On Thu, Sep 24 2020 at 10:34am -0400,
Mikulas Patocka <mpatocka@xxxxxxxxxx> wrote:
> Hi Mike
>
> Could you send this to Linus before v5.9 is released?
>
> Mikulas
>
>
>
> From: Mikulas Patocka <mpatocka@xxxxxxxxxx>
>
> If q->limits.discard_granularity is zero, the block core will warn in
> __blkdev_issue_discard. This patch sets it to a minimum - 512 bytes.
>
> Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
> Fixes: b35fd7422c2f ("block: check queue's limits.discard_granularity in __blkdev_issue_discard()")
> Fixes: 9b15d109a6b2 ("block: improve discard bio alignment in __blkdev_issue_discard()")
> Fixes: c52abf563049 ("loop: Better discard support for block devices")
>
> ---
> drivers/md/dm-table.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> Index: linux-2.6/drivers/md/dm-table.c
> ===================================================================
> --- linux-2.6.orig/drivers/md/dm-table.c 2020-08-31 12:08:27.000000000 +0200
> +++ linux-2.6/drivers/md/dm-table.c 2020-09-24 16:23:55.000000000 +0200
> @@ -1858,8 +1858,11 @@ void dm_table_set_restrictions(struct dm
> q->limits.discard_granularity = 0;
> q->limits.discard_alignment = 0;
> q->limits.discard_misaligned = 0;
> - } else
> + } else {
> blk_queue_flag_set(QUEUE_FLAG_DISCARD, q);
> + if (q->limits.discard_granularity < 512)
> + q->limits.discard_granularity = 512;
> + }
>
> if (dm_table_supports_secure_erase(t))
> blk_queue_flag_set(QUEUE_FLAG_SECERASE, q);
This patch is wrong, papers over something else. Please identify what
that something else is.
block core has _always_ cheecked if discard_granularity is non-zero to
allow discards.
Why is q->limits.discard_granularity < 512 if discard is supported by
the DM table and targets?
That shouldn't ever be.
Mike
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