From patchwork Thu Feb 10 16:51:42 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Goldwyn Rodrigues X-Patchwork-Id: 12742204 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 89673C433F5 for ; Thu, 10 Feb 2022 16:51:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244818AbiBJQvq (ORCPT ); Thu, 10 Feb 2022 11:51:46 -0500 Received: from mxb-00190b01.gslb.pphosted.com ([23.128.96.19]:35640 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S244375AbiBJQvp (ORCPT ); Thu, 10 Feb 2022 11:51:45 -0500 Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.220.28]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 98309EE; Thu, 10 Feb 2022 08:51:46 -0800 (PST) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id 4E1F121121; Thu, 10 Feb 2022 16:51:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1644511905; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type; bh=IYGYQc5+DmfMVKXLKY+jywQH8/yCGWAk5raliA2Ua8A=; b=KdU4IMRUtt07PIUbUWCPUNaVK1Op56Cm2m+sVGPj4s2RqN9fN59yX88oW/JI+NVDvwIDM+ 9x8C1YP2H6Cox1VVFF8GEbWcZI2mE7sMtFukj0VyVAA4KKEZpvPsUtBUMGUt9WZm7sWldL JVYFdgFeZ5FYdUfPj2f7I0odwbzCIqw= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1644511905; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type; bh=IYGYQc5+DmfMVKXLKY+jywQH8/yCGWAk5raliA2Ua8A=; b=BE5lRfziXErod1Fbvr6Yj+HYsNUjAqWSrDW+HXBKOvqyyLwh0j50rZ1KRPXY4NoAcG9AtJ mKNng34KDh1bhnBg== Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id D940513C14; Thu, 10 Feb 2022 16:51:44 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id BmoJKaBCBWL7PgAAMHmgww (envelope-from ); Thu, 10 Feb 2022 16:51:44 +0000 Date: Thu, 10 Feb 2022 10:51:42 -0600 From: Goldwyn Rodrigues To: linux-btrfs@vger.kernel.org, linux-fsdevel@vger.kernel.org Cc: dhowells@redhat.com, fvogt@suse.com Subject: [PATCH] Fix read-only superblock in case of subvol RO remount Message-ID: <20220210165142.7zfgotun5qdtx4rq@fiona> MIME-Version: 1.0 Content-Disposition: inline Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org If a read-write root mount is remounted as read-only, the subvolume is also set to read-only. Use a rw_mounts counter to check the number of read-write mounts, and change superblock to read-only only in case there are no read-write subvol mounts. Since sb->s_flags can change while calling legacy_reconfigure(), use sb->s_flags instead of fc->sb_flags to re-evaluate sb->s_flags in reconfigure_super(). Test case: dd if=/dev/zero of=btrfsfs seek=240 count=0 bs=1M mkfs.btrfs btrfsfs mount btrfsfs /mnt btrfs subvol create /mnt/sv mount -o remount,ro /mnt mount -osubvol=/sv btrfsfs /mnt/sv findmnt # /mnt is RO, /mnt/sv RW mount -o remount,ro /mnt findmnt # /mnt is RO, /mnt/sv RO as well umount /mnt{/sv,} rm btrfsfs Reported-by: Fabian Vogt Signed-off-by: Goldwyn Rodrigues diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h index a2991971c6b5..2bb6869f15af 100644 --- a/fs/btrfs/ctree.h +++ b/fs/btrfs/ctree.h @@ -1060,6 +1060,9 @@ struct btrfs_fs_info { spinlock_t zone_active_bgs_lock; struct list_head zone_active_bgs; + /* Count of subvol mounts read-write */ + int rw_mounts; + #ifdef CONFIG_BTRFS_FS_REF_VERIFY spinlock_t ref_verify_lock; struct rb_root block_tree; diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c index 33cfc9e27451..32941e11e551 100644 --- a/fs/btrfs/super.c +++ b/fs/btrfs/super.c @@ -1835,6 +1835,11 @@ static struct dentry *btrfs_mount(struct file_system_type *fs_type, int flags, /* mount_subvol() will free subvol_name and mnt_root */ root = mount_subvol(subvol_name, subvol_objectid, mnt_root); + if (!IS_ERR(root) && !(flags & SB_RDONLY)) { + struct btrfs_fs_info *fs_info = btrfs_sb(mnt_root->mnt_sb); + fs_info->rw_mounts++; + } + out: return root; } @@ -1958,6 +1963,9 @@ static int btrfs_remount(struct super_block *sb, int *flags, char *data) goto out; if (*flags & SB_RDONLY) { + + if (--fs_info->rw_mounts > 0) + goto out; /* * this also happens on 'umount -rf' or on shutdown, when * the filesystem is busy. @@ -2057,6 +2065,8 @@ static int btrfs_remount(struct super_block *sb, int *flags, char *data) if (ret) goto restore; + fs_info->rw_mounts++; + btrfs_clear_sb_rdonly(sb); set_bit(BTRFS_FS_OPEN, &fs_info->flags); diff --git a/fs/super.c b/fs/super.c index f1d4a193602d..fd528f76f14b 100644 --- a/fs/super.c +++ b/fs/super.c @@ -913,7 +913,8 @@ int reconfigure_super(struct fs_context *fc) } WRITE_ONCE(sb->s_flags, ((sb->s_flags & ~fc->sb_flags_mask) | - (fc->sb_flags & fc->sb_flags_mask))); + (sb->s_flags & fc->sb_flags_mask))); + /* Needs to be ordered wrt mnt_is_readonly() */ smp_wmb(); sb->s_readonly_remount = 0;