[PATCH] ocfs2: fix circular locking dependency in ocfs2_dio_end_io_write

[syzbot]

From: Aleksandr Nogikh <nog...@google.com>

A circular locking dependency involves INODE_ALLOC_SYSTEM_INODE,
EXTENT_ALLOC_SYSTEM_INODE, and ORPHAN_DIR_SYSTEM_INODE.

1. ocfs2_mknod() acquires INODE_ALLOC then EXTENT_ALLOC.
2. ocfs2_dio_end_io_write() acquires EXTENT_ALLOC for unwritten extents,
then ORPHAN_DIR via ocfs2_del_inode_from_orphan() while still holding
EXTENT_ALLOC.
3. ocfs2_wipe_inode() acquires ORPHAN_DIR then INODE_ALLOC via
ocfs2_remove_inode.

Break the cycle in ocfs2_dio_end_io_write() by freeing the allocation
contexts (releasing EXTENT_ALLOC) before acquiring ORPHAN_DIR.

WARNING: possible circular locking dependency detected
------------------------------------------------------
is trying to acquire lock:
ffff8881e78b33a0
(&ocfs2_sysfile_lock_key[INODE_ALLOC_SYSTEM_INODE]){+.+.}-{4:4}, at:
ocfs2_evict_inode+0x1539/0x43b0 fs/ocfs2/inode.c:1299

but task is already holding lock:
ffff8881e78b4fa0
(&ocfs2_sysfile_lock_key[ORPHAN_DIR_SYSTEM_INODE]){+.+.}-{4:4}, at:
ocfs2_evict_inode+0xe97/0x43b0 fs/ocfs2/inode.c:1299

the existing dependency chain (in reverse order) is:

-> #2 (&ocfs2_sysfile_lock_key[ORPHAN_DIR_SYSTEM_INODE]){+.+.}-{4:4}:
inode_lock include/linux/fs.h:1029 [inline]
ocfs2_del_inode_from_orphan+0x12e/0x7a0 fs/ocfs2/namei.c:2728
ocfs2_dio_end_io+0xf9c/0x1370 fs/ocfs2/aops.c:2418
dio_complete+0x25b/0x790 fs/direct-io.c:281

-> #1 (&ocfs2_sysfile_lock_key[EXTENT_ALLOC_SYSTEM_INODE]){+.+.}-{4:4}:
inode_lock include/linux/fs.h:1029 [inline]
ocfs2_reserve_suballoc_bits+0x16d/0x4840 fs/ocfs2/suballoc.c:882
ocfs2_reserve_new_metadata_blocks+0x415/0x9a0
fs/ocfs2/suballoc.c:1078
ocfs2_mknod+0x10f3/0x2260 fs/ocfs2/namei.c:351

-> #0 (&ocfs2_sysfile_lock_key[INODE_ALLOC_SYSTEM_INODE]){+.+.}-{4:4}:
__lock_acquire+0x15a5/0x2cf0 kernel/locking/lockdep.c:5237
lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5868
down_write+0x96/0x200 kernel/locking/rwsem.c:1625
inode_lock include/linux/fs.h:1029 [inline]
ocfs2_remove_inode fs/ocfs2/inode.c:733 [inline]
ocfs2_wipe_inode fs/ocfs2/inode.c:896 [inline]
ocfs2_delete_inode fs/ocfs2/inode.c:1157 [inline]
ocfs2_evict_inode+0x1539/0x43b0 fs/ocfs2/inode.c:1299

Chain exists of:
&ocfs2_sysfile_lock_key[INODE_ALLOC_SYSTEM_INODE] -->
&ocfs2_sysfile_lock_key[EXTENT_ALLOC_SYSTEM_INODE] -->
&ocfs2_sysfile_lock_key[ORPHAN_DIR_SYSTEM_INODE]

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&ocfs2_sysfile_lock_key[ORPHAN_DIR_SYSTEM_INODE]);
lock(&ocfs2_sysfile_lock_key[EXTENT_ALLOC_SYSTEM_INODE]);
lock(&ocfs2_sysfile_lock_key[ORPHAN_DIR_SYSTEM_INODE]);
lock(&ocfs2_sysfile_lock_key[INODE_ALLOC_SYSTEM_INODE]);

*** DEADLOCK ***

Fixes: d647c5b2fbf8 ("ocfs2: split transactions in dio completion to avoid credit exhaustion")
Assisted-by: Gemini:gemini-3.1-pro-preview Gemini:gemini-3-flash-preview syzbot
Reported-by: syzbot+b225d4...@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=b225d4dfce6219600c42
Link: https://syzkaller.appspot.com/ai_job?id=0b53ce1e-2972-4192-aa85-8097a702762c
Signed-off-by: Aleksandr Nogikh <nog...@google.com>

---
diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c
index 6ec198bda..4acdbb708 100644
--- a/fs/ocfs2/aops.c
+++ b/fs/ocfs2/aops.c
@@ -2372,6 +2372,15 @@ static int ocfs2_dio_end_io_write(struct inode *inode,
unlock:
up_write(&oi->ip_alloc_sem);

+ if (data_ac) {
+ ocfs2_free_alloc_context(data_ac);
+ data_ac = NULL;
+ }
+ if (meta_ac) {
+ ocfs2_free_alloc_context(meta_ac);
+ meta_ac = NULL;
+ }
+
/* everything looks good, let's start the cleanup */
if (!ret && dwc->dw_orphaned) {
BUG_ON(dwc->dw_writer_pid != task_pid_nr(current));
@@ -2383,10 +2392,6 @@ static int ocfs2_dio_end_io_write(struct inode *inode,
ocfs2_inode_unlock(inode, 1);
brelse(di_bh);
out:
- if (data_ac)
- ocfs2_free_alloc_context(data_ac);
- if (meta_ac)
- ocfs2_free_alloc_context(meta_ac);
ocfs2_run_deallocs(osb, &dealloc);
ocfs2_dio_free_write_ctx(inode, dwc);



base-commit: e7ae89a0c97ce2b68b0983cd01eda67cf373517d
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