[PATCH v2] mm/slab_common: Support the slub_debug boot option on specific object size

[PATCH v2] mm/slab_common: Support the slub_debug boot option on specific object size

[Gavin Guo]

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.

v1->v2
 - Adopted suggestion from Christoph to delete the dynamic name creation
   for kmalloc_caches.

Signed-off-by: Gavin Guo <gavin.guo@canonical.com>
---
 mm/slab_common.c | 41 ++++++++++++++++++++++++++---------------
 1 file changed, 26 insertions(+), 15 deletions(-)

diff --git a/mm/slab_common.c b/mm/slab_common.c
index 999bb34..61fbc4e 100644
--- 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);
 		}
 
@@ -845,27 +866,17 @@ void __init create_kmalloc_caches(unsigned long flags)
 		 * earlier power of two caches
 		 */
 		if (KMALLOC_MIN_SIZE <= 32 && !kmalloc_caches[1] && i == 6)
-			kmalloc_caches[1] = create_kmalloc_cache(NULL, 96, flags);
+			kmalloc_caches[1] = create_kmalloc_cache(
+						kmalloc_names[1], 96, flags);
 
 		if (KMALLOC_MIN_SIZE <= 64 && !kmalloc_caches[2] && i == 7)
-			kmalloc_caches[2] = create_kmalloc_cache(NULL, 192, flags);
+			kmalloc_caches[2] = create_kmalloc_cache(
+						 kmalloc_names[2], 192, flags);
 	}
 
 	/* Kmalloc array is now usable */
 	slab_state = UP;
 
-	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;
-		}
-	}
-
 #ifdef CONFIG_ZONE_DMA
 	for (i = 0; i <= KMALLOC_SHIFT_HIGH; i++) {
 		struct kmem_cache *s = kmalloc_caches[i];
-- 
2.0.0

Re: [PATCH v2] mm/slab_common: Support the slub_debug boot option on specific object size

[Christoph Lameter]

On Wed, 22 Apr 2015, Gavin Guo 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.

Acked-by: Christoph Lameter <cl@linux.com>

Re: [PATCH v2] mm/slab_common: Support the slub_debug boot option on specific object size

[Andrew Morton]

On Wed, 22 Apr 2015 16:33:38 +0800 Gavin Guo <gavin.guo@canonical.com> 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.

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?

Re: [PATCH v2] mm/slab_common: Support the slub_debug boot option on specific object size

[Andrew Morton]

On Wed, 22 Apr 2015 14:00:39 -0700 Andrew Morton <akpm@linux-foundation.org> wrote:

> slab_kmem_cache_release() still does kfree_const(s->name).  It will
> crash?

er, ignore this bit..

Re: [PATCH v2] mm/slab_common: Support the slub_debug boot option on specific object size

[Gavin Guo]

On Thu, Apr 23, 2015 at 5:00 AM, Andrew Morton
<akpm@linux-foundation.org> wrote:
> On Wed, 22 Apr 2015 16:33:38 +0800 Gavin Guo <gavin.guo@canonical.com> 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?
>

Re: [PATCH v2] mm/slab_common: Support the slub_debug boot option on specific object size

[Andrew Morton]

On Thu, 23 Apr 2015 11:10:40 +0800 Gavin Guo <gavin.guo@canonical.com> wrote:

> >>       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);
>                 }

The latter - initialize all the caches in a single loop.

Re: [PATCH v2] mm/slab_common: Support the slub_debug boot option on specific object size

[Rasmus Villemoes]

On Wed, Apr 22 2015, Gavin Guo <gavin.guo@canonical.com> wrote:

>  	/*
> +	 * 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[] = {

The array itself could be const, but more importantly it should be
marked __initconst so that the 27*sizeof(char*) bytes can be released after init.

> +		"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-4096"

> +		"kmalloc-32768",	"kmalloc-65536",
> +		"kmalloc-131072",	"kmalloc-262144",
> +		"kmalloc-524288",	"kmalloc-1048576",
> +		"kmalloc-2097152",	"kmalloc-4194304",
> +		"kmalloc-8388608",	"kmalloc-16777216",
> +		"kmalloc-33554432",	"kmalloc-67108864"
> +	};

On Wed, Apr 22 2015, Andrew Morton <akpm@linux-foundation.org> wrote:

> 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.

Eww. At least spell 8 as strlen("kmalloc-").

> 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 },
> 		...
> 	};

I'd vote for this color for the bikeshed :-)

Rasmus

Re: [PATCH v2] mm/slab_common: Support the slub_debug boot option on specific object size

[Gavin Guo]

Hi Rasmus,

On Thu, Apr 23, 2015 at 5:55 PM, Rasmus Villemoes
<linux@rasmusvillemoes.dk> wrote:
> On Wed, Apr 22 2015, Gavin Guo <gavin.guo@canonical.com> wrote:
>
>>       /*
>> +      * 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[] = {
>
> The array itself could be const, but more importantly it should be
> marked __initconst so that the 27*sizeof(char*) bytes can be released after init.
>
>> +             "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-4096"

Good catch!!

>
>> +             "kmalloc-32768",        "kmalloc-65536",
>> +             "kmalloc-131072",       "kmalloc-262144",
>> +             "kmalloc-524288",       "kmalloc-1048576",
>> +             "kmalloc-2097152",      "kmalloc-4194304",
>> +             "kmalloc-8388608",      "kmalloc-16777216",
>> +             "kmalloc-33554432",     "kmalloc-67108864"
>> +     };
>
> On Wed, Apr 22 2015, Andrew Morton <akpm@linux-foundation.org> wrote:
>
>> 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.
>
> Eww. At least spell 8 as strlen("kmalloc-").
>
>> 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 },
>>               ...
>>       };
>
> I'd vote for this color for the bikeshed :-)
>
> Rasmus

Thanks for the review! I'll come out another version soon.