Re: [PATCH] block: Optimize disk zone resource cleanup

[Niklas Cassel <cassel@kernel.org>]

On Fri, Jun 07, 2024 at 09:21:26AM +0900, Damien Le Moal wrote:
> For zoned block devices using zone write plugging, an rcu_barrier() call
> is needed in disk_free_zone_resources() to synchronize freeing of zone
> write plugs and the destrution of the mempool used to allocate the
> plugs. The barrier call does slow down a little teardown of zoned block
> devices but should not affect teardown of regular block devices or zoned
> block devices that do not use zone write plugging (e.g. zoned DM devices
> that do not require zone append emulation).
> 
> Modify disk_free_zone_resources() to return early if we do not have a
> mempool to start with, that is, if the device does not use zone write
> plugging. This avoids the costly rcu_barrier() and speeds up disk
> teardown.
> 
> Reported-by: Mikulas Patocka <mpatocka@redhat.com>
> Fixes: dd291d77cc90 ("block: Introduce zone write plugging")
> Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
> ---
>  block/blk-zoned.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/block/blk-zoned.c b/block/blk-zoned.c
> index 8f89705f5e1c..137842dbb59a 100644
> --- a/block/blk-zoned.c
> +++ b/block/blk-zoned.c
> @@ -1552,6 +1552,9 @@ static void disk_destroy_zone_wplugs_hash_table(struct gendisk *disk)
>  
>  void disk_free_zone_resources(struct gendisk *disk)
>  {
> +	if (!disk->zone_wplugs_pool)
> +		return;
> +
>  	cancel_work_sync(&disk->zone_wplugs_work);
>  
>  	if (disk->zone_wplugs_wq) {
> -- 
> 2.45.2
> 

Reviewed-by: Niklas Cassel <cassel@kernel.org>