============================================
WARNING: possible recursive locking detected
syzkaller #0 Not tainted
--------------------------------------------
syz-executor542/5622 is trying to acquire lock:
ffff8880277923c8 (&sb->s_type->i_mutex_key#9){++++}-{4:4}, at: inode_lock_shared include/linux/fs.h:1039 [inline]
ffff8880277923c8 (&sb->s_type->i_mutex_key#9){++++}-{4:4}, at: blkdev_buffered_write+0xb1/0x110 block/fops.c:734

but task is already holding lock:
ffff8880277923c8 (&sb->s_type->i_mutex_key#9){++++}-{4:4}, at: inode_lock_shared include/linux/fs.h:1039 [inline]
ffff8880277923c8 (&sb->s_type->i_mutex_key#9){++++}-{4:4}, at: blkdev_write_iter+0x6c8/0x810 block/fops.c:811

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

       CPU0
       ----
  lock(&sb->s_type->i_mutex_key#9);
  lock(&sb->s_type->i_mutex_key#9);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

locks held by syz-executor542/5622: 1, last CPU#1:
 #0: ffff8880277923c8 (&sb->s_type->i_mutex_key#9){++++}-{4:4}, at: inode_lock_shared include/linux/fs.h:1039 [inline]
 #0: ffff8880277923c8 (&sb->s_type->i_mutex_key#9){++++}-{4:4}, at: blkdev_write_iter+0x6c8/0x810 block/fops.c:811

stack backtrace:
CPU: 1 UID: 0 PID: 5622 Comm: syz-executor542 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/07/2026
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+0x92/0x200 kernel/locking/rwsem.c:1574
 inode_lock_shared include/linux/fs.h:1039 [inline]
 blkdev_buffered_write+0xb1/0x110 block/fops.c:734
 blkdev_write_iter+0x6d8/0x810 block/fops.c:812
 do_iter_readv_writev+0x624/0x8d0 fs/read_write.c:-1
 vfs_writev+0x34c/0x990 fs/read_write.c:1058
 do_writev+0x15a/0x2e0 fs/read_write.c:1104
 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: 0033:0x7f9da1485509
Code: c0 79 93 eb d5 48 8d 7c 1d 00 eb 99 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 d8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffff88cede8 EFLAGS: 00000246 ORIG_RAX: 0000000000000014
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f9da1485509
RDX: 0000000000000002 RSI: 0000200000000100 RDI: 0000000000000003
RBP: 0000000000000001 R08: 0000000000000006 R09: 0000000000000006
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffff88cef58
R13: 431bde82d7b634db R14: 00007f9da1518c40 R15: 0000000000000002
 </TASK>