Re: [PATCH V3 07/20] block: prevent adding/deleting disk during updating nr_hw_queues

[Hannes Reinecke <hare@suse.de>]

On 4/24/25 17:21, Ming Lei wrote:
> Both adding/deleting disk code are reader of `nr_hw_queues`, so we can't
> allow them in-progress when updating nr_hw_queues, kernel panic and
> kasan has been reported in [1].
> 
> Prevent adding/deleting disk during updating nr_hw_queues by adding
> rw_semaphore to tagset, write lock is grabbed in blk_mq_update_nr_hw_queues(),
> and read lock is acquired when adding/deleting disk.
> 
> Also mark GFP_NOIO allocation scope for adding/deleting disk because
> blk_mq_update_nr_hw_queues() is part of some driver's error handler.
> 
> This way avoids lot of trouble.
> 
> Suggested-by: Nilay Shroff <nilay@linux.ibm.com>
> Reported-by: Nilay Shroff <nilay@linux.ibm.com>
> Closes: https://lore.kernel.org/linux-block/a5896cdb-a59a-4a37-9f99-20522f5d2987@linux.ibm.com/
> Signed-off-by: Ming Lei <ming.lei@redhat.com>
> ---
>   block/blk-mq.c         |  4 ++
>   block/genhd.c          | 94 +++++++++++++++++++++++++++++++-----------
>   include/linux/blk-mq.h |  3 ++
>   3 files changed, 78 insertions(+), 23 deletions(-)
> 
Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                  Kernel Storage Architect
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