Ext4 file system has default lazy inode table initialization setup once
it is mounted. However, it has issue on computing the next schedule time
that makes the timeout same amount in jiffies but different real time in
secs if with various HZ values. Therefore, fix by measuring the current
time in a more granular unit nanoseconds and make the next schedule time
independent of the HZ value.

Fixes: bfff6873 ("ext4: add support for lazy inode table initialization")
Signed-off-by: NShaoying Xu <shaoyi@amazon.com>
Cc: stable@vger.kernel.org
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>
Link: https://lore.kernel.org/r/20210902164412.9994-2-shaoyi@amazon.comSigned-off-by: NTheodore Ts'o <tytso@mit.edu>