Patch "block: Skip destroyed blkg when restart in blkg_destroy_all()" has been added to the 6.2-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    block: Skip destroyed blkg when restart in blkg_destroy_all()

to the 6.2-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     block-skip-destroyed-blkg-when-restart-in-blkg_destr.patch
and it can be found in the queue-6.2 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit eaeb212b688ff5e2e98acc4f5f6c5a9be7723230
Author: Tao Su <tao1.su@xxxxxxxxxxxxxxx>
Date:   Fri Apr 28 12:51:49 2023 +0800

    block: Skip destroyed blkg when restart in blkg_destroy_all()
    
    [ 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@xxxxxxxxx>
    Tested-by: Xiangfei Ma <xiangfeix.ma@xxxxxxxxx>
    Tested-by: Farrah Chen <farrah.chen@xxxxxxxxx>
    Signed-off-by: Tao Su <tao1.su@xxxxxxxxxxxxxxx>
    Fixes: f1c006f1c685 ("blk-cgroup: synchronize pd_free_fn() from blkg_free_workfn() and blkcg_deactivate_policy()")
    Suggested-and-reviewed-by: Yu Kuai <yukuai3@xxxxxxxxxx>
    Link: https://lore.kernel.org/r/20230428045149.1310073-1-tao1.su@xxxxxxxxxxxxxxx
    Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 9ac1efb053e08..2d8a28e4e22f7 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -501,6 +501,9 @@ 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);