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

[PATCH bpf-next 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>
---
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          | 8 ++++----
 tools/testing/selftests/bpf/progs/wq_failures.c | 4 ++--
 4 files changed, 8 insertions(+), 8 deletions(-)
---
base-commit: fd8db07705c55a995c42b1e71afc42faad675b0b
change-id: 20240705-fix-wq-f069c7fb36c3

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

[PATCH bpf-next 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

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

[Eduard Zingerman]

On Fri, 2024-07-05 at 15:44 +0200, Benjamin Tissoires 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 *.
> 
> 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>
> ---

Reviewed-by: Eduard Zingerman <eddyz87@gmail.com>

[PATCH bpf-next 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>
---
 tools/testing/selftests/bpf/bpf_experimental.h  | 2 +-
 tools/testing/selftests/bpf/progs/wq.c          | 8 ++++----
 tools/testing/selftests/bpf/progs/wq_failures.c | 4 ++--
 3 files changed, 7 insertions(+), 7 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..e5ac0df59b86 100644
--- a/tools/testing/selftests/bpf/progs/wq.c
+++ b/tools/testing/selftests/bpf/progs/wq.c
@@ -53,7 +53,7 @@ __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;
@@ -84,7 +84,7 @@ 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 +114,7 @@ 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);
@@ -122,7 +122,7 @@ 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)
 {
 	bpf_kfunc_call_test_sleepable();
 	ok_sleepable |= (1 << *key);
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 2/2] selftests/bpf: amend for wrong bpf_wq_set_callback_impl signature

[Eduard Zingerman]

On Fri, 2024-07-05 at 15:44 +0200, Benjamin Tissoires wrote:
> 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>
> ---

Would it make sense to update one of the tests, so that it checks the
specific value put in the map?
E.g. extend struct elem:

struct elem {
	int answer_to_the_ultimate_question;
	struct bpf_wq w;
};

And put something in there?

[...]

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

[Alexei Starovoitov]

On Fri, Jul 5, 2024 at 1:54 PM Eduard Zingerman <eddyz87@gmail.com> wrote:
>
> On Fri, 2024-07-05 at 15:44 +0200, Benjamin Tissoires wrote:
> > 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>
> > ---
>
> Would it make sense to update one of the tests, so that it checks the
> specific value put in the map?
> E.g. extend struct elem:
>
> struct elem {
>         int answer_to_the_ultimate_question;
>         struct bpf_wq w;
> };
>
> And put something in there?

+1
let's tweak the selftest.
pw-bot: cr

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

[Benjamin Tissoires]

On Jul 06 2024, Alexei Starovoitov wrote:
> On Fri, Jul 5, 2024 at 1:54 PM Eduard Zingerman <eddyz87@gmail.com> wrote:
> >
> > On Fri, 2024-07-05 at 15:44 +0200, Benjamin Tissoires wrote:
> > > 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>
> > > ---
> >
> > Would it make sense to update one of the tests, so that it checks the
> > specific value put in the map?
> > E.g. extend struct elem:
> >
> > struct elem {
> >         int answer_to_the_ultimate_question;
> >         struct bpf_wq w;
> > };
> >
> > And put something in there?
> 
> +1
> let's tweak the selftest.

OK, v2 it is then :)

Cheers,
Benjamin