* [PATCH] trace: allocate fields with elt struct
@ 2026-05-20 22:31 Rosen Penev
2026-05-21 4:48 ` Masami Hiramatsu
2026-05-21 4:49 ` [PATCH] tracing: Do not call map->ops->elt_free() if elt_alloc() is not succeeded Masami Hiramatsu (Google)
0 siblings, 2 replies; 3+ messages in thread
From: Rosen Penev @ 2026-05-20 22:31 UTC (permalink / raw)
To: linux-trace-kernel
Cc: Steven Rostedt, Masami Hiramatsu, Mathieu Desnoyers,
open list:TRACING
Use a flexible array member to embed the fields array in the
tracing_map_elt allocation, reducing the number of allocations
per element.
Since the fields are now embedded in the struct, taking the address
of a field through a const-qualified elt pointer yields a
const-qualified pointer. Rather than adding casts, switch the
comparison functions to take const void * parameters. These are
all read-only operations.
Assisted-by: OpenCode:BigPickle
Signed-off-by: Rosen Penev <rosenp@gmail.com>
---
kernel/trace/tracing_map.c | 41 ++++++++++++++++----------------------
kernel/trace/tracing_map.h | 8 ++++----
2 files changed, 21 insertions(+), 28 deletions(-)
diff --git a/kernel/trace/tracing_map.c b/kernel/trace/tracing_map.c
index 1404bf752d99..97f7e3cde262 100644
--- a/kernel/trace/tracing_map.c
+++ b/kernel/trace/tracing_map.c
@@ -125,32 +125,32 @@ u64 tracing_map_read_var_once(struct tracing_map_elt *elt, unsigned int i)
return (u64)atomic64_read(&elt->vars[i]);
}
-int tracing_map_cmp_string(void *val_a, void *val_b)
+int tracing_map_cmp_string(const void *val_a, const void *val_b)
{
- char *a = val_a;
- char *b = val_b;
+ const char *a = val_a;
+ const char *b = val_b;
return strcmp(a, b);
}
-int tracing_map_cmp_none(void *val_a, void *val_b)
+int tracing_map_cmp_none(const void *val_a, const void *val_b)
{
return 0;
}
-static int tracing_map_cmp_atomic64(void *val_a, void *val_b)
+static int tracing_map_cmp_atomic64(const void *val_a, const void *val_b)
{
- u64 a = atomic64_read((atomic64_t *)val_a);
- u64 b = atomic64_read((atomic64_t *)val_b);
+ u64 a = atomic64_read((const atomic64_t *)val_a);
+ u64 b = atomic64_read((const atomic64_t *)val_b);
return (a > b) ? 1 : ((a < b) ? -1 : 0);
}
#define DEFINE_TRACING_MAP_CMP_FN(type) \
-static int tracing_map_cmp_##type(void *val_a, void *val_b) \
+static int tracing_map_cmp_##type(const void *val_a, const void *val_b) \
{ \
- type a = (type)(*(u64 *)val_a); \
- type b = (type)(*(u64 *)val_b); \
+ type a = (type)(*(const u64 *)val_a); \
+ type b = (type)(*(const u64 *)val_b); \
\
return (a > b) ? 1 : ((a < b) ? -1 : 0); \
}
@@ -385,7 +385,6 @@ static void tracing_map_elt_free(struct tracing_map_elt *elt)
if (elt->map->ops && elt->map->ops->elt_free)
elt->map->ops->elt_free(elt);
- kfree(elt->fields);
kfree(elt->vars);
kfree(elt->var_set);
kfree(elt->key);
@@ -397,7 +396,7 @@ static struct tracing_map_elt *tracing_map_elt_alloc(struct tracing_map *map)
struct tracing_map_elt *elt;
int err = 0;
- elt = kzalloc_obj(*elt);
+ elt = kzalloc_flex(*elt, fields, map->n_fields);
if (!elt)
return ERR_PTR(-ENOMEM);
@@ -409,12 +408,6 @@ static struct tracing_map_elt *tracing_map_elt_alloc(struct tracing_map *map)
goto free;
}
- elt->fields = kzalloc_objs(*elt->fields, map->n_fields);
- if (!elt->fields) {
- err = -ENOMEM;
- goto free;
- }
-
elt->vars = kzalloc_objs(*elt->vars, map->n_vars);
if (!elt->vars) {
err = -ENOMEM;
@@ -848,10 +841,10 @@ static int cmp_entries_sum(const void *A, const void *B)
