在 2016/12/11 23:36, Jia He 写道:
nsm_use_hostnames is a module parameter and it will be exported to sysctl
procfs. This is to let user sometimes change it from userspace. But the
minimal unit for sysctl procfs read/write it sizeof(int).
In big endian system, the converting from/to bool to/from int will cause
error for proc items.
hi, Jia
not only in BE system. :)
Current code is just touching a wrong pointer.
some tests based on yours
u8 __read_mostly nsm_use_hostnames[4]={1,2,3,4}; // an arrary of u8, and [0] passed to ctl_table as data
static struct ctl_table my_sysctl[] = {
{
.procname = "nsm_use_hostnames",
.data = &nsm_use_hostnames[0],//u8,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = &proc_dointvec,
},
{}
};
then run your tests and result will be
root@ltcalpine2-lp13:~/linux/bench# cat /proc/sys/mysysctl/nsm_use_hostnames
67305985( This is 0x4030201, expected be 0x1)
So your fix patch work around it. But I suggest we can support u8/u16, not only int/double int.
thanks
xinhui
This patch changes the type definition of nsm_use_hostnames.
The test case I used:
/***************************************************************/
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/sysctl.h>
bool __read_mostly nsm_use_hostnames;
module_param(nsm_use_hostnames, bool, 0644);
static struct ctl_table my_sysctl[] = {
{
.procname = "nsm_use_hostnames",
.data = &nsm_use_hostnames,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = &proc_dointvec,
},
{}
};
static struct ctl_table my_root[] = {
{
.procname = "mysysctl",
.mode = 0555,
.child = my_sysctl,
},
{}
};
static struct ctl_table_header * my_ctl_header;
static int __init sysctl_exam_init(void)
{
my_ctl_header = register_sysctl_table(&my_root);
if (my_ctl_header == NULL)
printk("error regiester sysctl");
return 0;
}
static void __exit sysctl_exam_exit(void)
{
unregister_sysctl_table(my_ctl_header);
}
module_init(sysctl_exam_init);
module_exit(sysctl_exam_exit);
MODULE_LICENSE("GPL");
/****************************************************************/
[root@bigendian my]# insmod -f /root/my/hello.ko nsm_use_hostnames=1
[root@bigendian my]# cat /proc/sys/mysysctl/nsm_use_hostnames
16777216
After I change the bool to int:
[root@bigendian my]# insmod -f /root/my/hello.ko nsm_use_hostnames=1
[root@bigendian my]# cat /proc/sys/mysysctl/nsm_use_hostnames
1
In little endian system, there is no such issue.
Jia He (1):
lockd: Change nsm_use_hostnames from bool to u32
fs/lockd/mon.c | 2 +-
fs/lockd/svc.c | 2 +-
include/linux/lockd/lockd.h | 2 +-
3 files changed, 3 insertions(+), 3 deletions(-)
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