syzbot

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BUG: KCSAN: data-race in blk_mq_dispatch_rq_list / blk_mq_dispatch_rq_list

read to 0xffff8881010172f8 of 4 bytes by task 45 on cpu 1:
 blk_mq_update_dispatch_busy block/blk-mq.c:1902 [inline]
 blk_mq_dispatch_rq_list+0xec2/0x10d0 block/blk-mq.c:2149
 __blk_mq_sched_dispatch_requests+0x1ce/0xd50 block/blk-mq-sched.c:301
 blk_mq_sched_dispatch_requests+0x78/0xe0 block/blk-mq-sched.c:331
 blk_mq_run_hw_queue+0x29c/0x4d0 block/blk-mq.c:2268
 blk_mq_run_hw_queues+0x15b/0x1e0 block/blk-mq.c:2317
 blk_mq_requeue_work+0x408/0x430 block/blk-mq.c:1486
 process_one_work kernel/workqueue.c:3254 [inline]
 process_scheduled_works+0x465/0x990 kernel/workqueue.c:3335
 worker_thread+0x526/0x730 kernel/workqueue.c:3416
 kthread+0x1d1/0x210 kernel/kthread.c:388
 ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

write to 0xffff8881010172f8 of 4 bytes by task 35 on cpu 0:
 blk_mq_dispatch_rq_list+0xee0/0x10d0
 __blk_mq_do_dispatch_sched block/blk-mq-sched.c:170 [inline]
 blk_mq_do_dispatch_sched block/blk-mq-sched.c:184 [inline]
 __blk_mq_sched_dispatch_requests+0x604/0xd50 block/blk-mq-sched.c:309
 blk_mq_sched_dispatch_requests+0x78/0xe0 block/blk-mq-sched.c:331
 blk_mq_run_hw_queue+0x29c/0x4d0 block/blk-mq.c:2268
 blk_mq_flush_plug_list+0x7bc/0xde0 block/blk-mq.c:2817
 __blk_flush_plug+0x216/0x290 block/blk-core.c:1190
 blk_finish_plug+0x48/0x70 block/blk-core.c:1217
 wb_writeback+0x6a2/0x6f0 fs/fs-writeback.c:2155
 wb_check_start_all fs/fs-writeback.c:2245 [inline]
 wb_do_writeback fs/fs-writeback.c:2271 [inline]
 wb_workfn+0x4ea/0x940 fs/fs-writeback.c:2304
 process_one_work kernel/workqueue.c:3254 [inline]
 process_scheduled_works+0x465/0x990 kernel/workqueue.c:3335
 worker_thread+0x526/0x730 kernel/workqueue.c:3416
 kthread+0x1d1/0x210 kernel/kthread.c:388
 ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

value changed: 0x00000002 -> 0x00000003

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 35 Comm: kworker/u8:2 Tainted: G        W          6.9.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
Workqueue: writeback wb_workfn (flush-8:0)
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