[PATCH bpf-next v2 0/2] Small API fix for bpf_wq

[PATCH bpf-next v2 0/2] Small API fix for bpf_wq

[Benjamin Tissoires]

I realized this while having a map containing both a struct bpf_timer and
a struct bpf_wq: the third argument provided to the bpf_wq callback is
not the struct bpf_wq pointer itself, but the pointer to the value in
the map.

Which means that the users need to double cast the provided "value" as
this is not a struct bpf_wq *.

This is a change of API, but there doesn't seem to be much users of bpf_wq
right now, so we should be able to go with this right now.

Signed-off-by: Benjamin Tissoires <bentiss@kernel.org>
---
Changes in v2:
- amended the selftests to retrieve something from the third argument of
  the callback
- Link to v1: https://lore.kernel.org/r/20240705-fix-wq-v1-0-91b4d82cd825@kernel.org

---
Benjamin Tissoires (2):
      bpf: helpers: fix bpf_wq_set_callback_impl signature
      selftests/bpf: amend for wrong bpf_wq_set_callback_impl signature

 kernel/bpf/helpers.c                            |  2 +-
 tools/testing/selftests/bpf/bpf_experimental.h  |  2 +-
 tools/testing/selftests/bpf/progs/wq.c          | 19 ++++++++++++++-----
 tools/testing/selftests/bpf/progs/wq_failures.c |  4 ++--
 4 files changed, 18 insertions(+), 9 deletions(-)
---
base-commit: fd8db07705c55a995c42b1e71afc42faad675b0b
change-id: 20240705-fix-wq-f069c7fb36c3

Best regards,
-- 
Benjamin Tissoires <bentiss@kernel.org>

[PATCH bpf-next v2 1/2] bpf: helpers: fix bpf_wq_set_callback_impl signature

[Benjamin Tissoires]

I realized this while having a map containing both a struct bpf_timer and
a struct bpf_wq: the third argument provided to the bpf_wq callback is
not the struct bpf_wq pointer itself, but the pointer to the value in
the map.

Which means that the users need to double cast the provided "value" as
this is not a struct bpf_wq *.

This is a change of API, but there doesn't seem to be much users of bpf_wq
right now, so we should be able to go with this right now.

Fixes: 81f1d7a583fa ("bpf: wq: add bpf_wq_set_callback_impl")
Signed-off-by: Benjamin Tissoires <bentiss@kernel.org>
---
 kernel/bpf/helpers.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 229396172026..5241ba671c5a 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -2734,7 +2734,7 @@ __bpf_kfunc int bpf_wq_start(struct bpf_wq *wq, unsigned int flags)
 }
 
 __bpf_kfunc int bpf_wq_set_callback_impl(struct bpf_wq *wq,
-					 int (callback_fn)(void *map, int *key, struct bpf_wq *wq),
+					 int (callback_fn)(void *map, int *key, void *value),
 					 unsigned int flags,
 					 void *aux__ign)
 {

-- 
2.44.0

[PATCH bpf-next v2 2/2] selftests/bpf: amend for wrong bpf_wq_set_callback_impl signature

[Benjamin Tissoires]

See the previous patch: the API was wrong, we were provided the pointer
to the value, not the actual struct bpf_wq *.

Signed-off-by: Benjamin Tissoires <bentiss@kernel.org>

---

changes in v2:
- amended to retrieve something from the third argument of the callback
---
 tools/testing/selftests/bpf/bpf_experimental.h  |  2 +-
 tools/testing/selftests/bpf/progs/wq.c          | 19 ++++++++++++++-----
 tools/testing/selftests/bpf/progs/wq_failures.c |  4 ++--
 3 files changed, 17 insertions(+), 8 deletions(-)

diff --git a/tools/testing/selftests/bpf/bpf_experimental.h b/tools/testing/selftests/bpf/bpf_experimental.h
index eede6fc2ccb4..828556cdc2f0 100644
--- a/tools/testing/selftests/bpf/bpf_experimental.h
+++ b/tools/testing/selftests/bpf/bpf_experimental.h
@@ -552,7 +552,7 @@ extern void bpf_iter_css_destroy(struct bpf_iter_css *it) __weak __ksym;
 extern int bpf_wq_init(struct bpf_wq *wq, void *p__map, unsigned int flags) __weak __ksym;
 extern int bpf_wq_start(struct bpf_wq *wq, unsigned int flags) __weak __ksym;
 extern int bpf_wq_set_callback_impl(struct bpf_wq *wq,
-		int (callback_fn)(void *map, int *key, struct bpf_wq *wq),
+		int (callback_fn)(void *map, int *key, void *value),
 		unsigned int flags__k, void *aux__ign) __ksym;
 #define bpf_wq_set_callback(timer, cb, flags) \
 	bpf_wq_set_callback_impl(timer, cb, flags, NULL)
diff --git a/tools/testing/selftests/bpf/progs/wq.c b/tools/testing/selftests/bpf/progs/wq.c
index 49e712acbf60..f8d3ae0c29ae 100644
--- a/tools/testing/selftests/bpf/progs/wq.c
+++ b/tools/testing/selftests/bpf/progs/wq.c
@@ -32,6 +32,7 @@ struct {
 } hmap_malloc SEC(".maps");
 
 struct elem {
+	int ok_offset;
 	struct bpf_wq w;
 };
 
