safe(blkg, n, &q->blkg_list, q_node) {
 		struct blkcg *blkcg = blkg->blkcg;
 
+		if (hlist_unhashed(&blkg->blkcg_node))
+			continue;
+
 		spin_lock(&blkcg->lock);
 		blkg_destroy(blkg);
 		spin_unlock(&blkcg->lock);
-- 
2.35.3