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SubjectRe: [RFC PATCH v2 1/3] meminfo_extra: introduce meminfo extra
On Mon, Mar 23, 2020 at 05:05:01PM +0900, Jaewon Kim wrote:
> Provide APIs to drivers so that they can show its memory usage on
> /proc/meminfo_extra.
>
> int register_meminfo_extra(atomic_long_t *val, int shift,
> const char *name);
> int unregister_meminfo_extra(atomic_long_t *val);

Nit, isn't it nicer to have the subsystem name first:
meminfo_extra_register()
meminfo_extra_unregister()
?



>
> Signed-off-by: Jaewon Kim <jaewon31.kim@samsung.com>
> ---
> v2: move to /proc/meminfo_extra as a new file, meminfo_extra.c
> use rcu to reduce lock overhead
> v1: print info at /proc/meminfo
> ---
> fs/proc/Makefile | 1 +
> fs/proc/meminfo_extra.c | 123 ++++++++++++++++++++++++++++++++++++++++++++++++
> include/linux/mm.h | 4 ++
> mm/page_alloc.c | 1 +
> 4 files changed, 129 insertions(+)
> create mode 100644 fs/proc/meminfo_extra.c
>
> diff --git a/fs/proc/Makefile b/fs/proc/Makefile
> index bd08616ed8ba..83d2f55591c6 100644
> --- a/fs/proc/Makefile
> +++ b/fs/proc/Makefile
> @@ -19,6 +19,7 @@ proc-y += devices.o
> proc-y += interrupts.o
> proc-y += loadavg.o
> proc-y += meminfo.o
> +proc-y += meminfo_extra.o
> proc-y += stat.o
> proc-y += uptime.o
> proc-y += util.o
> diff --git a/fs/proc/meminfo_extra.c b/fs/proc/meminfo_extra.c
> new file mode 100644
> index 000000000000..bd3f0d2b7fb7
> --- /dev/null
> +++ b/fs/proc/meminfo_extra.c
> @@ -0,0 +1,123 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#include <linux/mm.h>
> +#include <linux/proc_fs.h>
> +#include <linux/seq_file.h>
> +#include <linux/slab.h>
> +
> +static void show_val_kb(struct seq_file *m, const char *s, unsigned long num)
> +{
> + seq_put_decimal_ull_width(m, s, num << (PAGE_SHIFT - 10), 8);
> + seq_write(m, " kB\n", 4);
> +}
> +
> +static LIST_HEAD(meminfo_head);
> +static DEFINE_SPINLOCK(meminfo_lock);
> +
> +#define NAME_SIZE 15
> +#define NAME_BUF_SIZE (NAME_SIZE + 2) /* ':' and '\0' */
> +
> +struct meminfo_extra {
> + struct list_head list;
> + atomic_long_t *val;
> + int shift_for_page;
> + char name[NAME_BUF_SIZE];
> + char name_pad[NAME_BUF_SIZE];
> +};
> +
> +int register_meminfo_extra(atomic_long_t *val, int shift, const char *name)
> +{
> + struct meminfo_extra *meminfo, *memtemp;
> + int len;
> + int error = 0;
> +
> + meminfo = kzalloc(sizeof(*meminfo), GFP_KERNEL);
> + if (!meminfo) {
> + error = -ENOMEM;
> + goto out;
> + }
> +
> + meminfo->val = val;
> + meminfo->shift_for_page = shift;
> + strncpy(meminfo->name, name, NAME_SIZE);
> + len = strlen(meminfo->name);
> + meminfo->name[len] = ':';
> + strncpy(meminfo->name_pad, meminfo->name, NAME_BUF_SIZE);
> + while (++len < NAME_BUF_SIZE - 1)
> + meminfo->name_pad[len] = ' ';
> +
> + spin_lock(&meminfo_lock);
> + list_for_each_entry_rcu(memtemp, &meminfo_head, list) {
> + if (memtemp->val == val) {
> + error = -EINVAL;
> + break;
> + }
> + }
> + if (!error)
> + list_add_tail_rcu(&meminfo->list, &meminfo_head);
> + spin_unlock(&meminfo_lock);

If you have a lock, why are you needing rcu?



> + if (error)
> + kfree(meminfo);
> +out:
> +
> + return error;
> +}
> +EXPORT_SYMBOL(register_meminfo_extra);

EXPORT_SYMBOL_GPL()? I have to ask :)

thanks,

greg k-h

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