kern/46246: tmpfs does not support sparse files (!?)

[dholland%netbsd.org@localhost]

>Number:         46246
>Category:       kern
>Synopsis:       tmpfs does not support sparse files (!?)
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Thu Mar 22 16:50:01 +0000 2012
>Originator:     David A. Holland
>Release:        NetBSD 5.99.65
>Organization:
>Environment:
System: NetBSD  5.99.65 NetBSD 5.99.65 (GENERIC) #65: Mon Feb 13 01:38:30 EST 
2012  
dholland@valkyrie:/disk/disk1/home/dholland/netbsd/quotafix/src/sys/arch/i386/compile/obj.i386/GENERIC
 i386
Architecture: i386
Machine: i386
>Description:

tmpfs does not appear to support sparse files.

>How-To-Repeat:

# cat /root/x.c
#include <stdlib.h>
#include <unistd.h>
#include <err.h>

int main(int argc, char *argv[]) {
    if (truncate(argv[1], atol(argv[2])))
        err(1, "truncate");
    return 0;
}
# ls -l
# touch foo
# /root/x foo `expr 1024 \* 1024 \* 4`
# du foo
4096    foo
# 

>Fix:
send rmind chocolate? :-)