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BUG: KCSAN: data-race in __ext4_link / atime_needs_update

write to 0xffff8881068f3770 of 8 bytes by task 1768 on cpu 1:
 __ext4_link+0x266/0x490 fs/ext4/namei.c:3568
 ext4_link+0x140/0x150 fs/ext4/namei.c:3613
 vfs_link+0x52b/0x6e0 fs/namei.c:4310
 do_linkat+0x1e1/0x470 fs/namei.c:4380
 __do_sys_linkat fs/namei.c:4405 [inline]
 __se_sys_linkat fs/namei.c:4402 [inline]
 __x64_sys_linkat+0x62/0x70 fs/namei.c:4402
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff8881068f3770 of 8 bytes by task 1775 on cpu 0:
 timespec64_compare include/linux/time64.h:58 [inline]
 relatime_need_update fs/inode.c:1736 [inline]
 atime_needs_update+0x34b/0x390 fs/inode.c:1823
 touch_atime+0x54/0x240 fs/inode.c:1838
 file_accessed include/linux/fs.h:2455 [inline]
 ext4_file_mmap+0xd7/0x120 fs/ext4/file.c:780
 call_mmap include/linux/fs.h:2119 [inline]
 mmap_region+0xbcb/0x1400 mm/mmap.c:1808
 do_mmap+0x73f/0xc40 mm/mmap.c:1584
 vm_mmap_pgoff+0xf9/0x1d0 mm/util.c:519
 vm_mmap+0x8c/0xb0 mm/util.c:538
 elf_map+0x139/0x240 fs/binfmt_elf.c:392
 load_elf_binary+0xfeb/0x2790 fs/binfmt_elf.c:1141
 search_binary_handler fs/exec.c:1721 [inline]
 exec_binprm+0x1ca/0x6e0 fs/exec.c:1762
 bprm_execve+0x3b6/0x530 fs/exec.c:1831
 do_execveat_common+0x63b/0x700 fs/exec.c:1920
 do_execve fs/exec.c:1988 [inline]
 __do_sys_execve fs/exec.c:2064 [inline]
 __se_sys_execve fs/exec.c:2059 [inline]
 __x64_sys_execve+0x56/0x70 fs/exec.c:2059
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x000000003833c5a4 -> 0x0000000038cc5cde

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 1775 Comm: syz-executor.0 Not tainted 5.14.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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