block: add a report_zones method

Dispatching a report zones command through the request queue is a major
pain due to the command reply payload rewriting necessary. Given that
blkdev_report_zones() is executing everything synchronously, implement
report zones as a block device file operation instead, allowing major
simplification of the code in many places.

sd, null-blk, dm-linear and dm-flakey being the only block device
drivers supporting exposing zoned block devices, these drivers are
modified to provide the device side implementation of the
report_zones() block device file operation.

For device mappers, a new report_zones() target type operation is
defined so that the upper block layer calls blkdev_report_zones() can
be propagated down to the underlying devices of the dm targets.
Implementation for this new operation is added to the dm-linear and
dm-flakey targets.

Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
[Damien]
* Changed method block_device argument to gendisk
* Various bug fixes and improvements
* Added support for null_blk, dm-linear and dm-flakey.
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 3 insertions, 5 deletions

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 6bb845f9601a..51fe6472ce02 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -396,11 +396,6 @@ struct queue_limits {
 
 #ifdef CONFIG_BLK_DEV_ZONED
 
-struct blk_zone_report_hdr {
-        unsigned int    nr_zones;
-        u8              padding[60];
-};
-
 extern unsigned int blkdev_nr_zones(struct block_device *bdev);
 extern int blkdev_report_zones(struct block_device *bdev,
                                sector_t sector, struct blk_zone *zones,
@@ -1867,6 +1862,9 @@ struct block_device_operations {
         int (*getgeo)(struct block_device *, struct hd_geometry *);
         /* this callback is with swap_lock and sometimes page table lock held */
         void (*swap_slot_free_notify) (struct block_device *, unsigned long);
+        int (*report_zones)(struct gendisk *, sector_t sector,
+                            struct blk_zone *zones, unsigned int *nr_zones,
+                            gfp_t gfp_mask);
         struct module *owner;
         const struct pr_ops *pr_ops;
 };