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

Sasha Levin
2020-11-02T00:31:01Z

On Tue, Oct 27, 2020 at 08:19:59AM -0400, Mike Snitzer wrote:
>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.

I misread the series this patch was in as being a fix rather than only
the first patch, sorry :(

>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
>>
>

--
Thanks,
Sasha