From 2e76c69c85f9927ceddac0989238cadffc307f1b Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Mon, 14 Mar 2022 14:30:11 -1000 Subject: block: don't merge across cgroup boundaries if blkcg is enabled commit 6b2b04590b51aa4cf395fcd185ce439cab5961dc upstream. blk-iocost and iolatency are cgroup aware rq-qos policies but they didn't disable merges across different cgroups. This obviously can lead to accounting and control errors but more importantly to priority inversions - e.g. an IO which belongs to a higher priority cgroup or IO class may end up getting throttled incorrectly because it gets merged to an IO issued from a low priority cgroup. Fix it by adding blk_cgroup_mergeable() which is called from merge paths and rejects cross-cgroup and cross-issue_as_root merges. Signed-off-by: Tejun Heo Fixes: d70675121546 ("block: introduce blk-iolatency io controller") Cc: stable@vger.kernel.org # v4.19+ Cc: Josef Bacik Link: https://lore.kernel.org/r/Yi/eE/6zFNyWJ+qd@slm.duckdns.org Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman --- block/blk-merge.c | 11 +++++++++++ 1 file changed, 11 insertions(+) (limited to 'block') diff --git a/block/blk-merge.c b/block/blk-merge.c index 7a5c81c02c80..bbe66a9010bf 100644 --- a/block/blk-merge.c +++ b/block/blk-merge.c @@ -7,6 +7,7 @@ #include #include #include +#include #include @@ -561,6 +562,9 @@ static inline unsigned int blk_rq_get_max_segments(struct request *rq) static inline int ll_new_hw_segment(struct request *req, struct bio *bio, unsigned int nr_phys_segs) { + if (!blk_cgroup_mergeable(req, bio)) + goto no_merge; + if (blk_integrity_merge_bio(req->q, req, bio) == false) goto no_merge; @@ -657,6 +661,9 @@ static int ll_merge_requests_fn(struct request_queue *q, struct request *req, if (total_phys_segments > blk_rq_get_max_segments(req)) return 0; + if (!blk_cgroup_mergeable(req, next->bio)) + return 0; + if (blk_integrity_merge_rq(q, req, next) == false) return 0; @@ -863,6 +870,10 @@ bool blk_rq_merge_ok(struct request *rq, struct bio *bio) if (rq->rq_disk != bio->bi_bdev->bd_disk) return false; + /* don't merge across cgroup boundaries */ + if (!blk_cgroup_mergeable(rq, bio)) + return false; + /* only merge integrity protected bio into ditto rq */ if (blk_integrity_merge_bio(rq->q, rq, bio) == false) return false; -- cgit v1.2.3