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Sun, 01 Mar 2026 22:17:15 -0800 (PST) Received: from localhost.localdomain ([202.127.77.110]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3598b27b7a6sm2790995a91.11.2026.03.01.22.17.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 01 Mar 2026 22:17:15 -0800 (PST) From: Heming Zhao To: joseph.qi@linux.alibaba.com Cc: Heming Zhao , ocfs2-devel@lists.linux.dev, linux-kernel@vger.kernel.org, activprithvi@gmail.com, syzbot+78359d5fbb04318c35e9@syzkaller.appspotmail.com Subject: [PATCH v2] ocfs2: fix deadlock when creating quota file Date: Mon, 2 Mar 2026 14:17:05 +0800 Message-ID: <20260302061707.7092-1-heming.zhao@suse.com> X-Mailer: git-send-email 2.43.0 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 Content-Type: text/plain; charset="utf-8" syzbot detected a circular locking dependency. the scenarios: CPU0 CPU1 ---- ---- lock(&ocfs2_quota_ip_alloc_sem_key); lock(&ocfs2_sysfile_lock_key[USER_QUOTA_SYS= TEM_INODE]); lock(&ocfs2_quota_ip_alloc_sem_key); lock(&ocfs2_sysfile_lock_key[ORPHAN_DIR_SYSTEM_INODE]); or: CPU0 CPU1 ---- ---- lock(&ocfs2_quota_ip_alloc_sem_key); lock(&dquot->dq_lock); lock(&ocfs2_quota_ip_alloc_sem_key); lock(&ocfs2_sysfile_lock_key[ORPHAN_DIR_SYSTEM_INODE]); Following are the code paths for above scenarios: path_openat ocfs2_create ocfs2_mknod + ocfs2_reserve_new_inode | ocfs2_reserve_suballoc_bits | inode_lock(alloc_inode) //C0: hold INODE_ALLOC_SYSTEM_INODE | //ocfs2_free_alloc_context(inode_ac) is called at the end of | //caller ocfs2_mknod to handle the release | + ocfs2_get_init_inode __dquot_initialize dqget ocfs2_acquire_dquot + ocfs2_lock_global_qf | down_write(&OCFS2_I(oinfo->dqi_gqinode)->ip_alloc_sem)//A2:grabbi= ng + ocfs2_create_local_dquot down_write(&OCFS2_I(lqinode)->ip_alloc_sem)//A3:grabbing evict ocfs2_evict_inode ocfs2_delete_inode ocfs2_wipe_inode + inode_lock(orphan_dir_inode) //B0:hold + ... + ocfs2_remove_inode inode_lock(inode_alloc_inode) //INODE_ALLOC_SYSTEM_INODE down_write(&inode->i_rwsem) //C1:grabbing generic_file_direct_write ocfs2_direct_IO __blockdev_direct_IO dio_complete ocfs2_dio_end_io ocfs2_dio_end_io_write + down_write(&oi->ip_alloc_sem) //A0:hold + ocfs2_del_inode_from_orphan inode_lock(orphan_dir_inode) //B1:grabbing Root cause for the circular locking: DIO completion path: holds oi->ip_alloc_sem and is trying to acquire the orphan_dir_inode lock. evict path: holds the orphan_dir_inode lock and is trying to acquire the inode_alloc_inode lock. ocfs2_mknod path: Holds the inode_alloc_inode lock (to allocate a new quota file) and is blocked waiting for oi->ip_alloc_sem in ocfs2_acquire_dquot(). How to fix: Replace down_write() with down_write_trylock() in ocfs2_acquire_dquot(). If acquiring oi->ip_alloc_sem fails, return -EBUSY to abort the file creati= on routine and break the deadlock. Reported-by: syzbot+78359d5fbb04318c35e9@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=3D78359d5fbb04318c35e9 Signed-off-by: Heming Zhao Reviewed-by: Joseph Qi --- v1 -> v2: - revise commit: the explanation in ocfs2_mknod() path - fix error handling mistake in ocfs2_lock_global_qf and=20 ocfs2_create_local_dquot --- fs/ocfs2/quota_global.c | 16 +++++++++++++++- fs/ocfs2/quota_local.c | 4 +++- 2 files changed, 18 insertions(+), 2 deletions(-) diff --git a/fs/ocfs2/quota_global.c b/fs/ocfs2/quota_global.c index e85b1ccf81be..77b8f0363e94 100644 --- a/fs/ocfs2/quota_global.c +++ b/fs/ocfs2/quota_global.c @@ -311,11 +311,25 @@ int ocfs2_lock_global_qf(struct ocfs2_mem_dqinfo *oin= fo, int ex) spin_unlock(&dq_data_lock); if (ex) { inode_lock(oinfo->dqi_gqinode); - down_write(&OCFS2_I(oinfo->dqi_gqinode)->ip_alloc_sem); + if (!down_write_trylock(&OCFS2_I(oinfo->dqi_gqinode)->ip_alloc_sem)) { + inode_unlock(oinfo->dqi_gqinode); + status =3D -EBUSY; + goto bail; + } } else { down_read(&OCFS2_I(oinfo->dqi_gqinode)->ip_alloc_sem); } return 0; + +bail: + /* does a similar job as ocfs2_unlock_global_qf */ + ocfs2_inode_unlock(oinfo->dqi_gqinode, ex); + brelse(oinfo->dqi_gqi_bh); + spin_lock(&dq_data_lock); + if (!--oinfo->dqi_gqi_count) + oinfo->dqi_gqi_bh =3D NULL; + spin_unlock(&dq_data_lock); + return status; } =20 void ocfs2_unlock_global_qf(struct ocfs2_mem_dqinfo *oinfo, int ex) diff --git a/fs/ocfs2/quota_local.c b/fs/ocfs2/quota_local.c index c4e0117d8977..e749cd064c87 100644 --- a/fs/ocfs2/quota_local.c +++ b/fs/ocfs2/quota_local.c @@ -1224,7 +1224,9 @@ int ocfs2_create_local_dquot(struct dquot *dquot) int status; u64 pcount; =20 - down_write(&OCFS2_I(lqinode)->ip_alloc_sem); + if (!down_write_trylock(&OCFS2_I(lqinode)->ip_alloc_sem)) + return -EBUSY; + chunk =3D ocfs2_find_free_entry(sb, type, &offset); if (!chunk) { chunk =3D ocfs2_extend_local_quota_file(sb, type, &offset); --=20 2.43.0