dm: handle REQ_OP_ZONE_RESET_ALL

This commit implements processing of the REQ_OP_ZONE_RESET_ALL operation
for zoned mapped devices. Given that this operation always has a BIO
sector of 0 and a 0 size, processing through the regular BIO
__split_and_process_bio() function does not work because this function
would always select the first target. Instead, handling of this
operation is implemented using the function __send_zone_reset_all().

Similarly to the __send_empty_flush() function, the new
__send_zone_reset_all() function manually goes through all targets of a
mapped device table doing the following:
1) If the target can natively support REQ_OP_ZONE_RESET_ALL,
   __send_duplicate_bios() is used to forward the reset all operation to
   the target. This case is handled with the
   __send_zone_reset_all_native() function.
2) For other targets, the function __send_zone_reset_all_emulated() is
   executed to emulate the execution of REQ_OP_ZONE_RESET_ALL using
   regular REQ_OP_ZONE_RESET operations.

Targets that can natively support REQ_OP_ZONE_RESET_ALL are identified
using the new target field zone_reset_all_supported. This boolean is set
to true in for targets that have reliable zone limits, that is, targets
that map all sequential write required zones of their zoned device(s).
Setting this field is handled in dm_set_zones_restrictions() and
device_get_zone_resource_limits().

For targets with unreliable zone limits, REQ_OP_ZONE_RESET_ALL must be
emulated (case 2 above). This is implemented with
__send_zone_reset_all_emulated() and is similar to the block layer
function blkdev_zone_reset_all_emulated(): first a report zones is done
for the zones of the target to identify zones that need reset, that is,
any sequential write required zone that is not already empty. This is
done using a bitmap and the function dm_zone_get_reset_bitmap() which
sets to 1 the bit corresponding to a zone that needs reset. Next, this
zone bitmap is inspected and a clone BIO modified to use the
REQ_OP_ZONE_RESET operation issued for any zone with its bit set in the
zone bitmap.

This implementation is more efficient than what the block layer does
with blkdev_zone_reset_all_emulated(), which is always used for DM zoned
devices currently: as we can natively use REQ_OP_ZONE_RESET_ALL on
targets mapping all sequential write required zones, resetting all zones
of a zoned mapped device can be much faster compared to always emulating
this operation using regular per-zone reset. In the worst case, this
implementation is as-efficient as the block layer emulation. This
reduction in the time it takes to reset all zones of a zoned mapped
device depends directly on the mapped device targets mapping (reliable
zone limits or not).

Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Link: https://lore.kernel.org/r/20240704052816.623865-4-dlemoal@kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 3 insertions, 0 deletions

diff --git a/drivers/md/dm.h b/drivers/md/dm.h
index c984ecb64b1e..cc466ad5cb1d 100644
--- a/drivers/md/dm.h
+++ b/drivers/md/dm.h
@@ -110,6 +110,9 @@ int dm_blk_report_zones(struct gendisk *disk, sector_t sector,
 			unsigned int nr_zones, report_zones_cb cb, void *data);
 bool dm_is_zone_write(struct mapped_device *md, struct bio *bio);
 int dm_zone_map_bio(struct dm_target_io *io);
+int dm_zone_get_reset_bitmap(struct mapped_device *md, struct dm_table *t,
+			     sector_t sector, unsigned int nr_zones,
+			     unsigned long *need_reset);
 #else
 #define dm_blk_report_zones	NULL
 static inline bool dm_is_zone_write(struct mapped_device *md, struct bio *bio)