loop0: detected capacity change from 0 to 2048
 loop0: p1 p2 < > p3 < p5 p6 > p4
loop0: partition table partially beyond EOD, truncated
loop0: p2 start 4278190080 is beyond EOD, truncated
loop0: p4 size 8192 extends beyond EOD, truncated
loop0: p6 size 8192 extends beyond EOD, truncated

============================================
WARNING: possible recursive locking detected
syzkaller #0 Not tainted
--------------------------------------------
syz.0.0/5352 is trying to acquire lock:
ffff8880326207e8 (&sb->s_type->i_mutex_key#10){++++}-{4:4}, at: inode_lock_shared include/linux/fs.h:1039 [inline]
ffff8880326207e8 (&sb->s_type->i_mutex_key#10){++++}-{4:4}, at: blkdev_buffered_write+0xaf/0x110 block/fops.c:734

but task is already holding lock:
ffff8880326207e8 (&sb->s_type->i_mutex_key#10){++++}-{4:4}, at: inode_lock_shared include/linux/fs.h:1039 [inline]
ffff8880326207e8 (&sb->s_type->i_mutex_key#10){++++}-{4:4}, at: blkdev_write_iter+0x6c5/0x810 block/fops.c:811

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

       CPU0
       ----
  lock(&sb->s_type->i_mutex_key#10);
  lock(&sb->s_type->i_mutex_key#10);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

locks held by syz.0.0/5352: 1, last CPU#0:
 #0: ffff8880326207e8 (&sb->s_type->i_mutex_key#10){++++}-{4:4}, at: inode_lock_shared include/linux/fs.h:1039 [inline]
 #0: ffff8880326207e8 (&sb->s_type->i_mutex_key#10){++++}-{4:4}, at: blkdev_write_iter+0x6c5/0x810 block/fops.c:811

stack backtrace:
CPU: 0 UID: 0 PID: 5352 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_read+0x45/0x320 kernel/locking/rwsem.c:1574
 inode_lock_shared include/linux/fs.h:1039 [inline]
 blkdev_buffered_write+0xaf/0x110 block/fops.c:734
 blkdev_write_iter+0x6d5/0x810 block/fops.c:812
 new_sync_write fs/read_write.c:595 [inline]
 vfs_write+0x612/0xba0 fs/read_write.c:687
 ksys_write+0x150/0x270 fs/read_write.c:739
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f760499f559
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f760583cfe8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f7604c26090 RCX: 00007f760499f559
RDX: 00000000ffffffdb RSI: 0000000000000000 RDI: 0000000000000004
RBP: 00007f7604a36b20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f7604c26128 R14: 00007f7604c26090 R15: 00007fffbbecf998
 </TASK>