==================================================================
BUG: KCSAN: data-race in wbt_wait / wbt_wait

write to 0xffff888103a1f540 of 8 bytes by task 4877 on cpu 1:
 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+0x229/0x1000 block/blk-mq.c:2158
 __submit_bio_noacct_mq block/blk-core.c:1028 [inline]
 submit_bio_noacct+0x75d/0x910 block/blk-core.c:1061
 submit_bio+0x1f3/0x350 block/blk-core.c:1131
 ext4_mpage_readpages+0x1471/0x14c0 fs/ext4/readpage.c:412
 ext4_readahead+0x99/0xa0 fs/ext4/inode.c:3261
 read_pages+0xa0/0x6e0 mm/readahead.c:130
 page_cache_ra_unbounded+0x464/0x4c0 mm/readahead.c:238
 do_page_cache_ra+0xa7/0xc0 mm/readahead.c:267
 do_sync_mmap_readahead+0x32a/0x360 mm/filemap.c:2733
 filemap_fault+0x1ba/0xbf0 mm/filemap.c:2821
 ext4_filemap_fault+0x4b/0x60 fs/ext4/inode.c:6205
 __do_fault mm/memory.c:3625 [inline]
 do_read_fault+0x403/0x760 mm/memory.c:4019
 do_fault mm/memory.c:4147 [inline]
 handle_pte_fault mm/memory.c:4387 [inline]
 __handle_mm_fault mm/memory.c:4522 [inline]
 handle_mm_fault+0xff1/0x17b0 mm/memory.c:4620
 do_user_addr_fault+0x433/0x830 arch/x86/mm/fault.c:1393
 handle_page_fault arch/x86/mm/fault.c:1450 [inline]
 exc_page_fault+0x94/0x2a0 arch/x86/mm/fault.c:1506
 asm_exc_page_fault+0x1e/0x30 arch/x86/include/asm/idtentry.h:580

read to 0xffff888103a1f540 of 8 bytes by task 8426 on cpu 0:
 wb_timestamp block/blk-wbt.c:88 [inline]
 wbt_wait+0xcf/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+0x229/0x1000 block/blk-mq.c:2158
 __submit_bio_noacct_mq block/blk-core.c:1028 [inline]
 submit_bio_noacct+0x75d/0x910 block/blk-core.c:1061
 submit_bio+0x1f3/0x350 block/blk-core.c:1131
 ext4_mpage_readpages+0x1471/0x14c0 fs/ext4/readpage.c:412
 ext4_readahead+0x99/0xa0 fs/ext4/inode.c:3261
 read_pages+0xa0/0x6e0 mm/readahead.c:130
 page_cache_ra_unbounded+0x464/0x4c0 mm/readahead.c:238
 do_page_cache_ra+0xa7/0xc0 mm/readahead.c:267
 do_sync_mmap_readahead+0x32a/0x360 mm/filemap.c:2733
 filemap_fault+0x1ba/0xbf0 mm/filemap.c:2821
 ext4_filemap_fault+0x4b/0x60 fs/ext4/inode.c:6205
 __do_fault mm/memory.c:3625 [inline]
 do_read_fault+0x403/0x760 mm/memory.c:4019
 do_fault mm/memory.c:4147 [inline]
 handle_pte_fault mm/memory.c:4387 [inline]
 __handle_mm_fault mm/memory.c:4522 [inline]
 handle_mm_fault+0xff1/0x17b0 mm/memory.c:4620
 do_user_addr_fault+0x433/0x830 arch/x86/mm/fault.c:1393
 handle_page_fault arch/x86/mm/fault.c:1450 [inline]
 exc_page_fault+0x94/0x2a0 arch/x86/mm/fault.c:1506
 asm_exc_page_fault+0x1e/0x30 arch/x86/include/asm/idtentry.h:580

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 8426 Comm: syz-fuzzer Not tainted 5.11.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================