On Thu, 20 Sep 2018 21:00:16 +0100 Aaron Tomlin <[email protected]> wrote:
> Extend the slub_debug syntax to "slub_debug=<flags>[,<slub>]*", where <slub> > may contain an asterisk at the end. For example, the following would poison > all kmalloc slabs: > > slub_debug=P,kmalloc* > > and the following would apply the default flags to all kmalloc and all block > IO > slabs: > > slub_debug=,bio*,kmalloc* > > Please note that a similar patch was posted by Iliyan Malchev some time ago > but > was never merged: > > https://marc.info/?l=linux-mm&m=131283905330474&w=2 Fair enough, I guess. > --- 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. > - 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. `n' is a rotten identifier. Can't we think of something which communicates meaning? > + 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. > + 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? > + > + 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 ;)
