ficlonerange.py

2 files changed, 64 insertions, 1 deletions

diff --git a/Makefile b/Makefile
index 0914597..fd53307 100644
--- a/Makefile
+++ b/Makefile
@@ -49,7 +49,7 @@ btrfs-send-root.sh var.sh grub-efi.sh keygen.sh initrd.sh qemu.sh
 dnsmasq-dhcp-script.sh samizdat-password-agent samizdat-gpg-agent publish-ip.sh \
 selfstrap samizdat-daily-snapshot-root samizdat-diff-root kiki-export-stdout    \
 kiki-import-stdin store-child-permanently git-ll-remote usb                     \
-hostname.cryptonomic.net partvi ${dyndns_progs}
+hostname.cryptonomic.net partvi ficlonerange.py ${dyndns_progs}
 
 bin_programs=$(addprefix src/, $(src_bin_programs)) samizdat-paths.sh ${cc_files} ${btrfs_utils}
 
diff --git a/src/ficlonerange.py b/src/ficlonerange.py
new file mode 100755
index 0000000..8df96ad
--- /dev/null
+++ b/src/ficlonerange.py
@@ -0,0 +1,63 @@
+#!/usr/bin/python3
+
+import sys
+import os
+from fcntl import ioctl
+import struct
+import argparse
+import errno
+import textwrap
+
+def fail(message):
+    print(textwrap.fill("FICLONERANGE: " + message))
+    sys.exit(3)
+
+FICLONERANGE = 0x4020940d
+
+def struct_file_clone_range(src_fd, src_offset, src_length, dst_offset):
+    return struct.pack("qQQQ", src_fd, src_offset, src_length, dst_offset)
+
+parser = argparse.ArgumentParser(description="Reflink bytes from source file to destination. "
+    "If no optional parameters are provided, append contents of src to dest. See ioctl_ficlonerange(2) for details.")
+parser.add_argument("-s", type=int, default=0, help="Source file offset in bytes (default: 0)")
+parser.add_argument("-l", type=int, default=0, help="Number of bytes to reflink (default: all data)")
+parser.add_argument("-d", type=int,            help="Destination file offset in bytes (default: end of file)")
+parser.add_argument("src", help="Source filename")
+parser.add_argument("dest", help="Destination filename")
+args = parser.parse_args()
+
+src_fd = os.open(args.src, os.O_RDONLY)
+dst_fd = os.open(args.dest, os.O_WRONLY)
+
+try:
+    ioctl(dst_fd, FICLONERANGE, struct_file_clone_range(src_fd,
+        args.s or 0,
+        args.l or 0,
+        args.d if args.d is not None else os.fstat(dst_fd).st_size,
+    ))
+except OSError as e:
+    if e.errno == errno.EXDEV:
+        fail("src and dest are not on the same mounted filesystem")
+
+    if e.errno == errno.EISDIR:
+        fail("One of the files is a directory and the filesystem does not support shared regions in directories.")
+
+    if e.errno == errno.EINVAL:
+        fail("The filesystem does not support reflinking the ranges of the given files. This error can also appear "
+            "if either file descriptor represents a device, FIFO, or socket. Disk filesystems generally require the "
+            "offset and length arguments to be aligned to the fundamental block size ({} bytes). XFS and Btrfs do not support "
+            "overlapping reflink ranges in the same file.".format(os.fstat(dst_fd).st_blksize))
+
+    if e.errno == errno.EBADF:
+        fail("Filesystem does not support reflink (EBADF).")
+
+    if e.errno == errno.EPERM:
+        fail("dest is immutable.")
+
+    if e.errno == errno.ETXTBSY:
+        fail("One of the files is a swap file. Swap files cannot share storage.")
+
+    if e.errno == errno.EOPNOTSUPP:
+        fail("Filesystem does not support reflink (EOPNOTSUPP).")
+
+    raise