On Wed, Feb 20 2019 at 4:44pm -0500,
Mike Snitzer <snitzer@xxxxxxxxxx> wrote:
> There is no need to have DM core split discards on behalf of a DM target
> now that blk_queue_split() handles splitting discards based on the
> queue_limits. A DM target just needs to set max_discard_sectors,
> discard_granularity, etc, in queue_limits.
>
> Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
> ---
> drivers/md/dm-cache-target.c | 1 -
> drivers/md/dm-raid.c | 14 +++++++++-----
> drivers/md/dm-thin.c | 1 -
> drivers/md/dm-zoned-target.c | 1 -
> drivers/md/dm.c | 28 ++++++----------------------
> include/linux/device-mapper.h | 6 ------
> include/uapi/linux/dm-ioctl.h | 4 ++--
> 7 files changed, 17 insertions(+), 38 deletions(-)
>
...
> diff --git a/drivers/md/dm.c b/drivers/md/dm.c
> index 7a774fcd0194..b988e178a523 100644
> --- a/drivers/md/dm.c
> +++ b/drivers/md/dm.c
> @@ -1478,17 +1478,10 @@ static unsigned get_num_write_zeroes_bios(struct dm_target *ti)
> return ti->num_write_zeroes_bios;
> }
>
> -typedef bool (*is_split_required_fn)(struct dm_target *ti);
> -
> -static bool is_split_required_for_discard(struct dm_target *ti)
> -{
> - return ti->split_discard_bios;
> -}
> -
> static int __send_changing_extent_only(struct clone_info *ci, struct dm_target *ti,
> - unsigned num_bios, bool is_split_required)
> + unsigned num_bios)
> {
> - unsigned len;
> + unsigned len = ci->sector_count;
>
> /*
> * Even though the device advertised support for this type of
> @@ -1499,38 +1492,29 @@ static int __send_changing_extent_only(struct clone_info *ci, struct dm_target *
> if (!num_bios)
> return -EOPNOTSUPP;
>
> - if (!is_split_required)
> - len = min((sector_t)ci->sector_count, max_io_len_target_boundary(ci->sector, ti));
> - else
> - len = min((sector_t)ci->sector_count, max_io_len(ci->sector, ti));
> -
> __send_duplicate_bios(ci, ti, num_bios, &len);
>
> - ci->sector += len;
> - ci->sector_count -= len;
> -
> return 0;
> }
The above was bogus, ci->sector and ci->sector_count must be updated.
Reintroducing adjustments based on 'len' fixed a discard crash Ming
reported.
Now fixed in linux-next.
Mike
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