{
const struct tracing_map_elt *elt_a, *elt_b;
const struct tracing_map_sort_entry *a, *b;
- struct tracing_map_sort_key *sort_key;
- struct tracing_map_field *field;
+ const struct tracing_map_sort_key *sort_key;
+ const struct tracing_map_field *field;
tracing_map_cmp_fn_t cmp_fn;
- void *val_a, *val_b;
+ const void *val_a, *val_b;
int ret = 0;
a = *(const struct tracing_map_sort_entry **)A;
@@ -879,10 +872,10 @@ static int cmp_entries_key(const void *A, const void *B)
{
const struct tracing_map_elt *elt_a, *elt_b;
const struct tracing_map_sort_entry *a, *b;
- struct tracing_map_sort_key *sort_key;
- struct tracing_map_field *field;
+ const struct tracing_map_sort_key *sort_key;
+ const struct tracing_map_field *field;
tracing_map_cmp_fn_t cmp_fn;
- void *val_a, *val_b;
+ const void *val_a, *val_b;
int ret = 0;
a = *(const struct tracing_map_sort_entry **)A;
diff --git a/kernel/trace/tracing_map.h b/kernel/trace/tracing_map.h
index 18a02959d77b..90a7fde5dd02 100644
--- a/kernel/trace/tracing_map.h
+++ b/kernel/trace/tracing_map.h
@@ -13,7 +13,7 @@
#define TRACING_MAP_VARS_MAX 16
#define TRACING_MAP_SORT_KEYS_MAX 2
-typedef int (*tracing_map_cmp_fn_t) (void *val_a, void *val_b);
+typedef int (*tracing_map_cmp_fn_t) (const void *val_a, const void *val_b);
/*
* This is an overview of the tracing_map data structures and how they
@@ -137,11 +137,11 @@ struct tracing_map_field {
struct tracing_map_elt {
struct tracing_map *map;
- struct tracing_map_field *fields;
atomic64_t *vars;
bool *var_set;
void *key;
void *private_data;
+ struct tracing_map_field fields[];
};
struct tracing_map_entry {
@@ -260,8 +260,8 @@ tracing_map_lookup(struct tracing_map *map, void *key);
extern tracing_map_cmp_fn_t tracing_map_cmp_num(int field_size,
int field_is_signed);
-extern int tracing_map_cmp_string(void *val_a, void *val_b);
-extern int tracing_map_cmp_none(void *val_a, void *val_b);
+extern int tracing_map_cmp_string(const void *val_a, const void *val_b);
+extern int tracing_map_cmp_none(const void *val_a, const void *val_b);
extern void tracing_map_update_sum(struct tracing_map_elt *elt,
unsigned int i, u64 n);
--
2.54.0
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] trace: allocate fields with elt struct
2026-05-20 22:31 [PATCH] trace: allocate fields with elt struct Rosen Penev
@ 2026-05-21 4:48 ` Masami Hiramatsu
2026-05-21 4:49 ` [PATCH] tracing: Do not call map->ops->elt_free() if elt_alloc() is not succeeded Masami Hiramatsu (Google)
1 sibling, 0 replies; 3+ messages in thread
From: Masami Hiramatsu @ 2026-05-21 4:48 UTC (permalink / raw)
To: Rosen Penev
Cc: linux-trace-kernel, Steven Rostedt, Masami Hiramatsu,
Mathieu Desnoyers, open list:TRACING
Hi Rosen,
Please check Sashiko's comment:
https://sashiko.dev/#/patchset/20260520223101.34710-1-rosenp%40gmail.com
One actual bug was found. I'll sent a fix.
Thanks,
On Wed, 20 May 2026 15:31:01 -0700
Rosen Penev <rosenp@gmail.com> wrote:
> Use a flexible array member to embed the fields array in the
> tracing_map_elt allocation, reducing the number of allocations
> per element.
>
> Since the fields are now embedded in the struct, taking the address
> of a field through a const-qualified elt pointer yields a
> const-qualified pointer. Rather than adding casts, switch the
> comparison functions to take const void * parameters. These are
> all read-only operations.
