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 BBC97C433F5 for ; Mon, 30 May 2022 01:40:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232124AbiE3Bkr (ORCPT ); Sun, 29 May 2022 21:40:47 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52102 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230402AbiE3Bkm (ORCPT ); Sun, 29 May 2022 21:40:42 -0400 Received: from mail-pl1-x633.google.com (mail-pl1-x633.google.com [IPv6:2607:f8b0:4864:20::633]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6785C3EAA5 for ; Sun, 29 May 2022 18:40:41 -0700 (PDT) Received: by mail-pl1-x633.google.com with SMTP id q4so9026734plr.11 for ; Sun, 29 May 2022 18:40:41 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=AWJBJ3LOOu4SnET4tN5DM1OiJ2Kf/NcSkZ8EqxUPWQQ=; b=i/nKgztGfbo1Ha0TGaQGtTWebzP0RkhfYfOWIrMpkDcpKgQ0xz7xFDJfHj5z632fqx VnCVYvugwfgIRCxp5d6bbSGc+L1cmWrGQErLvJ42xVd/M+UcjtxIxgHjOahCVCrS+E5n 9WgTp5FmhdWAGeCFwg+GHj/RUeM9SfYRkCoPk= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=AWJBJ3LOOu4SnET4tN5DM1OiJ2Kf/NcSkZ8EqxUPWQQ=; b=VPP0bTJV4PGWQlOmK284vyIPnJoHfkbP15y1I2Q7g9daeuRPQtJwUyx9kGhU8qEl36 +PYw+xSCZIS4D40QfXNIkZYHPMNSeoQsxEMQvWKhZAzenldl+SXI00Wkyti4sJz0hPrQ cQ5+qGaV9Hf8piZ9IXuCMqRUJqHXGfU5GuEiwW2y9I9KyqmHKEC8B5pzHSDhZi24eekv XOYlfGJOpr6RTNIoDYI4iXDS9qhAiiV+V/JV1DwORVz9pqLVaqP0C/AzGQQCtnKHcM7M 6KK0rmh2Z2yBV4V8ov7J66QaS6LAjy8XSzsgOrsLu64fln93K7FawP1tB10bs+Jo34Qt TrZQ== X-Gm-Message-State: AOAM530fQcVlc4d/8G12JmAln9VtK1alNaw0B68VY35nXhAqp3db5nkT ZQQ49zPX8LugVgP4CTZ+SfCkNQ== X-Google-Smtp-Source: ABdhPJy6vgmM6oCmbiKRZKfOhfYOuU4pUrtx9loEVpyc7jhHu6V7fiQ0+dSGnc4Njs/M/G4TYHUBzA== X-Received: by 2002:a17:902:ebc8:b0:15f:3f5d:9d08 with SMTP id p8-20020a170902ebc800b0015f3f5d9d08mr53509172plg.121.1653874840928; Sun, 29 May 2022 18:40:40 -0700 (PDT) Received: from dlunevwfh.roam.corp.google.com (n122-107-196-14.sbr2.nsw.optusnet.com.au. [122.107.196.14]) by smtp.gmail.com with ESMTPSA id l9-20020a170902eb0900b0015f2d549b46sm662285plb.237.2022.05.29.18.40.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 29 May 2022 18:40:40 -0700 (PDT) From: Daniil Lunev To: linux-fsdevel@vger.kernel.org, miklos@szeredi.hu, viro@zeniv.linux.org.uk, hch@infradead.org, tytso@mit.edu Cc: fuse-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org, Daniil Lunev Subject: [PATCH v3 1/2] fs/super: function to prevent super re-use Date: Mon, 30 May 2022 11:39:57 +1000 Message-Id: <20220530113953.v3.1.I0e579520b03aa244906b8fe2ef1ec63f2ab7eecf@changeid> X-Mailer: git-send-email 2.31.0 In-Reply-To: <20220530013958.577941-1-dlunev@chromium.org> References: <20220530013958.577941-1-dlunev@chromium.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The function is to be called from filesystem-specific code to mark a superblock to be ignored by superblock test and thus never re-used. The function also unregisters bdi if the bdi is per-superblock to avoid collision if a new superblock is created to represent the filesystem. generic_shutdown_super() skips unregistering bdi for a retired superlock as it assumes retire function has already done it. Signed-off-by: Daniil Lunev --- Changes in v3: - Back to state tracking from v1 - Use s_iflag to mark superblocked ignored - Only unregister private bdi in retire, without freeing Changes in v2: - Remove super from list of superblocks instead of using a flag fs/super.c | 32 ++++++++++++++++++++++++++++---- include/linux/fs.h | 2 ++ 2 files changed, 30 insertions(+), 4 deletions(-) diff --git a/fs/super.c b/fs/super.c index f1d4a193602d6..cb092fc6d6d34 100644 --- a/fs/super.c +++ b/fs/super.c @@ -422,6 +422,30 @@ bool trylock_super(struct super_block *sb) return false; } +/** + * retire_super - prevernts superblock from being reused + * @sb: superblock to retire + * + * The function marks superblock to be ignored in superblock test, which + * prevents it from being reused for any new mounts. If the superblock has + * a private bdi, it also unregisters it, but doesn't reduce the refcount + * of the superblock to prevent potential races. The refcount is reduced + * by generic_shutdown_super(). The function can not be called concurrently + * with generic_shutdown_super(). It is safe to call the function multiple + * times, subsequent calls have no effect. + */ +void retire_super(struct super_block *sb) +{ + down_write(&sb->s_umount); + if (sb->s_bdi != &noop_backing_dev_info) { + if (sb->s_iflags & SB_I_PERSB_BDI && !(sb->s_iflags & SB_I_RETIRED)) + bdi_unregister(sb->s_bdi); + } + sb->s_iflags |= SB_I_RETIRED; + up_write(&sb->s_umount); +} +EXPORT_SYMBOL(retire_super); + /** * generic_shutdown_super - common helper for ->kill_sb() * @sb: superblock to kill @@ -468,12 +492,12 @@ void generic_shutdown_super(struct super_block *sb) } } spin_lock(&sb_lock); - /* should be initialized for __put_super_and_need_restart() */ hlist_del_init(&sb->s_instances); spin_unlock(&sb_lock); up_write(&sb->s_umount); if (sb->s_bdi != &noop_backing_dev_info) { - if (sb->s_iflags & SB_I_PERSB_BDI) + /* retire should have already unregistered bdi */ + if (sb->s_iflags & SB_I_PERSB_BDI && !(sb->s_iflags & SB_I_RETIRED)) bdi_unregister(sb->s_bdi); bdi_put(sb->s_bdi); sb->s_bdi = &noop_backing_dev_info; @@ -1216,7 +1240,7 @@ static int set_bdev_super_fc(struct super_block *s, struct fs_context *fc) static int test_bdev_super_fc(struct super_block *s, struct fs_context *fc) { - return s->s_bdev == fc->sget_key; + return !(s->s_iflags & SB_I_RETIRED) && s->s_bdev == fc->sget_key; } /** @@ -1307,7 +1331,7 @@ EXPORT_SYMBOL(get_tree_bdev); static int test_bdev_super(struct super_block *s, void *data) { - return (void *)s->s_bdev == data; + return !(s->s_iflags & SB_I_RETIRED) && (void *)s->s_bdev == data; } struct dentry *mount_bdev(struct file_system_type *fs_type, diff --git a/include/linux/fs.h b/include/linux/fs.h index bbde95387a23a..ef392fd2361bd 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -1411,6 +1411,7 @@ extern int send_sigurg(struct fown_struct *fown); #define SB_I_SKIP_SYNC 0x00000100 /* Skip superblock at global sync */ #define SB_I_PERSB_BDI 0x00000200 /* has a per-sb bdi */ #define SB_I_TS_EXPIRY_WARNED 0x00000400 /* warned about timestamp range expiry */ +#define SB_I_RETIRED 0x00000800 /* superblock shouldn't be reused */ /* Possible states of 'frozen' field */ enum { @@ -2424,6 +2425,7 @@ extern struct dentry *mount_nodev(struct file_system_type *fs_type, int flags, void *data, int (*fill_super)(struct super_block *, void *, int)); extern struct dentry *mount_subtree(struct vfsmount *mnt, const char *path); +void retire_super(struct super_block *sb); void generic_shutdown_super(struct super_block *sb); void kill_block_super(struct super_block *sb); void kill_anon_super(struct super_block *sb); -- 2.31.0