Some storage controllers preserve the request order per hardware queue.
Some but not all device mapper drivers preserve the bio order. Introduce
the request queue limit member variable 'driver_preserves_write_order' to
allow block drivers and device mapper 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@xxxxxxxxxx>
Cc: Hannes Reinecke <hare@xxxxxxx>
Cc: Nitesh Shetty <nj.shetty@xxxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Ming Lei <ming.lei@xxxxxxxxxx>
Signed-off-by: Bart Van Assche <bvanassche@xxxxxxx>
---
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 a000daafbfb4..bceb9a9cb5ba 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -814,6 +814,8 @@ 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 5f14c20c8bc0..4dec1d91b7f2 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -413,6 +413,11 @@ 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 per hardware queue. Set by the block driver.
+ */
+ bool driver_preserves_write_order;
/*
* Drivers that set dma_alignment to less than 511 must be prepared to
