syzbot

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BUG: KCSAN: data-race in blk_mq_start_request / bt_for_each

write to 0xffff888102b82480 of 8 bytes by task 2962 on cpu 1:
 blk_mq_start_request+0x23c/0x3d0 block/blk-mq.c:1386
 scsi_queue_rq+0xe08/0x1aa0 drivers/scsi/scsi_lib.c:1895
 blk_mq_dispatch_rq_list+0x2bc/0xf90 block/blk-mq.c:2148
 __blk_mq_do_dispatch_sched block/blk-mq-sched.c:168 [inline]
 blk_mq_do_dispatch_sched block/blk-mq-sched.c:182 [inline]
 __blk_mq_sched_dispatch_requests+0x7f0/0xc70 block/blk-mq-sched.c:307
 blk_mq_sched_dispatch_requests+0x86/0x120 block/blk-mq-sched.c:329
 blk_mq_run_hw_queue+0x17e/0x220 block/blk-mq.c:2386
 blk_mq_dispatch_list+0x85e/0xa40 arch/x86/include/asm/bitops.h:-1
 blk_mq_flush_plug_list+0x2ca/0x320 block/blk-mq.c:2997
 __blk_flush_plug+0x22c/0x2b0 block/blk-core.c:1230
 blk_finish_plug+0x47/0x70 block/blk-core.c:1257
 jbd2_journal_commit_transaction+0x1b84/0x3420 fs/jbd2/commit.c:788
 kjournald2+0x22e/0x3e0 fs/jbd2/journal.c:201
 kthread+0x22a/0x280 kernel/kthread.c:467
 ret_from_fork+0x150/0x360 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

read to 0xffff888102b82480 of 8 bytes by task 3152 on cpu 0:
 blk_mq_find_and_get_req block/blk-mq-tag.c:260 [inline]
 bt_iter block/blk-mq-tag.c:287 [inline]
 __sbitmap_for_each_set include/linux/sbitmap.h:269 [inline]
 sbitmap_for_each_set include/linux/sbitmap.h:290 [inline]
 bt_for_each+0x25c/0x470 block/blk-mq-tag.c:324
 blk_mq_queue_tag_busy_iter+0x1ef/0x3b0 block/blk-mq-tag.c:536
 blk_mq_timeout_work+0xc4/0x370 block/blk-mq.c:1762
 process_one_work kernel/workqueue.c:3275 [inline]
 process_scheduled_works+0x4de/0x9e0 kernel/workqueue.c:3358
 worker_thread+0x581/0x770 kernel/workqueue.c:3439
 kthread+0x22a/0x280 kernel/kthread.c:467
 ret_from_fork+0x150/0x360 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

value changed: 0xffff88810365b600 -> 0xffff888103661d40

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 3152 Comm: kworker/0:1H Tainted: G        W           syzkaller #0 PREEMPT(full) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Workqueue: kblockd blk_mq_timeout_work
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