block: avoid use-after-free in disk_free_zone_resources()

block: avoid use-after-free in disk_free_zone_resources()

The function disk_update_zone_resources() may call
disk_free_zone_resources() in case of error, and following this,
blk_revalidate_disk_zones() will again calls disk_free_zone_resources() if
disk_update_zone_resources() failed. If a zone worker thread is being used
(which is the default for a rotational media zoned device),
disk_free_zone_resources() will try to stop the zone worker thread twice
because disk->zone_wplugs_worker is not reset to NULL when the worker
thread is stopped the first time.

In disk_free_zone_resources(), fix this by correctly clearing
disk->zone_wplugs_worker to NULL when the worker thread is stopped.

And while at it, since disk_free_zone_resources() is always called after a
failed call to disk_update_zone_resources(), remove the unnecessary call
to disk_free_zone_resources() in disk_update_zone_resources().

Fixes: 1365b6904fd0 ("block: allow submitting all zone writes from a single context")
Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://patch.msgid.link/20260522115622.588535-1-dlemoal@kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>