[PATCH v9 01/17] block: Introduce more member variables related to zone write locking

Bart Van Assche
2023-08-16T19:55:53Z

Many but not all storage controllers require serialization of zoned writes.
Introduce two new request queue limit member variables related to write
serialization. 'driver_preserves_write_order' allows block drivers to
indicate that the order of write commands is preserved and hence that
serialization of writes per zone is not required. 'use_zone_write_lock' is
set by disk_set_zoned() if and only if the block device has zones and if
the block driver does not preserve the order of write requests.

Cc: Damien Le Moal <dlemoal@kernel.org>
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 | 15 +++++++++++++++
block/blk-zoned.c | 1 +
include/linux/blkdev.h | 10 ++++++++++
3 files changed, 26 insertions(+)

diff --git a/block/blk-settings.c b/block/blk-settings.c
index 0046b447268f..4c776c08f190 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -56,6 +56,8 @@ void blk_set_default_limits(struct queue_limits *lim)
lim->alignment_offset = 0;
lim->io_opt = 0;
lim->misaligned = 0;
+ lim->driver_preserves_write_order = false;
+ lim->use_zone_write_lock = false;
lim->zoned = BLK_ZONED_NONE;
lim->zone_write_granularity = 0;
lim->dma_alignment = 511;
@@ -82,6 +84,8 @@ void blk_set_stacking_limits(struct queue_limits *lim)
lim->max_dev_sectors = UINT_MAX;
lim->max_write_zeroes_sectors = UINT_MAX;
lim->max_zone_append_sectors = UINT_MAX;
+ /* Request-based stacking drivers do not reorder requests. */
+ lim->driver_preserves_write_order = true;
}
EXPORT_SYMBOL(blk_set_stacking_limits);

@@ -685,6 +689,10 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
b->max_secure_erase_sectors);
t->zone_write_granularity = max(t->zone_write_granularity,
b->zone_write_granularity);
+ t->driver_preserves_write_order = t->driver_preserves_write_order &&
+ b->driver_preserves_write_order;
+ t->use_zone_write_lock = t->use_zone_write_lock ||
+ b->use_zone_write_lock;
t->zoned = max(t->zoned, b->zoned);
return ret;
}
@@ -949,6 +957,13 @@ void disk_set_zoned(struct gendisk *disk, enum blk_zoned_model model)
}

q->limits.zoned = model;
+ /*
+ * Use the zone write lock only for zoned block devices and only if
+ * the block driver does not preserve the order of write commands.
+ */
+ q->limits.use_zone_write_lock = model != BLK_ZONED_NONE &&
+ !q->limits.driver_preserves_write_order;
+
if (model != BLK_ZONED_NONE) {
/*
* Set the zone write granularity to the device logical block
diff --git a/block/blk-zoned.c b/block/blk-zoned.c
index 619ee41a51cc..112620985bff 100644
--- a/block/blk-zoned.c
+++ b/block/blk-zoned.c
@@ -631,6 +631,7 @@ void disk_clear_zone_settings(struct gendisk *disk)
q->limits.chunk_sectors = 0;
q->limits.zone_write_granularity = 0;
q->limits.max_zone_append_sectors = 0;
+ q->limits.use_zone_write_lock = false;

blk_mq_unfreeze_queue(q);
}
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 4feed1fc141f..e6d5450c8488 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -316,6 +316,16 @@ struct queue_limits {
unsigned char misaligned;
unsigned char discard_misaligned;
unsigned char raid_partial_stripes_expensive;
+ /*
+ * Whether or not the block driver preserves the order of write
+ * requests. Set by the block driver.
+ */
+ bool driver_preserves_write_order;
+ /*
+ * Whether or not zone write locking should be used. Set by
+ * disk_set_zoned().
+ */
+ bool use_zone_write_lock;
enum blk_zoned_model zoned;

/*