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BUG: KCSAN: data-race in wbt_inflight_cb / wbt_wait

write to 0xffff888141e86840 of 8 bytes by task 19833 on cpu 0:
 wb_timestamp block/blk-wbt.c:89 [inline]
 wbt_wait+0x12b/0x2b0 block/blk-wbt.c:579
 __rq_qos_throttle+0x39/0x70 block/blk-rq-qos.c:72
 rq_qos_throttle block/blk-rq-qos.h:182 [inline]
 blk_mq_submit_bio+0x253/0x1060 block/blk-mq.c:2185
 __submit_bio_noacct_mq block/blk-core.c:1014 [inline]
 submit_bio_noacct+0x7c2/0x9a0 block/blk-core.c:1047
 submit_bio+0x200/0x370 block/blk-core.c:1118
 dio_bio_submit fs/direct-io.c:445 [inline]
 do_blockdev_direct_IO+0xd19/0x1360 fs/direct-io.c:1302
 __blockdev_direct_IO+0x5d/0x70 fs/direct-io.c:1367
 blockdev_direct_IO include/linux/fs.h:3157 [inline]
 fat_direct_IO+0x108/0x1c0 fs/fat/inode.c:288
 generic_file_read_iter+0x2e4/0x410 mm/filemap.c:2587
 call_read_iter include/linux/fs.h:1971 [inline]
 generic_file_splice_read+0x22a/0x310 fs/splice.c:311
 do_splice_to fs/splice.c:796 [inline]
 splice_direct_to_actor+0x2aa/0x650 fs/splice.c:870
 do_splice_direct+0xf5/0x170 fs/splice.c:979
 do_sendfile+0x7a6/0xe20 fs/read_write.c:1260
 __do_sys_sendfile64 fs/read_write.c:1325 [inline]
 __se_sys_sendfile64 fs/read_write.c:1311 [inline]
 __x64_sys_sendfile64+0xf2/0x130 fs/read_write.c:1311
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff888141e86840 of 8 bytes by task 19845 on cpu 1:
 close_io block/blk-wbt.c:444 [inline]
 get_limit block/blk-wbt.c:474 [inline]
 wbt_inflight_cb+0x19a/0x220 block/blk-wbt.c:495
 rq_qos_wait+0xac/0x220 block/blk-rq-qos.c:266
 __wbt_wait block/blk-wbt.c:518 [inline]
 wbt_wait+0x1bb/0x2b0 block/blk-wbt.c:583
 __rq_qos_throttle+0x39/0x70 block/blk-rq-qos.c:72
 rq_qos_throttle block/blk-rq-qos.h:182 [inline]
 blk_mq_submit_bio+0x253/0x1060 block/blk-mq.c:2185
 __submit_bio_noacct_mq block/blk-core.c:1014 [inline]
 submit_bio_noacct+0x7c2/0x9a0 block/blk-core.c:1047
 submit_bio+0x200/0x370 block/blk-core.c:1118
 submit_bh_wbc+0x36b/0x3b0 fs/buffer.c:3055
 __block_write_full_page+0x648/0xa10 fs/buffer.c:1810
 block_write_full_page+0x260/0x290 fs/buffer.c:2981
 fat_writepage+0x20/0x30 fs/fat/inode.c:199
 writeout mm/migrate.c:896 [inline]
 fallback_migrate_page mm/migrate.c:920 [inline]
 move_to_new_page+0x305/0x6c0 mm/migrate.c:971
 __unmap_and_move+0x437/0x6a0 mm/migrate.c:1133
 unmap_and_move+0x131/0x690 mm/migrate.c:1200
 migrate_pages+0x2f7/0xfb0 mm/migrate.c:1472
 do_mbind+0xe47/0x1030 mm/mempolicy.c:1357
 kernel_mbind mm/mempolicy.c:1478 [inline]
 __do_sys_mbind mm/mempolicy.c:1485 [inline]
 __se_sys_mbind mm/mempolicy.c:1481 [inline]
 __x64_sys_mbind+0x142/0x170 mm/mempolicy.c:1481
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 19845 Comm: syz-executor.1 Not tainted 5.12.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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