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@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? > + if (error) > + kfree(meminfo); > +out: > + > + return error; > +} > +EXPORT_SYMBOL(register_meminfo_extra); EXPORT_SYMBOL_GPL()? I have to ask :) thanks, greg k-h