block: add an API for Persistent Reservations

This commits adds a driver API and ioctls for controlling Persistent
Reservations s/genericly/generically/ at the block layer.  Persistent
Reservations are supported by SCSI and NVMe and allow controlling who gets
access to a device in a shared storage setup.

Note that we add a pr_ops structure to struct block_device_operations
instead of adding the members directly to avoid bloating all instances
of devices that will never support Persistent Reservations.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>

3 files changed, 68 insertions, 0 deletions

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 19c2e947d4d1..fe25da05e823 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -35,6 +35,7 @@ struct sg_io_hdr;
 struct bsg_job;
 struct blkcg_gq;
 struct blk_flush_queue;
+struct pr_ops;
 
 #define BLKDEV_MIN_RQ	4
 #define BLKDEV_MAX_RQ	128	/* Default maximum */
@@ -1633,6 +1634,7 @@ struct block_device_operations {
 	/* this callback is with swap_lock and sometimes page table lock held */
 	void (*swap_slot_free_notify) (struct block_device *, unsigned long);
 	struct module *owner;
+	const struct pr_ops *pr_ops;
 };
 
 extern int __blkdev_driver_ioctl(struct block_device *, fmode_t, unsigned int,
diff --git a/include/linux/pr.h b/include/linux/pr.h
new file mode 100644
index 000000000000..65c01c10b335
--- /dev/null
+++ b/include/linux/pr.h
@@ -0,0 +1,18 @@
+#ifndef LINUX_PR_H
+#define LINUX_PR_H
+
+#include <uapi/linux/pr.h>
+
+struct pr_ops {
+	int (*pr_register)(struct block_device *bdev, u64 old_key, u64 new_key,
+			u32 flags);
+	int (*pr_reserve)(struct block_device *bdev, u64 key,
+			enum pr_type type, u32 flags);
+	int (*pr_release)(struct block_device *bdev, u64 key,
+			enum pr_type type);
+	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);
+};
+
+#endif /* LINUX_PR_H */
diff --git a/include/uapi/linux/pr.h b/include/uapi/linux/pr.h
new file mode 100644
index 000000000000..57d7c0f916b6
--- /dev/null
+++ b/include/uapi/linux/pr.h
@@ -0,0 +1,48 @@
+#ifndef _UAPI_PR_H
+#define _UAPI_PR_H
+
+enum pr_type {
+	PR_WRITE_EXCLUSIVE		= 1,
+	PR_EXCLUSIVE_ACCESS		= 2,
+	PR_WRITE_EXCLUSIVE_REG_ONLY	= 3,
+	PR_EXCLUSIVE_ACCESS_REG_ONLY	= 4,
+	PR_WRITE_EXCLUSIVE_ALL_REGS	= 5,
+	PR_EXCLUSIVE_ACCESS_ALL_REGS	= 6,
+};
+
+struct pr_reservation {
+	__u64	key;
+	__u32	type;
+	__u32	flags;
+};
+
+struct pr_registration {
+	__u64	old_key;
+	__u64	new_key;
+	__u32	flags;
+	__u32	__pad;
+};
+
+struct pr_preempt {
+	__u64	old_key;
+	__u64	new_key;
+	__u32	type;
+	__u32	flags;
+};
+
+struct pr_clear {
+	__u64	key;
+	__u32	flags;
+	__u32	__pad;
+};
+
+#define PR_FL_IGNORE_KEY	(1 << 0)	/* ignore existing key */
+
+#define IOC_PR_REGISTER		_IOW('p', 200, struct pr_registration)
+#define IOC_PR_RESERVE		_IOW('p', 201, struct pr_reservation)
+#define IOC_PR_RELEASE		_IOW('p', 202, struct pr_reservation)
+#define IOC_PR_PREEMPT		_IOW('p', 203, struct pr_preempt)
+#define IOC_PR_PREEMPT_ABORT	_IOW('p', 204, struct pr_preempt)
+#define IOC_PR_CLEAR		_IOW('p', 205, struct pr_clear)
+
+#endif /* _UAPI_PR_H */