==================================================================
BUG: KCSAN: data-race in dd_has_work / dd_insert_requests

write to 0xffff8881022898a8 of 8 bytes by task 7702 on cpu 0:
 __list_add include/linux/list.h:70 [inline]
 list_add_tail include/linux/list.h:100 [inline]
 dd_insert_request block/mq-deadline.c:521 [inline]
 dd_insert_requests+0x38e/0x4f0 block/mq-deadline.c:537
 blk_mq_sched_insert_request+0x22c/0x280 block/blk-mq-sched.c:458
 blk_mq_submit_bio+0x88b/0x1040 block/blk-mq.c:2216
 __submit_bio_noacct_mq block/blk-core.c:1028 [inline]
 submit_bio_noacct+0x78d/0x960 block/blk-core.c:1061
 submit_bio+0x200/0x360 block/blk-core.c:1131
 submit_bh_wbc+0x39d/0x3e0 fs/buffer.c:3054
 submit_bh fs/buffer.c:3060 [inline]
 __sync_dirty_buffer+0x12c/0x1d0 fs/buffer.c:3155
 sync_dirty_buffer+0x16/0x20 fs/buffer.c:3168
 __ext4_handle_dirty_metadata+0x1d1/0x5a0 fs/ext4/ext4_jbd2.c:364
 ext4_handle_dirty_dirblock+0x184/0x330 fs/ext4/namei.c:407
 add_dirent_to_buf+0x4a8/0x610 fs/ext4/namei.c:2033
 ext4_add_entry+0x62e/0x21a0 fs/ext4/namei.c:2242
 ext4_add_nondir+0x50/0x1a0 fs/ext4/namei.c:2576
 ext4_symlink+0x538/0x780 fs/ext4/namei.c:3406
 vfs_symlink+0x216/0x2d0 fs/namei.c:3962
 do_symlinkat+0xee/0x280 fs/namei.c:3989
 __do_sys_symlink fs/namei.c:4008 [inline]
 __se_sys_symlink fs/namei.c:4006 [inline]
 __x64_sys_symlink+0x32/0x40 fs/namei.c:4006
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8881022898a8 of 8 bytes by task 2198 on cpu 1:
 list_empty_careful include/linux/list.h:319 [inline]
 dd_has_work+0xfe/0x110 block/mq-deadline.c:590
 __blk_mq_do_dispatch_sched block/blk-mq-sched.c:135 [inline]
 blk_mq_do_dispatch_sched+0x138/0x610 block/blk-mq-sched.c:199
 __blk_mq_sched_dispatch_requests+0x1fd/0x2a0 block/blk-mq-sched.c:310
 blk_mq_sched_dispatch_requests+0x9f/0x110 block/blk-mq-sched.c:341
 __blk_mq_run_hw_queue block/blk-mq.c:1515 [inline]
 blk_mq_run_work_fn+0xb3/0x130 block/blk-mq.c:1793
 process_one_work+0x3e1/0x950 kernel/workqueue.c:2275
 worker_thread+0x616/0xa70 kernel/workqueue.c:2421
 kthread+0x20b/0x230 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 2198 Comm: kworker/1:1H Not tainted 5.11.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: kblockd blk_mq_run_work_fn
==================================================================