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=-12.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham 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 EF762C433ED for ; Mon, 17 Aug 2020 22:10:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D13002063A for ; Mon, 17 Aug 2020 22:10:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387434AbgHQWKc (ORCPT ); Mon, 17 Aug 2020 18:10:32 -0400 Received: from out01.mta.xmission.com ([166.70.13.231]:46586 "EHLO out01.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730177AbgHQWKN (ORCPT ); Mon, 17 Aug 2020 18:10:13 -0400 Received: from in02.mta.xmission.com ([166.70.13.52]) by out01.mta.xmission.com with esmtps (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (Exim 4.93) (envelope-from ) id 1k7nKW-004vtM-PI; Mon, 17 Aug 2020 16:10:12 -0600 Received: from ip68-227-160-95.om.om.cox.net ([68.227.160.95] helo=x220.int.ebiederm.org) by in02.mta.xmission.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.87) (envelope-from ) id 1k7nKV-0004PB-W4; Mon, 17 Aug 2020 16:10:12 -0600 From: "Eric W. Biederman" To: linux-kernel@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org, criu@openvz.org, bpf@vger.kernel.org, Linus Torvalds , Alexander Viro , Christian Brauner , Oleg Nesterov , Cyrill Gorcunov , Jann Horn , Kees Cook , =?UTF-8?q?Daniel=20P=2E=20Berrang=C3=A9?= , Jeff Layton , Miklos Szeredi , Matthew Wilcox , "J. Bruce Fields" , Matthew Wilcox , Trond Myklebust , Chris Wright , Alexei Starovoitov , Daniel Borkmann , Martin KaFai Lau , Song Liu , Yonghong Song , Andrii Nakryiko , John Fastabend , KP Singh , "Eric W. Biederman" Date: Mon, 17 Aug 2020 17:04:18 -0500 Message-Id: <20200817220425.9389-10-ebiederm@xmission.com> X-Mailer: git-send-email 2.25.0 In-Reply-To: <87ft8l6ic3.fsf@x220.int.ebiederm.org> References: <87ft8l6ic3.fsf@x220.int.ebiederm.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-XM-SPF: eid=1k7nKV-0004PB-W4;;;mid=<20200817220425.9389-10-ebiederm@xmission.com>;;;hst=in02.mta.xmission.com;;;ip=68.227.160.95;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX1/rGzp3jrWwVWIWQnolVzaJMEaOuCOGy6w= X-SA-Exim-Connect-IP: 68.227.160.95 X-SA-Exim-Mail-From: ebiederm@xmission.com Subject: [PATCH 10/17] proc/fd: In proc_readfd_common use fnext_task X-SA-Exim-Version: 4.2.1 (built Thu, 05 May 2016 13:38:54 -0600) X-SA-Exim-Scanned: Yes (on in02.mta.xmission.com) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When discussing[1] exec and posix file locks it was realized that none of the callers of get_files_struct fundamentally needed to call get_files_struct, and that by switching them to helper functions instead it will both simplify their code and remove unnecessary increments of files_struct.count. Those unnecessary increments can result in exec unnecessarily unsharing files_struct which breaking posix locks, and it can result in fget_light having to fallback to fget reducing system performance. Using fnext_task simplifies proc_readfd_common, by moving the checking for the maximum file descritor into the generic code, and by remvoing the need for capturing and releasing a reference on files_struct. [1] https://lkml.kernel.org/r/20180915160423.GA31461@redhat.com Suggested-by: Oleg Nesterov Signed-off-by: Eric W. Biederman --- fs/proc/fd.c | 17 +++++------------ 1 file changed, 5 insertions(+), 12 deletions(-) diff --git a/fs/proc/fd.c b/fs/proc/fd.c index abfdcb21cc79..d9fee5390fd7 100644 --- a/fs/proc/fd.c +++ b/fs/proc/fd.c @@ -218,7 +218,6 @@ static int proc_readfd_common(struct file *file, struct dir_context *ctx, instantiate_t instantiate) { struct task_struct *p = get_proc_task(file_inode(file)); - struct files_struct *files; unsigned int fd; if (!p) @@ -226,22 +225,18 @@ static int proc_readfd_common(struct file *file, struct dir_context *ctx, if (!dir_emit_dots(file, ctx)) goto out; - files = get_files_struct(p); - if (!files) - goto out; rcu_read_lock(); - for (fd = ctx->pos - 2; - fd < files_fdtable(files)->max_fds; - fd++, ctx->pos++) { + for (fd = ctx->pos - 2;; fd++, ctx->pos++) { struct file *f; struct fd_data data; char name[10 + 1]; unsigned int len; - f = fcheck_files(files, fd); + f = fnext_task(p, &fd); + ctx->pos = fd; if (!f) - continue; + break; data.mode = f->f_mode; rcu_read_unlock(); data.fd = fd; @@ -250,13 +245,11 @@ static int proc_readfd_common(struct file *file, struct dir_context *ctx, if (!proc_fill_cache(file, ctx, name, len, instantiate, p, &data)) - goto out_fd_loop; + goto out; cond_resched(); rcu_read_lock(); } rcu_read_unlock(); -out_fd_loop: - put_files_struct(files); out: put_task_struct(p); return 0; -- 2.25.0