======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.2.809/11976 is trying to acquire lock:
ffff88803796c060 (&ocfs2_file_ip_alloc_sem_key){++++}-{4:4}, at: ocfs2_page_mkwrite+0x2ff/0xc40

but task is already holding lock:
ffff88802e2d8520 (sb_pagefaults#5){.+.+}-{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#5){.+.+}-{0:0}:
       lock_acquire+0x120/0x360
       ocfs2_page_mkwrite+0x1da/0xc40
       do_page_mkwrite+0x14d/0x310
       do_wp_page+0x268d/0x5800
       __handle_mm_fault+0x1033/0x5440
       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+0x888/0xc90
       do_vfs_ioctl+0x1173/0x1430
       __se_sys_ioctl+0x82/0x170
       do_syscall_64+0xfa/0x3b0
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&ocfs2_file_ip_alloc_sem_key){++++}-{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
       do_wp_page+0x268d/0x5800
       __handle_mm_fault+0x1033/0x5440
       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:
  &ocfs2_file_ip_alloc_sem_key --> &mm->mmap_lock --> sb_pagefaults#5

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  rlock(sb_pagefaults#5);
                               lock(&mm->mmap_lock);
                               lock(sb_pagefaults#5);
  lock(&ocfs2_file_ip_alloc_sem_key);

 *** DEADLOCK ***

2 locks held by syz.2.809/11976:
 #0: ffff88810d7d4d20 (&mm->mmap_lock){++++}-{4:4}, at: lock_mm_and_find_vma+0x32/0x300
 #1: ffff88802e2d8520 (sb_pagefaults#5){.+.+}-{0:0}, at: do_page_mkwrite+0x14d/0x310

stack backtrace:
CPU: 0 UID: 0 PID: 11976 Comm: syz.2.809 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
 do_wp_page+0x268d/0x5800
 __handle_mm_fault+0x1033/0x5440
 handle_mm_fault+0x40a/0x8e0
 do_user_addr_fault+0x764/0x1390
 exc_page_fault+0x76/0xf0
 asm_exc_page_fault+0x26/0x30
RIP: 0033:0x7f11deb5882f
Code: d0 eb 0b 0f 1f 84 00 00 00 00 00 48 89 f8 48 83 fa 10 0f 82 83 00 00 00 0f 10 06 48 83 fa 20 0f 87 e3 00 00 00 0f 10 4c 16 f0 <0f> 11 07 0f 11 4c 17 f0 c3 0f 1f 84 00 00 00 00 00 48 89 f8 48 01
RSP: 002b:00007ffc2fca6398 EFLAGS: 00010283
RAX: 00002000000002c0 RBX: 0000000000000004 RCX: 8000000000000017
RDX: 0000000000000017 RSI: 0000001b3362f37a RDI: 00002000000002c0
RBP: 00007f11dedb7da0 R08: 0000001b33a20000 R09: 0000000000000001
R10: 0000000000000001 R11: 0000000000000009 R12: 00007f11dedb5fac
R13: 00007f11dedb5fa0 R14: fffffffffffffffe R15: 00007ffc2fca64b0
 </TASK>
