From a561e19e76ef1ebf3f9a56977dfe87526b37146c Mon Sep 17 00:00:00 2001 From: Li RongQing Date: Thu, 4 Jun 2026 19:03:18 +0800 Subject: [PATCH] mm/mempool: Untangle CONFIG_SLUB_DEBUG_ON abuse and switch to static key 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. Suggested-by: Vlastimil Babka (SUSE) Signed-off-by: Li RongQing Cc: Vlastimil Babka Cc: Harry Yoo Cc: Andrew Morton Cc: Hao Li Cc: Christoph Lameter Cc: David Rientjes Cc: Roman Gushchin Cc: Matthew Wilcox Cc: Usama Arif Reviewed-by: SeongJae Park Reviewed-by: Harry Yoo (Oracle) Link: https://patch.msgid.link/20260604110318.2089-1-lirongqing@baidu.com Signed-off-by: Vlastimil Babka (SUSE) --- .../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 b5493a7f8f22..ca755fe185e5 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -3977,6 +3977,11 @@ 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: default : 0 diff --git a/mm/mempool.c b/mm/mempool.c index 473a029fa31f..cb74e718b2c6 100644 --- a/mm/mempool.c +++ b/mm/mempool.c @@ -16,11 +16,28 @@ #include #include #include +#include +#include #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; }