blk-cgroup: save IRQ state in blkg_tryget_closest()

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bio_set_dev() associates the bio with a blkg through bio_associate_blkg().
If the blkg lookup misses, blkg_tryget_closest() takes q->queue_lock with
spin_lock_irq() and releases it with spin_unlock_irq(), which
unconditionally enables local interrupts.

Callers may call bio_set_dev() with interrupts already disabled, e.g.
dm-thin's pool_map() does so while holding pool->lock taken with
spin_lock_irq().  The nested spin_unlock_irq() then enables interrupts
while pool->lock is still held, so an I/O completion softirq can run on
the same CPU, re-acquire pool->lock (thin_endio(), or overwrite_endio()
-> complete_mapping_preparation()) and deadlock.  lockdep reports this
as inconsistent SOFTIRQ-ON-W to IN-SOFTIRQ-W usage.

Commit 3a762de55b ("block: save irq state in blkg_lookup_create()")
fixed the same problem while the lock lived in blkg_lookup_create(), but
commit 9327a865e3 ("blk-cgroup: don't nest queue_lock under rcu in
blkg_lookup_create()") moved the locking into blkg_tryget_closest() and
reverted it to spin_lock_irq().

Save and restore the caller's IRQ state instead.

Fixes: 9327a865e3 ("blk-cgroup: don't nest queue_lock under rcu in blkg_lookup_create()")
Cc: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Hao Zhang <zhanghao1@kylinos.cn>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://patch.msgid.link/aqQmqb1k57PXj8Ef@192.168.1.215
Signed-off-by: Jens Axboe <axboe@kernel.dk>

...

This commit is contained in:

Hao Zhang 2026-09-12 00:04:57 +08:00 • committed by Jens Axboe

parent 94b1a3ca9b

commit 327c428ba7

1 changed files with 3 additions and 2 deletions

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block/blk-cgroup.c

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