* [PATCH v2] ocfs2: fix deadlock when creating quota file
@ 2026-03-02 6:17 Heming Zhao
2026-03-02 9:29 ` Joseph Qi
0 siblings, 1 reply; 2+ messages in thread
From: Heming Zhao @ 2026-03-02 6:17 UTC (permalink / raw)
To: joseph.qi
Cc: Heming Zhao, ocfs2-devel, linux-kernel, activprithvi,
syzbot+78359d5fbb04318c35e9
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 <heming.zhao@suse.com>
---
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);
--
2.43.0
^ permalink raw reply [flat|nested] 2+ messages in thread* Re: [PATCH v2] ocfs2: fix deadlock when creating quota file
2026-03-02 6:17 [PATCH v2] ocfs2: fix deadlock when creating quota file Heming Zhao
@ 2026-03-02 9:29 ` Joseph Qi
0 siblings, 0 replies; 2+ messages in thread
From: Joseph Qi @ 2026-03-02 9:29 UTC (permalink / raw)
To: Heming Zhao, akpm
Cc: ocfs2-devel, linux-kernel, activprithvi, syzbot+78359d5fbb04318c35e9
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 <heming.zhao@suse.com>
Looks fine.
Reviewed-by: Joseph Qi <joseph.qi@linux.alibaba.com>
> ---
> 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);
^ permalink raw reply [flat|nested] 2+ messages in thread
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2026-03-02 9:29 ` Joseph Qi
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