On Fri 2018-09-21 16:34 -0700, Andrew Morton wrote:
> On Thu, 20 Sep 2018 21:00:16 +0100 Aaron Tomlin <atomlin@xxxxxxxxxx> wrote:
> > --- a/mm/slub.c
> > +++ b/mm/slub.c
> > @@ -1283,9 +1283,37 @@ slab_flags_t kmem_cache_flags(unsigned int object_size,
> > /*
> > * Enable debugging if selected on the kernel commandline.
> > */
>
> The above comment is in a strange place. Can we please move it to
> above the function definition in the usual fashion? And make it
> better, if anything seems to be missing.
OK.
> > - if (slub_debug && (!slub_debug_slabs || (name &&
> > - !strncmp(slub_debug_slabs, name, strlen(slub_debug_slabs)))))
> > - flags |= slub_debug;
> > +
> > + char *end, *n, *glob;
>
> `end' and `glob' could be local to the loop which uses them, which I
> find a bit nicer.
OK.
> `n' is a rotten identifier. Can't we think of something which
> communicates meaning?
OK.
> > + int len = strlen(name);
> > +
> > + /* If slub_debug = 0, it folds into the if conditional. */
> > + if (!slub_debug_slabs)
> > + return flags | slub_debug;
>
> If we take the above return, the call to strlen() was wasted cycles.
> Presumably gcc is smart enough to prevent that, but why risk it.
OK.
> > + n = slub_debug_slabs;
> > + while (*n) {
> > + int cmplen;
> > +
> > + end = strchr(n, ',');
> > + if (!end)
> > + end = n + strlen(n);
> > +
> > + glob = strnchr(n, end - n, '*');
> > + if (glob)
> > + cmplen = glob - n;
> > + else
> > + cmplen = max(len, (int)(end - n));
>
> max_t() exists for this. Or maybe make `len' size_t, but I expect that
> will still warn - that subtraction returns a ptrdiff_t, yes?
I think max_t(size_t, ...) should be appropriate?
I'll address the above and in the next version.
> > +
> > + if (!strncmp(name, n, cmplen)) {
> > + flags |= slub_debug;
> > + break;
> > + }
> > +
> > + if (!*end)
> > + break;
> > + n = end + 1;
> > + }
> The code in this loop hurts my brain a bit. I hope it's correct ;)
It works :)
--
Aaron Tomlin
