From: Christoph Hellwig <hch@lst.de>
Date: Sat, 27 Jun 2020 09:31:48 +0200
Subject: [PATCH] block: really clone the block cgroup in
 bio_clone_blkg_association
References: bsc#1175995,jsc#SLE-15608
Git-commit: d92c370a16cbe0276954c761b874bd024a7e4fac
Patch-mainline: v5.9-rc1

bio_clone_blkg_association is supposed to clone the associatation, but
actually ends up doing a search with a tryget.  As we know we have a
reference on the source cgroup just get an unconditional additional
reference to it and call it a day.  That also removes the need for
a RCU critical section.

Acked-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Hannes Reinecke <hare@suse.de>
---
 block/bio.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/block/bio.c b/block/bio.c
index 1f91e17ea3f5..c133f45ea0c3 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -2275,12 +2275,12 @@ EXPORT_SYMBOL_GPL(bio_associate_blkg);
  */
 void bio_clone_blkg_association(struct bio *dst, struct bio *src)
 {
-	rcu_read_lock();
-
-	if (src->bi_blkg)
-		__bio_associate_blkg(dst, src->bi_blkg);
-
-	rcu_read_unlock();
+	if (src->bi_blkg) {
+		if (dst->bi_blkg)
+			blkg_put(dst->bi_blkg);
+		blkg_get(src->bi_blkg);
+		dst->bi_blkg = src->bi_blkg;
+	}
 }
 EXPORT_SYMBOL_GPL(bio_clone_blkg_association);
 #endif /* CONFIG_BLK_CGROUP */
-- 
2.16.4