netdev - [PATCH v3 bpf 1/3] bpf: iter_udp: Retry with a larger batch size without going back to the previous bucket

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Message-Id: <20240112190530.3751661-2-martin.lau@linux.dev>
Date: Fri, 12 Jan 2024 11:05:28 -0800
From: Martin KaFai Lau <martin.lau@...ux.dev>
To: bpf@...r.kernel.org
Cc: 'Alexei Starovoitov ' <ast@...nel.org>,
	'Andrii Nakryiko ' <andrii@...nel.org>,
	'Daniel Borkmann ' <daniel@...earbox.net>,
	netdev@...r.kernel.org,
	kernel-team@...a.com,
	Aditi Ghag <aditi.ghag@...valent.com>,
	Yonghong Song <yonghong.song@...ux.dev>
Subject: [PATCH v3 bpf 1/3] bpf: iter_udp: Retry with a larger batch size without going back to the previous bucket

From: Martin KaFai Lau <martin.lau@...nel.org>

The current logic is to use a default size 16 to batch the whole bucket.
If it is too small, it will retry with a larger batch size.

The current code accidentally does a state->bucket-- before retrying.
This goes back to retry with the previous bucket which has already
been done. This patch fixed it.

It is hard to create a selftest. I added a WARN_ON(state->bucket < 0),
forced a particular port to be hashed to the first bucket,
created >16 sockets, and observed the for-loop went back
to the "-1" bucket.

Cc: Aditi Ghag <aditi.ghag@...valent.com>
Fixes: c96dac8d369f ("bpf: udp: Implement batching for sockets iterator")
Acked-by: Yonghong Song <yonghong.song@...ux.dev>
Signed-off-by: Martin KaFai Lau <martin.lau@...nel.org>
---
 net/ipv4/udp.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 89e5a806b82e..978b83d3c094 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -3213,7 +3213,6 @@ static struct sock *bpf_iter_udp_batch(struct seq_file *seq)
 		/* After allocating a larger batch, retry one more time to grab
 		 * the whole bucket.
 		 */
-		state->bucket--;
 		goto again;
 	}
 done:
-- 
2.34.1