Re: [PATCH 13/26] block: move cache control settings out of queue->flags

[Hannes Reinecke <hare@xxxxxxx>]

On 6/17/24 08:04, Christoph Hellwig wrote:
> Move the cache control settings into the queue_limits so that the flags
> can be set atomically with the device queue frozen.
>
> Add new features and flags field for the driver set flags, and internal
> (usually sysfs-controlled) flags in the block layer.  Note that we'll
> eventually remove enough field from queue_limits to bring it back to the
> previous size.
>
> The disable flag is inverted compared to the previous meaning, which
> means it now survives a rescan, similar to the max_sectors and
> max_discard_sectors user limits.
>
> The FLUSH and FUA flags are now inherited by blk_stack_limits, which
> simplified the code in dm a lot, but also causes a slight behavior
> change in that dm-switch and dm-unstripe now advertise a write cache
> despite setting num_flush_bios to 0.  The I/O path will handle this
> gracefully, but as far as I can tell the lack of num_flush_bios
> and thus flush support is a pre-existing data integrity bug in those
> targets that really needs fixing, after which a non-zero num_flush_bios
> should be required in dm for targets that map to underlying devices.
>
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> Acked-by: Ulf Hansson <ulf.hansson@xxxxxxxxxx> [mmc]
> ---
Reviewed-by: Hannes Reinecke <hare@xxxxxxx>

Cheers,

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