From patchwork Thu Jan 6 21:50:55 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Hao Luo X-Patchwork-Id: 12705841 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 E136BC433FE for ; Thu, 6 Jan 2022 21:51:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244544AbiAFVvU (ORCPT ); Thu, 6 Jan 2022 16:51:20 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45524 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S244511AbiAFVvT (ORCPT ); Thu, 6 Jan 2022 16:51:19 -0500 Received: from mail-yb1-xb4a.google.com (mail-yb1-xb4a.google.com [IPv6:2607:f8b0:4864:20::b4a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AAAEBC061245 for ; Thu, 6 Jan 2022 13:51:19 -0800 (PST) Received: by mail-yb1-xb4a.google.com with SMTP id n2-20020a255902000000b0060f9d75eafeso7687481ybb.1 for ; Thu, 06 Jan 2022 13:51:19 -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=sXsPIbfQ05P0repzOjAvu6+3E/heYEca8fbLMQGQFvE=; b=C1W8WQ3q+cmeGWXi6BFv9NecPmQIAGB176bAGZnRgwIGol82lcSMwFd2Kg8P8dATef AfmUHuuMk3WbMhiyUGUA4zx+NSk28vH6jo6mmTQ4ZQQ2CrqeY3jhbUsHeQF8CIiiDkOp QP9vjypboOOBAWwy7FCYf9jp1UUHazevP3JOU6TVUJBICQPRkuwWDq/Ym0ngAlUR36wi pbySI8V6t5qDmFZmdYEfFUzz54Nz74VlhuV4NwLv8g2wN7legWlcVzx9VrbOMpS0Csuh YUduTG2qwTo1/XHGzKVliwnhLaBRMo9TZlEI11uclsNQQ7/2CoPpXHaWzsdxru31EisU edPw== 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=sXsPIbfQ05P0repzOjAvu6+3E/heYEca8fbLMQGQFvE=; b=kFPa8wMxIJecG6m7l4ZyrblGPiCj8ZxY6ZpRujerkh5ZEs6ad9k1VPAwbUvauBdmvE 73ul5z4c8JxnzAg61EfQ+8AazGCFmCcwsOO8/sCyMUkq60rm4G84vt4RGyh9Tln955nP WzGEt4rVy4qowSGj5AS12ja3NRSYIT100ahcjIpSAOO7RHN37ROBKNN1i5zrgiI1VbfV 5j5PRcMuq/JP+eP8ugA9kIHMZ28LMNyVNZrK7fYkvx1MhiWDd3GRCWvyt2pqTNcRBfg0 +qYWhuISjwuBhEP4HIEfP5w8DndBnxKWIcNGGACK4l6WHDHEDlsVlR43C5TieDwqf45u V7Ww== X-Gm-Message-State: AOAM533BLgs5lzwb+qee/yCrGi3cur9a9Xbabx7lO4bHVI7/DBYHGcFh S4/KEWJZ/8WZngAqvkMRbBaVMgDh4G0= X-Google-Smtp-Source: ABdhPJxETQssjG1CpTafGjdgKn/nIgR1Kz7orjkpzH5foiYucXFWWqV5PDY7nDIiJ+8hrOzFe3mES8S+2UM= X-Received: from haoluo.svl.corp.google.com ([2620:15c:2cd:202:3a2:a76c:b77f:b671]) (user=haoluo job=sendgmr) by 2002:a25:2315:: with SMTP id j21mr71106173ybj.672.1641505878976; Thu, 06 Jan 2022 13:51:18 -0800 (PST) Date: Thu, 6 Jan 2022 13:50:55 -0800 In-Reply-To: <20220106215059.2308931-1-haoluo@google.com> Message-Id: <20220106215059.2308931-5-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 4/8] bpf: Support removing kernfs entries 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 a bpf object has been exposed in kernfs, there should be a way to remove it. Kernfs doesn't implement unlink, therefore one can not remove the entry in a normal way. To remove the file, we can allow writing a special command to the new entry, which can trigger a remove_self() for removal. So far there are two ways to remove an entry that is created by pinning bpf objects in kernfs: 1. unpin the object from bpffs. 2. write a special command to the kernfs entry. Signed-off-by: Hao Luo --- kernel/bpf/kernfs_node.c | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) diff --git a/kernel/bpf/kernfs_node.c b/kernel/bpf/kernfs_node.c index c1c45f7b948b..3d331d8357db 100644 --- a/kernel/bpf/kernfs_node.c +++ b/kernel/bpf/kernfs_node.c @@ -9,6 +9,9 @@ /* file_operations for kernfs file system */ +/* Command for removing a kernfs entry */ +#define REMOVE_CMD "rm" + /* Handler when the watched inode is freed. */ static void kn_watch_free_inode(void *obj, enum bpf_type type, void *kn) { @@ -22,8 +25,27 @@ static const struct notify_ops notify_ops = { .free_inode = kn_watch_free_inode, }; +static ssize_t bpf_generic_write(struct kernfs_open_file *of, char *buf, + size_t bytes, loff_t off) +{ + if (sysfs_streq(buf, REMOVE_CMD)) { + kernfs_remove_self(of->kn); + return bytes; + } + + return -EINVAL; +} + +static ssize_t bpf_generic_read(struct kernfs_open_file *of, char *buf, + size_t bytes, loff_t off) +{ + return -EIO; +} + /* Kernfs file operations for bpf created files. */ static const struct kernfs_ops bpf_generic_ops = { + .write = bpf_generic_write, + .read = bpf_generic_read, }; /* Test whether a given dentry is a kernfs entry. */