On Sun, Nov 01, 2020 at 01:04:35PM -0800, Joe Perches wrote:
> On Sun, 2020-11-01 at 20:48 +0000, Matthew Wilcox wrote:
> > On Sun, Nov 01, 2020 at 12:12:51PM -0800, Joe Perches wrote:
> > > @@ -4024,7 +4024,7 @@ int __init shmem_init(void)
> > >
> > >
> > > #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && defined(CONFIG_SYSFS)
> > > static ssize_t shmem_enabled_show(struct kobject *kobj,
> > > - struct kobj_attribute *attr, char *buf)
> > > + struct kobj_attribute *attr, char *buf)
> > > {
> > > static const int values[] = {
> > > SHMEM_HUGE_ALWAYS,
> >
> > Why?
>
> why what?
Why did you change this?
> > > @@ -4034,16 +4034,19 @@ static ssize_t shmem_enabled_show(struct kobject *kobj,
> > > SHMEM_HUGE_DENY,
> > > SHMEM_HUGE_FORCE,
> > > };
> > > - int i, count;
> > > -
> > > - for (i = 0, count = 0; i < ARRAY_SIZE(values); i++) {
> > > - const char *fmt = shmem_huge == values[i] ? "[%s] " : "%s ";
> > > + int len = 0;
> > > + int i;
> >
> > Better:
> > int i, len = 0;
>
> I generally disagree as I think it better to have each declaration on an
> individual line.
You're wrong.
> > > - count += sprintf(buf + count, fmt,
> > > - shmem_format_huge(values[i]));
> > > + for (i = 0; i < ARRAY_SIZE(values); i++) {
> > > + len += sysfs_emit_at(buf, len,
> > > + shmem_huge == values[i] ? "%s[%s]" : "%s%s",
> > > + i ? " " : "",
> > > + shmem_format_huge(values[i]));
> >
> > This is ... complicated. I thought the point of doing all the sysfs_emit
> > stuff was to simplify things.
>
> The removal of fmt allows the format and argument to be __printf verified.
> Indirected formats do not generally allow that.
>
> And using sysfs_emit is not really intended to simplify output code, it's
> used to make sure there isn't a overflow of the PAGE_SIZE output buf when
> using sprintf/snprintf.
Look, this isn't performance sensitive code. Just do something simple.
if (shmem_huge == values[i])
buf += sysfs_emit(buf, "[%s]",
shmem_format_huge(values[i]));
else
buf += sysfs_emit(buf, "%s",
shmem_format_huge(values[i]));
if (i == ARRAY_SIZE(values) - 1)
buf += sysfs_emit(buf, "\n");
else
buf += sysfs_emit(buf, " ");
Shame there's no sysfs_emitc, but there you go.
