[dm-devel] block: Fix a WRITE SAME BUG_ON

[Martin K. Petersen]

Hi Zhang,

> ping.
>
> Anyone can help merge this patch? or any other solutions?

+	/* If the logical block size is different, forbid write same */
+	if (t->logical_block_size != b->logical_block_size &&
+	    t->max_write_same_sectors != UINT_MAX)
+		t->max_write_same_sectors = 0;
+	else
+		t->max_write_same_sectors = min(t->max_write_same_sectors,
+						b->max_write_same_sectors);
+

I am not particularly keen on this UINT_MAX magic. I would prefer to
have the stacking driver default for lbs be set to 0 so the stacking
function could avoid special-casing the first iteration. But I am not
sure whether that would break any assumptions in DM/MD wrt. the logical
block size being non-zero prior to calling the stacking function.

Mike? Any comments?

If we stick with the UINT_MAX check, the comment should at least point
out why it's there.

-- 
Martin K. Petersen	Oracle Linux Engineering