Re: [PATCH] block, loop: support partitions without scanning

[Ming Lei <ming.lei@redhat.com>]

On Fri, May 27, 2022 at 07:58:06AM +0200, Christoph Hellwig wrote:
> Historically we did distinguish between a flag that surpressed partition
> scanning, and a combinations of the minors variable and another flag if
> any partitions were supported.  This was generally confusing and doesn't
> make much sense, but some corner case uses of the loop driver actually
> do want to support manually added partitions on a device that does not
> actively scan for partitions.  To make things worsee the loop driver
> also wants to dynamically toggle the scanning for partitions on a live
> gendisk, which makes the disk->flags updates non-atomic.
> 
> Introduce a new GD_SUPPRESS_PART_SCAN bit in disk->state that disables
> just scanning for partitions, and toggle that instead of GENHD_FL_NO_PART
> in the loop driver.
> 
> Fixes: 1ebe2e5f9d68 ("block: remove GENHD_FL_EXT_DEVT")
> Reported-by: Ming Lei <ming.lei@redhat.com>
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Reviewed-by: Ming Lei <ming.lei@redhat.com>

Thanks,
Ming