loop4: detected capacity change from 0 to 32768
ocfs2: Mounting device (7,4) on (node local, slot 0) with ordered data mode.
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.4.1721/13166 is trying to acquire lock:
ffff888103680660 (&ocfs2_file_ip_alloc_sem_key){++++}-{4:4}, at: ocfs2_page_mkwrite+0x2ff/0xc40

but task is already holding lock:
ffff88803d0ca520 (sb_pagefaults#6){.+.+}-{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#6){.+.+}-{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
       rep_movs_alternative+0x54/0x90
       _copy_to_iter+0x24f/0x1790
       copy_page_to_iter+0x10c/0x1c0
       filemap_read+0x7c0/0x11a0
       ocfs2_file_read_iter+0x3fa/0xa80
       vfs_read+0x55a/0xa30
       ksys_read+0x145/0x250
       do_syscall_64+0xfa/0x3b0
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #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 (&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
       __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
       rep_movs_alternative+0x54/0x90
       _copy_to_iter+0x24f/0x1790
       copy_page_to_iter+0x10c/0x1c0
       filemap_read+0x7c0/0x11a0
       ocfs2_file_read_iter+0x3fa/0xa80
       vfs_read+0x55a/0xa30
       ksys_read+0x145/0x250
       do_syscall_64+0xfa/0x3b0
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

Chain exists of:
  &ocfs2_file_ip_alloc_sem_key --> &mm->mmap_lock --> sb_pagefaults#6

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  rlock(sb_pagefaults#6);
                               lock(&mm->mmap_lock);
                               lock(sb_pagefaults#6);
  lock(&ocfs2_file_ip_alloc_sem_key);

 *** DEADLOCK ***

3 locks held by syz.4.1721/13166:
 #0: ffff88811a79d8f8 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x247/0x320
 #1: ffff8880238c2ce0 (&mm->mmap_lock){++++}-{4:4}, at: lock_mm_and_find_vma+0x32/0x300
 #2: ffff88803d0ca520 (sb_pagefaults#6){.+.+}-{0:0}, at: do_page_mkwrite+0x14d/0x310

stack backtrace:
CPU: 1 UID: 0 PID: 13166 Comm: syz.4.1721 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: 0010:rep_movs_alternative+0x54/0x90
Code: 00 00 00 0f 1f 00 48 8b 06 48 89 07 48 83 c6 08 48 83 c7 08 83 e9 08 74 db 83 f9 08 73 e8 eb c5 eb 05 c3 cc cc cc cc 48 8b 06 <48> 89 07 48 8d 47 08 48 83 e0 f8 48 29 f8 48 01 c7 48 01 c6 48 29
RSP: 0018:ffffc900064cf6d8 EFLAGS: 00010206
RAX: 0000000000000000 RBX: ffff88811ae5e000 RCX: 0000000000001000
RDX: 0000000000000000 RSI: ffff88811ae5e000 RDI: 0000200000004880
RBP: ffffc900064cf848 R08: ffff88811ae5efff R09: 1ffff110235cbdff
R10: dffffc0000000000 R11: ffffed10235cbe00 R12: 1ffff92000c99faf
R13: 0000200000004880 R14: ffffc900064cfd88 R15: 0000000000001000
 _copy_to_iter+0x24f/0x1790
 copy_page_to_iter+0x10c/0x1c0
 filemap_read+0x7c0/0x11a0
 ocfs2_file_read_iter+0x3fa/0xa80
 vfs_read+0x55a/0xa30
 ksys_read+0x145/0x250
 do_syscall_64+0xfa/0x3b0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f1276d8ebe9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f1274ff6038 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 00007f1276fb5fa0 RCX: 00007f1276d8ebe9
RDX: 00000000ffffffbc RSI: 0000200000004880 RDI: 0000000000000004
RBP: 00007f1276e11e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f1276fb6038 R14: 00007f1276fb5fa0 R15: 00007ffcf0d1e7c8
 </TASK>
