block: add 'read_keys' persistent reservation ioctl

The persistent reservation operations already have a callback for
'read_keys', but this is not accessible via an ioctl (unlike the
other callbacks). So add a new persistent reservation ioctl 'READ_KEYS'
to allow userspace to use this functionality.

Signed-off-by: Hannes Reinecke <[email protected]>

Author: Hannes Reinecke

block/ioctl.c

@@ -422,6 +422,43 @@ static int blkdev_pr_clear(struct block_device *bdev, blk_mode_t mode,
 	return ops->pr_clear(bdev, c.key);
 }
 
+static int blkdev_pr_read_keys(struct block_device *bdev, blk_mode_t mode,
+		struct pr_keys __user *arg)
+{
+	const struct pr_ops *ops = bdev->bd_disk->fops->pr_ops;
+	struct pr_keys k_in, *k_out;
+	size_t k_len;
+	int ret, num_keys;
+
+	if (!blkdev_pr_allowed(bdev, mode))
+		return -EPERM;
+	if (!ops || !ops->pr_read_keys)
+		return -EOPNOTSUPP;
+
+	if (copy_from_user(&k_in, arg, sizeof(k_in)))
+		return -EFAULT;
+
+	num_keys = k_in.num_keys;
+	k_out = kzalloc(sizeof(struct pr_keys) + num_keys * sizeof(u64),
+			GFP_KERNEL);
+	if (!k_out)
+		return -ENOMEM;
+
+	k_out->num_keys = num_keys;
+	ret = ops->pr_read_keys(bdev, k_out);
+	if (ret) {
+		kfree(k_out);
+		return ret;
+	}
+
+	k_len = sizeof(k_in) + num_keys * sizeof(u64);
+	if (copy_to_user(arg, k_out, k_len))
+		ret = -EFAULT;
+
+	kfree(k_out);
+	return ret;
+}
+
 static int blkdev_flushbuf(struct block_device *bdev, unsigned cmd,
 		unsigned long arg)
 {
@@ -643,6 +680,8 @@ static int blkdev_common_ioctl(struct block_device *bdev, blk_mode_t mode,
 		return blkdev_pr_preempt(bdev, mode, argp, true);
 	case IOC_PR_CLEAR:
 		return blkdev_pr_clear(bdev, mode, argp);
+	case IOC_PR_READ_KEYS:
+		return blkdev_pr_read_keys(bdev, mode, argp);
 	default:
 		return -ENOIOCTLCMD;
 	}

include/linux/pr.h

@@ -4,12 +4,6 @@
 
 #include <uapi/linux/pr.h>
 
-struct pr_keys {
-	u32	generation;
-	u32	num_keys;
-	u64	keys[];
-};
-
 struct pr_held_reservation {
 	u64		key;
 	u32		generation;

include/uapi/linux/pr.h

@@ -56,6 +56,12 @@ struct pr_clear {
 	__u32	__pad;
 };
 
+struct pr_keys {
+	__u32	generation;
+	__u32	num_keys;
+	__u64	keys[];
+};
+
 #define PR_FL_IGNORE_KEY	(1 << 0)	/* ignore existing key */
 
 #define IOC_PR_REGISTER		_IOW('p', 200, struct pr_registration)
@@ -64,5 +70,6 @@ struct pr_clear {
 #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)
+#define IOC_PR_READ_KEYS	_IOWR('p', 206, struct pr_keys)
 
 #endif /* _UAPI_PR_H */