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BUG: KCSAN: data-race in ext4_mark_iloc_dirty / generic_update_time

write to 0xffff8880bb13ba30 of 16 bytes by task 13605 on cpu 1:
 generic_update_time+0x5c/0x270 fs/inode.c:1668
 update_time+0x7d/0x90 fs/inode.c:1694
 touch_atime+0x13f/0x150 fs/inode.c:1765
 file_accessed include/linux/fs.h:2220 [inline]
 generic_file_buffered_read mm/filemap.c:2236 [inline]
 generic_file_read_iter+0x1167/0x1490 mm/filemap.c:2302
 ext4_file_read_iter fs/ext4/file.c:131 [inline]
 ext4_file_read_iter+0x103/0x360 fs/ext4/file.c:114
 call_read_iter include/linux/fs.h:1895 [inline]
 generic_file_splice_read+0x2df/0x470 fs/splice.c:313
 do_splice_to+0xc7/0x100 fs/splice.c:892
 splice_direct_to_actor+0x1b9/0x540 fs/splice.c:971
 do_splice_direct+0x152/0x1d0 fs/splice.c:1080
 do_sendfile+0x396/0x810 fs/read_write.c:1520
 __do_sys_sendfile64 fs/read_write.c:1581 [inline]
 __se_sys_sendfile64 fs/read_write.c:1567 [inline]
 __x64_sys_sendfile64+0x121/0x140 fs/read_write.c:1567
 do_syscall_64+0xc7/0x390 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8880bb13ba38 of 8 bytes by task 13602 on cpu 0:
 ext4_do_update_inode fs/ext4/inode.c:4959 [inline]
 ext4_mark_iloc_dirty+0x506/0x1500 fs/ext4/inode.c:5578
 ext4_mark_inode_dirty+0xe6/0x420 fs/ext4/inode.c:5771
 mpage_map_and_submit_extent fs/ext4/inode.c:2479 [inline]
 ext4_writepages+0x12e4/0x1d40 fs/ext4/inode.c:2772
 do_writepages+0x6b/0x170 mm/page-writeback.c:2344
 __filemap_fdatawrite_range+0x1bb/0x220 mm/filemap.c:421
 __filemap_fdatawrite mm/filemap.c:429 [inline]
 filemap_flush+0x2a/0x40 mm/filemap.c:456
 ext4_alloc_da_blocks+0x72/0x170 fs/ext4/inode.c:3146
 ext4_release_file+0x107/0x200 fs/ext4/file.c:142
 __fput+0x1c3/0x4f0 fs/file_table.c:280
 ____fput+0x1b/0x30 fs/file_table.c:313
 task_work_run+0xf5/0x130 kernel/task_work.c:113
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_usermode_loop+0x2ae/0x2c0 arch/x86/entry/common.c:164
 prepare_exit_to_usermode arch/x86/entry/common.c:195 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:278 [inline]
 do_syscall_64+0x36e/0x390 arch/x86/entry/common.c:304
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 13602 Comm: syz-executor.3 Not tainted 5.6.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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