block: Add PR callouts for read keys and reservation

Add callouts for reading keys and reservations. This allows LIO to support
the READ_KEYS and READ_RESERVATION commands so it can export devices to
VMs for software like windows clustering.

Signed-off-by: Mike Christie <michael.christie@oracle.com>
Link: https://lore.kernel.org/r/20230407200551.12660-2-michael.christie@oracle.com
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

diff --git a/include/linux/pr.h b/include/linux/pr.h
index 94ceec713afeed4e1de2bd704f95176218349d3d..3003daec28a551798105722328482a09dea551f2 100644 (file)
--- a/include/linux/pr.h
+++ b/include/linux/pr.h
@@ -4,6 +4,18 @@
 
 #include <uapi/linux/pr.h>
 
+struct pr_keys {
+       u32     generation;
+       u32     num_keys;
+       u64     keys[];
+};
+
+struct pr_held_reservation {
+       u64             key;
+       u32             generation;
+       enum pr_type    type;
+};
+
 struct pr_ops {
        int (*pr_register)(struct block_device *bdev, u64 old_key, u64 new_key,
                        u32 flags);
@@ -14,6 +26,19 @@ struct pr_ops {
        int (*pr_preempt)(struct block_device *bdev, u64 old_key, u64 new_key,
                        enum pr_type type, bool abort);
        int (*pr_clear)(struct block_device *bdev, u64 key);
+       /*
+        * pr_read_keys - Read the registered keys and return them in the
+        * pr_keys->keys array. The keys array will have been allocated at the
+        * end of the pr_keys struct, and pr_keys->num_keys must be set to the
+        * number of keys the array can hold. If there are more than can fit
+        * in the array, success will still be returned and pr_keys->num_keys
+        * will reflect the total number of keys the device contains, so the
+        * caller can retry with a larger array.
+        */
+       int (*pr_read_keys)(struct block_device *bdev,
+                       struct pr_keys *keys_info);
+       int (*pr_read_reservation)(struct block_device *bdev,
+                       struct pr_held_reservation *rsv);
 };
 
 #endif /* LINUX_PR_H */