On Thu, Apr 23, 2015 at 5:00 AM, Andrew Morton
<akpm@xxxxxxxxxxxxxxxxxxxx> wrote:
> On Wed, 22 Apr 2015 16:33:38 +0800 Gavin Guo <gavin.guo@xxxxxxxxxxxxx> wrote:
>
>> The slub_debug=PU,kmalloc-xx cannot work because in the
>> create_kmalloc_caches() the s->name is created after the
>> create_kmalloc_cache() is called. The name is NULL in the
>> create_kmalloc_cache() so the kmem_cache_flags() would not set the
>> slub_debug flags to the s->flags. The fix here set up a kmalloc_names
>> string array for the initialization purpose and delete the dynamic
>> name creation of kmalloc_caches.
>>
>> --- a/mm/slab_common.c
>> +++ b/mm/slab_common.c
>> @@ -793,6 +793,26 @@ void __init create_kmalloc_caches(unsigned long flags)
>> int i;
>>
>> /*
>> + * The kmalloc_names is for temporary usage to make
>> + * slub_debug=,kmalloc-xx option work in the boot time. The
>> + * kmalloc_index() support to 2^26=64MB. So, the final entry of the
>> + * table is kmalloc-67108864.
>> + */
>> + static const char *kmalloc_names[] = {
>> + "0", "kmalloc-96", "kmalloc-192",
>> + "kmalloc-8", "kmalloc-16", "kmalloc-32",
>> + "kmalloc-64", "kmalloc-128", "kmalloc-256",
>> + "kmalloc-512", "kmalloc-1024", "kmalloc-2048",
>> + "kmalloc-4196", "kmalloc-8192", "kmalloc-16384",
>> + "kmalloc-32768", "kmalloc-65536",
>> + "kmalloc-131072", "kmalloc-262144",
>> + "kmalloc-524288", "kmalloc-1048576",
>> + "kmalloc-2097152", "kmalloc-4194304",
>> + "kmalloc-8388608", "kmalloc-16777216",
>> + "kmalloc-33554432", "kmalloc-67108864"
>> + };
>> +
>> + /*
>> * Patch up the size_index table if we have strange large alignment
>> * requirements for the kmalloc array. This is only the case for
>> * MIPS it seems. The standard arches will not generate any code here.
>> @@ -835,7 +855,8 @@ void __init create_kmalloc_caches(unsigned long flags)
>> }
>> for (i = KMALLOC_SHIFT_LOW; i <= KMALLOC_SHIFT_HIGH; i++) {
>> if (!kmalloc_caches[i]) {
>> - kmalloc_caches[i] = create_kmalloc_cache(NULL,
>> + kmalloc_caches[i] = create_kmalloc_cache(
>> + kmalloc_names[i],
>> 1 << i, flags);
>> }
>
> You could do something like
>
> kmalloc_caches[i] = create_kmalloc_cache(
> kmalloc_names[i],
> kstrtoul(kmalloc_names[i] + 8),
> flags);
>
> here, and remove those weird "96" and "192" cases.
Thanks for your reply. I'm not sure if I am following your idea. Would you
mean to simply replace the string like:
kmalloc_caches[1] = create_kmalloc_cache(
kmalloc_names[1], 96, flags);
as follows:
kmalloc_caches[1] = create_kmalloc_cache(
kmalloc_names[1],
kstrtoul(kmalloc_names[i] + 8),
flags);
or if you like to merge the last 2 if conditions for 96 and 192 cases to
the first if condition check:
if (!kmalloc_caches[i]) {
kmalloc_caches[i] = create_kmalloc_cache(NULL,
1 << i, flags);
}
>
> Or if that's considered too messy, make it
>
> static const struct {
> const char *name;
> unsigned size;
> } kmalloc_cache_info[] = {
> { NULL, 0 },
> { "kmalloc-96", 96 },
> ...
> };
>
> but I'm thinking the kstrtoul() trick will be OK.
>
>> - for (i = 0; i <= KMALLOC_SHIFT_HIGH; i++) {
>> - struct kmem_cache *s = kmalloc_caches[i];
>> - char *n;
>> -
>> - if (s) {
>> - n = kasprintf(GFP_NOWAIT, "kmalloc-%d", kmalloc_size(i));
>> -
>> - BUG_ON(!n);
>> - s->name = n;
>> - }
>> - }
>> -
>
> slab_kmem_cache_release() still does kfree_const(s->name). It will
> crash?
>
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