misc/113668: scandir(3) uses st_size of directory in unsupported manner

[David Schultz]

The following reply was made to PR kern/113668; it has been noted by GNATS.

From: David Schultz <das at FreeBSD.ORG>
To: Ed Ravin <eravin at panix.com>
Cc: freebsd-gnats-submit at FreeBSD.ORG
Subject: Re: misc/113668: scandir(3) uses st_size of directory in unsupported manner
Date: Sun, 13 Jan 2008 05:03:10 -0500

 In the original Unix, directories were just files. FreeBSD has
 always supported that philosophy; you can still `cat' a directory,
 and so it makes sense that st_size gives you the size in bytes.
 It's not scandir's fault that System V made directories more
 magical, then POSIX came along and had to cope with it, then the
 ZFS team exploited the underspecification in POSIX for their own
 nefarious purposes. :) That said, given that FreeBSD now has ZFS,
 and some of the ZFS utils probably assume the new ZFS rules for
 st_size, I guess we ought to do something!
 
 Note that this is just a performance problem, since scandir will
 realloc the array as necessary. However, it does the increases in
 increments of 10 entries, and it should probably realloc
 multiplicatively so the amortized cost of the reallocs is linear.
 I'm not sure what to do about the initial estimate, though.
 If we really want to support every old st_size value filesystem
 designers come up with, we need to worry about st_size being too
 large as well, so we basically shouldn't use it at all...