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BUG: KCSAN: data-race in blk_mq_get_request / blk_mq_get_request

write to 0xffff8880bb097148 of 8 bytes by task 16136 on cpu 0:
 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
 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:2050 [inline]
 generic_file_read_iter+0xeb6/0x1440 mm/filemap.c:2323
 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

read to 0xffff8880bb097148 of 8 bytes by task 16131 on cpu 1:
 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
 submit_bh_wbc+0x40f/0x460 fs/buffer.c:3095
 submit_bh fs/buffer.c:3101 [inline]
 __bread_slow fs/buffer.c:1177 [inline]
 __bread_gfp+0xe7/0x1e0 fs/buffer.c:1359
 sb_bread include/linux/buffer_head.h:307 [inline]
 fat__get_entry+0x35e/0x4f0 fs/fat/dir.c:100
 fat_get_entry fs/fat/dir.c:128 [inline]
 fat_get_short_entry+0x103/0x200 fs/fat/dir.c:877
 fat_subdirs+0x6b/0x110 fs/fat/dir.c:943
 fat_read_root fs/fat/inode.c:1416 [inline]
 fat_fill_super+0x1552/0x1f50 fs/fat/inode.c:1862
 vfat_fill_super+0x3b/0x50 fs/fat/namei_vfat.c:1050
 mount_bdev+0x262/0x2d0 fs/super.c:1415
 vfat_mount+0x3e/0x60 fs/fat/namei_vfat.c:1057

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 16131 Comm: syz-executor.0 Not tainted 5.4.0-rc3+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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