Re: [PATCH 10/26] dm: Use the block layer zone append emulation

Damien Le Moal
2024-02-05T05:38:27Z

On 2/4/24 02:58, Mike Snitzer wrote:
> Love the overall improvement to the DM core code and the broader block
> layer by switching to this bio-based ZWP approach.
>
> Reviewed-by: Mike Snitzer <snitzer@kernel.org>

Thanks Mike !

> But one incremental suggestion inlined below.

I made this change, but in a lightly different form as I noticed that I was
getting compile errors when CONFIG_BLK_DEV_ZONED is disabled.
The change look like this now:

static void dm_split_and_process_bio(struct mapped_device *md,
struct dm_table *map, struct bio *bio)
{
...
need_split = is_abnormal = is_abnormal_io(bio);
if (static_branch_unlikely(&zoned_enabled))
need_split = is_abnormal || dm_zone_bio_needs_split(md, bio);

...

/*
* Use the block layer zone write plugging for mapped devices that
* need zone append emulation (e.g. dm-crypt).
*/
if (static_branch_unlikely(&zoned_enabled) &&
dm_zone_write_plug_bio(md, bio))
return;

...

with these added to dm-core.h:

static inline bool dm_zone_bio_needs_split(struct mapped_device *md,
struct bio *bio)
{
return md->emulate_zone_append && bio_straddle_zones(bio);
}
static inline bool dm_zone_write_plug_bio(struct mapped_device *md,
struct bio *bio)
{
return md->emulate_zone_append && blk_zone_write_plug_bio(bio, 0);
}

These 2 helpers define to "return false" for !CONFIG_BLK_DEV_ZONED.
I hope this works for you. Otherwise, I will drop your review tag when posting V2.

--
Damien Le Moal
Western Digital Research