From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794063205; b=gjpkRP91h9yHVG7fP052pixU/AnsArz58tnIiFHhoCW4zok8na8bNqvZPVTNHZ5KLghL /AUwbhct8b1IcXQ7uT9GYuCYtPflJrxTrQeAB+4YzVhkAsyktjmVdnGwvKm0pmJuO7xgS 9DDaZhE3xGrkvq/yHmcSUNQr2Yl3/H63B6mBzTZFgnPEXGsqfYkbMLKz5tTWaa8ozhT9b XQdEvryQzOPUwtTmCXrcKuJa0g0Ggnv8Az9pxD1q51FH4BD2HY2cIGgR29QmePghzuUAf TqPTe4sXIggNVLdLUdcybNOGV2BhVg728oQqDu7v2sp3t9FQQFC5huOPx/aAZ7EPAmQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794063205; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=w8eYhpG5PCHmZiNnbwuDo6/7rfn44uyeb8MvV0fCTA4=; b=K6VplADu1CgiAQT0Qru7hSN8c67nBrAW5b0LW0w/sfAGL3XRRvf+VtPJNPiJO67iAPuu Ce60hqDHqM3qJCSRSjW3LbFHNd+BUjWnSNSSgyVNBczoAplv3d628eAYY/M6umdjo50oN joB94C9VL3xwR7t/0lKMzRzg6QXD6lmhkOiBX8OOhShk0BcWtExilUHdzeYnhmLFnWq/7 ciujITlDISvzTLbb4YxU+DwKJo23ZNzyD7RXJHj+Ht2mc9CcrIeXnTImPl8/3M/HfX88d I2/ST1BgvqQLgxp0dEM4v/EYw7TanSNYZHLcDqI4znLnwL06lDnc1Qq9gQrKSLJkIoA== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=AObhtO4a; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0048C606D818; Sat, 7 Nov 2026 14:53:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=AObhtO4a Received: by smtp.kernel.org (Postfix) with ESMTPSA id A32E51F0089F; Sat, 7 Nov 2026 14:53:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1794063204; bh=w8eYhpG5PCHmZiNnbwuDo6/7rfn44uyeb8MvV0fCTA4=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=AObhtO4ao+uJDDh0yi0tCKbFhaHLdXHItUoWmEzXyXQ8cTD3AXIjsM1fQADJvGkSP 4ZfdyETH10lIDMNq/CHYHmhS8g3gv0lR08k/MFkPjesYBZOtaBk/BvjfVYO3IPIanH WSmHbNd6pIm0+nmgZ2cgbx2Vf7ciChAP8uWnohK4= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Hsiu-Hsien Lee , Jan Kara , Theodore Tso , Sasha Levin Subject: [PATCH 6.18 417/869] ext4: fix fast commit replay failing on a read-only mount Date: Sat, 7 Nov 2026 08:51:39 -0500 Message-ID: <20261107134907.552080761@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261107134852.069646174@linuxfoundation.org> References: <20261107134852.069646174@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Hsiu-Hsien Lee [ Upstream commit e1a881ea4674876721cab97680d1d8308f90e9a4 ] A filesystem with fast_commit that needs recovery cannot be mounted read-only: EXT4-fs (dm-0): INFO: recovery required on readonly filesystem EXT4-fs (dm-0): write access will be enabled during recovery WARNING: CPU: 22 PID: 5544 at fs/ext4/ext4_jbd2.c:73 ext4_journal_check_start __ext4_journal_start_sb __ext4_unlink ext4_fc_replay do_one_pass jbd2_journal_recover jbd2_journal_load __ext4_fill_super JBD2: journal recovery failed EXT4-fs (dm-0): error loading journal Fast commit replay runs ext4 metadata operations instead of writing blocks through the buffer cache: ext4_fc_replay_{unlink,link,create}() reach __ext4_unlink() and __ext4_link(), which start a handle. ext4_journal_check_start() returns -EROFS on a read-only sb, and as that is not -ENOENT it propagates out of jbd2_journal_recover() and kills the whole recovery. The EXT4_FC_REPLAY check that would hand out a no-journal handle sits after the sb_rdonly() test, so replay can never complete read-only. ext4_load_journal() has already promised that write access will be enabled during recovery, so make that true for the superblock as well: clear SB_RDONLY across jbd2_journal_load() when recovery is needed on a read-only mount and the devices are writable, as ext4_orphan_cleanup() does. Unlike ext4_handle_error(), which avoids SB_RDONLY because it would need s_umount, the sb here is still inside ext4_fill_super() and not published, so nothing can observe it. The failure is not clean either: the replay handlers passing a NULL handle (ext4_fc_replay_inode(), _add_range(), _del_range()) never hit ext4_journal_check_start() and do write, leaving a partially applied fast commit behind. Reproducer, where the unlink only ever reaches the fast commit area: mke2fs -q -F -t ext4 -O fast_commit -b 4096 /dev/sdb3 262144 mount /dev/sdb3 /mnt dd if=/dev/zero of=/mnt/victim bs=4k count=1 conv=fsync sync # victim now in a full commit rm /mnt/victim dd if=/dev/zero of=/mnt/trigger bs=4k count=1 conv=fsync mount -o ro /dev/sdb3 /mnt Without this patch that mount fails; with it recovery completes and victim is gone, i.e. the UNLINK record was really replayed. Fixes: 8016e29f4362 ("ext4: fast commit recovery path") Cc: stable@vger.kernel.org Signed-off-by: Hsiu-Hsien Lee Reviewed-by: Jan Kara Link: https://patch.msgid.link/20260812044353.1018268-1-swinds24@gmail.com Signed-off-by: Theodore Ts'o Signed-off-by: Sasha Levin --- fs/ext4/super.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/fs/ext4/super.c b/fs/ext4/super.c index b4ff7e692986b..2762628bbfc95 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -6016,6 +6016,7 @@ static int ext4_load_journal(struct super_block *sb, int err = 0; int really_read_only; int journal_dev_ro; + bool enable_write = false; if (WARN_ON_ONCE(!ext4_has_feature_journal(sb))) return -EFSCORRUPTED; @@ -6072,6 +6073,7 @@ static int ext4_load_journal(struct super_block *sb, } ext4_msg(sb, KERN_INFO, "write access will " "be enabled during recovery"); + enable_write = true; } } @@ -6088,7 +6090,19 @@ static int ext4_load_journal(struct super_block *sb, if (save) memcpy(save, ((char *) es) + EXT4_S_ERR_START, EXT4_S_ERR_LEN); + /* + * Fast commit replay performs regular ext4 metadata updates + * (see ext4_fc_replay()) which refuse to run on a read-only + * superblock. We promised write access above, so make that + * true for the duration of the recovery, the same way + * ext4_orphan_cleanup() does. The superblock is not published + * yet, so nothing can observe the transient state. + */ + if (enable_write) + sb->s_flags &= ~SB_RDONLY; err = jbd2_journal_load(journal); + if (enable_write) + sb->s_flags |= SB_RDONLY; if (save && memcmp(((char *) es) + EXT4_S_ERR_START, save, EXT4_S_ERR_LEN)) { memcpy(((char *) es) + EXT4_S_ERR_START, -- 2.53.0