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BUG: KCSAN: data-race in blk_mq_get_request / blk_mq_get_request

write to 0xffff88812a1c9948 of 8 bytes by task 8849 on cpu 1:
 blk_mq_get_request+0x8e1/0xb50 block/blk-mq.c:418
 blk_mq_make_request+0x2d9/0xf60 block/blk-mq.c:1974
 generic_make_request block/blk-core.c:1064 [inline]
 generic_make_request+0x196/0x740 block/blk-core.c:1006
 submit_bio+0x96/0x3c0 block/blk-core.c:1190
 submit_bh_wbc+0x40f/0x460 fs/buffer.c:3095
 submit_bh fs/buffer.c:3101 [inline]
 write_dirty_buffer fs/buffer.c:3169 [inline]
 write_dirty_buffer+0x83/0x100 fs/buffer.c:3160
 fat_sync_bhs+0x59/0x14b fs/fat/misc.c:349
 fat_alloc_clusters+0xae6/0xc40 fs/fat/fatent.c:539
 fat_add_cluster+0x3d/0xd0 fs/fat/inode.c:107
 __fat_get_block fs/fat/inode.c:154 [inline]
 fat_get_block+0x3ae/0x4e0 fs/fat/inode.c:189
 __block_write_begin_int+0x2ea/0xf20 fs/buffer.c:1968
 __block_write_begin fs/buffer.c:2018 [inline]
 block_write_begin+0x77/0x160 fs/buffer.c:2077
 cont_write_begin+0x3d6/0x670 fs/buffer.c:2426
 fat_write_begin+0x72/0xc0 fs/fat/inode.c:235
 generic_perform_write+0x136/0x320 mm/filemap.c:3305
 __generic_file_write_iter+0x2eb/0x380 mm/filemap.c:3402
 generic_file_write_iter+0x28c/0x390 mm/filemap.c:3466
 call_write_iter include/linux/fs.h:1895 [inline]
 new_sync_write+0x388/0x4a0 fs/read_write.c:483
 __vfs_write+0xb1/0xc0 fs/read_write.c:496
 vfs_write fs/read_write.c:558 [inline]
 vfs_write+0x18a/0x390 fs/read_write.c:542
 ksys_write+0xd5/0x1b0 fs/read_write.c:611
 __do_sys_write fs/read_write.c:623 [inline]
 __se_sys_write fs/read_write.c:620 [inline]
 __x64_sys_write+0x4c/0x60 fs/read_write.c:620
 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88812a1c9948 of 8 bytes by task 8853 on cpu 0:
 blk_mq_get_request+0x8ce/0xb50 block/blk-mq.c:418
 blk_mq_make_request+0x2d9/0xf60 block/blk-mq.c:1974
 generic_make_request block/blk-core.c:1064 [inline]
 generic_make_request+0x196/0x740 block/blk-core.c:1006
 submit_bio+0x96/0x3c0 block/blk-core.c:1190
 mpage_bio_submit fs/mpage.c:66 [inline]
 mpage_readpages+0x36c/0x3c0 fs/mpage.c:410
 blkdev_readpages+0x36/0x50 fs/block_dev.c:620
 read_pages+0xa2/0x2d0 mm/readahead.c:126
 __do_page_cache_readahead+0x353/0x390 mm/readahead.c:212
 force_page_cache_readahead+0x13a/0x1f0 mm/readahead.c:243
 page_cache_sync_readahead+0x1cf/0x1e0 mm/readahead.c:522
 generic_file_buffered_read mm/filemap.c:2051 [inline]
 generic_file_read_iter+0xeb6/0x1440 mm/filemap.c:2324
 blkdev_read_iter+0xb2/0xe0 fs/block_dev.c:2010
 call_read_iter include/linux/fs.h:1889 [inline]
 new_sync_read+0x389/0x4f0 fs/read_write.c:414
 __vfs_read+0xb1/0xc0 fs/read_write.c:427
 vfs_read fs/read_write.c:461 [inline]
 vfs_read+0x143/0x2c0 fs/read_write.c:446
 ksys_read+0xd5/0x1b0 fs/read_write.c:587
 __do_sys_read fs/read_write.c:597 [inline]
 __se_sys_read fs/read_write.c:595 [inline]
 __x64_sys_read+0x4c/0x60 fs/read_write.c:595
 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 8853 Comm: blkid Not tainted 5.4.0-rc6+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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