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Date: Mon, 18 May 2015 17:37:00 -0300
From: Arnaldo Carvalho de Melo <acme@kernel.org>
To: Alexei Starovoitov <ast@plumgrid.com>
Cc: Wang Nan <wangnan0@huawei.com>, paulus@samba.org, a.p.zijlstra@chello.nl,
        mingo@redhat.com, namhyung@kernel.org, jolsa@kernel.org,
        dsahern@gmail.com, daniel@iogearbox.net, brendan.d.gregg@gmail.com,
        masami.hiramatsu.pt@hitachi.com, lizefan@huawei.com,
        linux-kernel@vger.kernel.org, pi3orama@163.com
Subject: Re: [RFC PATCH v3 21/37] bpf tools: Create eBPF maps defined in an
 object file
Message-ID: <20150518203700.GH18563@kernel.org>
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 <555A3419.4040207@plumgrid.com>
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Em Mon, May 18, 2015 at 11:48:57AM -0700, Alexei Starovoitov escreveu:
> On 5/17/15 3:56 AM, Wang Nan wrote:
> >This patch creates maps based on 'map' section in object file using
> >bpf_create_map(), and store the fds into an array in
> >'struct bpf_object'. Since the byte order of the object may differ
> >from the host, swap map definition before processing.
> >
> >This is the first patch in 'loading' phase. Previous patches parse ELF
> >object file and create needed data structure, but doesnnt play with
> >kernel. They belong to 'opening' phase.
> >
> >Signed-off-by: Wang Nan <wangnan0@huawei.com>
> ...
> >+			for (j = 0; j < i; j++) {
> >+				close(obj->maps_fds[j]);
> >+				obj->maps_fds[j] = -1;
> 
> this line is unnecessary, since you're freeing the whole array
> at the line below:

I guess this is kinda of a zfree() that he wants to achieve, i.e. if a
bug creeps in that makes some code use the deleted maps_fds, he rather
wants it to access a -1 fd than an some reused fd, no?
 
> >+			}
> >+			free(obj->maps_fds);

> >+			obj->maps_fds = NULL;
> 
> ...
> 
> >  void bpf_close_object(struct bpf_object *obj)
> >  {
> >  	if (!obj)
> >  		return;
> >
> >  	bpf_obj_clear_elf(obj);
> >+	bpf_unload_object(obj);
> 
> just realized that this API keeps elf file open for the whole
> life time. I think that should be split up.
> bpf_open_object() can do elf parsing, creation of maps and
> bpf loading.
> bpf_close_object() can unload programs, maps. That's fine,
> but closing of elf file and freeing memory associated
> with parsing sections should be a separate call.