linux-user: Add support for a group of btrfs ioctls used for subvolumes

This patch implements functionality of following ioctls:

BTRFS_IOC_SUBVOL_CREATE - Creating a btrfs subvolume

    Create a btrfs subvolume. The subvolume is created using the ioctl's
    third argument which represents a pointer to a following structure
    type:

    struct btrfs_ioctl_vol_args {
	__s64 fd;
	char name[BTRFS_PATH_NAME_MAX + 1];
    };

    Before calling this ioctl, the fields of this structure should be filled
    with aproppriate values. The fd field represents the file descriptor
    value of the subvolume and the name field represents the subvolume
    path.

BTRFS_IOC_SUBVOL_GETFLAGS - Getting subvolume flags

    Read the flags of the btrfs subvolume. The flags are read using
    the ioctl's third argument that is a pointer of __u64 (unsigned long).
    The third argument represents a bit mask that can be composed of following
    values:
    BTRFS_SUBVOL_RDONLY           (1ULL << 1)
    BTRFS_SUBVOL_QGROUP_INHERIT   (1ULL << 2)
    BTRFS_DEVICE_SPEC_BY_ID       (1ULL << 3)
    BTRFS_SUBVOL_SPEC_BY_ID       (1ULL << 4)

BTRFS_IOC_SUBVOL_SETFLAGS - Setting subvolume flags

    Set the flags of the btrfs subvolume. The flags are set using the
    ioctl's third argument that is a pointer of __u64 (unsigned long).
    The third argument represents a bit mask that can be composed of same
    values as in the case of previous ioctl (BTRFS_IOC_SUBVOL_GETFLAGS).

BTRFS_IOC_SUBVOL_GETINFO - Getting subvolume information

    Read information about the subvolume. The subvolume information is
    returned in the ioctl's third argument which represents a pointer to
    a following structure type:

    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];
     };

     All of the fields of this structure are filled after the ioctl call.

Implementation notes:

    Ioctls BTRFS_IOC_SUBVOL_CREATE and BTRFS_IOC_SUBVOL_GETINFO have structure
    types as third arguments. That is the reason why a corresponding definition
    are added in file 'linux-user/syscall_types.h'.

    The line '#include <linux/btrfs.h>' is added in file 'linux-user/syscall.c' to
    recognise preprocessor definitions for these ioctls. Since the file "linux/btrfs.h"
    was added in the kernel version 3.9, it is enwrapped in an #ifdef statement
    with parameter CONFIG_BTRFS which is defined in 'configure' if the
    header file is present.

Signed-off-by: Filip Bozuta <Filip.Bozuta@syrmia.com>
Tested-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20200823195014.116226-2-Filip.Bozuta@syrmia.com>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>

1 files changed, 9 insertions, 0 deletions

diff --git a/configure b/configure
index 8a3acef..277b70f 100755
--- a/configure
+++ b/configure
@@ -4920,6 +4920,12 @@ if check_include sys/kcov.h ; then
     kcov=yes
 fi
 
+# check for btrfs filesystem support (kernel must be 3.9+)
+btrfs=no
+if check_include linux/btrfs.h ; then
+    btrfs=yes
+fi
+
 # If we're making warnings fatal, apply this to Sphinx runs as well
 sphinx_werror=""
 if test "$werror" = "yes"; then
@@ -6898,6 +6904,9 @@ fi
 if test "$kcov" = "yes" ; then
   echo "CONFIG_KCOV=y" >> $config_host_mak
 fi
+if test "$btrfs" = "yes" ; then
+  echo "CONFIG_BTRFS=y" >> $config_host_mak
+fi
 if test "$inotify" = "yes" ; then
   echo "CONFIG_INOTIFY=y" >> $config_host_mak
 fi