============================================
WARNING: possible recursive locking detected
syzkaller #0 Tainted: G             L      
--------------------------------------------
syz.0.757/8735 is trying to acquire lock:
ffff888024d71ee8 (&sb->s_type->i_mutex_key#10){++++}-{4:4}, at: inode_lock_shared include/linux/fs.h:1039 [inline]
ffff888024d71ee8 (&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:
ffff888024d71ee8 (&sb->s_type->i_mutex_key#10){++++}-{4:4}, at: inode_lock_shared include/linux/fs.h:1039 [inline]
ffff888024d71ee8 (&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.0.757/8735: 1, last CPU#0:
 #0: ffff888024d71ee8 (&sb->s_type->i_mutex_key#10){++++}-{4:4}, at: inode_lock_shared include/linux/fs.h:1039 [inline]
 #0: ffff888024d71ee8 (&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: 8735 Comm: syz.0.757 Tainted: G             L       syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
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+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
 iter_file_splice_write+0xa31/0x1240 fs/splice.c:736
 do_splice_from fs/splice.c:936 [inline]
 direct_splice_actor+0x101/0x160 fs/splice.c:1187
 splice_direct_to_actor+0x57b/0xcb0 fs/splice.c:1096
 do_splice_direct_actor fs/splice.c:1230 [inline]
 do_splice_direct+0x195/0x290 fs/splice.c:1256
 do_sendfile+0x52e/0x7c0 fs/read_write.c:1371
 __do_sys_sendfile64 fs/read_write.c:1432 [inline]
 __se_sys_sendfile64+0x144/0x1a0 fs/read_write.c:1418
 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: 0033:0x7f167a59f559
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:00007f167b43f028 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 00007f167a826090 RCX: 00007f167a59f559
RDX: 0000000000000000 RSI: 0000000000000007 RDI: 0000000000000008
RBP: 00007f167a636b20 R08: 0000000000000000 R09: 0000000000000000
R10: 00000001002000ff R11: 0000000000000246 R12: 0000000000000000
R13: 00007f167a826128 R14: 00007f167a826090 R15: 00007f167a94fa48
 </TASK>
Page cache invalidation failure on direct I/O.  Possible data corruption due to collision with buffered I/O!
File: /dev/nullb0 PID: 8735 Comm: syz.0.757