diff options
| author | Nilay Shroff <nilay@linux.ibm.com> | 2025-03-04 15:52:33 +0530 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2025-03-10 07:30:18 -0600 |
| commit | 1bf70d08cc3b55abd1763e6dff5855cb8dd8318b (patch) | |
| tree | 11ec9cc9c02828e4b9416163102eff1eee5b5ae3 /include/linux/blkdev.h | |
| parent | d23977fee1ee838316fb1b00945064a146460843 (diff) | |
block: introduce a dedicated lock for protecting queue elevator updates
A queue's elevator can be updated either when modifying nr_hw_queues
or through the sysfs scheduler attribute. Currently, elevator switching/
updating is protected using q->sysfs_lock, but this has led to lockdep
splats[1] due to inconsistent lock ordering between q->sysfs_lock and
the freeze-lock in multiple block layer call sites.
As the scope of q->sysfs_lock is not well-defined, its (mis)use has
resulted in numerous lockdep warnings. To address this, introduce a new
q->elevator_lock, dedicated specifically for protecting elevator
switches/updates. And we'd now use this new q->elevator_lock instead of
q->sysfs_lock for protecting elevator switches/updates.
While at it, make elv_iosched_load_module() a static function, as it is
only called from elv_iosched_store(). Also, remove redundant parameters
from elv_iosched_load_module() function signature.
[1] https://lore.kernel.org/all/67637e70.050a0220.3157ee.000c.GAE@google.com/
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Nilay Shroff <nilay@linux.ibm.com>
Link: https://lore.kernel.org/r/20250304102551.2533767-5-nilay@linux.ibm.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'include/linux/blkdev.h')
| -rw-r--r-- | include/linux/blkdev.h | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index 248416ecd01c..31b1b635c710 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -560,6 +560,14 @@ struct request_queue { struct blk_flush_queue *fq; struct list_head flush_list; + /* + * Protects against I/O scheduler switching, specifically when + * updating q->elevator. To ensure proper locking order during + * an elevator update, first freeze the queue, then acquire + * ->elevator_lock. + */ + struct mutex elevator_lock; + struct mutex sysfs_lock; struct mutex limits_lock; |