>
> Assisted-by: OpenCode:BigPickle
> Signed-off-by: Rosen Penev <rosenp@gmail.com>
> ---
> kernel/trace/tracing_map.c | 41 ++++++++++++++++----------------------
> kernel/trace/tracing_map.h | 8 ++++----
> 2 files changed, 21 insertions(+), 28 deletions(-)
>
> diff --git a/kernel/trace/tracing_map.c b/kernel/trace/tracing_map.c
> index 1404bf752d99..97f7e3cde262 100644
> --- a/kernel/trace/tracing_map.c
> +++ b/kernel/trace/tracing_map.c
> @@ -125,32 +125,32 @@ u64 tracing_map_read_var_once(struct tracing_map_elt *elt, unsigned int i)
> return (u64)atomic64_read(&elt->vars[i]);
> }
>
> -int tracing_map_cmp_string(void *val_a, void *val_b)
> +int tracing_map_cmp_string(const void *val_a, const void *val_b)
> {
> - char *a = val_a;
> - char *b = val_b;
> + const char *a = val_a;
> + const char *b = val_b;
>
> return strcmp(a, b);
> }
>
> -int tracing_map_cmp_none(void *val_a, void *val_b)
> +int tracing_map_cmp_none(const void *val_a, const void *val_b)
> {
> return 0;
> }
>
> -static int tracing_map_cmp_atomic64(void *val_a, void *val_b)
> +static int tracing_map_cmp_atomic64(const void *val_a, const void *val_b)
> {
> - u64 a = atomic64_read((atomic64_t *)val_a);
> - u64 b = atomic64_read((atomic64_t *)val_b);
> + u64 a = atomic64_read((const atomic64_t *)val_a);
> + u64 b = atomic64_read((const atomic64_t *)val_b);
>
> return (a > b) ? 1 : ((a < b) ? -1 : 0);
> }
>
> #define DEFINE_TRACING_MAP_CMP_FN(type) \
> -static int tracing_map_cmp_##type(void *val_a, void *val_b) \
> +static int tracing_map_cmp_##type(const void *val_a, const void *val_b) \
> { \
> - type a = (type)(*(u64 *)val_a); \
> - type b = (type)(*(u64 *)val_b); \
> + type a = (type)(*(const u64 *)val_a); \
> + type b = (type)(*(const u64 *)val_b); \
> \
> return (a > b) ? 1 : ((a < b) ? -1 : 0); \
> }
> @@ -385,7 +385,6 @@ static void tracing_map_elt_free(struct tracing_map_elt *elt)
>
> if (elt->map->ops && elt->map->ops->elt_free)
> elt->map->ops->elt_free(elt);
> - kfree(elt->fields);
> kfree(elt->vars);
> kfree(elt->var_set);
> kfree(elt->key);
> @@ -397,7 +396,7 @@ static struct tracing_map_elt *tracing_map_elt_alloc(struct tracing_map *map)
> struct tracing_map_elt *elt;
> int err = 0;
>
> - elt = kzalloc_obj(*elt);
> + elt = kzalloc_flex(*elt, fields, map->n_fields);
> if (!elt)
> return ERR_PTR(-ENOMEM);
>
> @@ -409,12 +408,6 @@ static struct tracing_map_elt *tracing_map_elt_alloc(struct tracing_map *map)
> goto free;
> }
>
> - elt->fields = kzalloc_objs(*elt->fields, map->n_fields);
> - if (!elt->fields) {
> - err = -ENOMEM;
> - goto free;
> - }
> -
> elt->vars = kzalloc_objs(*elt->vars, map->n_vars);
> if (!elt->vars) {
> err = -ENOMEM;
> @@ -848,10 +841,10 @@ static int cmp_entries_sum(const void *A, const void *B)
> {
> const struct tracing_map_elt *elt_a, *elt_b;
> const struct tracing_map_sort_entry *a, *b;
> - struct tracing_map_sort_key *sort_key;
> - struct tracing_map_field *field;
> + const struct tracing_map_sort_key *sort_key;
> + const struct tracing_map_field *field;
> tracing_map_cmp_fn_t cmp_fn;
> - void *val_a, *val_b;
> + const void *val_a, *val_b;
> int ret = 0;
>
> a = *(const struct tracing_map_sort_entry **)A;
> @@ -879,10 +872,10 @@ static int cmp_entries_key(const void *A, const void *B)
> {
> const struct tracing_map_elt *elt_a, *elt_b;
> const struct tracing_map_sort_entry *a, *b;
> - struct tracing_map_sort_key *sort_key;
> - struct tracing_map_field *field;
> + const struct tracing_map_sort_key *sort_key;
> + const struct tracing_map_field *field;
> tracing_map_cmp_fn_t cmp_fn;
> - void *val_a, *val_b;
> + const void *val_a, *val_b;
> int ret = 0;
>
> a = *(const struct tracing_map_sort_entry **)A;
> diff --git a/kernel/trace/tracing_map.h b/kernel/trace/tracing_map.h
> index 18a02959d77b..90a7fde5dd02 100644
> --- a/kernel/trace/tracing_map.h
> +++ b/kernel/trace/tracing_map.h
> @@ -13,7 +13,7 @@
> #define TRACING_MAP_VARS_MAX 16
> #define TRACING_MAP_SORT_KEYS_MAX 2
