From patchwork Tue Jan 12 22:00:46 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Christian Brauner X-Patchwork-Id: 12015103 X-Patchwork-Delegate: paul@paul-moore.com 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=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 B1C65C432C3 for ; Tue, 12 Jan 2021 22:03:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7763E2312E for ; Tue, 12 Jan 2021 22:03:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2393878AbhALWDj (ORCPT ); Tue, 12 Jan 2021 17:03:39 -0500 Received: from youngberry.canonical.com ([91.189.89.112]:42912 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2393849AbhALWDi (ORCPT ); Tue, 12 Jan 2021 17:03:38 -0500 Received: from ip5f5af0a0.dynamic.kabel-deutschland.de ([95.90.240.160] helo=wittgenstein.fritz.box) by youngberry.canonical.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.86_2) (envelope-from ) id 1kzRka-0003bd-SB; Tue, 12 Jan 2021 22:02:52 +0000 From: Christian Brauner To: Alexander Viro , Christoph Hellwig , linux-fsdevel@vger.kernel.org Cc: John Johansen , James Morris , Mimi Zohar , Dmitry Kasatkin , Stephen Smalley , Casey Schaufler , Arnd Bergmann , Andreas Dilger , OGAWA Hirofumi , Geoffrey Thomas , Mrunal Patel , Josh Triplett , Andy Lutomirski , Theodore Tso , Alban Crequy , Tycho Andersen , David Howells , James Bottomley , Seth Forshee , =?utf-8?q?St=C3=A9phane_Graber?= , Linus Torvalds , Aleksa Sarai , Lennart Poettering , "Eric W. Biederman" , smbarber@chromium.org, Phil Estes , Serge Hallyn , Kees Cook , Todd Kjos , Paul Moore , Jonathan Corbet , containers@lists.linux-foundation.org, linux-security-module@vger.kernel.org, linux-api@vger.kernel.org, linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org, linux-integrity@vger.kernel.org, selinux@vger.kernel.org, Christian Brauner , Christoph Hellwig Subject: [PATCH v5 04/42] fs: split out functions to hold writers Date: Tue, 12 Jan 2021 23:00:46 +0100 Message-Id: <20210112220124.837960-5-christian.brauner@ubuntu.com> X-Mailer: git-send-email 2.30.0 In-Reply-To: <20210112220124.837960-1-christian.brauner@ubuntu.com> References: <20210112220124.837960-1-christian.brauner@ubuntu.com> MIME-Version: 1.0 X-Patch-Hashes: v=1; h=sha256; i=tA4kasRGHqyT9lXmq5D7y93eprXCx71LRmCCdBBaY00=; m=nI7OMzVl1+0j2kjIaa7/usg9c4r2VoQ64Pjs5BnWA4U=; p=veHrsX8JHuzzEFPnrDDzG6jRQQ6VJXMdTLmV/Ias+FE=; g=4b5ff4be4775a50ca22b9c4a0244a22bea618b32 X-Patch-Sig: m=pgp; i=christian.brauner@ubuntu.com; s=0x0x91C61BC06578DCA2; b=iHUEABYKAB0WIQRAhzRXHqcMeLMyaSiRxhvAZXjcogUCX/4YtQAKCRCRxhvAZXjcok/NAQDZl7g IMc+hu3azYgiyrffuzboK1p/OvP+06fVleHk9qQD9H3HRtaTr8Y5KdnnZgV9UsILzObq0ONhA0f3m 5I6ZBQw= Precedence: bulk List-ID: X-Mailing-List: selinux@vger.kernel.org When a mount is marked read-only we set MNT_WRITE_HOLD on it if there aren't currently any active writers. Split this logic out into simple helpers that we can use in follow-up patches. Suggested-by: Christoph Hellwig Cc: David Howells Cc: Al Viro Cc: linux-fsdevel@vger.kernel.org Reviewed-by: Christoph Hellwig Signed-off-by: Christian Brauner --- /* v2 */ patch not present /* v3 */ patch not present /* v4 */ patch introduced /* v5 */ base-commit: 7c53f6b671f4aba70ff15e1b05148b10d58c2837 --- fs/namespace.c | 24 ++++++++++++++++++------ 1 file changed, 18 insertions(+), 6 deletions(-) diff --git a/fs/namespace.c b/fs/namespace.c index 5177bf6d810e..4aab396e5f21 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -469,10 +469,8 @@ void mnt_drop_write_file(struct file *file) } EXPORT_SYMBOL(mnt_drop_write_file); -static int mnt_make_readonly(struct mount *mnt) +static inline int mnt_hold_writers(struct mount *mnt) { - int ret = 0; - mnt->mnt.mnt_flags |= MNT_WRITE_HOLD; /* * After storing MNT_WRITE_HOLD, we'll read the counters. This store @@ -497,15 +495,29 @@ static int mnt_make_readonly(struct mount *mnt) * we're counting up here. */ if (mnt_get_writers(mnt) > 0) - ret = -EBUSY; - else - mnt->mnt.mnt_flags |= MNT_READONLY; + return -EBUSY; + + return 0; +} + +static inline void mnt_unhold_writers(struct mount *mnt) +{ /* * MNT_READONLY must become visible before ~MNT_WRITE_HOLD, so writers * that become unheld will see MNT_READONLY. */ smp_wmb(); mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD; +} + +static int mnt_make_readonly(struct mount *mnt) +{ + int ret; + + ret = mnt_hold_writers(mnt); + if (!ret) + mnt->mnt.mnt_flags |= MNT_READONLY; + mnt_unhold_writers(mnt); return ret; }