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Message-ID: <6a8b1a57-c7b6-81c6-5e77-759cb041a77b@wangsu.com>
Date: Mon, 22 Jul 2024 09:54:38 +0800
From: Lin Feng <linf@...gsu.com>
To: Daniel Borkmann <daniel@...earbox.net>, ast@...nel.org
Cc: bpf@...r.kernel.org, linux-kernel@...r.kernel.org,
yonghong.song@...ux.dev, Hou Tao <houtao1@...wei.com>,
Brian Vazquez <brianvv@...gle.com>
Subject: Re: [PATCH] bpf: fix excessively checking for elem_flags in batch
update mode
Hi Daniel,
Thanks for your reply! Without basic knowledge of rules of thumb for patch in
bpf, I didn't expect a single line change need that many more considerations,
and will do some more work on it following your sugguestion!
Thanks,
linfeng
On 7/20/24 00:22, Daniel Borkmann wrote:
> On 7/17/24 1:15 PM, Lin Feng wrote:
>> Currently generic_map_update_batch will reject all valid command flags for
>> BPF_MAP_UPDATE_ELEM other than BPF_F_LOCK, which is overkill, map updating
>> semantic does allow specify BPF_NOEXIST or BPF_EXIST even for batching
>> update.
>>
>> Signed-off-by: Lin Feng <linf@...gsu.com>
>
> [ +Hou/Brian ]
>
> Please also add a BPF selftest along with this extension which exercises the
> batch update and validates the behavior for the various flags which are now enabled.
>
> Also, please discuss the semantics in the commit msg.. errors due to BPF_EXIST and
> BPF_NOEXIST will cause bpf_map_update_value() to fail and then break the loop. It's
> probably fine given batch.count (cp) will be propagated back to user space to tell
> how many elements could actually get updated.
>
>> ---
>> kernel/bpf/syscall.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
>> index 869265852d51..d85361f9a9b8 100644
>> --- a/kernel/bpf/syscall.c
>> +++ b/kernel/bpf/syscall.c
>> @@ -1852,7 +1852,7 @@ int generic_map_update_batch(struct bpf_map *map, struct file *map_file,
>> void *key, *value;
>> int err = 0;
>>
>> - if (attr->batch.elem_flags & ~BPF_F_LOCK)
>> + if ((attr->batch.elem_flags & ~BPF_F_LOCK) > BPF_EXIST)
>> return -EINVAL;
>>
>> if ((attr->batch.elem_flags & BPF_F_LOCK) &&
>>
>
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