From c24cff01242005a958f1c0921f8a783ec0591911 Mon Sep 17 00:00:00 2001 From: Jan Kara Date: Thu, 2 Jun 2022 10:12:42 +0200 Subject: [PATCH] block: fix bio_clone_blkg_association() to associate with proper blkcg_gq commit 22b106e5355d6e7a9c3b5cb5ed4ef22ae585ea94 upstream. Commit d92c370a16cb ("block: really clone the block cgroup in bio_clone_blkg_association") changed bio_clone_blkg_association() to just clone bio->bi_blkg reference from source to destination bio. This is however wrong if the source and destination bios are against different block devices because struct blkcg_gq is different for each bdev-blkcg pair. This will result in IOs being accounted (and throttled as a result) multiple times against the same device (src bdev) while throttling of the other device (dst bdev) is ignored. In case of BFQ the inconsistency can even result in crashes in bfq_bic_update_cgroup(). Fix the problem by looking up correct blkcg_gq for the cloned bio. Reported-by: Logan Gunthorpe Reported-and-tested-by: Donald Buczek Fixes: d92c370a16cb ("block: really clone the block cgroup in bio_clone_blkg_association") CC: stable@vger.kernel.org Reviewed-by: Christoph Hellwig Signed-off-by: Jan Kara Link: https://lore.kernel.org/r/20220602081242.7731-1-jack@suse.cz Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman --- block/blk-cgroup.c | 8 ++------ 1 file changed, 2 insertions(+), 6 deletions(-) diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c index 07a2524..ce5858d 100644 --- a/block/blk-cgroup.c +++ b/block/blk-cgroup.c @@ -1886,12 +1886,8 @@ EXPORT_SYMBOL_GPL(bio_associate_blkg); */ void bio_clone_blkg_association(struct bio *dst, struct bio *src) { - if (src->bi_blkg) { - if (dst->bi_blkg) - blkg_put(dst->bi_blkg); - blkg_get(src->bi_blkg); - dst->bi_blkg = src->bi_blkg; - } + if (src->bi_blkg) + bio_associate_blkg_from_css(dst, &bio_blkcg(src)->css); } EXPORT_SYMBOL_GPL(bio_clone_blkg_association); -- 2.7.4