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BUG: KCSAN: data-race in generic_file_buffered_read / set_blocksize

write to 0xffff88810be95906 of 1 bytes by task 15188 on cpu 0:
 set_blocksize+0x21f/0x2b0 fs/block_dev.c:153
 sb_set_blocksize+0x2c/0xa0 fs/block_dev.c:163
 ext4_fill_super+0x24a2/0x7fc0 fs/ext4/super.c:4485
 mount_bdev+0x1e2/0x280 fs/super.c:1419
 ext4_mount+0x2d/0x40 fs/ext4/super.c:6580
 legacy_get_tree+0x70/0xc0 fs/fs_context.c:592
 vfs_get_tree+0x4a/0x190 fs/super.c:1549
 do_new_mount fs/namespace.c:2875 [inline]
 path_mount+0x119d/0x1c10 fs/namespace.c:3205
 do_mount fs/namespace.c:3218 [inline]
 __do_sys_mount fs/namespace.c:3426 [inline]
 __se_sys_mount+0x23d/0x2e0 fs/namespace.c:3403
 __x64_sys_mount+0x63/0x70 fs/namespace.c:3403
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88810be95906 of 1 bytes by task 15187 on cpu 1:
 generic_file_buffered_read+0x6c0/0x2110 mm/filemap.c:2268
 generic_file_read_iter+0x80/0x3d0 mm/filemap.c:2535
 blkdev_read_iter+0xb3/0xc0 fs/block_dev.c:1925
 call_read_iter include/linux/fs.h:1881 [inline]
 new_sync_read fs/read_write.c:415 [inline]
 vfs_read+0x552/0x5c0 fs/read_write.c:496
 ksys_read+0xce/0x180 fs/read_write.c:634
 __do_sys_read fs/read_write.c:644 [inline]
 __se_sys_read fs/read_write.c:642 [inline]
 __x64_sys_read+0x3e/0x50 fs/read_write.c:642
 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: 15187 Comm: systemd-udevd Not tainted 5.10.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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