Hi Balbir,
Balbir Singh wrote:
>> If writing an invalid value on a file of cgroup fs, write(2) returns -1
>> with a right errno. But fprintf(3) does not return it, because fprintf(3)
>> write on some buffer. So it is better that we check the return value of
>> write(2).
>>
>
> Hi, Kenichi,
>
> Does the code fragment (diff) below work for you?
> Please note, it is not an appliable diff, it is a part of bigger
> patch.
>
>
> static int cg_set_control_value(char *path, char *val)
> {
> + int ret = 0;
> FILE *control_file = NULL;
> if (!cg_test_mounted_fs())
> return ECGROUPNOTMOUNTED;
> @@ -1078,9 +1080,14 @@ static int cg_set_control_value(char *path, char *val)
> return ECGROUPVALUENOTEXIST;
> }
>
> - fprintf(control_file, "%s", val);
> + ret = fprintf(control_file, "%s", val);
> + if (ret < 0 || ret < strlen(val) + 1) {
> + last_errno = errno;
> + ret = ECGOTHER;
> + } else
> + ret = 0;
> fclose(control_file);
> - return 0;
> + return ret;
> }
If the following /etc/cgconfig.conf, cgconfig should succeed.
But it failed after applying your patch:
# cat /etc/cgconfig.conf
mount {
cpuset = /mnt/cgroups/cpuset;
}
group usergroup {
cpuset {
cpuset.cpus = 0;
cpuset.mems = 0;
}
}
# service cgconfig stop
Stopping cgconfig service: [ OK ]
# service cgconfig start
Starting cgconfig service: Loading configuration file /etc/cgconfig.conf failed
Success
Failed to parse /etc/cgconfig.conf [FAILED]
#
If you want to use fprintf(3), how about the attached patch ?
The error handling against fclose(3) is added into the patch.
fclose(3) write the buffer to a file, and it returns -1 if a writing
error happens.
Thanks
Ken'ichi Ohmichi
----
[PATCH-v2] Add the write error handling to cg_set_control_value().
Changelog since v1:
o Use fopen/fprintf/fclose instead of open/write/close.
o Add the error handling against fclose.
cg_set_control_value() is the function for setting a value to a file
of cgroup file system. And current function does not handle the error
of writing to a file. So we cannot know whether setting value is
enable or not. This patch add the error handling for knowing it.
Signed-off-by: Ken'ichi Ohmichi <[email protected]>
diff --git a/src/api.c b/src/api.c
index 28c0c3d..0b1bec0 100644
--- a/src/api.c
+++ b/src/api.c
@@ -1078,8 +1078,15 @@ static int cg_set_control_value(char *path, char *val)
return ECGROUPVALUENOTEXIST;
}
- fprintf(control_file, "%s", val);
- fclose(control_file);
+ if (fprintf(control_file, "%s", val) < 0) {
+ last_errno = errno;
+ fclose(control_file);
+ return ECGOTHER;
+ }
+ if (fclose(control_file) < 0) {
+ last_errno = errno;
+ return ECGOTHER;
+ }
return 0;
}
------------------------------------------------------------------------------
Join us December 9, 2009 for the Red Hat Virtual Experience,
a free event focused on virtualization and cloud computing.
Attend in-depth sessions from your desk. Your couch. Anywhere.
http://p.sf.net/sfu/redhat-sfdev2dev
_______________________________________________
Libcg-devel mailing list
[email protected]
https://lists.sourceforge.net/lists/listinfo/libcg-devel
