Re: [PATCH v7 09/16] block: serialize zone revalidation

[Hannes Reinecke <hare@suse.de>]

On 9/8/26 10:57 AM, Damien Le Moal wrote:
> The zone related fields of struct gendisk can be modified by
> blk_revalidate_disk_zones() either on the first scan of the disk, or
> during user triggered scans or device revalidation, if some
> characteristics of the disk has changed (e.g. the disk capacity). Changes
> to these fields are always done with the disk request queue frozen so that
> BIO processing does not see any inconsistent state of the zones. This
> implies a contract that reading these zone related fields must always be
> done while holding a usage count on the request queue of the disk.
> 
> However, increasing the usage count of the disk request queue cannot be
> done from the context of blk_revalidate_disk_zones() itself, as that would
> prevent freezing the disk queue and result in a deadlock. This prevents
> blk_revalidate_disk_zones() from consulting the zone related fields of
> struct gendisk to detect, for instance, a change in the number of zones of
> the disk. For such case, we want to detect the change, take appropriate
> measures and revalidate exclusively revalidate the zones to avoid
> concurrent revalidation calls to see the same change while corrections are
> already on-going.
> 
> A simple solution to avoid this issue is to introduce a mutex to serialize
> calls to blk_revalidate_disk_zones() and ensure only a single context at a
> time can modify the zone related fields of a gendisk. In preparation for
> handling disk capacity revalidation in blk_revalidate_disk_zones(), do so
> with the mutex zone_revalidate_mutex. This mutex is initialized in
> disk_init_zone_resources(), destroyed in disk_release_zone_resources() and
> taken and released only in blk_revalidate_disk_zones() to serialize the
> execution of this function.
> 
> Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
> ---
>   block/blk-zoned.c      | 17 +++++++++++++++--
>   include/linux/blkdev.h |  9 ++++++---
>   2 files changed, 21 insertions(+), 5 deletions(-)
> 
Reviewed-by: Hannes Reinecke <hare@kernel.org>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                  Kernel Storage Architect
hare@suse.de                                +49 911 74053 688
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