syzbot

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kernfs: can not remove 'nr_tags', no directory
WARNING: CPU: 0 PID: 12812 at fs/kernfs/dir.c:1503 kernfs_remove_by_name_ns+0x9f/0xb0 fs/kernfs/dir.c:1503
Kernel panic - not syncing: panic_on_warn set ...
CPU: 0 PID: 12812 Comm: syz-executor.1 Not tainted 5.3.0-rc7+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x172/0x1f0 lib/dump_stack.c:113
 panic+0x2dc/0x755 kernel/panic.c:219
 __warn.cold+0x20/0x4c kernel/panic.c:576
 report_bug+0x263/0x2b0 lib/bug.c:186
 fixup_bug arch/x86/kernel/traps.c:179 [inline]
 fixup_bug arch/x86/kernel/traps.c:174 [inline]
 do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:272
 do_invalid_op+0x37/0x50 arch/x86/kernel/traps.c:291
 invalid_op+0x23/0x30 arch/x86/entry/entry_64.S:1028
RIP: 0010:kernfs_remove_by_name_ns+0x9f/0xb0 fs/kernfs/dir.c:1503
Code: 97 ff 48 c7 c7 20 0d ea 88 41 bc fe ff ff ff e8 87 e9 61 05 eb d7 e8 a0 2c 97 ff 4c 89 ee 48 c7 c7 a0 78 99 87 e8 09 b5 68 ff <0f> 0b 41 bc fe ff ff ff eb b9 0f 1f 80 00 00 00 00 55 48 89 e5 41
RSP: 0018:ffff888055347798 EFLAGS: 00010286
RAX: 0000000000000000 RBX: ffffffff89134b48 RCX: 0000000000000000
RDX: 0000000000000003 RSI: ffffffff815c26f6 RDI: ffffed100aa68ee5
RBP: ffff8880553477b0 R08: 0000000000200000 R09: 0000000000007ec0
R10: 00000000000fd808 R11: 000000000001fafc R12: 0000000000000000
R13: ffffffff87c4bec0 R14: 0000000000000000 R15: ffffffff87c4be00
 kernfs_remove_by_name include/linux/kernfs.h:567 [inline]
 remove_files.isra.0+0x7b/0x190 fs/sysfs/group.c:27
 sysfs_remove_group+0xb6/0x1b0 fs/sysfs/group.c:288
 sysfs_remove_groups fs/sysfs/group.c:312 [inline]
 sysfs_remove_groups+0x61/0xb0 fs/sysfs/group.c:304
 kobject_del+0x9c/0x170 lib/kobject.c:621
 blk_mq_unregister_hctx.part.0+0x126/0x170 block/blk-mq-sysfs.c:243
 blk_mq_unregister_hctx block/blk-mq-sysfs.c:237 [inline]
 blk_mq_sysfs_unregister+0x16b/0x200 block/blk-mq-sysfs.c:373
 __blk_mq_update_nr_hw_queues block/blk-mq.c:3272 [inline]
 blk_mq_update_nr_hw_queues+0x4f9/0xd20 block/blk-mq.c:3307
 nbd_start_device+0x14c/0xac0 drivers/block/nbd.c:1168
 nbd_start_device_ioctl drivers/block/nbd.c:1209 [inline]
 __nbd_ioctl drivers/block/nbd.c:1289 [inline]
 nbd_ioctl+0x5d5/0xc40 drivers/block/nbd.c:1329
 __blkdev_driver_ioctl block/ioctl.c:304 [inline]
 blkdev_ioctl+0xedb/0x1c1a block/ioctl.c:606
 block_ioctl+0xee/0x130 fs/block_dev.c:1954
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:509 [inline]
 do_vfs_ioctl+0xdb6/0x13e0 fs/ioctl.c:696
 ksys_ioctl+0xab/0xd0 fs/ioctl.c:713
 __do_sys_ioctl fs/ioctl.c:720 [inline]
 __se_sys_ioctl fs/ioctl.c:718 [inline]
 __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:718
 do_syscall_64+0xfd/0x6a0 arch/x86/entry/common.c:296
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x459879
Code: fd b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 0f 83 cb b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f02d1dfdc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000002 RCX: 0000000000459879
RDX: 0000000000000000 RSI: 000000000000ab03 RDI: 0000000000000004
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f02d1dfe6d4
R13: 00000000004c3190 R14: 00000000004d68f8 R15: 00000000ffffffff
Kernel Offset: disabled
Rebooting in 86400 seconds..