linux-user: Add support for two btrfs ioctls used for subvolume

This patch implements functionality for following ioctl:

BTRFS_IOC_DEFAULT_SUBVOL - Setting a default subvolume

    Set a default subvolume for a btrfs filesystem. The third
    ioctl's argument is a '__u64' (unsigned long long) which
    represents the id of a subvolume that is to be set as
    the default.

BTRFS_IOC_GET_SUBVOL_ROOTREF - Getting tree and directory id of subvolumes

    Read tree and directory id of subvolumes from a btrfs
    filesystem. The tree and directory id's are returned in the
    ioctl's third argument which represents a pointer to a
    following type:

    struct btrfs_ioctl_get_subvol_rootref_args {
		/* in/out, minimum id of rootref's treeid to be searched */
		__u64 min_treeid;

		/* out */
		struct {
			__u64 treeid;
			__u64 dirid;
		} rootref[BTRFS_MAX_ROOTREF_BUFFER_NUM];

		/* out, number of found items */
		__u8 num_items;
		__u8 align[7];
     };

     Before calling this ioctl, 'min_treeid' field should be filled
     with value that represent the minimum value for the tree id.

Implementation notes:

    Ioctl BTRFS_IOC_GET_SUBVOL_ROOTREF uses the above mentioned structure
    type as third argument. That is the reason why a aproppriate thunk
    structure definition is added in file 'syscall_types.h'.

Signed-off-by: Filip Bozuta <Filip.Bozuta@syrmia.com>
Tested-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20200823195014.116226-7-Filip.Bozuta@syrmia.com>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>

linux-user/ioctls.h

@@ -206,6 +206,9 @@
      IOCTL(BTRFS_IOC_INO_LOOKUP, IOC_RW,
            MK_PTR(MK_STRUCT(STRUCT_btrfs_ioctl_ino_lookup_args)))
 #endif
+#ifdef BTRFS_IOC_DEFAULT_SUBVOL
+     IOCTL(BTRFS_IOC_DEFAULT_SUBVOL, IOC_W, MK_PTR(TYPE_ULONGLONG))
+#endif
 #ifdef BTRFS_IOC_SUBVOL_GETFLAGS
      IOCTL(BTRFS_IOC_SUBVOL_GETFLAGS, IOC_R, MK_PTR(TYPE_ULONGLONG))
 #endif
@@ -248,6 +251,10 @@
      IOCTL(BTRFS_IOC_GET_SUBVOL_INFO, IOC_R,
            MK_PTR(MK_STRUCT(STRUCT_btrfs_ioctl_get_subvol_info_args)))
 #endif
+#ifdef BTRFS_IOC_GET_SUBVOL_ROOTREF
+     IOCTL(BTRFS_IOC_GET_SUBVOL_ROOTREF, IOC_RW,
+           MK_PTR(MK_STRUCT(STRUCT_btrfs_ioctl_get_subvol_rootref_args)))
+#endif
 #ifdef BTRFS_IOC_INO_LOOKUP_USER
      IOCTL(BTRFS_IOC_INO_LOOKUP_USER, IOC_RW,
            MK_PTR(MK_STRUCT(STRUCT_btrfs_ioctl_ino_lookup_user_args)))

linux-user/syscall_defs.h

@@ -1014,6 +1014,8 @@ struct target_rtc_pll_info {
 #define TARGET_BTRFS_IOC_SUBVOL_CREATE          TARGET_IOWU(BTRFS_IOCTL_MAGIC, 14)
 #define TARGET_BTRFS_IOC_SNAP_DESTROY           TARGET_IOWU(BTRFS_IOCTL_MAGIC, 15)
 #define TARGET_BTRFS_IOC_INO_LOOKUP             TARGET_IOWRU(BTRFS_IOCTL_MAGIC, 18)
+#define TARGET_BTRFS_IOC_DEFAULT_SUBVOL         TARGET_IOW(BTRFS_IOCTL_MAGIC, 19,\
+                                                           abi_ullong)
 #define TARGET_BTRFS_IOC_SUBVOL_GETFLAGS        TARGET_IOR(BTRFS_IOCTL_MAGIC, 25,\
                                                            abi_ullong)
 #define TARGET_BTRFS_IOC_SUBVOL_SETFLAGS        TARGET_IOW(BTRFS_IOCTL_MAGIC, 26,\
@@ -1027,6 +1029,7 @@ struct target_rtc_pll_info {
 #define TARGET_BTRFS_IOC_GET_SUPPORTED_FEATURES TARGET_IORU(BTRFS_IOCTL_MAGIC, 57)
 #define TARGET_BTRFS_IOC_LOGICAL_INO_V2         TARGET_IOWRU(BTRFS_IOCTL_MAGIC, 59)
 #define TARGET_BTRFS_IOC_GET_SUBVOL_INFO        TARGET_IORU(BTRFS_IOCTL_MAGIC, 60)
+#define TARGET_BTRFS_IOC_GET_SUBVOL_ROOTREF     TARGET_IOWRU(BTRFS_IOCTL_MAGIC, 61)
 #define TARGET_BTRFS_IOC_INO_LOOKUP_USER        TARGET_IOWRU(BTRFS_IOCTL_MAGIC, 62)
 
 /* usb ioctls */

linux-user/syscall_types.h

@@ -435,6 +435,19 @@ STRUCT(btrfs_ioctl_dev_info_args,
        MK_ARRAY(TYPE_CHAR, BTRFS_DEVICE_PATH_NAME_MAX)) /* path */
 #endif
 
+#ifdef BTRFS_IOC_GET_SUBVOL_ROOTREF
+STRUCT(rootref,
+       TYPE_ULONGLONG, /* treeid */
+       TYPE_ULONGLONG) /* dirid */
+
+STRUCT(btrfs_ioctl_get_subvol_rootref_args,
+       TYPE_ULONGLONG, /* min_treeid */
+       MK_ARRAY(MK_STRUCT(STRUCT_rootref),
+                BTRFS_MAX_ROOTREF_BUFFER_NUM), /* rootref */
+       TYPE_CHAR, /* num_items */
+       MK_ARRAY(TYPE_CHAR, 7)) /* align */
+#endif
+
 #ifdef BTRFS_IOC_GET_DEV_STATS
 STRUCT(btrfs_ioctl_get_dev_stats,
        TYPE_ULONGLONG, /* devid */