Re: [RFC v8 01/10] mm/damon/debugfs: Allow users to set initial monitoring target regions

Marco Elver
2020-08-31T18:08:59Z

On Mon, Aug 31, 2020 at 12:47PM +0200, SeongJae Park wrote:
[...]
> diff --git a/mm/damon.c b/mm/damon.c
> index 7e3c8c82a010..9815d22fc4de 100644
> --- a/mm/damon.c
> +++ b/mm/damon.c
> @@ -2001,6 +2001,147 @@ static ssize_t debugfs_record_write(struct file *file,
> return ret;
> }
>
> +static ssize_t sprint_init_regions(struct damon_ctx *c, char *buf, ssize_t len)
> +{
> + struct damon_target *t;
> + struct damon_region *r;
> + int written = 0;
> + int rc;
> +
> + damon_for_each_target(t, c) {
> + damon_for_each_region(r, t) {
> + rc = snprintf(&buf[written], len - written,
> + "%lu %lu %lu\n",
> + t->id, r->ar.start, r->ar.end);

This most likely will not work as intended, because snprintf() returns
"[...] the number of characters which would be generated for the given
input, excluding the trailing null [...]". Would scnprintf() -- which
returns "[...] the number of characters written into @buf not including
the trailing '\0' [...]" -- do what you intended?

> + if (!rc)
> + return -ENOMEM;
> + written += rc;
> + }
> + }
> + return written;
> +} …