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authorTejun Heo <tj@kernel.org>2022-03-14 14:30:11 -1000
committerJens Axboe <axboe@kernel.dk>2022-03-14 19:14:37 -0600
commit6b2b04590b51aa4cf395fcd185ce439cab5961dc (patch)
treeca7f907498c68799e2f0ddb8e128464012a26b60 /block/blk-merge.c
parentaa1b46dcdc7baaf5fec0be25782ef24b26aa209e (diff)
block: don't merge across cgroup boundaries if blkcg is enabled
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 <tj@kernel.org> Fixes: d70675121546 ("block: introduce blk-iolatency io controller") Cc: stable@vger.kernel.org # v4.19+ Cc: Josef Bacik <jbacik@fb.com> Link: https://lore.kernel.org/r/Yi/eE/6zFNyWJ+qd@slm.duckdns.org Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block/blk-merge.c')
-rw-r--r--block/blk-merge.c11
1 files changed, 11 insertions, 0 deletions
diff --git a/block/blk-merge.c b/block/blk-merge.c
index 8d8177f71ebd..ea6968313b4a 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -9,6 +9,7 @@
#include <linux/blk-integrity.h>
#include <linux/scatterlist.h>
#include <linux/part_stat.h>
+#include <linux/blk-cgroup.h>
#include <trace/events/block.h>
@@ -598,6 +599,9 @@ static inline unsigned int blk_rq_get_max_sectors(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;
@@ -694,6 +698,9 @@ 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;
@@ -902,6 +909,10 @@ bool blk_rq_merge_ok(struct request *rq, struct bio *bio)
if (bio_data_dir(bio) != rq_data_dir(rq))
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;