On 2020년 03월 23일 18:53, Greg KH wrote:
> 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()
> ?
OK. Name can be changed.
>
>
>> Signed-off-by: Jaewon Kim <jaewon31.kim@xxxxxxxxxxx>
>> ---
>> 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?
I think _rcu should be removed out of list_for_each_entry_rcu.
But I'm confused about what you meant.
I used rcu_read_lock on __meminfo_extra,
and I think spin_lock is also needed for addition and deletion to handle multiple modifiers.
>
>
>
>> + if (error)
>> + kfree(meminfo);
>> +out:
>> +
>> + return error;
>> +}
>> +EXPORT_SYMBOL(register_meminfo_extra);
> EXPORT_SYMBOL_GPL()? I have to ask :)
I can use EXPORT_SYMBOL_GPL.
>
> thanks,
>
> greg k-h
>
>
Hello
Thank you for your comment.
By the way there was not resolved discussion on v1 patch as I mentioned on cover page.
I'd like to hear your opinion on this /proc/meminfo_extra node.
Do you think this is meaningful or cannot co-exist with other future sysfs based API.