@@ -53,7 +54,7 @@ __u32 ok;
 __u32 ok_sleepable;
 
 static int test_elem_callback(void *map, int *key,
-		int (callback_fn)(void *map, int *key, struct bpf_wq *wq))
+		int (callback_fn)(void *map, int *key, void *value))
 {
 	struct elem init = {}, *val;
 	struct bpf_wq *wq;
@@ -70,6 +71,8 @@ static int test_elem_callback(void *map, int *key,
 	if (!val)
 		return -2;
 
+	val->ok_offset = *key;
+
 	wq = &val->w;
 	if (bpf_wq_init(wq, map, 0) != 0)
 		return -3;
@@ -84,7 +87,7 @@ static int test_elem_callback(void *map, int *key,
 }
 
 static int test_hmap_elem_callback(void *map, int *key,
-		int (callback_fn)(void *map, int *key, struct bpf_wq *wq))
+		int (callback_fn)(void *map, int *key, void *value))
 {
 	struct hmap_elem init = {}, *val;
 	struct bpf_wq *wq;
@@ -114,7 +117,7 @@ static int test_hmap_elem_callback(void *map, int *key,
 }
 
 /* callback for non sleepable workqueue */
-static int wq_callback(void *map, int *key, struct bpf_wq *work)
+static int wq_callback(void *map, int *key, void *value)
 {
 	bpf_kfunc_common_test();
 	ok |= (1 << *key);
@@ -122,10 +125,16 @@ static int wq_callback(void *map, int *key, struct bpf_wq *work)
 }
 
 /* callback for sleepable workqueue */
-static int wq_cb_sleepable(void *map, int *key, struct bpf_wq *work)
+static int wq_cb_sleepable(void *map, int *key, void *value)
 {
+	struct elem *data = (struct elem *)value;
+	int offset = data->ok_offset;
+
+	if (*key != offset)
+		return 0;
+
 	bpf_kfunc_call_test_sleepable();
-	ok_sleepable |= (1 << *key);
+	ok_sleepable |= (1 << offset);
 	return 0;
 }
 
diff --git a/tools/testing/selftests/bpf/progs/wq_failures.c b/tools/testing/selftests/bpf/progs/wq_failures.c
index 4cbdb425f223..25b51a72fe0f 100644
--- a/tools/testing/selftests/bpf/progs/wq_failures.c
+++ b/tools/testing/selftests/bpf/progs/wq_failures.c
@@ -28,14 +28,14 @@ struct {
 } lru SEC(".maps");
 
 /* callback for non sleepable workqueue */
-static int wq_callback(void *map, int *key, struct bpf_wq *work)
+static int wq_callback(void *map, int *key, void *value)
 {
 	bpf_kfunc_common_test();
 	return 0;
 }
 
 /* callback for sleepable workqueue */
-static int wq_cb_sleepable(void *map, int *key, struct bpf_wq *work)
+static int wq_cb_sleepable(void *map, int *key, void *value)
 {
 	bpf_kfunc_call_test_sleepable();
 	return 0;

-- 
2.44.0

Re: [PATCH bpf-next v2 0/2] Small API fix for bpf_wq

[patchwork-bot+netdevbpf]

Hello:

This series was applied to bpf/bpf-next.git (master)
by Alexei Starovoitov <ast@kernel.org>:

On Mon, 08 Jul 2024 11:52:56 +0200 you wrote:
> I realized this while having a map containing both a struct bpf_timer and
> a struct bpf_wq: the third argument provided to the bpf_wq callback is
> not the struct bpf_wq pointer itself, but the pointer to the value in
> the map.
> 
> Which means that the users need to double cast the provided "value" as
> this is not a struct bpf_wq *.
> 
> [...]

Here is the summary with links:
  - [bpf-next,v2,1/2] bpf: helpers: fix bpf_wq_set_callback_impl signature
    https://git.kernel.org/bpf/bpf-next/c/f56f4d541eab
  - [bpf-next,v2,2/2] selftests/bpf: amend for wrong bpf_wq_set_callback_impl signature
    https://git.kernel.org/bpf/bpf-next/c/16e86f2e8199

You are awesome, thank you!
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