diff mbox series

[4/5] bfq: Split shared queues on move between cgroups

Message ID 20220105143639.31266-4-jack@suse.cz (mailing list archive)
State New, archived
Headers show
Series bfq: Avoid use-after-free when moving processes between cgroups | expand

Commit Message

Jan Kara Jan. 5, 2022, 2:36 p.m. UTC 
When bfqq is shared by multiple processes it can happen that one of the
processes gets moved to a different cgroup (or just starts submitting IO
for different cgroup). In case that happens we need to split the merged
bfqq as otherwise we will have IO for multiple cgroups in one bfqq and
we will just account IO time to wrong entities etc.

Similarly if the bfqq is scheduled to merge with another bfqq but the
merge didn't happen yet, cancel the merge as it need not be valid
anymore.

CC: stable@vger.kernel.org
Fixes: e21b7a0b9887 ("block, bfq: add full hierarchical scheduling and cgroups support")
Signed-off-by: Jan Kara <jack@suse.cz>
---
 block/bfq-cgroup.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c
index 24a5c5329bcd..a78d86805bd5 100644
--- a/block/bfq-cgroup.c
+++ b/block/bfq-cgroup.c
@@ -730,8 +730,19 @@  static struct bfq_group *__bfq_bic_change_cgroup(struct bfq_data *bfqd,
 
 	if (sync_bfqq) {
 		entity = &sync_bfqq->entity;
-		if (entity->sched_data != &bfqg->sched_data)
+		if (entity->sched_data != &bfqg->sched_data) {
+			/*
+			 * Moving bfqq that is shared with another process?
+			 * Split the queues at the nearest occasion as the
+			 * processes can be in different cgroups now.
+			 */
+			if (bfq_bfqq_coop(sync_bfqq)) {
+				bic->stably_merged = false;
+				bfq_mark_bfqq_split_coop(sync_bfqq);
+			}
+			WARN_ON_ONCE(sync_bfqq->new_bfqq);
 			bfq_bfqq_move(bfqd, sync_bfqq, bfqg);
+		}
 	}
 
 	return bfqg;