======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.4.32/6172 is trying to acquire lock:
ffff888112fc4ee0 (&oi->ip_alloc_sem){++++}-{4:4}, at: ocfs2_page_mkwrite+0x2ff/0xc40

but task is already holding lock:
ffff888112adc520 (sb_pagefaults#3){.+.+}-{0:0}, at: do_page_mkwrite+0x14d/0x310

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (sb_pagefaults#3){.+.+}-{0:0}:
       lock_acquire+0x120/0x360
       ocfs2_page_mkwrite+0x1da/0xc40
       do_page_mkwrite+0x14d/0x310
       __handle_mm_fault+0x1916/0x5440
       handle_mm_fault+0x40a/0x8e0
       do_user_addr_fault+0x764/0x1390
       exc_page_fault+0x76/0xf0
       asm_exc_page_fault+0x26/0x30

-> #1 (&mm->mmap_lock){++++}-{4:4}:
       lock_acquire+0x120/0x360
       __might_fault+0xcc/0x130
       _copy_to_user+0x2c/0xb0
       fiemap_fill_next_extent+0x1c0/0x390
       ocfs2_fiemap+0x9dc/0xc90
       do_vfs_ioctl+0x1173/0x1430
       __se_sys_ioctl+0x82/0x170
       do_syscall_64+0xfa/0x3b0
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&oi->ip_alloc_sem){++++}-{4:4}:
       validate_chain+0xb9b/0x2140
       __lock_acquire+0xab9/0xd20
       lock_acquire+0x120/0x360
       down_write+0x96/0x1f0
       ocfs2_page_mkwrite+0x2ff/0xc40
       do_page_mkwrite+0x14d/0x310
       __handle_mm_fault+0x1916/0x5440
       handle_mm_fault+0x40a/0x8e0
       do_user_addr_fault+0x764/0x1390
       exc_page_fault+0x76/0xf0
       asm_exc_page_fault+0x26/0x30

other info that might help us debug this:

Chain exists of:
  &oi->ip_alloc_sem --> &mm->mmap_lock --> sb_pagefaults#3

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  rlock(sb_pagefaults#3);
                               lock(&mm->mmap_lock);
                               lock(sb_pagefaults#3);
  lock(&oi->ip_alloc_sem);

 *** DEADLOCK ***

2 locks held by syz.4.32/6172:
 #0: ffff88802389e2a0 (&mm->mmap_lock){++++}-{4:4}, at: lock_mm_and_find_vma+0x32/0x300
 #1: ffff888112adc520 (sb_pagefaults#3){.+.+}-{0:0}, at: do_page_mkwrite+0x14d/0x310

stack backtrace:
CPU: 1 UID: 0 PID: 6172 Comm: syz.4.32 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250
 print_circular_bug+0x2ee/0x310
 check_noncircular+0x134/0x160
 validate_chain+0xb9b/0x2140
 __lock_acquire+0xab9/0xd20
 lock_acquire+0x120/0x360
 down_write+0x96/0x1f0
 ocfs2_page_mkwrite+0x2ff/0xc40
 do_page_mkwrite+0x14d/0x310
 __handle_mm_fault+0x1916/0x5440
 handle_mm_fault+0x40a/0x8e0
 do_user_addr_fault+0x764/0x1390
 exc_page_fault+0x76/0xf0
 asm_exc_page_fault+0x26/0x30
RIP: 0033:0x7fac6a9588c6
Code: 4c 17 f0 c3 83 fa 08 73 2b 83 fa 04 73 16 83 fa 01 7c 10 8a 0e 74 0a 0f b7 74 16 fe 66 89 74 17 fe 88 0f c3 8b 4c 16 fc 8b 36 <89> 4c 17 fc 89 37 c3 0f 1f 00 48 8b 4c 16 f8 48 8b 36 48 89 37 48
RSP: 002b:00007ffcf2ba52d8 EFLAGS: 00010202
RAX: 0000200000000200 RBX: 0000000000000004 RCX: 0000000000737562
RDX: 0000000000000006 RSI: 0000000075622f2e RDI: 0000200000000200
RBP: 00007fac6abb7da0 R08: 0000001b2de20000 R09: 0000000000000001
R10: 0000000000000001 R11: 0000000000000009 R12: 00007fac6abb5fac
R13: 00007fac6abb5fa0 R14: fffffffffffffffe R15: 00007ffcf2ba53f0
 </TASK>
