diff mbox series

[v2,bpf,1/3] bpf: iter_udp: Retry with a larger batch size without going back to the previous bucket

Message ID 20240110175743.2220907-2-martin.lau@linux.dev (mailing list archive)
State Superseded
Delegated to: BPF
Headers show
Series bpf: Fix backward progress bug in bpf_iter_udp | expand

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Commit Message

Martin KaFai Lau Jan. 10, 2024, 5:57 p.m. UTC 
From: Martin KaFai Lau <martin.lau@kernel.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@isovalent.com>
Fixes: c96dac8d369f ("bpf: udp: Implement batching for sockets iterator")
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
---
 net/ipv4/udp.c | 1 -
 1 file changed, 1 deletion(-)

Comments

Yonghong Song Jan. 12, 2024, 4:52 a.m. UTC | #1 
On 1/10/24 9:57 AM, Martin KaFai Lau wrote:
> From: Martin KaFai Lau <martin.lau@kernel.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@isovalent.com>
> Fixes: c96dac8d369f ("bpf: udp: Implement batching for sockets iterator")
> Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>

Acked-by: Yonghong Song <yonghong.song@linux.dev>
diff mbox series

Patch

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: