From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9CDAAC4741F for ; Wed, 30 Sep 2020 18:30:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 45F7D206D9 for ; Wed, 30 Sep 2020 18:30:39 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="dHPwsxT2" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725799AbgI3Sah (ORCPT ); Wed, 30 Sep 2020 14:30:37 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42158 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725355AbgI3Sah (ORCPT ); Wed, 30 Sep 2020 14:30:37 -0400 Received: from mail-yb1-xb41.google.com (mail-yb1-xb41.google.com [IPv6:2607:f8b0:4864:20::b41]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 35160C061755; Wed, 30 Sep 2020 11:30:37 -0700 (PDT) Received: by mail-yb1-xb41.google.com with SMTP id b142so2006793ybg.9; Wed, 30 Sep 2020 11:30:37 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=2OiY48v5fupX3OLmM/AQ2RxdhAtrUz7JvwXHvaAkGCE=; b=dHPwsxT2vG8Jr1e93nNF1wFKJkBQ5rGgaqzWhn2YHJCNKCbz7VbnkcKFqX20jk/mCT hg5t0EpyfIo6pfvLwDYpZsTF/UzWhCRSPhFW87Khixo+5PCGIffW6jCUi3ZuxXQacljV 7A/EunvnOXAWTxCkR6AF2B3aETa2ff6KBt12dUj0PENpI1EFAhifj+XAPFBJZWeaASkK PhcKjacGXvsoMRne3PKLmc5nREROg08BXj9lvq+3EQ3mXREQnm/yRyTjHntA922jJiqQ muW0ZdWmppPhw/efQB/9ZkKBWjlaqOHHt4neOKina01U5dwysZgerVobp8gHEOsgFFIQ YcCQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=2OiY48v5fupX3OLmM/AQ2RxdhAtrUz7JvwXHvaAkGCE=; b=DE419lR60SHpI+bnZlpl+PGPZvQgvg1X5cCJc8fXusRd68m1Tbd0LcY7A9qG5DLYYL bipQxfSymRA4B1YuNB7LVQ/RY4tqbyMPC9aq7YZc8FU5kNxRHDF5QhXQaXwVwttVjOph jikhxhvJl2C7RLwpNBkSIXpXqqCVDxSgkFZ9Fm8PX8KpScKrPv/GtqH/mAFO0p1jLlim tH3mkme3jwv0X9NhSphKI9OOXaK7Vq0Yet+4BqeHrZ3C+J3WrnQRA3+QP0s3JnZYYzr8 W59lBBb36wWjW4yQBUp8Ug62pGii1t3HFshQY5jse8hjySmHDycKKzYiekaJftNaZvxE 47FA== X-Gm-Message-State: AOAM533Z5myyemfcfJNOXnoNltLHskr3dAe5/rPgt51hQ74qUWHZ7cUy Nty6tNxihZYunQ7U72W18+Y2ZN7O3JUjY9tA5X7edNbITJc= X-Google-Smtp-Source: ABdhPJwvWrr1EpSTIlgxCIwZTY5EuqRhQ0MNvn7CHiSqQ1hsrr4ux8KuzlxGNQFPyP8noyzC5BZFiYNSze8nruswALA= X-Received: by 2002:a25:2d41:: with SMTP id s1mr5018629ybe.459.1601490636277; Wed, 30 Sep 2020 11:30:36 -0700 (PDT) MIME-Version: 1.0 References: <20200929031845.751054-1-liuhangbin@gmail.com> <20200929094232.GG2531@dhcp-12-153.nay.redhat.com> <20200930023405.GH2531@dhcp-12-153.nay.redhat.com> In-Reply-To: <20200930023405.GH2531@dhcp-12-153.nay.redhat.com> From: Andrii Nakryiko Date: Wed, 30 Sep 2020 11:30:25 -0700 Message-ID: Subject: Re: [PATCH bpf-next] libbpf: export bpf_object__reuse_map() to libbpf api To: Hangbin Liu Cc: bpf , Networking , =?UTF-8?B?VG9rZSBIw7hpbGFuZC1Kw7hyZ2Vuc2Vu?= , Jiri Benc , Jesper Dangaard Brouer , Daniel Borkmann , Alexei Starovoitov , Stephen Hemminger , Song Liu , Yonghong Song Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Tue, Sep 29, 2020 at 7:34 PM Hangbin Liu wrote: > > On Tue, Sep 29, 2020 at 04:03:45PM -0700, Andrii Nakryiko wrote: > > > bpf_map__set_pin_path() > > > bpf_create_map_in_map() <- create inner or outer map > > > bpf_map__reuse_fd(map, inner/outer_fd) > > > bpf_object__load(obj) > > > - bpf_object__load_xattr() > > > - bpf_object__create_maps() > > > - if (map->fd >= 0) > > > continue <- this will skip pinning map > > > > so maybe that's the part that needs to be fixed?.. > > Hmm...maybe, let me see > > > > > I'm still not sure. And to be honest your examples are still a bit too > > succinct for me to follow where the problem is exactly. Can you please > > elaborate a bit more? > > Let's take iproute2 legacy map for example, if it's a map-in-map type with > pin path defined. In user space we could do like: > > if (bpf_obj_get(pathname) < 0) { > bpf_create_map_in_map(); > bpf_map__reuse_fd(map, map_fd); > } > bpf_map__set_pin_path(map, pathname); > bpf_object__load(obj) > > So in libbpf we need > > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c > index 32dc444224d8..5412aa7169db 100644 > --- a/tools/lib/bpf/libbpf.c > +++ b/tools/lib/bpf/libbpf.c > @@ -4215,7 +4215,7 @@ bpf_object__create_maps(struct bpf_object *obj) > if (map->fd >= 0) { > pr_debug("map '%s': skipping creation (preset fd=%d)\n", > map->name, map->fd); > - continue; > + goto check_pin_path; > } > > err = bpf_object__create_map(obj, map); > @@ -4258,6 +4258,7 @@ bpf_object__create_maps(struct bpf_object *obj) > map->init_slots_sz = 0; > } > > +check_pin_path: > if (map->pin_path && !map->pinned) { > err = bpf_map__pin(map, NULL); > if (err) { > > > Do you think if this change be better? Yes, of course. Just don't do it through use of goto. Guard map creation with that if instead. > > Thanks > Hangbin