The following reply was made to PR kern/31944; it has been noted by GNATS.

From: David Laight <david@l8s.co.uk>
To: "Julio M. Merino Vidal" <jmmv84@gmail.com>
Cc: tech-kern@netbsd.org, gnats-bugs@netbsd.org
Subject: Re: kern/31944 - Fix to reduce tmpfs memory usage
Date: Sun, 23 Apr 2006 19:26:28 +0100

 On Fri, Apr 14, 2006 at 07:51:14PM +0200, Julio M. Merino Vidal wrote:
 > Hello,
 > 
 > PR kern/31944 lists three issues that make tmpfs consume too much
 > memory.  The attached patch addresses the first of them.  It does the
 > following:
 > 
 > - Only keep the node identifier/generation number when deleting a node.
 >   The size of tmpfs_nid is much smaller than that of tmpfs_node.
 > - Avoid keeping nodes that were initialized but then discarded due to some
 >   error.  See the keepit parameter to the tmpfs_free_node function.
 > 
 > I have read the replies to that PR but the proposed solutions seem to be
 > "not right".  Also, one question that arises... can there be two live files in
 > a file system with the same node number?  If not, all those solutions do not
 > seem to address this...
 
 As pointed out by others, POSIX requires that a file be uniquelly identifyable
 by its device/inode pair.  This is visible to userland via stat().
 
 The NetBSD kernel was recently changed to support 64bit inode numbers, so
 maybe you just use increment a 64bit inode number on every create?
 (with a random(ish) generation number).
 
 Alternatively you just need to keep the last used generation number for
 each inode number - which should just cost 4 bytes/inode, and ought to
 be pagable.
 
 	David
 
 -- 
 David Laight: david@l8s.co.uk