Re: [PATCH AUTOSEL 5.9 089/147] dm: change max_io_len() to use blk_max_size_offset()

Mike Snitzer
2020-10-27T13:20:35Z

On Mon, Oct 26 2020 at 7:48pm -0400,
Sasha Levin <sashal@kernel.org> wrote:

> From: Mike Snitzer <snitzer@redhat.com>
>
> [ Upstream commit 5091cdec56faeaefa79de4b6cb3c3c55e50d1ac3 ]
>
> Using blk_max_size_offset() enables DM core's splitting to impose
> ti->max_io_len (via q->limits.chunk_sectors) and also fallback to
> respecting q->limits.max_sectors if chunk_sectors isn't set.
>
> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
> Signed-off-by: Sasha Levin <sashal@kernel.org>

Not sure why this commit elevated to stable@ picking it up, please
explain.

But you cannot take this commit standalone. These commits are prereqs:

22ada802ede8 block: use lcm_not_zero() when stacking chunk_sectors
07d098e6bbad block: allow 'chunk_sectors' to be non-power-of-2
882ec4e609c1 dm table: stack 'chunk_sectors' limit to account for target-specific splitting

This goes for all stable@ trees you AUTOSEL'd commit 5091cdec56f for.

Mike

> ---
> drivers/md/dm.c | 20 ++++++++------------
> 1 file changed, 8 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/md/dm.c b/drivers/md/dm.c
> index 6ed05ca65a0f8..3982012b1309c 100644
> --- a/drivers/md/dm.c
> +++ b/drivers/md/dm.c
> @@ -1051,22 +1051,18 @@ static sector_t max_io_len_target_boundary(sector_t sector, struct dm_target *ti
> static sector_t max_io_len(sector_t sector, struct dm_target *ti)
> {
> sector_t len = max_io_len_target_boundary(sector, ti);
> - sector_t offset, max_len;
> + sector_t max_len;
>
> /*
> * Does the target need to split even further?
> + * - q->limits.chunk_sectors reflects ti->max_io_len so
> + * blk_max_size_offset() provides required splitting.
> + * - blk_max_size_offset() also respects q->limits.max_sectors
> */
> - if (ti->max_io_len) {
> - offset = dm_target_offset(ti, sector);
> - if (unlikely(ti->max_io_len & (ti->max_io_len - 1)))
> - max_len = sector_div(offset, ti->max_io_len);
> - else
> - max_len = offset & (ti->max_io_len - 1);
> - max_len = ti->max_io_len - max_len;
> -
> - if (len > max_len)
> - len = max_len;
> - }
> + max_len = blk_max_size_offset(dm_table_get_md(ti->table)->queue,
> + dm_target_offset(ti, sector));
> + if (len > max_len)
> + len = max_len;
>
> return len;
> }
> --
> 2.25.1
>