============================================
WARNING: possible recursive locking detected
syzkaller #0 Not tainted
--------------------------------------------
syz.0.0/5339 is trying to acquire lock:
ffff8880450fdda0 (&ocfs2_sysfile_lock_key[GLOBAL_BITMAP_SYSTEM_INODE]){+.+.}-{4:4}, at: inode_lock include/linux/fs.h:1024 [inline]
ffff8880450fdda0 (&ocfs2_sysfile_lock_key[GLOBAL_BITMAP_SYSTEM_INODE]){+.+.}-{4:4}, at: ocfs2_reserve_suballoc_bits+0x170/0x4850 fs/ocfs2/suballoc.c:904

but task is already holding lock:
ffff8880450fdda0 (&ocfs2_sysfile_lock_key[GLOBAL_BITMAP_SYSTEM_INODE]){+.+.}-{4:4}, at: inode_lock include/linux/fs.h:1024 [inline]
ffff8880450fdda0 (&ocfs2_sysfile_lock_key[GLOBAL_BITMAP_SYSTEM_INODE]){+.+.}-{4:4}, at: ocfs2_reserve_suballoc_bits+0x170/0x4850 fs/ocfs2/suballoc.c:904

other info that might help us debug this:
 Possible unsafe locking scenario:

       CPU0
       ----
  lock(&ocfs2_sysfile_lock_key[GLOBAL_BITMAP_SYSTEM_INODE]);
  lock(&ocfs2_sysfile_lock_key[GLOBAL_BITMAP_SYSTEM_INODE]);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

locks held by syz.0.0/5339: 4, last CPU#0:
 #0: ffff888040fe8460 (sb_writers#12){.+.+}-{0:0}, at: mnt_want_write+0x41/0x90 fs/namespace.c:527
 #1: ffff8880452425a0 (&type->i_mutex_dir_key#8){++++}-{4:4}, at: inode_lock include/linux/fs.h:1024 [inline]
 #1: ffff8880452425a0 (&type->i_mutex_dir_key#8){++++}-{4:4}, at: lookup_open+0x242/0x1a40 fs/namei.c:4487
 #2: ffff8880450fc1a0 (&ocfs2_sysfile_lock_key[INODE_ALLOC_SYSTEM_INODE]){+.+.}-{4:4}, at: inode_lock include/linux/fs.h:1024 [inline]
 #2: ffff8880450fc1a0 (&ocfs2_sysfile_lock_key[INODE_ALLOC_SYSTEM_INODE]){+.+.}-{4:4}, at: ocfs2_reserve_suballoc_bits+0x170/0x4850 fs/ocfs2/suballoc.c:904
 #3: ffff8880450fdda0 (&ocfs2_sysfile_lock_key[GLOBAL_BITMAP_SYSTEM_INODE]){+.+.}-{4:4}, at: inode_lock include/linux/fs.h:1024 [inline]
 #3: ffff8880450fdda0 (&ocfs2_sysfile_lock_key[GLOBAL_BITMAP_SYSTEM_INODE]){+.+.}-{4:4}, at: ocfs2_reserve_suballoc_bits+0x170/0x4850 fs/ocfs2/suballoc.c:904

stack backtrace:
CPU: 0 UID: 0 PID: 5339 Comm: syz.0.0 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_deadlock_bug+0x27a/0x290 kernel/locking/lockdep.c:3085
 check_deadlock kernel/locking/lockdep.c:3137 [inline]
 validate_chain kernel/locking/lockdep.c:3939 [inline]
 __lock_acquire+0x25db/0x2de0 kernel/locking/lockdep.c:5288
 lock_acquire+0x115/0x350 kernel/locking/lockdep.c:5942
 down_write+0x96/0x200 kernel/locking/rwsem.c:1631
 inode_lock include/linux/fs.h:1024 [inline]
 ocfs2_reserve_suballoc_bits+0x170/0x4850 fs/ocfs2/suballoc.c:904
 ocfs2_reserve_cluster_bitmap_bits fs/ocfs2/suballoc.c:1250 [inline]
 ocfs2_reserve_clusters_with_limit+0x3bc/0xc20 fs/ocfs2/suballoc.c:1295
 ocfs2_mknod+0xe8b/0x21a0 fs/ocfs2/namei.c:358
 ocfs2_create+0x195/0x460 fs/ocfs2/namei.c:678
 lookup_open+0xc0d/0x1a40 fs/namei.c:4596
 open_last_lookups fs/namei.c:4796 [inline]
 path_openat+0x677/0x1d60 fs/namei.c:5026
 do_file_open+0x23e/0x4a0 fs/namei.c:5058
 file_open_name fs/open.c:1375 [inline]
 filp_open+0x16d/0x1d0 fs/open.c:1392
 coredump_file fs/coredump.c:929 [inline]
 do_coredump fs/coredump.c:1099 [inline]
 vfs_coredump+0x206e/0x4520 fs/coredump.c:1195
 get_signal+0x1094/0x12c0 kernel/signal.c:3097
 arch_do_signal_or_restart+0xbb/0x860 arch/x86/kernel/signal.c:337
 __exit_to_user_mode_loop kernel/entry/common.c:66 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:101 [inline]
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
 irqentry_exit_to_user_mode_prepare include/linux/irq-entry-common.h:244 [inline]
 irqentry_exit_to_user_mode include/linux/irq-entry-common.h:315 [inline]
 irqentry_exit+0x2c0/0x920 kernel/entry/common.c:165
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:595
RIP: 0033:0x7035
Code: Unable to access opcode bytes at 0x700b.
RSP: 002b:0000200000000018 EFLAGS: 00010217
RAX: 0000000000000000 RBX: 00007f0fcae25fa0 RCX: 00007f0fcab9e559
RDX: 0000200000000080 RSI: 0000200000000010 RDI: 0000000000808000
RBP: 00007f0fcac358b0 R08: 0000200000000100 R09: 0000200000000100
R10: 00002000000000c0 R11: 0000000000000206 R12: 0000000000000000
R13: 00007f0fcae26038 R14: 00007f0fcae25fa0 R15: 00007ffe3020ab98
 </TASK>