From patchwork Thu Jan 6 21:50:53 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Hao Luo X-Patchwork-Id: 12705839 X-Patchwork-Delegate: bpf@iogearbox.net Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D6635C433F5 for ; Thu, 6 Jan 2022 21:51:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244569AbiAFVvP (ORCPT ); Thu, 6 Jan 2022 16:51:15 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45494 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S244537AbiAFVvO (ORCPT ); Thu, 6 Jan 2022 16:51:14 -0500 Received: from mail-yb1-xb49.google.com (mail-yb1-xb49.google.com [IPv6:2607:f8b0:4864:20::b49]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A0054C061245 for ; Thu, 6 Jan 2022 13:51:14 -0800 (PST) Received: by mail-yb1-xb49.google.com with SMTP id e2-20020a25d302000000b0060c57942183so7582114ybf.18 for ; Thu, 06 Jan 2022 13:51:14 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=WLIXWpZVKEATWJu5eTPegEpeW0twWlWVehQQ8+8FOxE=; b=d4Eb78p99yJIn1xo1Wwjw4zWFHf0yTijZN7NGh1lQLCRI6SJGS8nwFCEFBT0xvd2DL vbxOjXA03U3WQWyHcCjakIYzimDOcwi5mdDhaSAGysCUZPs7zouSUGHMr7xXakRhxri/ vg/46fCjnjTiM7q5qsuH7wF414qBKpHNWuymKu3NqfbdSJZ1cUWp+2Qvu2iB/3ZHwCoI /rVrzQ71cuFCgX0YjY11FoESmXmUueSrkS5g1Zj1Z3WbeDy79oz2OcOLUhFx4vCwNA9N oM9iWe9BMu5Jx88oYGatKmSk1w4+o4VUfqhAmqke2O7xhs/12SS7lazz5Sb1MGxL8E25 4pJg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=WLIXWpZVKEATWJu5eTPegEpeW0twWlWVehQQ8+8FOxE=; b=ddClQYoCBToDlzDwmCjGHfR/XBalgEDWKNwhcnq7U6i2xq12k+wcjvTcKgs9VrTBlA fS4DBlZXOgWaKhyIx2hG07nlr+BhJ7XSvFgrROFnzBh+9x8umvb0QFo4k7Agn8eFdktA wG2wZE804StV+rz95/A5jBTOwEOc/WR103Gy71l60HRqV0fgkBr1731FMe/siCV1OEpg 5k6vihc0YQGuexoSfvi1/tlgCv0kGPeaCxvm6uBM82DDcv2X2W3l+OfkHYD1LeDesrGh pQpH38L3y3gUjrAHpAnGCKBnuTe4PxVlur8/F9ZEXxYbzAUZ1V4JbdpLn0YR8HAIEZY/ OqMQ== X-Gm-Message-State: AOAM533LgVvvcKf4Q01OaAgz92VYaAytz3xkqhNhmOIKUFF9O8twv3H7 gqmlJksSP5wAylc6uaArw3Bl08OvE+0= X-Google-Smtp-Source: ABdhPJx4Jw3NSHcpmtkltSPTO45oGZ6FD9mC2qur7dLiMLtyHCOjOG3fXizC8t/lybUOAj3impYyMNcFlWY= X-Received: from haoluo.svl.corp.google.com ([2620:15c:2cd:202:3a2:a76c:b77f:b671]) (user=haoluo job=sendgmr) by 2002:a05:6902:702:: with SMTP id k2mr41109066ybt.66.1641505873833; Thu, 06 Jan 2022 13:51:13 -0800 (PST) Date: Thu, 6 Jan 2022 13:50:53 -0800 In-Reply-To: <20220106215059.2308931-1-haoluo@google.com> Message-Id: <20220106215059.2308931-3-haoluo@google.com> Mime-Version: 1.0 References: <20220106215059.2308931-1-haoluo@google.com> X-Mailer: git-send-email 2.34.1.448.ga2b2bfdf31-goog Subject: [PATCH RFC bpf-next v1 2/8] bpf: Record back pointer to the inode in bpffs From: Hao Luo To: Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann Cc: Martin KaFai Lau , Song Liu , Yonghong Song , KP Singh , Shakeel Butt , Joe Burton , Stanislav Fomichev , bpf@vger.kernel.org, Hao Luo Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net X-Patchwork-State: RFC When an object is pinned in bpffs, record the bpffs inode in the object. The previous patch introduced bpf_watch_inode(), which can also be used to watch the bpffs inode. This capability will be used in the following patches to expose bpf objects to file systems where the nodes in the file system are not backed by an inode. Signed-off-by: Hao Luo --- include/linux/bpf.h | 5 +++- kernel/bpf/inode.c | 60 ++++++++++++++++++++++++++++++++++++++++++++- kernel/bpf/inode.h | 9 +++++++ 3 files changed, 72 insertions(+), 2 deletions(-) diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 6e947cd91152..2ec693c3d6f6 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -184,7 +184,8 @@ struct bpf_map { char name[BPF_OBJ_NAME_LEN]; bool bypass_spec_v1; bool frozen; /* write-once; write-protected by