btrfs: Add unprivileged ioctl which returns subvolume information

Add new unprivileged ioctl BTRFS_IOC_GET_SUBVOL_INFO which returns
the information of subvolume containing this inode.
(i.e. returns the information in ROOT_ITEM and ROOT_BACKREF.)

Reviewed-by: Gu Jinxiang <gujx@cn.fujitsu.com>
Tested-by: Gu Jinxiang <gujx@cn.fujitsu.com>
Signed-off-by: Tomohiro Misono <misono.tomohiro@jp.fujitsu.com>
[ minor style fixes, update struct comments ]
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 62 insertions, 0 deletions

diff --git a/include/uapi/linux/btrfs.h b/include/uapi/linux/btrfs.h
index c8d99b9ca550..f8f20d72b852 100644
--- a/include/uapi/linux/btrfs.h
+++ b/include/uapi/linux/btrfs.h
@@ -725,6 +725,66 @@ struct btrfs_ioctl_send_args {
 	__u64 reserved[4];		/* in */
 };
 
+/*
+ * Information about a fs tree root.
+ *
+ * All items are filled by the ioctl
+ */
+struct btrfs_ioctl_get_subvol_info_args {
+	/* Id of this subvolume */
+	__u64 treeid;
+
+	/* Name of this subvolume, used to get the real name at mount point */
+	char name[BTRFS_VOL_NAME_MAX + 1];
+
+	/*
+	 * Id of the subvolume which contains this subvolume.
+	 * Zero for top-level subvolume or a deleted subvolume.
+	 */
+	__u64 parent_id;
+
+	/*
+	 * Inode number of the directory which contains this subvolume.
+	 * Zero for top-level subvolume or a deleted subvolume
+	 */
+	__u64 dirid;
+
+	/* Latest transaction id of this subvolume */
+	__u64 generation;
+
+	/* Flags of this subvolume */
+	__u64 flags;
+
+	/* UUID of this subvolume */
+	__u8 uuid[BTRFS_UUID_SIZE];
+
+	/*
+	 * UUID of the subvolume of which this subvolume is a snapshot.
+	 * All zero for a non-snapshot subvolume.
+	 */
+	__u8 parent_uuid[BTRFS_UUID_SIZE];
+
+	/*
+	 * UUID of the subvolume from which this subvolume was received.
+	 * All zero for non-received subvolume.
+	 */
+	__u8 received_uuid[BTRFS_UUID_SIZE];
+
+	/* Transaction id indicating when change/create/send/receive happened */
+	__u64 ctransid;
+	__u64 otransid;
+	__u64 stransid;
+	__u64 rtransid;
+	/* Time corresponding to c/o/s/rtransid */
+	struct btrfs_ioctl_timespec ctime;
+	struct btrfs_ioctl_timespec otime;
+	struct btrfs_ioctl_timespec stime;
+	struct btrfs_ioctl_timespec rtime;
+
+	/* Must be zero */
+	__u64 reserved[8];
+};
+
 /* Error codes as returned by the kernel */
 enum btrfs_err_code {
 	BTRFS_ERROR_DEV_RAID1_MIN_NOT_MET = 1,
@@ -843,5 +903,7 @@ enum btrfs_err_code {
 				   struct btrfs_ioctl_vol_args_v2)
 #define BTRFS_IOC_LOGICAL_INO_V2 _IOWR(BTRFS_IOCTL_MAGIC, 59, \
 					struct btrfs_ioctl_logical_ino_args)
+#define BTRFS_IOC_GET_SUBVOL_INFO _IOR(BTRFS_IOCTL_MAGIC, 60, \
+				struct btrfs_ioctl_get_subvol_info_args)
 
 #endif /* _UAPI_LINUX_BTRFS_H */