I was wondering whether there was any particular reason why the
limitations below are still present given that these were changed
between 2.4 and 2.6 linux kernels?
Eg:
LVM2/tools/lvmcmdline.c
int minor_arg(struct cmd_context *cmd __attribute((unused)), struct arg *a)
{
char *ptr;
if (!_get_int_arg(a, &ptr) || (*ptr) || (a->sign == SIGN_MINUS))
return 0;
if (a->i_value > 255) {
log_error("Minor number outside range 0-255");
return 0;
}
return 1;
}
int major_arg(struct cmd_context *cmd __attribute((unused)), struct arg *a)
{
char *ptr;
if (!_get_int_arg(a, &ptr) || (*ptr) || (a->sign == SIGN_MINUS))
return 0;
if (a->i_value > 255) {
log_error("Major number outside range 0-255");
return 0;
}
/* FIXME Also Check against /proc/devices */
return 1;
}
Linux 2.4 kernel appears to have a major number of 8 bits, likewise for
the minor number.
By comparison, 2.6 appears to have 12 bits for the major and 20 bits for
the minor, significantly larger, eg:
4 #define MINORBITS 20
5 #define MINORMASK ((1U << MINORBITS) - 1)
6
7 #define MAJOR(dev) ((unsigned int) ((dev) >> MINORBITS))
8 #define MINOR(dev) ((unsigned int) ((dev) & MINORMASK))
9 #define MKDEV(ma,mi) (((ma) << MINORBITS) | (mi))
Whilst these LVM2 hardcoded limits do not prevent device nodes being
created during normal operation they do prevent the user from specifying
specific major/minor numbers via the cmdline, eg:
# lvcreate -n bigminor -l 5 -M y --major 253 --minor 270 vgtest
Minor number outside range 0-255
Invalid argument 270
Error during parsing of command line.
Rebuilding without these limits (a quick hack/test) produces a device
node that seems to work just fine:
# ./lvm lvcreate -n highminor -l 5 -M y --major 253 --minor 260 vgtest
Logical volume "highminor" created
# ll /dev/mapper/
total 128
drwxr-xr-x 2 root root 4096 Feb 12 16:29 .
drwxr-xr-x 35 root root 122880 Feb 12 16:29 ..
lrwxrwxrwx 1 root root 16 Feb 12 15:52 control -> ../device-mapper
brw------- 1 root root 253, 260 Feb 12 16:29 vgtest-highminor
brw------- 1 root root 253, 250 Feb 12 16:04 vgtest-lowminor
brw------- 1 root root 253, 0 Feb 12 16:04 vgtest-nominor
Can this limitation be either removed or updated to bring it in line
with more recent kernel functionality? Or is there some reason that I
am missing for their continued existence/assigned values.....
Thanks & regards
--
Darren Lavender <dl1@hppine99.gbr.hp.com>
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