[Devel] Re: [PATCH 1/2] [RFC] Add file f_flags to cgroup write_string ops

[KAMEZAWA Hiroyuki]

On Mon, 26 Oct 2009 08:15:29 -0700
Matt Helsley <matthltc at us.ibm.com> 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 at us.ibm.com>
> Cc: Nathan Lynch <ntl at pobox.com>
> Cc: Paul Menage <menage at google.com>
> Cc: Li Zefan <lizf at cn.fujitsu.com>
> 
> (Cc'ing mem controller maintainers in case they find this useful..)
> Cc: Balbir Singh <balbir at linux.vnet.ibm.com>
> Cc: Pavel Emelyanov <xemul at openvz.org>
> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu at jp.fujitsu.com>

Hmm, maybe useful if we decided to add memory.drop_memory or some...
But now, we have no plan to add backup thread(for asynchronous job).
or some trylock ops.
Anyway, no objection from me if you want this.

-Kame




> ---
>  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);
>  	/*
>  	 * trigger() callback can be used to get some kick from the
>  	 * userspace, when the actual string written is not important
> diff --git a/kernel/cgroup.c b/kernel/cgroup.c
> index b6eadfe..af07d05 100644
> --- a/kernel/cgroup.c
> +++ b/kernel/cgroup.c
> @@ -1449,7 +1449,7 @@ bool cgroup_lock_live_group(struct cgroup *cgrp)
>  }
>  
>  static int cgroup_release_agent_write(struct cgroup *cgrp, struct cftype *cft,
> -				      const char *buffer)
> +				      unsigned int f_flags, const char *buffer)
>  {
>  	BUILD_BUG_ON(sizeof(cgrp->root->release_agent_path) < PATH_MAX);
>  	if (!cgroup_lock_live_group(cgrp))
> @@ -1534,7 +1534,8 @@ static ssize_t cgroup_write_string(struct cgroup *cgrp, struct cftype *cft,
>  
>  	buffer[nbytes] = 0;     /* nul-terminate */
>  	strstrip(buffer);
> -	retval = cft->write_string(cgrp, cft, buffer);
> +	retval = cft->write_string(cgrp, cft, file->f_flags & CFTYPE_F_FLAGS,
> +				   buffer);
>  	if (!retval)
>  		retval = nbytes;
>  out:
> diff --git a/kernel/cgroup_freezer.c b/kernel/cgroup_freezer.c
> index 7925850..c97680f 100644
> --- a/kernel/cgroup_freezer.c
> +++ b/kernel/cgroup_freezer.c
> @@ -343,9 +343,8 @@ out:
>  	return retval;
>  }
>  
> -static int freezer_write(struct cgroup *cgroup,
> -			 struct cftype *cft,
> -			 const char *buffer)
> +static int freezer_write(struct cgroup *cgroup, struct cftype *cft,
> +			 unsigned int f_flags, const char *buffer)
>  {
>  	int retval;
>  	enum freezer_state goal_state;
> diff --git a/kernel/cpuset.c b/kernel/cpuset.c
> index 7e75a41..de7f397 100644
> --- a/kernel/cpuset.c
> +++ b/kernel/cpuset.c
> @@ -1470,7 +1470,7 @@ static int cpuset_write_s64(struct cgroup *cgrp, struct cftype *cft, s64 val)
>   * Common handling for a write to a "cpus" or "mems" file.
>   */
>  static int cpuset_write_resmask(struct cgroup *cgrp, struct cftype *cft,
> -				const char *buf)
> +				unsigned int f_flags, const char *buf)
>  {
>  	int retval = 0;
>  	struct cpuset *cs = cgroup_cs(cgrp);
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index fd4529d..fd9c737 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -2072,7 +2072,7 @@ static u64 mem_cgroup_read(struct cgroup *cont, struct cftype *cft)
>   * RES_LIMIT.
>   */
>  static int mem_cgroup_write(struct cgroup *cont, struct cftype *cft,
> -			    const char *buffer)
> +			    unsigned int f_flags, const char *buffer)
>  {
>  	struct mem_cgroup *memcg = mem_cgroup_from_cont(cont);
>  	int type, name;
> diff --git a/security/device_cgroup.c b/security/device_cgroup.c
> index b8186ba..65d32ce 100644
> --- a/security/device_cgroup.c
> +++ b/security/device_cgroup.c
> @@ -428,7 +428,7 @@ handle:
>  }
>  
>  static int devcgroup_access_write(struct cgroup *cgrp, struct cftype *cft,
> -				  const char *buffer)
> +				  unsigned int f_flags, const char *buffer)
>  {
>  	int retval;
>  
> -- 
> 1.5.6.3
> 
> 
> 

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