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=-13.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 D096DC4338F for ; Mon, 9 Aug 2021 09:52:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B9FDA60F11 for ; Mon, 9 Aug 2021 09:52:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233238AbhHIJws (ORCPT ); Mon, 9 Aug 2021 05:52:48 -0400 Received: from mail.kernel.org ([198.145.29.99]:50012 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232944AbhHIJws (ORCPT ); Mon, 9 Aug 2021 05:52:48 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 9F6A160F11; Mon, 9 Aug 2021 09:52:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1628502748; bh=JcFdmL1yqMs5GyZAdlm01Li/8XUWupyp3IqhMdZipEc=; h=Subject:To:Cc:From:Date:From; b=gv2znH/zJHMFCmatvKbiIkWLrFGI+W2dkq9u7SFz9eiPA2/LuLQ9GV7eAwseTUCTW 2C5nAyYU+PHhGlvVlA9h8CoVGMIxWyKoWuzylkKX0Z0RP/fTMJTgiOJdxOlepFuivj /PVdelH1pqOqJkMx1AjijkSsK02rmqKZU7EKA+CU= Subject: FAILED: patch "[PATCH] pipe: increase minimum default pipe size to 2 pages" failed to apply to 4.4-stable tree To: alex_y_xu@yahoo.ca, stable@vger.kernel.org, torvalds@linux-foundation.org Cc: From: Date: Mon, 09 Aug 2021 11:52:25 +0200 Message-ID: <162850274511123@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org The patch below does not apply to the 4.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 46c4c9d1beb7f5b4cec4dd90e7728720583ee348 Mon Sep 17 00:00:00 2001 From: "Alex Xu (Hello71)" Date: Thu, 5 Aug 2021 10:40:47 -0400 Subject: [PATCH] pipe: increase minimum default pipe size to 2 pages This program always prints 4096 and hangs before the patch, and always prints 8192 and exits successfully after: int main() { int pipefd[2]; for (int i = 0; i < 1025; i++) if (pipe(pipefd) == -1) return 1; size_t bufsz = fcntl(pipefd[1], F_GETPIPE_SZ); printf("%zd\n", bufsz); char *buf = calloc(bufsz, 1); write(pipefd[1], buf, bufsz); read(pipefd[0], buf, bufsz-1); write(pipefd[1], buf, 1); } Note that you may need to increase your RLIMIT_NOFILE before running the program. Fixes: 759c01142a ("pipe: limit the per-user amount of pages allocated in pipes") Cc: Link: https://lore.kernel.org/lkml/1628086770.5rn8p04n6j.none@localhost/ Link: https://lore.kernel.org/lkml/1628127094.lxxn016tj7.none@localhost/ Signed-off-by: Alex Xu (Hello71) Signed-off-by: Linus Torvalds diff --git a/fs/pipe.c b/fs/pipe.c index 9ef4231cce61..8e6ef62aeb1c 100644 --- a/fs/pipe.c +++ b/fs/pipe.c @@ -31,6 +31,21 @@ #include "internal.h" +/* + * New pipe buffers will be restricted to this size while the user is exceeding + * their pipe buffer quota. The general pipe use case needs at least two + * buffers: one for data yet to be read, and one for new data. If this is less + * than two, then a write to a non-empty pipe may block even if the pipe is not + * full. This can occur with GNU make jobserver or similar uses of pipes as + * semaphores: multiple processes may be waiting to write tokens back to the + * pipe before reading tokens: https://lore.kernel.org/lkml/1628086770.5rn8p04n6j.none@localhost/. + * + * Users can reduce their pipe buffers with F_SETPIPE_SZ below this at their + * own risk, namely: pipe writes to non-full pipes may block until the pipe is + * emptied. + */ +#define PIPE_MIN_DEF_BUFFERS 2 + /* * The max size that a non-root user is allowed to grow the pipe. Can * be set by root in /proc/sys/fs/pipe-max-size @@ -781,8 +796,8 @@ struct pipe_inode_info *alloc_pipe_info(void) user_bufs = account_pipe_buffers(user, 0, pipe_bufs); if (too_many_pipe_buffers_soft(user_bufs) && pipe_is_unprivileged_user()) { - user_bufs = account_pipe_buffers(user, pipe_bufs, 1); - pipe_bufs = 1; + user_bufs = account_pipe_buffers(user, pipe_bufs, PIPE_MIN_DEF_BUFFERS); + pipe_bufs = PIPE_MIN_DEF_BUFFERS; } if (too_many_pipe_buffers_hard(user_bufs) && pipe_is_unprivileged_user())