bcachefs: add BCH_IOCTL_READ_SUPER

2 files changed, 53 insertions, 0 deletions

diff --git a/fs/bcachefs/bcachefs_ioctl.h b/fs/bcachefs/bcachefs_ioctl.h
index 079e2b556afd..e02e7ebf7f66 100644
--- a/fs/bcachefs/bcachefs_ioctl.h
+++ b/fs/bcachefs/bcachefs_ioctl.h
@@ -15,6 +15,8 @@
 
 #define BCH_BY_INDEX			(1 << 4)
 
+#define BCH_READ_DEV			(1 << 5)
+
 /* global control dev: */
 
 #define BCH_IOCTL_ASSEMBLE	_IOW(0xbc, 1, struct bch_ioctl_assemble)
@@ -46,6 +48,7 @@ struct bch_ioctl_incremental {
 #define BCH_IOCTL_DISK_EVACUATE	_IOW(0xbc,	9,  struct bch_ioctl_disk)
 #define BCH_IOCTL_DATA		_IOW(0xbc,	10, struct bch_ioctl_data)
 #define BCH_IOCTL_USAGE		_IOWR(0xbc,	11, struct bch_ioctl_usage)
+#define BCH_IOCTL_READ_SUPER	_IOW(0xbc,	12, struct bch_ioctl_read_super)
 
 struct bch_ioctl_query_uuid {
 	uuid_le			uuid;
@@ -123,4 +126,12 @@ struct bch_ioctl_usage {
 	struct bch_ioctl_dev_usage devs[0];
 };
 
+struct bch_ioctl_read_super {
+	__u32			flags;
+	__u32			pad;
+	__u64			dev;
+	__u64			size;
+	__u64			sb;
+};
+
 #endif /* _BCACHEFS_IOCTL_H */
diff --git a/fs/bcachefs/chardev.c b/fs/bcachefs/chardev.c
index 1ab36ac9f519..ccccd98f5a3e 100644
--- a/fs/bcachefs/chardev.c
+++ b/fs/bcachefs/chardev.c
@@ -363,6 +363,46 @@ static long bch2_ioctl_usage(struct bch_fs *c,
 	return 0;
 }
 
+static long bch2_ioctl_read_super(struct bch_fs *c,
+				  struct bch_ioctl_read_super arg)
+{
+	struct bch_dev *ca = NULL;
+	struct bch_sb *sb;
+	int ret = 0;
+
+	if ((arg.flags & ~(BCH_BY_INDEX|BCH_READ_DEV)) ||
+	    arg.pad)
+		return -EINVAL;
+
+	mutex_lock(&c->sb_lock);
+
+	if (arg.flags & BCH_READ_DEV) {
+		ca = bch2_device_lookup(c, arg.dev, arg.flags);
+
+		if (IS_ERR(ca)) {
+			ret = PTR_ERR(ca);
+			goto err;
+		}
+
+		sb = ca->disk_sb.sb;
+	} else {
+		sb = c->disk_sb;
+	}
+
+	if (vstruct_bytes(sb) > arg.size) {
+		ret = -ERANGE;
+		goto err;
+	}
+
+	ret = copy_to_user((void __user *)(unsigned long)arg.sb,
+			   sb, vstruct_bytes(sb));
+err:
+	if (ca)
+		percpu_ref_put(&ca->ref);
+	mutex_unlock(&c->sb_lock);
+	return ret;
+}
+
 #define BCH_IOCTL(_name, _argtype)					\
 do {									\
 	_argtype i;							\
@@ -404,6 +444,8 @@ long bch2_fs_ioctl(struct bch_fs *c, unsigned cmd, void __user *arg)
 		BCH_IOCTL(disk_set_state, struct bch_ioctl_disk_set_state);
 	case BCH_IOCTL_DISK_EVACUATE:
 		BCH_IOCTL(disk_evacuate, struct bch_ioctl_disk);
+	case BCH_IOCTL_READ_SUPER:
+		BCH_IOCTL(read_super, struct bch_ioctl_read_super);
 
 	default:
 		return -ENOTTY;