block: use lcm_not_zero() when stacking chunk_sectors (22ada802) · Commits · 戴 / test

Like 'io_opt', blk_stack_limits() should stack 'chunk_sectors' using lcm_not_zero() rather than min_not_zero() -- otherwise the final 'chunk_sectors' could result in sub-optimal alignment of IO to component devices in the IO stack. Also, if 'chunk_sectors' isn't a multiple of 'physical_block_size' then it is a bug in the driver and the device should be flagged as 'misaligned'. Reviewed-by:

Ming Lei <ming.lei@redhat.com> Reviewed-by:

Martin K. Petersen <martin.petersen@oracle.com> Signed-off-by:

Mike Snitzer <snitzer@redhat.com> Signed-off-by:

Jens Axboe <axboe@kernel.dk>

block/blk-settings.c

+8 −4

Original line number	Diff line number	Diff line
		@@ -534,6 +534,7 @@ int blk_stack_limits(struct queue_limits t, struct queue_limits b,

		t->io_min = max(t->io_min, b->io_min);
		t->io_opt = lcm_not_zero(t->io_opt, b->io_opt);
		t->chunk_sectors = lcm_not_zero(t->chunk_sectors, b->chunk_sectors);

		/* Physical block size a multiple of the logical block size? */
		if (t->physical_block_size & (t->logical_block_size - 1)) {
		@@ -556,6 +557,13 @@ int blk_stack_limits(struct queue_limits t, struct queue_limits b,
		ret = -1;
		}

		/* chunk_sectors a multiple of the physical block size? */
		if ((t->chunk_sectors << 9) & (t->physical_block_size - 1)) {
		t->chunk_sectors = 0;
		t->misaligned = 1;
		ret = -1;
		}

		t->raid_partial_stripes_expensive =
		max(t->raid_partial_stripes_expensive,
		b->raid_partial_stripes_expensive);
		@@ -594,10 +602,6 @@ int blk_stack_limits(struct queue_limits t, struct queue_limits b,
		t->discard_granularity;
		}

		if (b->chunk_sectors)
		t->chunk_sectors = min_not_zero(t->chunk_sectors,
		b->chunk_sectors);

		t->zoned = max(t->zoned, b->zoned);
		return ret;
		}

Admin message