On Wed, 2013-12-11 at 08:05 +0000, Al Viro wrote:
> On Wed, Dec 11, 2013 at 07:55:26AM +0000, Al Viro wrote:
>
> > This sucker should return 0. Insufficiently large buffer will be handled
> > by caller, TYVM, if you give that caller a chance to do so. Returning 1
> > from ->show() is a bug in almost all cases, and definitely so in this one.
> >
> > Just in case somebody decides that above is worth copying: It Is Not.
> > Original code is buggy, plain and simple. This one trades the older
> > bug ("fail with -EINVAL whenever the buffer is too small") with just as
> > buggy
> > "silently skip an entry entirely whenever the buffer is too small".
> >
> > Don't Do That.
>
> Pardon - Joe has made seq_overflow return -1 instead of true. Correction
> to the above, then - s/This trades.*\./This is just as buggy./
Yeah, I started to use true/false, 0/1, but thought
I needed to match what seq_printf/seq_vprintf does.
> Conclusion is still the same - Don't Do That. Returning -1 on insufficiently
> large buffer is a bug, plain and simple.
int seq_vprintf(struct seq_file *m, const char *f, va_list args)
{
int len;
if (m->count < m->size) {
len = vsnprintf(m->buf + m->count, m->size - m->count, f, args);
if (m->count + len < m->size) {
m->count += len;
return 0;
}
}
seq_set_overflow(m);
return -1;
}
EXPORT_SYMBOL(seq_vprintf);
int seq_printf(struct seq_file *m, const char *f, ...)
{
int ret;
va_list args;
va_start(args, f);
ret = seq_vprintf(m, f, args);
va_end(args);
return ret;
}
EXPORT_SYMBOL(seq_printf);
> And this patch series is completely misguided - it doesn't fix any bugs
> *and* it provides a misleading example for everyone. See the reaction
> right in this thread, proposing to spread the same bug to currently
> working iterators.
Anyway, changing seq_overflow is easy enough
You prefer this?
bool seq_overflow(struct seq_file *seq)
{
return m->count == m->size;
}
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