slub: extend slub debug to handle multiple slabs

slub_debug=<Debug-Options>

	Enable options for all slabs

slub_debug=<Debug-Options>,<slab name>

	Enable options only for select slabs

slub_debug=<Debug-Options>,<slab name1>,<slab name2>,...

	Enable options only for select slabs (no spaces

	after a comma)

Possible debug options are::

	slub_debug=,dentry

to only enable debugging on the dentry cache.

to only enable debugging on the dentry cache.  You may use an asterisk at the

end of the slab name, in order to cover all slabs with the same prefix.  For

example, here's how you can poison the dentry cache as well as all kmalloc

slabs:

	slub_debug=P,kmalloc-*,dentry

Red zoning and tracking may realign the slab.  We can just apply sanity checks

to the dentry cache with::

__setup("slub_debug", setup_slub_debug);

/*

 * kmem_cache_flags - apply debugging options to the cache

 * @object_size:	the size of an object without meta data

 * @flags:		flags to set

 * @name:		name of the cache

 * @ctor:		constructor function

 *

 * Debug option(s) are applied to @flags. In addition to the debug

 * option(s), if a slab name (or multiple) is specified i.e.

 * slub_debug=<Debug-Options>,<slab name1>,<slab name2> ...

 * then only the select slabs will receive the debug option(s).

 */

slab_flags_t kmem_cache_flags(unsigned int object_size,

	slab_flags_t flags, const char *name,

	void (*ctor)(void *))

{

	/*

	 * Enable debugging if selected on the kernel commandline.

	 */

	if (slub_debug && (!slub_debug_slabs || (name &&

		!strncmp(slub_debug_slabs, name, strlen(slub_debug_slabs)))))

	char *iter;

	size_t len;

	/* If slub_debug = 0, it folds into the if conditional. */

	if (!slub_debug_slabs)

		return flags | slub_debug;

	len = strlen(name);

	iter = slub_debug_slabs;

	while (*iter) {

		char *end, *glob;

		size_t cmplen;

		end = strchr(iter, ',');

		if (!end)

			end = iter + strlen(iter);

		glob = strnchr(iter, end - iter, '*');

		if (glob)

			cmplen = glob - iter;

		else

			cmplen = max_t(size_t, len, (end - iter));

		if (!strncmp(name, iter, cmplen)) {

			flags |= slub_debug;

			break;

		}

		if (!*end)

			break;

		iter = end + 1;

	}

	return flags;

}