[PATCH v3 3/5] block: factor path limits out of blk_stack_limits

[Yao Sang]

Same-LBA multipath needs to stack path limits without applying
mapped-range topology calculations.

Factor this path limit stacking into blk_stack_path_limits(). It covers
execution features, sector and segment limits, write zeroes, discard
segments, zone append and DMA alignment.

There is no behavior change for existing callers.

Signed-off-by: Yao Sang <sangyao at kylinos.cn>
---
 block/blk-settings.c | 77 +++++++++++++++++++++-----------------------
 1 file changed, 37 insertions(+), 40 deletions(-)

diff --git a/block/blk-settings.c b/block/blk-settings.c
index 9e7cdaaefbca..f1a2e4fe4e77 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -756,6 +756,39 @@ static void blk_stack_atomic_writes_limits(struct queue_limits *t,
 	t->atomic_write_hw_boundary = 0;
 }
 
+#define STACK_MIN_NOT_ZERO(t, b, field) \
+	((t)->field = min_not_zero((t)->field, (b)->field))
+#define STACK_MIN(t, b, field) \
+	((t)->field = min((t)->field, (b)->field))
+
+static void blk_stack_path_limits(struct queue_limits *t,
+		const struct queue_limits *b)
+{
+	/*
+	 * These features must be supported by the top queue and every path that
+	 * can execute I/O. Clear them when a path does not support them.
+	 */
+	if (!(b->features & BLK_FEAT_NOWAIT))
+		t->features &= ~BLK_FEAT_NOWAIT;
+	if (!(b->features & BLK_FEAT_POLL))
+		t->features &= ~BLK_FEAT_POLL;
+	if (!(b->features & BLK_FEAT_PCI_P2PDMA))
+		t->features &= ~BLK_FEAT_PCI_P2PDMA;
+
+	STACK_MIN_NOT_ZERO(t, b, max_hw_sectors);
+	STACK_MIN_NOT_ZERO(t, b, max_dev_sectors);
+	STACK_MIN_NOT_ZERO(t, b, seg_boundary_mask);
+	STACK_MIN_NOT_ZERO(t, b, virt_boundary_mask);
+	STACK_MIN_NOT_ZERO(t, b, max_segments);
+	STACK_MIN_NOT_ZERO(t, b, max_integrity_segments);
+	STACK_MIN_NOT_ZERO(t, b, max_segment_size);
+	STACK_MIN(t, b, max_write_zeroes_sectors);
+	STACK_MIN(t, b, max_hw_wzeroes_unmap_sectors);
+	STACK_MIN_NOT_ZERO(t, b, max_discard_segments);
+	STACK_MIN(t, b, max_hw_zone_append_sectors);
+	t->dma_alignment = max(t->dma_alignment, b->dma_alignment);
+}
+
 /*
  * Stack block sizes, I/O granularities, chunk boundaries and alignment for a
  * bottom-device range mapped at @start. Round maximum sector limits after the
@@ -873,51 +906,14 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
 	int ret;
 
 	t->features |= (b->features & BLK_FEAT_INHERIT_MASK);
-
-	/*
-	 * Some feaures need to be supported both by the stacking driver and all
-	 * underlying devices.  The stacking driver sets these flags before
-	 * stacking the limits, and this will clear the flags if any of the
-	 * underlying devices does not support it.
-	 */
-	if (!(b->features & BLK_FEAT_NOWAIT))
-		t->features &= ~BLK_FEAT_NOWAIT;
-	if (!(b->features & BLK_FEAT_POLL))
-		t->features &= ~BLK_FEAT_POLL;
-	if (!(b->features & BLK_FEAT_PCI_P2PDMA))
-		t->features &= ~BLK_FEAT_PCI_P2PDMA;
+	blk_stack_path_limits(t, b);
 
 	t->max_sectors = min_not_zero(t->max_sectors, b->max_sectors);
 	t->max_user_sectors = min_not_zero(t->max_user_sectors,
 			b->max_user_sectors);
-	t->max_hw_sectors = min_not_zero(t->max_hw_sectors, b->max_hw_sectors);
-	t->max_dev_sectors = min_not_zero(t->max_dev_sectors, b->max_dev_sectors);
-	t->max_write_zeroes_sectors = min(t->max_write_zeroes_sectors,
-					b->max_write_zeroes_sectors);
 	t->max_user_wzeroes_unmap_sectors =
 			min(t->max_user_wzeroes_unmap_sectors,
 			    b->max_user_wzeroes_unmap_sectors);
-	t->max_hw_wzeroes_unmap_sectors =
-			min(t->max_hw_wzeroes_unmap_sectors,
-			    b->max_hw_wzeroes_unmap_sectors);
-
-	t->max_hw_zone_append_sectors = min(t->max_hw_zone_append_sectors,
-					b->max_hw_zone_append_sectors);
-
-	t->seg_boundary_mask = min_not_zero(t->seg_boundary_mask,
-					    b->seg_boundary_mask);
-	t->virt_boundary_mask = min_not_zero(t->virt_boundary_mask,
-					    b->virt_boundary_mask);
-
-	t->max_segments = min_not_zero(t->max_segments, b->max_segments);
-	t->max_discard_segments = min_not_zero(t->max_discard_segments,
-					       b->max_discard_segments);
-	t->max_integrity_segments = min_not_zero(t->max_integrity_segments,
-						 b->max_integrity_segments);
-
-	t->max_segment_size = min_not_zero(t->max_segment_size,
-					   b->max_segment_size);
-	t->dma_alignment = max(t->dma_alignment, b->dma_alignment);
 
 	ret = blk_stack_topology_limits(t, b, start);
 
@@ -927,8 +923,9 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
 
 		t->max_discard_sectors = min_not_zero(t->max_discard_sectors,
 						      b->max_discard_sectors);
-		t->max_hw_discard_sectors = min_not_zero(t->max_hw_discard_sectors,
-							 b->max_hw_discard_sectors);
+		t->max_hw_discard_sectors =
+			min_not_zero(t->max_hw_discard_sectors,
+				     b->max_hw_discard_sectors);
 		t->discard_granularity = max(t->discard_granularity,
 					     b->discard_granularity);
 		t->discard_alignment = lcm_not_zero(t->discard_alignment, alignment) %
-- 
2.25.1