freeze_mutex */ - /* 14 bytes hole */ + struct inode *backing_inode; /* back pointer to the inode in bpffs */ + /* 6 bytes hole */ /* The 3rd and 4th cacheline with misc members to avoid false sharing * particularly with refcounting. @@ -991,6 +992,7 @@ struct bpf_prog_aux { struct work_struct work; struct rcu_head rcu; }; + struct inode *backing_inode; /* back pointer to the inode in bpffs */ }; struct bpf_array_aux { @@ -1018,6 +1020,7 @@ struct bpf_link { const struct bpf_link_ops *ops; struct bpf_prog *prog; struct work_struct work; + struct inode *backing_inode; /* back pointer to the inode in bpffs */ }; struct bpf_link_ops { diff --git a/kernel/bpf/inode.c b/kernel/bpf/inode.c index b4066dd986a8..9ba10912cbf8 100644 --- a/kernel/bpf/inode.c +++ b/kernel/bpf/inode.c @@ -226,6 +226,57 @@ static int bpf_inode_type(const struct inode *inode, enum bpf_type *type) return 0; } +/* Conditionally set an object's backing inode. */ +static void cond_set_backing_inode(void *obj, enum bpf_type type, + struct inode *old, struct inode *new) +{ + struct inode **ptr; + + if (type == BPF_TYPE_PROG) { + struct bpf_prog *prog = obj; + ptr = &prog->aux->backing_inode; + } else if (type == BPF_TYPE_MAP) { + struct bpf_map *map = obj; + ptr = &map->backing_inode; + } else if (type == BPF_TYPE_LINK) { + struct bpf_link *link = obj; + ptr = &link->backing_inode; + } else { + return; + } + + if (*ptr == old) + *ptr = new; +} + +struct inode *get_backing_inode(void *obj, enum bpf_type type) +{ + struct inode *inode = NULL; + + if (type == BPF_TYPE_PROG) { + struct bpf_prog *prog = obj; + inode = prog->aux->backing_inode; + } else if (type == BPF_TYPE_MAP) { + struct bpf_map *map = obj; + inode = map->backing_inode; + } else if (type == BPF_TYPE_LINK) { + struct bpf_link *link = obj; + inode = link->backing_inode; + } + + if (!inode) + return NULL; + + spin_lock(&inode->i_lock); + if (inode->i_state & (I_FREEING | I_WILL_FREE | I_NEW)) { + spin_unlock(&inode->i_lock); + return NULL; + } + __iget(inode); + spin_unlock(&inode->i_lock); + return inode; +} + static void bpf_dentry_finalize(struct dentry *dentry, struct inode *inode, struct inode *dir) { @@ -418,6 +469,8 @@ static int bpf_mkobj_ops(struct dentry *dentry, umode_t mode, void *raw, { struct inode *dir = dentry->d_parent->d_inode; struct inode *inode = bpf_get_inode(dir->i_sb, dir, mode); + enum bpf_type type; + if (IS_ERR(inode)) return PTR_ERR(inode); @@ -425,6 +478,9 @@ static int bpf_mkobj_ops(struct dentry *dentry, umode_t mode, void *raw, inode->i_fop = fops; inode->i_private = raw; + if (!bpf_inode_type(inode, &type)) + cond_set_backing_inode(raw, type, NULL, inode); + bpf_dentry_finalize(dentry, inode, dir); return 0; } @@ -703,8 +759,10 @@ static void bpf_free_inode(struct inode *inode) if (S_ISLNK(inode->i_mode)) kfree(inode->i_link); - if (!bpf_inode_type(inode, &type)) + if (!bpf_inode_type(inode, &type)) { + cond_set_backing_inode(inode->i_private, type, inode, NULL); bpf_any_put(inode->i_private, type); + } free_inode_nonrcu(inode); } diff --git a/kernel/bpf/inode.h b/kernel/bpf/inode.h index 3f53a4542028..e7fe8137be80 100644 --- a/kernel/bpf/inode.h +++ b/kernel/bpf/inode.h @@ -30,4 +30,13 @@ int bpf_watch_inode(struct inode *inode, const struct notify_ops *ops, } #endif // CONFIG_FSNOTIFY +/* Get the backing inode of a bpf object. When an object is pinned in bpf + * file system, an inode is associated with the object. This function returns + * that inode. + * + * On success, the inode is returned with refcnt incremented. + * On failure, NULL is returned. + */ +struct inode *get_backing_inode(void *obj, enum bpf_type); + #endif // __BPF_INODE_H_