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Tue, 18 Mar 2025 07:53:07 GMT Received: from smtpav02.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id A709020040; Tue, 18 Mar 2025 07:53:07 +0000 (GMT) Received: from smtpav02.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id CE3B220043; Tue, 18 Mar 2025 07:53:05 +0000 (GMT) Received: from li-dc0c254c-257c-11b2-a85c-98b6c1322444.ibm.com (unknown [9.39.27.85]) by smtpav02.fra02v.mail.ibm.com (Postfix) with ESMTP; Tue, 18 Mar 2025 07:53:05 +0000 (GMT) From: Ojaswin Mujoo To: linux-ext4@vger.kernel.org, "Theodore Ts'o" Cc: Jan Kara , Baokun Li , Ritesh Harjani , linux-kernel@vger.kernel.org, Mahesh Kumar Subject: [PATCH v4 2/3] ext4: avoid journaling sb update on error if journal is destroying Date: Tue, 18 Mar 2025 13:22:56 +0530 Message-ID: <9613c465d6ff00cd315602f99283d5f24018c3f7.1742279837.git.ojaswin@linux.ibm.com> X-Mailer: git-send-email 2.48.1 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: eyISuN_Gjy7nB416ZjLR8azaD-kWGOlz X-Proofpoint-GUID: PjGfiTZ7RDnmkI_YfDUUYk528kI7Yu-u X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1093,Hydra:6.0.680,FMLib:17.12.68.34 definitions=2025-03-18_03,2025-03-17_03,2024-11-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 bulkscore=0 mlxlogscore=999 priorityscore=1501 adultscore=0 suspectscore=0 impostorscore=0 mlxscore=0 lowpriorityscore=0 clxscore=1015 phishscore=0 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2502280000 definitions=main-2503180052 Content-Type: text/plain; charset="utf-8" Presently we always BUG_ON if trying to start a transaction on a journal ma= rked with JBD2_UNMOUNT, since this should never happen. However, while ltp runni= ng stress tests, it was observed that in case of some error handling paths, it= is possible for update_super_work to start a transaction after the journal is destroyed eg: (umount) ext4_kill_sb kill_block_super generic_shutdown_super sync_filesystem /* commits all txns */ evict_inodes /* might start a new txn */ ext4_put_super flush_work(&sbi->s_sb_upd_work) /* flush the workqueue */ jbd2_journal_destroy journal_kill_thread journal->j_flags |=3D JBD2_UNMOUNT; jbd2_journal_commit_transaction jbd2_journal_get_descriptor_buffer jbd2_journal_bmap ext4_journal_bmap ext4_map_blocks ... ext4_inode_error ext4_handle_error schedule_work(&sbi->s_sb_upd_work) /* work queue kicks in */ update_super_work jbd2_journal_start start_this_handle BUG_ON(journal->j_flag= s & JBD2_UNMOUNT) Hence, introduce a new mount flag to indicate journal is destroying and onl= y do a journaled (and deferred) update of sb if this flag is not set. Otherwise,= just fallback to an un-journaled commit. Further, in the journal destroy path, we have the following sequence: 1. Set mount flag indicating journal is destroying 2. force a commit and wait for it 3. flush pending sb updates This sequence is important as it ensures that, after this point, there is n= o sb update that might be journaled so it is safe to update the sb outside the journal. (To avoid race discussed in 2d01ddc86606) Also, we don't need a similar check in ext4_grp_locked_error since it is on= ly called from mballoc and AFAICT it would be always valid to schedule work he= re. Fixes: 2d01ddc86606 ("ext4: save error info to sb through journal if availa= ble") Reported-by: Mahesh Kumar Signed-off-by: Ojaswin Mujoo Reviewed-by: Jan Kara --- fs/ext4/ext4.h | 3 ++- fs/ext4/ext4_jbd2.h | 15 +++++++++++++++ fs/ext4/super.c | 16 ++++++++-------- 3 files changed, 25 insertions(+), 9 deletions(-) diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h index 2b7d781bfcad..0685bb68e64a 100644 --- a/fs/ext4/ext4.h +++ b/fs/ext4/ext4.h @@ -1823,7 +1823,8 @@ static inline int ext4_valid_inum(struct super_block = *sb, unsigned long ino) */ enum { EXT4_MF_MNTDIR_SAMPLED, - EXT4_MF_FC_INELIGIBLE /* Fast commit ineligible */ + EXT4_MF_FC_INELIGIBLE, /* Fast commit ineligible */ + EXT4_MF_JOURNAL_DESTROY /* Journal is in process of destroying */ }; =20 static inline void ext4_set_mount_flag(struct super_block *sb, int bit) diff --git a/fs/ext4/ext4_jbd2.h b/fs/ext4/ext4_jbd2.h index 9b3c9df02a39..3221714d9901 100644 --- a/fs/ext4/ext4_jbd2.h +++ b/fs/ext4/ext4_jbd2.h @@ -437,6 +437,21 @@ static inline int ext4_journal_destroy(struct ext4_sb_= info *sbi, journal_t *jour { int err =3D 0; =20 + /* + * At this point only two things can be operating on the journal. + * JBD2 thread performing transaction commit and s_sb_upd_work + * issuing sb update through the journal. Once we set + * EXT4_JOURNAL_DESTROY, new ext4_handle_error() calls will not + * queue s_sb_upd_work and ext4_force_commit() makes sure any + * ext4_handle_error() calls from the running transaction commit are + * finished. Hence no new s_sb_upd_work can be queued after we + * flush it here. + */ + ext4_set_mount_flag(sbi->s_sb, EXT4_MF_JOURNAL_DESTROY); + + ext4_force_commit(sbi->s_sb); + flush_work(&sbi->s_sb_upd_work); + err =3D jbd2_journal_destroy(journal); sbi->s_journal =3D NULL; =20 diff --git a/fs/ext4/super.c b/fs/ext4/super.c index 8ad664d47806..46f7c9922cda 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -704,9 +704,13 @@ static void ext4_handle_error(struct super_block *sb, = bool force_ro, int error, * In case the fs should keep running, we need to writeout * superblock through the journal. Due to lock ordering * constraints, it may not be safe to do it right here so we - * defer superblock flushing to a workqueue. + * defer superblock flushing to a workqueue. We just need to be + * careful when the journal is already shutting down. If we get + * here in that case, just update the sb directly as the last + * transaction won't commit anyway. */ - if (continue_fs && journal) + if (continue_fs && journal && + !ext4_test_mount_flag(sb, EXT4_MF_JOURNAL_DESTROY)) schedule_work(&EXT4_SB(sb)->s_sb_upd_work); else ext4_commit_super(sb); @@ -1291,7 +1295,6 @@ static void ext4_put_super(struct super_block *sb) ext4_unregister_li_request(sb); ext4_quotas_off(sb, EXT4_MAXQUOTAS); =20 - flush_work(&sbi->s_sb_upd_work); destroy_workqueue(sbi->rsv_conversion_wq); ext4_release_orphan_info(sb); =20 @@ -1301,7 +1304,8 @@ static void ext4_put_super(struct super_block *sb) if ((err < 0) && !aborted) { ext4_abort(sb, -err, "Couldn't clean up the journal"); } - } + } else + flush_work(&sbi->s_sb_upd_work); =20 ext4_es_unregister_shrinker(sbi); timer_shutdown_sync(&sbi->s_err_report); @@ -4957,8 +4961,6 @@ static int ext4_load_and_init_journal(struct super_bl= ock *sb, return 0; =20 out: - /* flush s_sb_upd_work before destroying the journal. */ - flush_work(&sbi->s_sb_upd_work); ext4_journal_destroy(sbi, sbi->s_journal); return -EINVAL; } @@ -5648,8 +5650,6 @@ failed_mount8: __maybe_unused sbi->s_ea_block_cache =3D NULL; =20 if (sbi->s_journal) { - /* flush s_sb_upd_work before journal destroy. */ - flush_work(&sbi->s_sb_upd_work); ext4_journal_destroy(sbi, sbi->s_journal); } failed_mount3a: --=20 2.48.1