Matt Helsley wrote:
> cgroup subsystems may find the O_APPEND and O_NONBLOCK flags useful
> in determining the way they handle writes. For now only pass these
> flags through the write_string op.
>
> A subsequent patch will make use of the O_NONBLOCK flag in the
> cgroup freezer write_string op.
>
> Signed-off-by: Matt Helsley <matthltc@xxxxxxxxxx>
> Cc: Nathan Lynch <ntl@xxxxxxxxx>
> Cc: Paul Menage <menage@xxxxxxxxxx>
> Cc: Li Zefan <lizf@xxxxxxxxxxxxxx>
>
> (Cc'ing mem controller maintainers in case they find this useful..)
> Cc: Balbir Singh <balbir@xxxxxxxxxxxxxxxxxx>
> Cc: Pavel Emelyanov <xemul@xxxxxxxxxx>
> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
> ---
> include/linux/cgroup.h | 3 ++-
> kernel/cgroup.c | 5 +++--
> kernel/cgroup_freezer.c | 5 ++---
> kernel/cpuset.c | 2 +-
> mm/memcontrol.c | 2 +-
> security/device_cgroup.c | 2 +-
> 6 files changed, 10 insertions(+), 9 deletions(-)
>
> diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
> index 90bba9e..627da35 100644
> --- a/include/linux/cgroup.h
> +++ b/include/linux/cgroup.h
> @@ -315,8 +315,9 @@ struct cftype {
> * buffer of maximum length determined by max_write_len.
> * Returns 0 or -ve error code.
> */
> +#define CFTYPE_F_FLAGS (O_APPEND|O_NONBLOCK)
> int (*write_string)(struct cgroup *cgrp, struct cftype *cft,
> - const char *buffer);
> + unsigned int f_flags, const char *buffer);
I think maybe it's better to store struct file *file to struct cftype,
so we don't need to change write_string(), write(), write_u64()
and write_s64().
> /*
> * trigger() callback can be used to get some kick from the
> * userspace, when the actual string written is not important
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