Documentation/admin-guide/kernel-parameters.txt | 5 ++++ mm/mempool.c | 32 ++++++++++++++++++------- 2 files changed, 28 insertions(+), 9 deletions(-)
From: Li RongQing <lirongqing@baidu.com>
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) <vbabka@kernel.org>
Signed-off-by: Li RongQing <lirongqing@baidu.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Harry Yoo <harry@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Hao Li <hao.li@linux.dev>
Cc: Christoph Lameter <cl@gentwo.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Usama Arif <usama.arif@linux.dev>
---
Diff with v1:
Rewrite commit message, change early_param to __setup
Documentation/admin-guide/kernel-parameters.txt | 5 ++++
mm/mempool.c | 32 ++++++++++++++++++-------
2 files changed, 28 insertions(+), 9 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..71e4b54 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)
{
@@ -73,6 +89,9 @@ static void __check_element(struct mempool *pool, void *element, size_t size)
static void check_element(struct mempool *pool, void *element)
{
+ if (!static_branch_unlikely(&mempool_debug_enabled))
+ return;
+
/* Skip checking: KASAN might save its metadata in the element. */
if (kasan_enabled())
return;
@@ -112,6 +131,9 @@ static void __poison_element(void *element, size_t size)
static void poison_element(struct mempool *pool, void *element)
{
+ if (!static_branch_unlikely(&mempool_debug_enabled))
+ return;
+
/* Skip poisoning: KASAN might save its metadata in the element. */
if (kasan_enabled())
return;
@@ -140,14 +162,6 @@ 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)
--
2.9.4On 6/2/26 08:21, lirongqing wrote:
> From: Li RongQing <lirongqing@baidu.com>
>
> 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) <vbabka@kernel.org>
> Signed-off-by: Li RongQing <lirongqing@baidu.com>
> Cc: Vlastimil Babka <vbabka@kernel.org>
> Cc: Harry Yoo <harry@kernel.org>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Hao Li <hao.li@linux.dev>
> Cc: Christoph Lameter <cl@gentwo.org>
> Cc: David Rientjes <rientjes@google.com>
> Cc: Roman Gushchin <roman.gushchin@linux.dev>
> Cc: Matthew Wilcox <willy@infradead.org>
> Cc: Usama Arif <usama.arif@linux.dev>
> ---
> Diff with v1:
> Rewrite commit message, change early_param to __setup
>
> Documentation/admin-guide/kernel-parameters.txt | 5 ++++
> mm/mempool.c | 32 ++++++++++++++++++-------
> 2 files changed, 28 insertions(+), 9 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..71e4b54 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)
> {
> @@ -73,6 +89,9 @@ static void __check_element(struct mempool *pool, void *element, size_t size)
>
> static void check_element(struct mempool *pool, void *element)
> {
> + if (!static_branch_unlikely(&mempool_debug_enabled))
> + return;
With static keys it's better to have the check in the caller of
check_element so we skip over that call if it's disabled, and not do a call
that immediately returns. Since there's a single caller, there's no need for
an extra inline wrapper.
> +
> /* Skip checking: KASAN might save its metadata in the element. */
> if (kasan_enabled())
> return;
> @@ -112,6 +131,9 @@ static void __poison_element(void *element, size_t size)
>
> static void poison_element(struct mempool *pool, void *element)
> {
> + if (!static_branch_unlikely(&mempool_debug_enabled))
> + return;
Ditto.
> +
> /* Skip poisoning: KASAN might save its metadata in the element. */
> if (kasan_enabled())
> return;
> @@ -140,14 +162,6 @@ 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)
> On 6/2/26 08:21, lirongqing wrote:
> > From: Li RongQing <lirongqing@baidu.com>
> >
> > 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) <vbabka@kernel.org>
> > Signed-off-by: Li RongQing <lirongqing@baidu.com>
> > Cc: Vlastimil Babka <vbabka@kernel.org>
> > Cc: Harry Yoo <harry@kernel.org>
> > Cc: Andrew Morton <akpm@linux-foundation.org>
> > Cc: Hao Li <hao.li@linux.dev>
> > Cc: Christoph Lameter <cl@gentwo.org>
> > Cc: David Rientjes <rientjes@google.com>
> > Cc: Roman Gushchin <roman.gushchin@linux.dev>
> > Cc: Matthew Wilcox <willy@infradead.org>
> > Cc: Usama Arif <usama.arif@linux.dev>
> > ---
> > Diff with v1:
> > Rewrite commit message, change early_param to __setup
> >
> > Documentation/admin-guide/kernel-parameters.txt | 5 ++++
> > mm/mempool.c | 32
> ++++++++++++++++++-------
> > 2 files changed, 28 insertions(+), 9 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..71e4b54
> 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)
> > {
> > @@ -73,6 +89,9 @@ static void __check_element(struct mempool *pool,
> > void *element, size_t size)
> >
> > static void check_element(struct mempool *pool, void *element) {
> > + if (!static_branch_unlikely(&mempool_debug_enabled))
> > + return;
>
> With static keys it's better to have the check in the caller of check_element so
> we skip over that call if it's disabled, and not do a call that immediately
> returns. Since there's a single caller, there's no need for an extra inline
> wrapper.
>
Ok, I will change it in next version
Thanks
[Li,Rongqing]
> > +
> > /* Skip checking: KASAN might save its metadata in the element. */
> > if (kasan_enabled())
> > return;
> > @@ -112,6 +131,9 @@ static void __poison_element(void *element, size_t
> > size)
> >
> > static void poison_element(struct mempool *pool, void *element) {
> > + if (!static_branch_unlikely(&mempool_debug_enabled))
> > + return;
>
> Ditto.
>
> > +
> > /* Skip poisoning: KASAN might save its metadata in the element. */
> > if (kasan_enabled())
> > return;
> > @@ -140,14 +162,6 @@ 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)
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