On Fri, 12 Jan 2018 10:58:11 -0800 Andrei Vagin <avagin@xxxxxxxxxx> wrote:
> seq_put_hex_ll() prints a number in hexadecimal notation and works
> faster than seq_printf().
>
> ...
>
> --- a/fs/seq_file.c
> +++ b/fs/seq_file.c
> @@ -670,6 +670,26 @@ void seq_puts(struct seq_file *m, const char *s)
> }
> EXPORT_SYMBOL(seq_puts);
>
> +static inline void seq_put_delimeter(struct seq_file *m, const char *delimiter)
> +{
> + int len;
> +
> + if (!delimiter || !delimiter[0])
> + return;
> +
> + if (delimiter[1] == 0)
> + return seq_putc(m, delimiter[0]);
> +
> + len = strlen(delimiter);
> + if (m->count + len >= m->size) {
> + seq_set_overflow(m);
> + return;
> + }
> +
> + memcpy(m->buf + m->count, delimiter, len);
> + m->count += len;
> +}
Can we please have a nice comment describing this function's role and
behaviour?
I don't think the `inline' is needed or desirable - gcc can figure that
out, and with three callsites a `noinline' would be more justified!
That `return seq_putc(...)' will generate a warning in some situations
- seq_putc() returns void. Let's split it into 'seq_putc(...);
return;' please.
> +/**
> + * seq_put_hex_ll - put a number in hexadecimal notation
> + * @m: seq_file identifying the buffer to which data should be written
> + * @delimiter: a string which is printed before the number
> + * @v: the number
> + * @width: a minimum field width
> + *
> + * seq_put_hex_ll(m, "", v, 8) is equal to seq_printf(m, "0x08llx", v)
> + *
> + * This routine is very quick when you show lots of numbers.
> + * In usual cases, it will be better to use seq_printf(). It's easier to read.
> + */
> +void seq_put_hex_ll(struct seq_file *m, const char *delimiter,
> + unsigned long long v, int width)
> +{
> + int i, len;
> +
> + seq_put_delimeter(m, delimiter);
> +
> + len = (sizeof(v) * 8 - __builtin_clzll(v) + 3) / 4;
> +
> + if (unlikely(len == 0))
> + len = 1;
> +
> + if (len < width)
> + len = width;
> +
> + if (m->count + len > m->size)
> + goto overflow;
> +
> + for (i = len - 1; i >= 0; i--) {
> + m->buf[m->count + i] = hex_asc[0xf & v];
> + v = v >> 4;
> + }
> + m->count += len;
> + return;
> +overflow:
> + seq_set_overflow(m);
> +}
I don't think we need the goto. Just do "seq_set_overflow(m); return;".
