ioctl contants are platform dependent. It should be the same on
x86, aarch64 and s390x but it is indeed different on ppc64le.
This lead to the call to `ioctl_blockdev_flushbuf` actually
raising an exception of `OSError: [Errno 22] Invalid argument`.
The constant was calculated with a little python snippet that
in theory could also go directly into the code, but for now
the simpler condition in this patch is enough.
The snippet is a port of the defines from the Linux kernel,
specifically /usr/include/asm-generic/ioctl.h.
class IOConstants:
"""IO Commands for Linux"""
if platform.machine() == "ppc64le":
NRBITS = 8
TYPEBITS = 8
SIZEBITS = 13
DIR_NONE = 1
else:
NRBITS = 8
TYPEBITS = 8
SIZEBITS = 14
DIR_NONE = 0
NRSHIFT = 0
TYPESHIFT = NRSHIFT+NRBITS
SIZESHIFT = TYPESHIFT+TYPEBITS
DIRSHIFT = SIZESHIFT+SIZEBITS
@classmethod
def make(cls, directory, iotype, nr, size):
return ((directory << cls.DIRSHIFT) |
(iotype << cls.TYPESHIFT) |
(nr << cls.NRSHIFT) |
(size << cls.SIZESHIFT))
@classmethod
def make_dir_none(cls, iotype, nr):
return cls.make(cls.DIR_NONE, iotype, nr, 0)
This is used to get the value for `BLKFLSBUF` taken from the
include `/usr/include/linux/fs.h`:
#define BLKFLSBUF _IO(0x12,97) /* flush buffer cache */
The value is then obtained via:
print("0x%x" % IOConstants.make_dir_none(0x12,97))
0x20001261
0f670829a3