Re: [PATCH v3 bpf-next 05/11] resolve_btfids: Tag the functions that return errors

["Alexei Starovoitov" <alexei.starovoitov@gmail.com>]

On Sat, Nov 14, 2026 at 11:37 AM David Windsor <dwindsor@gmail.com> wrote:
> Do we also need -EBUSY here as an exception? crypto_enqueue_request
> uses it to mean the request was queued on the backlog (not that it
> failed)

Good point. -EBUSY is not a failure there, -ENOSPC is.
A prog that returns -EBUSY skips the list_add_tail().
crypto_wait_req() then waits for a completion that never comes.

In most other functions -EBUSY is a plain failure, so means_failure()
can't drop it for all.
ccp_enqueue_cmd() and qat_alg_send_message_maybacklog() have such
a backlog too. All three also return -EINPROGRESS.
So drop -EBUSY only if the function returns -EINPROGRESS too.
crypto_enqueue_request() stays a target with -ENOSPC.

Here is proposed follow up... other ideas?

diff --git a/tools/bpf/resolve_btfids/fmodret.c b/tools/bpf/resolve_btfids/fmodret.c
index 0751519..e1afdb6 100644
--- a/tools/bpf/resolve_btfids/fmodret.c
+++ b/tools/bpf/resolve_btfids/fmodret.c
@@ -61,9 +61,15 @@ static bool fits_trampoline(const struct btf *btf, const struct btf_type *func)
  * -EAGAIN, -EMSGSIZE and -EINPROGRESS tell the caller to retry, to go on or to
  * wait, not that the function failed. Their numbers are those of the kernel, in
  * asm-generic/errno.h. The errno.h of the build host can have other numbers.
+ *
+ * ASYNC: the function returns -EINPROGRESS too. Then its -EBUSY is no failure
+ * either. In the crypto API it says that the request is queued on the backlog:
+ * crypto_wait_req() waits after both.
  */
-static bool means_failure(int error)
+static bool means_failure(int error, bool async)
 {
+	if (async && error == -16)
+		return false;
 	return error > -512 && error != -11 && error != -90 && error != -115;
 }
 
@@ -82,13 +88,16 @@ static int cmp_error(const void *va, const void *vb)
  */
 static bool format_tag(char *tag, const int64_t *values, size_t nr, __u32 size)
 {
+	bool async = false;
 	size_t i, n = 0;
 	int errors[nr];
 
+	for (i = 0; i < nr; i++)
+		async |= (int)values[i] == -115;
 	for (i = 0; i < nr; i++) {
 		int error = values[i];
 
-		if ((size == 4 || values[i] == error) && means_failure(error))
+		if ((size == 4 || values[i] == error) && means_failure(error, async))
 			errors[n++] = error;
 	}
 	qsort(errors, n, sizeof(*errors), cmp_error);
diff --git a/tools/testing/selftests/bpf/prog_tests/fmodret_retval.c b/tools/testing/selftests/bpf/prog_tests/fmodret_retval.c
index 1db55d8..281c619 100644
--- a/tools/testing/selftests/bpf/prog_tests/fmodret_retval.c
+++ b/tools/testing/selftests/bpf/prog_tests/fmodret_retval.c
@@ -17,6 +17,7 @@ static const struct {
 	{ "bpf_testmod_retval_minus_one",	"" },
 	{ "bpf_testmod_retval_eperm",		"-2,-1" },
 	{ "bpf_testmod_retval_denied",		"-13" },
+	{ "bpf_testmod_retval_backlog",		"-28" },
 	{ "bpf_testmod_retval_effect",		"-22" },
 	{ "bpf_testmod_retval_effect_late",	"-22" },
 	{ "bpf_testmod_retval_effect_two_regs",	"-22" },
diff --git a/tools/testing/selftests/bpf/test_kmods/bpf_testmod_retval.c b/tools/testing/selftests/bpf/test_kmods/bpf_testmod_retval.c
index c6263d7..85722e4 100644
--- a/tools/testing/selftests/bpf/test_kmods/bpf_testmod_retval.c
+++ b/tools/testing/selftests/bpf/test_kmods/bpf_testmod_retval.c
@@ -51,6 +51,14 @@ static __used noinline int bpf_testmod_retval_denied(int a, int b, int c, int d)
 	return d ? -ERESTARTSYS : -EIOCBQUEUED;
 }
 
+/* As crypto_enqueue_request(): next to -EINPROGRESS, -EBUSY is "queued on the backlog" */
+static __used noinline int bpf_testmod_retval_backlog(int free, int may_backlog)
+{
+	if (free)
+		return -EINPROGRESS;
+	return may_backlog ? -EBUSY : -ENOSPC;
+}
+
 /* A caller which gets -EBUSY relies on the unlock */
 static __used noinline int bpf_testmod_retval_effect(struct mutex *lock, int value)
 {