block: fix queue freeze vs limits lock order in sysfs store methods
queue_attr_store() always freezes a device queue before calling the attribute store operation. For attributes that control queue limits, the store operation will also lock the queue limits with a call to queue_limits_start_update(). However, some drivers (e.g. SCSI sd) may need to issue commands to a device to obtain limit values from the hardware with the queue limits locked. This creates a potential ABBA deadlock situation if a user attempts to modify a limit (thus freezing the device queue) while the device driver starts a revalidation of the device queue limits. Avoid such deadlock by not freezing the queue before calling the ->store_limit() method in struct queue_sysfs_entry and instead use the queue_limits_commit_update_frozen helper to freeze the queue after taking the limits lock. This also removes taking the sysfs lock for the store_limit method as it doesn't protect anything here, but creates even more nesting. Hopefully it will go away from the actual sysfs methods entirely soon. (commit log adapted from a similar patch from Damien Le Moal) Fixes: ff956a3b ("block: use queue_limits_commit_update in queue_discard_max_store") Fixes: 0327ca9d ("block: use queue_limits_commit_update in queue_max_sectors_store") Signed-off-by:Christoph Hellwig <hch@lst.de> Reviewed-by:
Ming Lei <ming.lei@redhat.com> Reviewed-by:
Damien Le Moal <dlemoal@kernel.org> Reviewed-by:
Martin K. Petersen <martin.petersen@oracle.com> Reviewed-by:
Nilay Shroff <nilay@linux.ibm.com> Reviewed-by:
Johannes Thumshirn <johannes.thumshirn@wdc.com> Link: https://lore.kernel.org/r/20250110054726.1499538-7-hch@lst.de Signed-off-by:
Jens Axboe <axboe@kernel.dk>
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