[PATCH bpf-next] libbpf: fix bail out from 'ringbuf_process_ring()' on error

From: Pedro Tammela <pctammela@gmail.com>
To: unlisted-recipients:; (no To-header on input)
Cc: Pedro Tammela <pctammela@mojatatu.com>,
	Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Andrii Nakryiko <andrii@kernel.org>,
	Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
	Yonghong Song <yhs@fb.com>,
	John Fastabend <john.fastabend@gmail.com>,
	KP Singh <kpsingh@kernel.org>,
	netdev@vger.kernel.org, bpf@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: [PATCH bpf-next] libbpf: fix bail out from 'ringbuf_process_ring()' on error
Date: Thu, 25 Mar 2021 12:01:15 -0300	[thread overview]
Message-ID: <20210325150115.138750-1-pctammela@mojatatu.com> (raw)

The current code bails out with negative and positive returns.
If the callback returns a positive return code, 'ring_buffer__consume()'
and 'ring_buffer__poll()' will return a spurious number of records
consumed, but mostly important will continue the processing loop.

This patch makes positive returns from the callback a no-op.

Signed-off-by: Pedro Tammela <pctammela@mojatatu.com>
---
 tools/lib/bpf/ringbuf.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/lib/bpf/ringbuf.c b/tools/lib/bpf/ringbuf.c
index 8caaafe7e312..e7a8d847161f 100644
--- a/tools/lib/bpf/ringbuf.c
+++ b/tools/lib/bpf/ringbuf.c
@@ -227,7 +227,7 @@ static int ringbuf_process_ring(struct ring* r)
 			if ((len & BPF_RINGBUF_DISCARD_BIT) == 0) {
 				sample = (void *)len_ptr + BPF_RINGBUF_HDR_SZ;
 				err = r->sample_cb(r->ctx, sample, len);
-				if (err) {
+				if (err < 0) {
 					/* update consumer pos and bail out */
 					smp_store_release(r->consumer_pos,
 							  cons_pos);
-- 
2.25.1

