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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