linux-kernel - Re: [PATCH bpf-next v1] tools/bpftool: create map of maps

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Date:   Tue, 5 Mar 2019 09:32:40 -0800
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     Alban Crequy <alban.crequy@...il.com>
Cc:     ast@...nel.org, daniel@...earbox.net, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, alban@...volk.io, iago@...volk.io
Subject: Re: [PATCH bpf-next v1] tools/bpftool: create map of maps

On Tue,  5 Mar 2019 17:38:03 +0100, Alban Crequy wrote:
> From: Alban Crequy <alban@...volk.io>
> 
> Before this patch, there was no way to fill attr.inner_map_fd, necessary
> for array_of_maps or hash_of_maps.
> 
> This patch adds keyword 'innermap' to pass the innermap, either as an id
> or as a pinned map.
> 
> Example of commands:
> 
> $ sudo bpftool map create /sys/fs/bpf/innermap type hash \
>         key 8 value 8 entries 64 name innermap flags 1
> $ sudo bpftool map create /sys/fs/bpf/outermap type hash_of_maps \
>         innermap pinned /sys/fs/bpf/innermap key 64 value 4 \
>         entries 64 name myoutermap flags 1
> $ sudo bpftool map show pinned /sys/fs/bpf/outermap
> 47: hash_of_maps  name myoutermap  flags 0x1
> 	key 64B  value 4B  max_entries 64  memlock 12288B
> 
> Documentation and bash completion updated as well.
> 
> Signed-off-by: Alban Crequy <alban@...volk.io>

bpf-next is closed let's continue reviewing, but you'll probably have
to repost after the merge window :(

> diff --git a/tools/bpf/bpftool/map.c b/tools/bpf/bpftool/map.c
> index e0c650d91784..7d8ce903a471 100644
> --- a/tools/bpf/bpftool/map.c
> +++ b/tools/bpf/bpftool/map.c
> @@ -1151,6 +1151,9 @@ static int do_create(int argc, char **argv)
>  				return -1;
>  			}
>  			NEXT_ARG();
> +		} else if (is_prefix(*argv, "innermap")) {
> +			NEXT_ARG();
> +			attr.inner_map_fd = map_parse_fd(&argc, &argv);

You need to check if the return value is not -1, and also close this
file descriptor (a) when done, (b) when error happens.

>  		}
>  	}
>