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BUG: KCSAN: data-race in do_mpage_readpage / set_blocksize

write to 0xffff8881202c2c66 of 1 bytes by task 23027 on cpu 1:
 set_blocksize+0x1ef/0x280 fs/block_dev.c:134
 sb_set_blocksize+0x2c/0xa0 fs/block_dev.c:144
 ext4_fill_super+0x260b/0x7a00 fs/ext4/super.c:4217
 mount_bdev+0x1ca/0x270 fs/super.c:1417
 ext4_mount+0x2d/0x40 fs/ext4/super.c:6203
 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:2874 [inline]
 do_mount+0x115c/0x1bd0 fs/namespace.c:3199
 __do_sys_mount fs/namespace.c:3409 [inline]
 __se_sys_mount+0xd3/0x100 fs/namespace.c:3386
 __x64_sys_mount+0x63/0x70 fs/namespace.c:3386
 do_syscall_64+0x51/0xb0 arch/x86/entry/common.c:384
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8881202c2c66 of 1 bytes by task 10931 on cpu 0:
 do_mpage_readpage+0x6c/0x10c0 fs/mpage.c:160
 mpage_readahead+0x152/0x330 fs/mpage.c:391
 blkdev_readahead+0x18/0x20 fs/block_dev.c:618
 read_pages+0xa0/0x6b0 mm/readahead.c:130
 page_cache_readahead_unbounded+0x3ef/0x440 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+0x2ae/0x1800 mm/filemap.c:2033
 generic_file_read_iter+0x7d/0x3e0 mm/filemap.c:2307
 blkdev_read_iter+0xb3/0xc0 fs/block_dev.c:2044
 call_read_iter include/linux/fs.h:1901 [inline]
 new_sync_read fs/read_write.c:415 [inline]
 __vfs_read+0x2d5/0x330 fs/read_write.c:428
 vfs_read+0x131/0x2a0 fs/read_write.c:462
 ksys_read+0xce/0x180 fs/read_write.c:588
 __do_sys_read fs/read_write.c:598 [inline]
 __se_sys_read fs/read_write.c:596 [inline]
 __x64_sys_read+0x3e/0x50 fs/read_write.c:596
 do_syscall_64+0x51/0xb0 arch/x86/entry/common.c:384
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 10931 Comm: systemd-udevd Not tainted 5.8.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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