On Wed, Jun 08, 2022 at 01:45:28PM +0200, Jan Kara wrote:
> 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 <logang@xxxxxxxxxxxx>
> Reported-and-tested-by: Donald Buczek <buczek@xxxxxxxxxxxxx>
> Fixes: d92c370a16cb ("block: really clone the block cgroup in bio_clone_blkg_association")
> CC: stable@xxxxxxxxxxxxxxx
> Reviewed-by: Christoph Hellwig <hch@xxxxxx>
> Signed-off-by: Jan Kara <jack@xxxxxxx>
> Link: https://lore.kernel.org/r/20220602081242.7731-1-jack@xxxxxxx
> Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
> ---
> block/blk-cgroup.c | 8 ++------
> 1 file changed, 2 insertions(+), 6 deletions(-)
>
> This patch should be a backport for 5.15, 5.17, and 5.18 stable branches.
Now queued up, thanks.
greg k-h
