[PATCH v2 10/28] block: Allow zero value of max_zone_append_sectors queue limit

Damien Le Moal
2024-03-25T04:45:15Z

In preparation for adding a generic zone append emulation using zone
write plugging, allow device drivers supporting zoned block device to
set a the max_zone_append_sectors queue limit of a device to 0 to
indicate the lack of native support for zone append operations and that
the block layer should emulate these operations using regular write
operations.

blk_queue_max_zone_append_sectors() is modified to allow passing 0 as
the max_zone_append_sectors argument. The function
queue_max_zone_append_sectors() is also modified to ensure that the
minimum of the max_hw_sectors and chunk_sectors limit is used whenever
the max_zone_append_sectors limit is 0. This minimum is consistent with
the value set for the max_zone_append_sectors limit by the function
blk_validate_zoned_limits() when limits for a queue are validated.

The helper functions queue_emulates_zone_append() and
bdev_emulates_zone_append() are added to test if a queue (or block
device) emulates zone append operations.

In order for blk_revalidate_disk_zones() to accept zoned block devices
relying on zone append emulation, the direct check to the
max_zone_append_sectors queue limit of the disk is replaced by a check
using the value returned by queue_max_zone_append_sectors(). Similarly,
queue_zone_append_max_show() is modified to use the same accessor so
that the sysfs attribute advertizes the non-zero limit that will be
used, regardless if it is for native or emulated commands.

For stacking drivers, a top device should not need to care if the
underlying devices have native or emulated zone append operations.
blk_stack_limits() is thus modified to set the top device
max_zone_append_sectors limit using the new accessor
queue_limits_max_zone_append_sectors(). queue_max_zone_append_sectors()
is modified to use this function as well. Stacking drivers that require
zone append emulation, e.g. dm-crypt, can still request this feature by
calling blk_queue_max_zone_append_sectors() with a 0 limit.

Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Hannes Reinecke <hare@suse.de>
---
block/blk-core.c | 2 +-
block/blk-settings.c | 30 +++++++++++++++++++-----------
block/blk-sysfs.c | 2 +-
block/blk-zoned.c | 2 +-
include/linux/blkdev.h | 23 ++++++++++++++++++++---
5 files changed, 42 insertions(+), 17 deletions(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index b6bc1978207d..c6d41e1c7a0a 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -602,7 +602,7 @@ static inline blk_status_t blk_check_zone_append(struct request_queue *q,
return BLK_STS_IOERR;

/* Make sure the BIO is small enough and will not get split */
- if (nr_sectors > q->limits.max_zone_append_sectors)
+ if (nr_sectors > queue_max_zone_append_sectors(q))
return BLK_STS_IOERR;

bio->bi_opf |= REQ_NOMERGE;
diff --git a/block/blk-settings.c b/block/blk-settings.c
index 3c7d8d638ab5..82c61d2e4bb8 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -413,24 +413,32 @@ EXPORT_SYMBOL(blk_queue_max_write_zeroes_sectors);
* blk_queue_max_zone_append_sectors - set max sectors for a single zone append
* @q: the request queue for the device
* @max_zone_append_sectors: maximum number of sectors to write per command
+ *
+ * Sets the maximum number of sectors allowed for zone append commands. If
+ * Specifying 0 for @max_zone_append_sectors indicates that the queue does
+ * not natively support zone append operations and that the block layer must
+ * emulate these operations using regular writes.
**/
void blk_queue_max_zone_append_sectors(struct request_queue *q,
unsigned int max_zone_append_sectors)
{
- unsigned int max_sectors;
+ unsigned int max_sectors = 0;

if (WARN_ON(!blk_queue_is_zoned(q)))
return;

- max_sectors = min(q->limits.max_hw_sectors, max_zone_append_sectors);
- max_sectors = min(q->limits.chunk_sectors, max_sectors);
+ if (max_zone_append_sectors) {
+ max_sectors = min(q->limits.max_hw_sectors,
+ max_zone_append_sectors);
+ max_sectors = min(q->limits.chunk_sectors, max_sectors);

- /*
- * Signal eventual driver bugs resulting in the max_zone_append sectors limit
- * being 0 due to a 0 argument, the chunk_sectors limit (zone size) not set,
- * or the max_hw_sectors limit not set.
- */
- WARN_ON(!max_sectors);
+ /*
+ * Signal eventual driver bugs resulting in the max_zone_append
+ * sectors limit being 0 due to the chunk_sectors limit (zone
+ * size) not set or the max_hw_sectors limit not set.
+ */
+ WARN_ON_ONCE(!max_sectors);
+ }

q->limits.max_zone_append_sectors = max_sectors;
}
@@ -757,8 +765,8 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
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_zone_append_sectors = min(t->max_zone_append_sectors,
- b->max_zone_append_sectors);
+ t->max_zone_append_sectors = min(queue_limits_max_zone_append_sectors(t),
+ queue_limits_max_zone_append_sectors(b));
t->bounce = max(t->bounce, b->bounce);

t->seg_boundary_mask = min_not_zero(t->seg_boundary_mask,
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 8c8f69d8ba48..e3ed5a921aff 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -224,7 +224,7 @@ static ssize_t queue_zone_write_granularity_show(struct request_queue *q,

static ssize_t queue_zone_append_max_show(struct request_queue *q, char *page)
{
- unsigned long long max_sectors = q->limits.max_zone_append_sectors;
+ unsigned long long max_sectors = queue_max_zone_append_sectors(q);

return sprintf(page, "%llu\n", max_sectors << SECTOR_SHIFT);
}
diff --git a/block/blk-zoned.c b/block/blk-zoned.c
index 33dea8ca9a6f..27ea88e976c2 100644
--- a/block/blk-zoned.c
+++ b/block/blk-zoned.c
@@ -1629,7 +1629,7 @@ int blk_revalidate_disk_zones(struct gendisk *disk,
return -ENODEV;
}

- if (!q->limits.max_zone_append_sectors) {
+ if (!queue_max_zone_append_sectors(q)) {
pr_warn("%s: Invalid 0 maximum zone append limit\n",
disk->disk_name);
return -ENODEV;
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 8eb99cab7221..916334f173a2 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1177,12 +1177,29 @@ static inline unsigned int queue_max_segment_size(const struct request_queue *q)
return q->limits.max_segment_size;
}

-static inline unsigned int queue_max_zone_append_sectors(const struct request_queue *q)
+static inline unsigned int queue_limits_max_zone_append_sectors(struct queue_limits *l)
{
+ unsigned int max_sectors = min(l->chunk_sectors, l->max_hw_sectors);

- const struct queue_limits *l = &q->limits;
+ return min_not_zero(l->max_zone_append_sectors, max_sectors);
+}
+
+static inline unsigned int queue_max_zone_append_sectors(struct request_queue *q)
+{
+ if (!blk_queue_is_zoned(q))
+ return 0;

- return min(l->max_zone_append_sectors, l->max_sectors);
+ return queue_limits_max_zone_append_sectors(&q->limits);
+}
+
+static inline bool queue_emulates_zone_append(struct request_queue *q)
+{
+ return blk_queue_is_zoned(q) && !q->limits.max_zone_append_sectors;
+}
+
+static inline bool bdev_emulates_zone_append(struct block_device *bdev)
+{
+ return queue_emulates_zone_append(bdev_get_queue(bdev));
}

static inline unsigned int
--
2.44.0