blkg_free() may be called in atomic context, either spin lock is held,
or run in rcu callback. Meantime either request queue's release handler
or ->pd_free_fn can sleep.
Fix the issue by scheduling work function for freeing blkcg_gq instance.
[ 148.553894] BUG: sleeping function called from invalid context at block/blk-sysfs.c:767
[ 148.557381] in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 0, name: swapper/13
[ 148.560741] preempt_count: 101, expected: 0
[ 148.562577] RCU nest depth: 0, expected: 0
[ 148.564379] 1 lock held by swapper/13/0:
[ 148.566127] #0: ffffffff82615f80 (rcu_callback){....}-{0:0}, at: rcu_lock_acquire+0x0/0x1b
[ 148.569640] Preemption disabled at:
[ 148.569642] [<ffffffff8123f9c3>] ___slab_alloc+0x554/0x661
[ 148.573559] CPU: 13 PID: 0 Comm: swapper/13 Kdump: loaded Not tainted 5.17.0_up+ #110
[ 148.576834] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.14.0-1.fc33 04/01/2014
[ 148.579768] Call Trace:
[ 148.580567] <IRQ>
[ 148.581262] dump_stack_lvl+0x56/0x7c
[ 148.582367] ? ___slab_alloc+0x554/0x661
[ 148.583526] __might_resched+0x1af/0x1c8
[ 148.584678] blk_release_queue+0x24/0x109
[ 148.585861] kobject_cleanup+0xc9/0xfe
[ 148.586979] blkg_free+0x46/0x63
[ 148.587962] rcu_do_batch+0x1c5/0x3db
[ 148.589057] rcu_core+0x14a/0x184
[ 148.590065] __do_softirq+0x14d/0x2c7
[ 148.591167] __irq_exit_rcu+0x7a/0xd4
[ 148.592264] sysvec_apic_timer_interrupt+0x82/0xa5
[ 148.593649] </IRQ>
[ 148.594354] <TASK>
[ 148.595058] asm_sysvec_apic_timer_interrupt+0x12/0x20
Cc: Tejun Heo <tj@xxxxxxxxxx>
Fixes: 0a9a25ca7843 ("block: let blkcg_gq grab request queue's refcnt")
Reported-by: Christoph Hellwig <hch@xxxxxx>
Link: https://lore.kernel.org/linux-block/20220322093322.GA27283@xxxxxx/
Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
---
V2:
- fix document
- move 'blkg' check into blkg_free()
- make sure no warning in clang build
- add call trace in commit log as suggested by Tejun
block/blk-cgroup.c | 32 ++++++++++++++++++++++----------
include/linux/blk-cgroup.h | 5 ++++-
2 files changed, 26 insertions(+), 11 deletions(-)
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index d53b0d69dd73..6ed43fc0e6ab 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -65,19 +65,12 @@ static bool blkcg_policy_enabled(struct request_queue *q,
return pol && test_bit(pol->plid, q->blkcg_pols);
}
-/**
- * blkg_free - free a blkg
- * @blkg: blkg to free
- *
- * Free @blkg which may be partially allocated.
- */
-static void blkg_free(struct blkcg_gq *blkg)
+static void blkg_free_workfn(struct work_struct *work)
{
+ struct blkcg_gq *blkg = container_of(work, struct blkcg_gq,
+ free_work);
int i;
- if (!blkg)
- return;
-
for (i = 0; i < BLKCG_MAX_POLS; i++)
if (blkg->pd[i])
blkcg_policy[i]->pd_free_fn(blkg->pd[i]);
@@ -89,6 +82,25 @@ static void blkg_free(struct blkcg_gq *blkg)
kfree(blkg);
}
+/**
+ * blkg_free - free a blkg
+ * @blkg: blkg to free
+ *
+ * Free @blkg which may be partially allocated.
+ */
+static void blkg_free(struct blkcg_gq *blkg)
+{
+ if (!blkg)
+ return;
+
+ /*
+ * Both ->pd_free_fn() and request queue's release handler may
+ * sleep, so free us by scheduling one work func
+ */
+ INIT_WORK(&blkg->free_work, blkg_free_workfn);
+ schedule_work(&blkg->free_work);
+}
+
static void __blkg_release(struct rcu_head *rcu)
{
struct blkcg_gq *blkg = container_of(rcu, struct blkcg_gq, rcu_head);
diff --git a/include/linux/blk-cgroup.h b/include/linux/blk-cgroup.h
index f2ad8ed8f777..652cd05b0924 100644
--- a/include/linux/blk-cgroup.h
+++ b/include/linux/blk-cgroup.h
@@ -95,7 +95,10 @@ struct blkcg_gq {
spinlock_t async_bio_lock;
struct bio_list async_bios;
- struct work_struct async_bio_work;
+ union {
+ struct work_struct async_bio_work;
+ struct work_struct free_work;
+ };
atomic_t use_delay;
atomic64_t delay_nsec;
--
2.31.1
