[Devel] Re: [PATCH] Simplify memory controller and resource counter I/O

Paul Menage menage at google.com
Thu Oct 4 17:55:32 PDT 2007


Hi Balbir,

Any thoughts on this patch?

Cheers,

Paul

On 9/25/07, Paul Menage <menage at google.com> wrote:
> Simplify the memory controller and resource counter I/O routines
>
> This patch strips out some I/O boilerplate from resource counters and
> the memory controller. It also adds locking to the resource counter
> reads and writes, and forbids writes to the root memory cgroup's limit
> file.
>
> One arguable drawback to this patch is that the use of memparse() is
> lost in the cleanup. Having said that, given the existing of shell
> arithmetic, it's not clear to me that typing
>
> echo $[2<<30] > memory.limit
>
> is especially harder than
>
> echo 2G > memory.limit
>
> Signed-off-by: Paul Menage <menage at google.com>
>
> ---
>  include/linux/res_counter.h |   13 +----
>  kernel/res_counter.c        |   64 +++++----------------------
>  mm/memcontrol.c             |  103 ++++++++++----------------------------------
>  3 files changed, 43 insertions(+), 137 deletions(-)
>
> Index: container-2.6.23-rc8-mm1/include/linux/res_counter.h
> ===================================================================
> --- container-2.6.23-rc8-mm1.orig/include/linux/res_counter.h
> +++ container-2.6.23-rc8-mm1/include/linux/res_counter.h
> @@ -46,17 +46,12 @@ struct res_counter {
>   *
>   * @counter:     the counter in question
>   * @member:  the field to work with (see RES_xxx below)
> - * @buf:     the buffer to opeate on,...
> - * @nbytes:  its size...
> - * @pos:     and the offset.
> + * @val:     the value passed by the user (for write)
>   */
>
> -ssize_t res_counter_read(struct res_counter *counter, int member,
> -               const char __user *buf, size_t nbytes, loff_t *pos,
> -               int (*read_strategy)(unsigned long long val, char *s));
> -ssize_t res_counter_write(struct res_counter *counter, int member,
> -               const char __user *buf, size_t nbytes, loff_t *pos,
> -               int (*write_strategy)(char *buf, unsigned long long *val));
> +unsigned long long res_counter_read(struct res_counter *counter, int member);
> +int res_counter_write(struct res_counter *counter, int member,
> +                     unsigned long long val);
>
>  /*
>   * the field descriptors. one for each member of res_counter
> Index: container-2.6.23-rc8-mm1/kernel/res_counter.c
> ===================================================================
> --- container-2.6.23-rc8-mm1.orig/kernel/res_counter.c
> +++ container-2.6.23-rc8-mm1/kernel/res_counter.c
> @@ -75,58 +75,22 @@ res_counter_member(struct res_counter *c
>         return NULL;
>  }
>
> -ssize_t res_counter_read(struct res_counter *counter, int member,
> -               const char __user *userbuf, size_t nbytes, loff_t *pos,
> -               int (*read_strategy)(unsigned long long val, char *st_buf))
> +unsigned long long res_counter_read(struct res_counter *counter, int member)
>  {
> -       unsigned long long *val;
> -       char buf[64], *s;
> -
> -       s = buf;
> -       val = res_counter_member(counter, member);
> -       if (read_strategy)
> -               s += read_strategy(*val, s);
> -       else
> -               s += sprintf(s, "%llu\n", *val);
> -       return simple_read_from_buffer((void __user *)userbuf, nbytes,
> -                       pos, buf, s - buf);
> +       unsigned long long val;
> +       unsigned long flags;
> +       spin_lock_irqsave(&counter->lock, flags);
> +       val = *res_counter_member(counter, member);
> +       spin_unlock_irqrestore(&counter->lock, flags);
> +       return val;
>  }
>
> -ssize_t res_counter_write(struct res_counter *counter, int member,
> -               const char __user *userbuf, size_t nbytes, loff_t *pos,
> -               int (*write_strategy)(char *st_buf, unsigned long long *val))
> +int res_counter_write(struct res_counter *counter, int member,
> +                     unsigned long long val)
>  {
> -       int ret;
> -       char *buf, *end;
> -       unsigned long long tmp, *val;
> -
> -       buf = kmalloc(nbytes + 1, GFP_KERNEL);
> -       ret = -ENOMEM;
> -       if (buf == NULL)
> -               goto out;
> -
> -       buf[nbytes] = '\0';
> -       ret = -EFAULT;
> -       if (copy_from_user(buf, userbuf, nbytes))
> -               goto out_free;
> -
> -       ret = -EINVAL;
> -
> -       if (write_strategy) {
> -               if (write_strategy(buf, &tmp)) {
> -                       goto out_free;
> -               }
> -       } else {
> -               tmp = simple_strtoull(buf, &end, 10);
> -               if (*end != '\0')
> -                       goto out_free;
> -       }
> -
> -       val = res_counter_member(counter, member);
> -       *val = tmp;
> -       ret = nbytes;
> -out_free:
> -       kfree(buf);
> -out:
> -       return ret;
> +       unsigned long flags;
> +       spin_lock_irqsave(&counter->lock, flags);
> +       *res_counter_member(counter, member) = val;
> +       spin_unlock_irqrestore(&counter->lock, flags);
> +       return 0;
>  }
> Index: container-2.6.23-rc8-mm1/mm/memcontrol.c
