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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 150D1CD5484 for ; Tue, 19 Sep 2023 07:38:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231864AbjISHih (ORCPT ); Tue, 19 Sep 2023 03:38:37 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49308 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231812AbjISHiP (ORCPT ); Tue, 19 Sep 2023 03:38:15 -0400 Received: from mail-lf1-x133.google.com (mail-lf1-x133.google.com [IPv6:2a00:1450:4864:20::133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 309DD13A for ; Tue, 19 Sep 2023 00:38:08 -0700 (PDT) Received: by mail-lf1-x133.google.com with SMTP id 2adb3069b0e04-502e6d632b6so8257522e87.0 for ; Tue, 19 Sep 2023 00:38:08 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ionos.com; s=google; t=1695109087; x=1695713887; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=TYhAeXJ6n0p1NLvV6l5GcJ19JSLs3+6aIPIDGI6CfRk=; b=Yps8gmkeTmp9JUZIsf1OHZOR5CVvG3FM9iwqX/oT2nQFL1/5tUX0m05MNvJox0Qzm1 xbeRaRvq9pJeHQEOmQSt70InTnK20NjKouJmjluTYVXFV4988iHPky+1cBfL5i8OQxvB /8TkroWxHiRJgQdvaEGbVCZf+Y9GS6zI4irb0efd26czhZnJdMEVZ6TjY6ZqUouIskR8 Tbyzbf45ACYDvxZNiJoo3+uv/y2blGxLbJ/PJ7U/QJYQ6Tw+PxrMjxB2QAHYyqyb5uqa 83UF6b+8GqYDwJVQl8Kpstb/ljJN33a6QpWWM3FWcgbrnmOCvFhcGc+gg7FQnHfHMYhE DgEA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1695109087; x=1695713887; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=TYhAeXJ6n0p1NLvV6l5GcJ19JSLs3+6aIPIDGI6CfRk=; b=dtVa51RQuTYPNRnVe1rhzf1bwe3ftXQLiaQEFkw8qu9P2NAAFAQq8aVznMFdwiaeHE s6mskHd0H6/2nQf7tBCHHrPTMe0pgY9GA9K+YL5k6aMTAFD2dHN+u20ZiJVX9RITmb77 dXtPVq1sFeJk9rKR4L8vwJwnlpIjI9ZdOgjMPAqBsGLC6ZCNJUHMoqnJVh6QCaFGdJ58 QAT61A6dQk1MqmgAFYiO7DS1nxkJWy90OpRNmZMABMtJEDckfumMTKojIBb8PK+HyuOW z+S1U03oEWbfwIgGVbQBfzpgwgXHLvYvDXnjLS1Kar6B3Vq5vO0yv7nQMkjkFF84ZXta fdmQ== X-Gm-Message-State: AOJu0Yy7VGpEkUWgRCtF1Lt8Jrm9nukt/p5wQWILj58WAyCSeaIKnxjx ecd1iEB2j+FTFhC42I96VbbCrw== X-Google-Smtp-Source: AGHT+IEy4V776q3dOVrHfVXYIIbgCPjMiR68Dh28Ik0ewLQPT/Azb7+uWm//NNL3crh6azWctXVQ+w== X-Received: by 2002:ac2:4285:0:b0:503:19d9:4b6f with SMTP id m5-20020ac24285000000b0050319d94b6fmr3374875lfh.0.1695109086944; Tue, 19 Sep 2023 00:38:06 -0700 (PDT) Received: from heron.intern.cm-ag (p200300dc6f209c00529a4cfffe3dd983.dip0.t-ipconnect.de. [2003:dc:6f20:9c00:529a:4cff:fe3d:d983]) by smtp.gmail.com with ESMTPSA id v4-20020aa7d644000000b0052567e6586bsm7049439edr.38.2023.09.19.00.38.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 19 Sep 2023 00:38:06 -0700 (PDT) From: Max Kellermann To: Arnd Bergmann , Greg Kroah-Hartman Cc: Max Kellermann , linux-kernel@vger.kernel.org Subject: [PATCH] drivers/char/mem: implement splice() for /dev/zero, /dev/full Date: Tue, 19 Sep 2023 09:37:42 +0200 Message-Id: <20230919073743.1066313-1-max.kellermann@ionos.com> X-Mailer: git-send-email 2.39.2 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This allows splicing zeroed pages into a pipe, and allows discarding pages from a pipe by splicing them to /dev/zero. Writing to /dev/zero should have the same effect as writing to /dev/null, and a "splice_write" implementation exists only for /dev/null. (The /dev/zero splice_read implementation could be optimized by pushing references to the global zero page to the pipe, but that's an optimization for another day.) Signed-off-by: Max Kellermann --- drivers/char/mem.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/drivers/char/mem.c b/drivers/char/mem.c index 1052b0f2d4cf..263c19cd6fb9 100644 --- a/drivers/char/mem.c +++ b/drivers/char/mem.c @@ -640,6 +640,7 @@ static int open_port(struct inode *inode, struct file *filp) #define full_lseek null_lseek #define write_zero write_null #define write_iter_zero write_iter_null +#define splice_write_zero splice_write_null #define open_mem open_port static const struct file_operations __maybe_unused mem_fops = { @@ -677,6 +678,8 @@ static const struct file_operations zero_fops = { .read_iter = read_iter_zero, .read = read_zero, .write_iter = write_iter_zero, + .splice_read = copy_splice_read, + .splice_write = splice_write_zero, .mmap = mmap_zero, .get_unmapped_area = get_unmapped_area_zero, #ifndef CONFIG_MMU @@ -688,6 +691,7 @@ static const struct file_operations full_fops = { .llseek = full_lseek, .read_iter = read_iter_zero, .write = write_full, + .splice_read = copy_splice_read, }; static const struct memdev { -- 2.39.2