readdir and d_ino set to 0

[Eric Blake]

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According to Eric Norum on 9/3/2009 7:00 PM:
> If I recall my Unix V7 code correctly, I think that inode 0 was reserved
> for holding a list of bad blocks.  Of course if your disk had a bad
> block that was *in* the inode table you were pretty much out of luck.....

Also, modern-day BSD union mounts read all the entries from several layers
of directories, sort them, then discard duplicate names by changing d_ino
to 0.  In other words, there are still live systems where readdir returns
such dead entries.

- --
Don't work too hard, make some time for fun as well!

Eric Blake             ebb9@byu.net
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