On 09/15/2014 01:29 PM, Jan Chaloupka wrote:
> As of now, libcgroup does not support multiline values setting from
> configuration files. i.e. values in a form:
>
> net_prio.ifpriomap="lo 7
> eth0 66
> eth1 5
> eth2 4
> eth3 3";
>
> Thus, setting of more network interfaces can not be done from configuration
> file. Or
>
> devices.allow="a *:* w
> c 8:* r";
>
> thus setting list of allow devices can not be set as well. The only way is to
> set it from userspace, e.g.:
> # echo "lo 7" > /sys/fs/cgroup/net_prio/testGroup/net_prio.ifpriomap
> # echo "eth 0" > /sys/fs/cgroup/net_prio/testGroup/net_prio.ifpriomap
> # echo "eth 1" > /sys/fs/cgroup/net_prio/testGroup/net_prio.ifpriomap
> # echo "eth 2" > /sys/fs/cgroup/net_prio/testGroup/net_prio.ifpriomap
> # echo "eth 3" > /sys/fs/cgroup/net_prio/testGroup/net_prio.ifpriomap
>
> This patch allows setting of multiline variables.
>
> How this support works:
> Multiline value is broken in lines and each line is set by write (man 2
> write) syscall (without bufferring).
> This implies change of fopen with open, fclose with close.
> There is no control on multiline value, thus "eth0\n \t\n" can be set.
> However, setting
> of " \t" will fail as write command returns -1. Thus administrator has to
> set correct
> multiline values.
>
> Tested on virtual machine with fedora and rhel with network interface lo,
> eth0-eth3. Configuration file:
>
> # cat /etc/cgconfig.conf
> group testGroup {
> net_prio {
> net_prio.ifpriomap="lo 7
> eth0 66
> eth1 5
> eth2 4
> eth3 3";
> }
> }
>
> net_prio has to be created before:
> # modprobe netprio_cgroup
> # mkdir /sys/fs/cgroup/net_prio
> # mount -t cgroup -onet_prio none /sys/fs/cgroup/net_prio
>
> Changelog:
> test of success of strdup call
> free str_val before return (str_val is changing in while cycle,
> thus str_start_val points to the start of str_val before while)
>
> Signed-off-by: Jan Chaloupka <jchal...@redhat.com>
Acked-By: Jan Safranek <jsafr...@redhat.com>
Thanks for the patch!
> ---
> src/api.c | 50 ++++++++++++++++++++++++++++++++++++++++++++------
> 1 file changed, 44 insertions(+), 6 deletions(-)
>
> diff --git a/src/api.c b/src/api.c
> index 5751b8f..d6c9d3a 100644
> --- a/src/api.c
> +++ b/src/api.c
> @@ -1495,13 +1495,18 @@ static int cg_create_control_group(const char *path)
> */
> static int cg_set_control_value(char *path, const char *val)
> {
> - FILE *control_file = NULL;
> + int ctl_file;
> + char *str_val;
> + char *str_val_start;
> + char *pos;
> + size_t len;
> +
> if (!cg_test_mounted_fs())
> return ECGROUPNOTMOUNTED;
>
> - control_file = fopen(path, "r+e");
> + ctl_file = open(path, O_RDWR | O_CLOEXEC);
>
> - if (!control_file) {
> + if (ctl_file == -1) {
> if (errno == EPERM) {
> /*
> * We need to set the correct error value, does the
> @@ -1512,6 +1517,7 @@ static int cg_set_control_value(char *path, const char
> *val)
> */
> char *path_dir_end;
> char *tasks_path;
> + FILE *control_file;
>
> path_dir_end = strrchr(path, '/');
> if (path_dir_end == NULL)
> @@ -1543,15 +1549,47 @@ static int cg_set_control_value(char *path, const
> char *val)
> return ECGROUPVALUENOTEXIST;
> }
>
> - if (fprintf(control_file, "%s", val) < 0) {
> + /* Split the multiline value into lines. */
> + /* One line is a special case of multiline value. */
> + str_val = strdup(val);
> + if (str_val == NULL) {
> last_errno = errno;
> - fclose(control_file);
> + close(ctl_file);
> return ECGOTHER;
> }
> - if (fclose(control_file) < 0) {
> +
> + str_val_start = str_val;
> + pos = str_val;
> +
> + do {
> + str_val = pos;
> + pos = strchr(str_val, '\n');
> +
> + if (pos) {
> + *pos = '\0';
> + ++pos;
> + }
> +
> + len = strlen(str_val);
> + if (len > 0) {
> + if (write(ctl_file, str_val, len) == -1) {
> + last_errno = errno;
> + free(str_val_start);
> + close(ctl_file);
> + return ECGOTHER;
> + }
> + } else
> + cgroup_warn("Warning: skipping empty line for %s\n",
> + path);
> + } while(pos);
> +
> + if (close(ctl_file)) {
> last_errno = errno;
> + free(str_val_start);
> return ECGOTHER;
> }
> +
> + free(str_val_start);
> return 0;
> }
>
>
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