[PATCH v17 01/14] block: Support block drivers that preserve the order of write requests

[Bart Van Assche <bvanassche@acm.org>]

Some storage controllers preserve the request order per hardware queue.
Introduce the request queue limit member variable
'driver_preserves_write_order' to allow block drivers to indicate that
the order of write commands is preserved per hardware queue and hence
that serialization of writes per zone is not required if all pending
writes are submitted to the same hardware queue.

Cc: Damien Le Moal <dlemoal@kernel.org>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Nitesh Shetty <nj.shetty@samsung.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
 block/blk-settings.c   | 2 ++
 include/linux/blkdev.h | 5 +++++
 2 files changed, 7 insertions(+)

diff --git a/block/blk-settings.c b/block/blk-settings.c
index c8368ee8de2e..18bcf6e6dc60 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -796,6 +796,8 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
 	}
 	t->max_secure_erase_sectors = min_not_zero(t->max_secure_erase_sectors,
 						   b->max_secure_erase_sectors);
+	t->driver_preserves_write_order = t->driver_preserves_write_order &&
+		b->driver_preserves_write_order;
 	t->zone_write_granularity = max(t->zone_write_granularity,
 					b->zone_write_granularity);
 	if (!(t->features & BLK_FEAT_ZONED)) {
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 7ac153e4423a..df9887412a9e 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -399,6 +399,11 @@ struct queue_limits {
 
 	unsigned int		max_open_zones;
 	unsigned int		max_active_zones;
+	/*
+	 * Whether or not the block driver preserves the order of write
+	 * requests. Set by the block driver.
+	 */
+	bool			driver_preserves_write_order;
 
 	/*
 	 * Drivers that set dma_alignment to less than 511 must be prepared to