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BUG: KCSAN: data-race in __ext4_update_other_inode_time / writeback_single_inode

write to 0xffff88800b20bc58 of 8 bytes by task 21313 on cpu 0:
 writeback_single_inode+0x109/0x580 fs/fs-writeback.c:1567
 sync_inode fs/fs-writeback.c:2602 [inline]
 sync_inode_metadata+0x52/0x70 fs/fs-writeback.c:2622
 ext4_fsync_nojournal fs/ext4/fsync.c:92 [inline]
 ext4_sync_file+0x359/0x6c0 fs/ext4/fsync.c:170
 vfs_fsync_range+0x107/0x120 fs/sync.c:200
 generic_write_sync include/linux/fs.h:2737 [inline]
 ext4_buffered_write_iter+0x384/0x3d0 fs/ext4/file.c:278
 ext4_file_write_iter+0x45e/0x1090 fs/ext4/file.c:503
 call_write_iter include/linux/fs.h:1901 [inline]
 do_iter_readv_writev+0x2cb/0x360 fs/read_write.c:740
 do_iter_write+0x112/0x4b0 fs/read_write.c:866
 vfs_iter_write+0x4c/0x70 fs/read_write.c:907
 iter_file_splice_write+0x42a/0x780 fs/splice.c:686
 do_splice_from fs/splice.c:764 [inline]
 direct_splice_actor+0x80/0xa0 fs/splice.c:933
 splice_direct_to_actor+0x345/0x650 fs/splice.c:888
 do_splice_direct+0xf5/0x170 fs/splice.c:976
 do_sendfile+0x5db/0xca0 fs/read_write.c:1257
 __do_sys_sendfile64 fs/read_write.c:1312 [inline]
 __se_sys_sendfile64 fs/read_write.c:1304 [inline]
 __x64_sys_sendfile64+0xa9/0x130 fs/read_write.c:1304
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88800b20bc58 of 8 bytes by task 8489 on cpu 1:
 __ext4_update_other_inode_time+0x45/0x550 fs/ext4/inode.c:4955
 ext4_update_other_inodes_time fs/ext4/inode.c:5002 [inline]
 ext4_do_update_inode fs/ext4/inode.c:5131 [inline]
 ext4_mark_iloc_dirty+0x1286/0x1650 fs/ext4/inode.c:5712
 __ext4_mark_inode_dirty+0x450/0x610 fs/ext4/inode.c:5906
 ext4_mkdir+0x349/0x730 fs/ext4/namei.c:2810
 vfs_mkdir+0x288/0x350 fs/namei.c:3650
 do_mkdirat+0x132/0x220 fs/namei.c:3673
 __do_sys_mkdir fs/namei.c:3689 [inline]
 __se_sys_mkdir fs/namei.c:3687 [inline]
 __x64_sys_mkdir+0x32/0x40 fs/namei.c:3687
 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: 8489 Comm: syz-executor.5 Not tainted 5.10.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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