> ===================================================================
> --- container-2.6.23-rc8-mm1.orig/mm/memcontrol.c
> +++ container-2.6.23-rc8-mm1/mm/memcontrol.c
> @@ -437,112 +437,59 @@ void mem_cgroup_uncharge(struct page_cgr
>         }
>  }
>
> -int mem_cgroup_write_strategy(char *buf, unsigned long long *tmp)
> -{
> -       *tmp = memparse(buf, &buf);
> -       if (*buf != '\0')
> -               return -EINVAL;
> -
> -       /*
> -        * Round up the value to the closest page size
> -        */
> -       *tmp = ((*tmp + PAGE_SIZE - 1) >> PAGE_SHIFT) << PAGE_SHIFT;
> -       return 0;
> -}
> -
> -static ssize_t mem_cgroup_read(struct cgroup *cont,
> -                       struct cftype *cft, struct file *file,
> -                       char __user *userbuf, size_t nbytes, loff_t *ppos)
> +static unsigned long long mem_cgroup_read(struct cgroup *cont,
> +                                         struct cftype *cft)
>  {
>         return res_counter_read(&mem_cgroup_from_cont(cont)->res,
> -                               cft->private, userbuf, nbytes, ppos,
> -                               NULL);
> +                               cft->private);
>  }
>
> -static ssize_t mem_cgroup_write(struct cgroup *cont, struct cftype *cft,
> -                               struct file *file, const char __user *userbuf,
> -                               size_t nbytes, loff_t *ppos)
> +static int mem_cgroup_write(struct cgroup *cont, struct cftype *cft,
> +                           unsigned long long val)
>  {
> +       /* Don't allow the limit to be set for the root cgroup */
> +       if (!cont->parent)
> +               return -EINVAL;
>         return res_counter_write(&mem_cgroup_from_cont(cont)->res,
> -                               cft->private, userbuf, nbytes, ppos,
> -                               mem_cgroup_write_strategy);
> +                                cft->private, PAGE_ALIGN(val));
>  }
>
> -static ssize_t mem_control_type_write(struct cgroup *cont,
> -                       struct cftype *cft, struct file *file,
> -                       const char __user *userbuf,
> -                       size_t nbytes, loff_t *pos)
> -{
> -       int ret;
> -       char *buf, *end;
> -       unsigned long tmp;
> -       struct mem_cgroup *mem;
> -
> -       mem = mem_cgroup_from_cont(cont);
> -       buf = kmalloc(nbytes + 1, GFP_KERNEL);
> -       ret = -ENOMEM;
> -       if (buf == NULL)
> -               goto out;
> -
> -       buf[nbytes] = 0;
> -       ret = -EFAULT;
> -       if (copy_from_user(buf, userbuf, nbytes))
> -               goto out_free;
> -
> -       ret = -EINVAL;
> -       tmp = simple_strtoul(buf, &end, 10);
> -       if (*end != '\0')
> -               goto out_free;
> -
> -       if (tmp <= MEM_CGROUP_TYPE_UNSPEC || tmp >= MEM_CGROUP_TYPE_MAX)
> -               goto out_free;
> -
> -       mem->control_type = tmp;
> -       ret = nbytes;
> -out_free:
> -       kfree(buf);
> -out:
> -       return ret;
> +static int mem_control_type_write(struct cgroup *cont, struct cftype *cft,
> +                                 u64 val)
> +{
> +       if (val <= MEM_CGROUP_TYPE_UNSPEC || val >= MEM_CGROUP_TYPE_MAX)
> +               return -EINVAL;
> +       mem_cgroup_from_cont(cont)->control_type = val;
> +       return 0;
>  }
>
> -static ssize_t mem_control_type_read(struct cgroup *cont,
> -                               struct cftype *cft,
> -                               struct file *file, char __user *userbuf,
> -                               size_t nbytes, loff_t *ppos)
> +static u64 mem_control_type_read(struct cgroup *cont,
> +                                struct cftype *cft)
>  {
> -       unsigned long val;
> -       char buf[64], *s;
> -       struct mem_cgroup *mem;
> -
> -       mem = mem_cgroup_from_cont(cont);
> -       s = buf;
> -       val = mem->control_type;
> -       s += sprintf(s, "%lu\n", val);
> -       return simple_read_from_buffer((void __user *)userbuf, nbytes,
> -                       ppos, buf, s - buf);
> +       return mem_cgroup_from_cont(cont)->control_type;
>  }
>
>  static struct cftype mem_cgroup_files[] = {
>         {
>                 .name = "usage_in_bytes",
>                 .private = RES_USAGE,
> -               .read = mem_cgroup_read,
> +               .read_uint = mem_cgroup_read,
>         },
>         {
>                 .name = "limit_in_bytes",
>                 .private = RES_LIMIT,
> -               .write = mem_cgroup_write,
> -               .read = mem_cgroup_read,
> +               .write_uint = mem_cgroup_write,
> +               .read_uint = mem_cgroup_read,
>         },
>         {
>                 .name = "failcnt",
>                 .private = RES_FAILCNT,
> -               .read = mem_cgroup_read,
> +               .read_uint = mem_cgroup_read,
>         },
>         {
>                 .name = "control_type",
> -               .write = mem_control_type_write,
> -               .read = mem_control_type_read,
> +               .write_uint = mem_control_type_write,
> +               .read_uint = mem_control_type_read,
>         },
>  };
>
>
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