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Mon, 02 Mar 2026 17:29:47 +0800 Message-ID: <0f2ed4dc-8ad9-4dba-834c-a672de0cee97@linux.alibaba.com> Date: Mon, 2 Mar 2026 17:29:47 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] ocfs2: fix deadlock when creating quota file To: Heming Zhao , akpm Cc: ocfs2-devel@lists.linux.dev, linux-kernel@vger.kernel.org, activprithvi@gmail.com, syzbot+78359d5fbb04318c35e9@syzkaller.appspotmail.com References: <20260302061707.7092-1-heming.zhao@suse.com> From: Joseph Qi In-Reply-To: <20260302061707.7092-1-heming.zhao@suse.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 3/2/26 2:17 PM, Heming Zhao wrote: > syzbot detected a circular locking dependency. the scenarios: > > CPU0 CPU1 > ---- ---- > lock(&ocfs2_quota_ip_alloc_sem_key); > lock(&ocfs2_sysfile_lock_key[USER_QUOTA_SYSTEM_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:grabbing > + 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 creation > routine and break the deadlock. > > Reported-by: syzbot+78359d5fbb04318c35e9@syzkaller.appspotmail.com > Closes: https://syzkaller.appspot.com/bug?extid=78359d5fbb04318c35e9 > Signed-off-by: Heming Zhao Looks fine. Reviewed-by: Joseph Qi > --- > v1 -> v2: > - revise commit: the explanation in ocfs2_mknod() path > - fix error handling mistake in ocfs2_lock_global_qf and > 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 *oinfo, 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 = -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 = NULL; > + spin_unlock(&dq_data_lock); > + return status; > } > > 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; > > - down_write(&OCFS2_I(lqinode)->ip_alloc_sem); > + if (!down_write_trylock(&OCFS2_I(lqinode)->ip_alloc_sem)) > + return -EBUSY; > + > chunk = ocfs2_find_free_entry(sb, type, &offset); > if (!chunk) { > chunk = ocfs2_extend_local_quota_file(sb, type, &offset);