Re: 答复: [PATCH v3] mm/mempool: Untangle CONFIG_SLUB_DEBUG_ON abuse and switch to static key

[Vlastimil Babka (SUSE)]

On 6/12/26 12:12, Li,Rongqing wrote:
>> 主题: [PATCH v3] mm/mempool: Untangle CONFIG_SLUB_DEBUG_ON abuse
>> and switch to static key
>> 
>> From: Li RongQing <lirongqing@xxxxxxxxx>
>> 
>> The mempool subsystem historically wrapped its debugging logic inside an
>> merely defines compile-time defaults for SLUB and caused two flaws:
>> 
>> 1. On production kernels where CONFIG_SLUB_DEBUG=y but
>>    CONFIG_SLUB_DEBUG_ON=n, mempool debugging was completely
>> compiled out
>>    at compile time.
>> 2. On kernels with CONFIG_SLUB_DEBUG_ON=y, mempool debugging stayed
>> active
>>    even if a user explicitly disabled slub debugging at boot time.
>> 
>> Clean up this mess by removing the #ifdef and switching to a runtime static
>> key (mempool_debug_enabled), allowing mempool debugging to be toggled
>> cleanly via its own boot parameter.
>> 
> Ping 
> 
> Thanks

Sorry, missed this. Since it's just before merge window and it's not
critical, will queue it after merge window for 7.3. Thanks!

> [Li,Rongqing] 
> 
> 
> 
>> Suggested-by: Vlastimil Babka (SUSE) <vbabka@xxxxxxxxxx>
>> Signed-off-by: Li RongQing <lirongqing@xxxxxxxxx>
>> Cc: Vlastimil Babka <vbabka@xxxxxxxxxx>
>> Cc: Harry Yoo <harry@xxxxxxxxxx>
>> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
>> Cc: Hao Li <hao.li@xxxxxxxxx>
>> Cc: Christoph Lameter <cl@xxxxxxxxxx>
>> Cc: David Rientjes <rientjes@xxxxxxxxxx>
>> Cc: Roman Gushchin <roman.gushchin@xxxxxxxxx>
>> Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
>> Cc: Usama Arif <usama.arif@xxxxxxxxx>
>> ---
>> Diff with v2: Move the check out of check_element/poison_element Diff with
>> v1: Rewrite commit message, change early_param to __setup
>> 
>>  Documentation/admin-guide/kernel-parameters.txt |  5 ++++
>>  mm/mempool.c                                    | 35
>> +++++++++++++++++--------
>>  2 files changed, 29 insertions(+), 11 deletions(-)
>> 
>> diff --git a/Documentation/admin-guide/kernel-parameters.txt
>> b/Documentation/admin-guide/kernel-parameters.txt
>> index 642659b..89b5994 100644
>> --- a/Documentation/admin-guide/kernel-parameters.txt
>> +++ b/Documentation/admin-guide/kernel-parameters.txt
>> @@ -3980,6 +3980,11 @@ Kernel parameters
>>  			Note that even when enabled, there are a few cases where
>>  			the feature is not effective.
>> 
>> +	mempool_debug	[MM]
>> +			Enable mempool debugging. This enables element
>> +			poison checking when freeing elements back to the
>> +			pool. Useful for debugging mempool corruption.
>> +
>>  	memtest=	[KNL,X86,ARM,M68K,PPC,RISCV,EARLY] Enable memtest
>>  			Format: <integer>
>>  			default : 0 <disable>
>> diff --git a/mm/mempool.c b/mm/mempool.c index db23e0e..dabe05c
>> 100644
>> --- a/mm/mempool.c
>> +++ b/mm/mempool.c
>> @@ -16,11 +16,28 @@
>>  #include <linux/export.h>
>>  #include <linux/mempool.h>
>>  #include <linux/writeback.h>
>> +#include <linux/static_key.h>
>> +#include <linux/init.h>
>>  #include "slab.h"
>> 
>>  static DECLARE_FAULT_ATTR(fail_mempool_alloc);
>>  static DECLARE_FAULT_ATTR(fail_mempool_alloc_bulk);
>> 
>> +/*
>> + * Debugging support for mempool using static key.
>> + *
>> + * This allows enabling mempool debug at boot time via:
>> + *   mempool_debug
>> + */
>> +static DEFINE_STATIC_KEY_FALSE(mempool_debug_enabled);
>> +
>> +static int __init mempool_debug_setup(char *str) {
>> +	static_branch_enable(&mempool_debug_enabled);
>> +	return 1;
>> +}
>> +__setup("mempool_debug", mempool_debug_setup);
>> +
>>  static int __init mempool_faul_inject_init(void)  {
>>  	int error;
>> @@ -37,7 +54,6 @@ static int __init mempool_faul_inject_init(void)  }
>> late_initcall(mempool_faul_inject_init);
>> 
>> -#ifdef CONFIG_SLUB_DEBUG_ON
>>  static void poison_error(struct mempool *pool, void *element, size_t size,
>>  			 size_t byte)
>>  {
>> @@ -140,14 +156,6 @@ static void poison_element(struct mempool *pool,
>> void *element)  #endif
>>  	}
>>  }
>> -#else /* CONFIG_SLUB_DEBUG_ON */
>> -static inline void check_element(struct mempool *pool, void *element) -{ -}
>> -static inline void poison_element(struct mempool *pool, void *element) -{ -}
>> -#endif /* CONFIG_SLUB_DEBUG_ON */
>> 
>>  static __always_inline bool kasan_poison_element(struct mempool *pool,
>>  		void *element)
>> @@ -175,7 +183,10 @@ static void kasan_unpoison_element(struct
>> mempool *pool, void *element)  static __always_inline void
>> add_element(struct mempool *pool, void *element)  {
>>  	BUG_ON(pool->min_nr != 0 && pool->curr_nr >= pool->min_nr);
>> -	poison_element(pool, element);
>> +
>> +	if (static_branch_unlikely(&mempool_debug_enabled))
>> +		poison_element(pool, element);
>> +
>>  	if (kasan_poison_element(pool, element))
>>  		pool->elements[pool->curr_nr++] = element;  } @@ -186,7 +197,9
>> @@ static void *remove_element(struct mempool *pool)
>> 
>>  	BUG_ON(pool->curr_nr < 0);
>>  	kasan_unpoison_element(pool, element);
>> -	check_element(pool, element);
>> +
>> +	if (static_branch_unlikely(&mempool_debug_enabled))
>> +		check_element(pool, element);
>>  	return element;
>>  }
>> 
>> --
>> 2.9.4
>