>
> -typedef int (*tracing_map_cmp_fn_t) (void *val_a, void *val_b);
> +typedef int (*tracing_map_cmp_fn_t) (const void *val_a, const void *val_b);
>
> /*
> * This is an overview of the tracing_map data structures and how they
> @@ -137,11 +137,11 @@ struct tracing_map_field {
>
> struct tracing_map_elt {
> struct tracing_map *map;
> - struct tracing_map_field *fields;
> atomic64_t *vars;
> bool *var_set;
> void *key;
> void *private_data;
> + struct tracing_map_field fields[];
> };
>
> struct tracing_map_entry {
> @@ -260,8 +260,8 @@ tracing_map_lookup(struct tracing_map *map, void *key);
>
> extern tracing_map_cmp_fn_t tracing_map_cmp_num(int field_size,
> int field_is_signed);
> -extern int tracing_map_cmp_string(void *val_a, void *val_b);
> -extern int tracing_map_cmp_none(void *val_a, void *val_b);
> +extern int tracing_map_cmp_string(const void *val_a, const void *val_b);
> +extern int tracing_map_cmp_none(const void *val_a, const void *val_b);
>
> extern void tracing_map_update_sum(struct tracing_map_elt *elt,
> unsigned int i, u64 n);
> --
> 2.54.0
>
--
Masami Hiramatsu (Google) <mhiramat@kernel.org>
^ permalink raw reply [flat|nested] 3+ messages in thread
* [PATCH] tracing: Do not call map->ops->elt_free() if elt_alloc() is not succeeded
2026-05-20 22:31 [PATCH] trace: allocate fields with elt struct Rosen Penev
2026-05-21 4:48 ` Masami Hiramatsu
@ 2026-05-21 4:49 ` Masami Hiramatsu (Google)
1 sibling, 0 replies; 3+ messages in thread
From: Masami Hiramatsu (Google) @ 2026-05-21 4:49 UTC (permalink / raw)
To: Steven Rostedt, Tom Zanussi
Cc: linux-trace-kernel, linux-kernel, Masami Hiramatsu,
Mathieu Desnoyers, Rosen Penev
From: Masami Hiramatsu (Google) <mhiramat@kernel.org>
In paths where tracing_map_elt_alloc() failed to allocate objects,
the map->ops->elt_alloc() call was never successful. In this case,
map->ops->elt_free() should not be called.
This bug was found by Sashiko.
Link: https://sashiko.dev/#/patchset/20260520223101.34710-1-rosenp%40gmail.com
Fixes: 2734b629525a ("tracing: Add per-element variable support to tracing_map")
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Cc: stable@vger.kernel.org
---
kernel/trace/tracing_map.c | 17 +++++++++++++----
1 file changed, 13 insertions(+), 4 deletions(-)
diff --git a/kernel/trace/tracing_map.c b/kernel/trace/tracing_map.c
index bf1a507695b6..0dd7927df22a 100644
--- a/kernel/trace/tracing_map.c
+++ b/kernel/trace/tracing_map.c
@@ -386,13 +386,11 @@ static void tracing_map_elt_init_fields(struct tracing_map_elt *elt)
}
}
-static void tracing_map_elt_free(struct tracing_map_elt *elt)
+static void __tracing_map_elt_free(struct tracing_map_elt *elt)
{
if (!elt)
return;
- if (elt->map->ops && elt->map->ops->elt_free)
- elt->map->ops->elt_free(elt);
kfree(elt->fields);
kfree(elt->vars);
kfree(elt->var_set);
@@ -400,6 +398,17 @@ static void tracing_map_elt_free(struct tracing_map_elt *elt)
kfree(elt);
}
+static void tracing_map_elt_free(struct tracing_map_elt *elt)
+{
+ if (!elt)
+ return;
+
+ /* Only objects initialized with alloc_elt() should be passed to free_elt().*/
+ if (elt->map->ops && elt->map->ops->elt_free)
+ elt->map->ops->elt_free(elt);
+ __tracing_map_elt_free(elt);
+}
+
static struct tracing_map_elt *tracing_map_elt_alloc(struct tracing_map *map)
{
struct tracing_map_elt *elt;
@@ -444,7 +453,7 @@ static struct tracing_map_elt *tracing_map_elt_alloc(struct tracing_map *map)
}
return elt;
free:
- tracing_map_elt_free(elt);
+ __tracing_map_elt_free(elt);
return ERR_PTR(err);
}
^ permalink raw reply related [flat|nested] 3+ messages in thread
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2026-05-20 22:31 [PATCH] trace: allocate fields with elt struct Rosen Penev
2026-05-21 4:48 ` Masami Hiramatsu
2026-05-21 4:49 ` [PATCH] tracing: Do not call map->ops->elt_free() if elt_alloc() is not succeeded Masami Hiramatsu (Google)
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