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BUG: KCSAN: data-race in do_mpage_readpage / set_blocksize

write to 0xffff88812b830b46 of 1 bytes by task 20581 on cpu 0:
 set_blocksize+0x21f/0x2b0 fs/block_dev.c:124
 sb_set_blocksize+0x2c/0xa0 fs/block_dev.c:134
 fat_fill_super+0x12fe/0x2a90 fs/fat/inode.c:1681
 msdos_fill_super+0x29/0x30 fs/fat/namei_msdos.c:653
 mount_bdev+0x1e8/0x290 fs/super.c:1417
 msdos_mount+0x2d/0x40 fs/fat/namei_msdos.c:660
 legacy_get_tree+0x70/0xc0 fs/fs_context.c:592
 vfs_get_tree+0x4d/0x1a0 fs/super.c:1547
 do_new_mount fs/namespace.c:2875 [inline]
 path_mount+0x118d/0x1c70 fs/namespace.c:3192
 do_mount fs/namespace.c:3205 [inline]
 __do_sys_mount fs/namespace.c:3413 [inline]
 __se_sys_mount+0x126/0x180 fs/namespace.c:3390
 __x64_sys_mount+0x63/0x70 fs/namespace.c:3390
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88812b830b46 of 1 bytes by task 31138 on cpu 1:
 do_mpage_readpage+0x6c/0x10c0 fs/mpage.c:160
 mpage_readahead+0x151/0x340 fs/mpage.c:391
 blkdev_readahead+0x18/0x20 fs/block_dev.c:608
 read_pages+0x9c/0x700 mm/readahead.c:130
 page_cache_readahead_unbounded+0x41a/0x470 mm/readahead.c:244
 __do_page_cache_readahead mm/readahead.c:273 [inline]
 force_page_cache_readahead+0x1ec/0x220 mm/readahead.c:303
 page_cache_sync_readahead+0x191/0x1a0 mm/readahead.c:580
 generic_file_buffered_read+0x2ec/0x1f60 mm/filemap.c:2101
 generic_file_read_iter+0x7d/0x3e0 mm/filemap.c:2405
 blkdev_read_iter+0xb3/0xc0 fs/block_dev.c:1927
 call_read_iter include/linux/fs.h:1876 [inline]
 new_sync_read fs/read_write.c:415 [inline]
 vfs_read+0x57a/0x5e0 fs/read_write.c:481
 ksys_read+0xce/0x180 fs/read_write.c:607
 __do_sys_read fs/read_write.c:617 [inline]
 __se_sys_read fs/read_write.c:615 [inline]
 __x64_sys_read+0x3e/0x50 fs/read_write.c:615
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 31138 Comm: systemd-udevd Not tainted 5.9.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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