block: introduce alloc_sched_data and free_sched_data elevator methods

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[ Upstream commit 61019afdf6 ]

The recent lockdep splat [1] highlights a potential deadlock risk
involving ->elevator_lock and ->freeze_lock dependencies on -pcpu_alloc_
mutex. The trace shows that the issue occurs when the Kyber scheduler
allocates dynamic memory for its elevator data during initialization.

To address this, introduce two new elevator operation callbacks:
->alloc_sched_data and ->free_sched_data. The subsequent patch would
build upon these newly introduced methods to suppress lockdep splat[1].

[1] https://lore.kernel.org/all/CAGVVp+VNW4M-5DZMNoADp6o2VKFhi7KxWpTDkcnVyjO0=-D5+A@mail.gmail.com/

Signed-off-by: Nilay Shroff <nilay@linux.ibm.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Stable-dep-of: 9869d3a6fe ("block: fix race between wbt_enable_default and IO submission")
Signed-off-by: Sasha Levin <sashal@kernel.org>

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Nilay Shroff 2025-11-13 14:28:20 +05:30 • committed by Greg Kroah-Hartman

parent aa81ed74af

commit 93869ded0c

2 changed files with 26 additions and 0 deletions

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24

block/blk-mq-sched.h

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2

block/elevator.h

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