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=1794404760; b=3e8fCl/u/S1Cn2tDIQ9am8kIlsioE4nXrGK6kC4tHXbOGhGxmiJpCtxHOpSxBEZFuhQW kvBVmwtfXpNXG03qFXObo3RIF2O+AjoSNVHWRUfBaUyJUocUBVd5PV3TebFQBa3X+LdoE JPSLvCVX6BTlfzZxdmyhS4ZCgu85T/WBcL8hUZQupD8eUFmOYd7kwevkU6Yg8W5efzZ0/ 3+RXIGNBzXgG6D4fsb7QIU0fg/rx2tMpxPfVxOnbBnJbSDZXrDpk+3ZkcbLIS7bg2ziav 7I/5fHMWzt2TPR34azq61thozblEQxLBb4eu6UngMiG9Qoz4RbacXEyeovsqLGO+ogA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794404760; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=fwbMj1yWYGZi1OYf9CHrCwPOZeyOX2ZRNCOK1hAUYEo=; b=FDVkNPtSvq/BkbN6woxCrR81xuKtva4niyob51O4adYSVpECBqoPeYUfAn7PZlDU9WNG P29LcF9vShfXnBrQEX/fJCq7yJ6U0YBWKsaF5DpT/7LA3CXxXcwyRLk8PB85LTLrd//Ud dWs0vGqDACq1/K2yMVUZnNFhbUOWJOSIoYKPC9Ld9gSHB9jXHMhcbq0GxqFLt2zC1LOwv nF8bjuCdUaxcVjR9bGJNq+PjFtxHrWaVCy2+5etsdZ/FWv1uac06s50zZ+Tgiz14xpmw2 tZdkReHbUWev5nzvO2G1FEfPC+0P9s8eDXiaQEbDb65o07vbk+5sFXKqUNfxoMXdlig== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=PViGSOjW; 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 E9E7A606A321 for ; Wed, 11 Nov 2026 13:45:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=PViGSOjW Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4239C1F00A08; Wed, 11 Nov 2026 13:45:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794404759; bh=fwbMj1yWYGZi1OYf9CHrCwPOZeyOX2ZRNCOK1hAUYEo=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=PViGSOjWy3F9FDj9ABJg93P0b8gLIXxrTK580eKuNlynwYjG9g7JpwYGSD7hZeU4H t6dynhmynqnWYtES/lo726erhRlJ6TLpq32a2kpE7ym4omt6fag8AR56h69QjO8yAe 9zM16Af36df0cn/bifL3aaXg/FINdGXuFaTi27kL6AJv7qPBeC0JOdsS1vkCkYI0tk NDg2Vx1KYY0T+qHyUUPza7ybPHKHQQEUUsf8jQPaLrz9xHf1NIz7Y0ZuqIFMXIAPvp oS+78/sT5qysaIs/JGcTgAvvPvjSPG/AUmM3oJhm4PhXCKH0/nw6CAzC7rNbrruzRu FSUMukqsTfkNw== From: Sasha Levin To: stable@vger.kernel.org Cc: Hsiu-Hsien Lee , Jan Kara , Theodore Ts'o , Sasha Levin Subject: [PATCH 5.15.y 3/3] ext4: fix fast commit replay failing on a read-only mount Date: Wed, 11 Nov 2026 08:45:56 -0500 Message-ID: <20261111134523.2064738-3-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261111134523.2064738-1-sashal@kernel.org> References: <20261107060307-failed-5.15-e1a881ea4674@kernel.org> <20261111134523.2064738-1-sashal@kernel.org> 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 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 0a4ca26ed11f9..908f247ccccba 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -5334,6 +5334,7 @@ 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; @@ -5390,6 +5391,7 @@ static int ext4_load_journal(struct super_block *sb, } ext4_msg(sb, KERN_INFO, "write access will " "be enabled during recovery"); + enable_write = true; } } @@ -5406,7 +5408,19 @@ 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