GDB shows this:

mtjm@earendil:~/apr/src/apr-1.4.6/test$ gdb ./testall
GNU gdb (GDB) 7.4.1
Copyright (C) 2012 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
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There is NO WARRANTY, to the extent permitted by law.  Type "show copying" 
and "show warranty" for details.
This GDB was configured as "mips64el-unknown-linux-gnu".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>...
/home/mtjm/.gdbinit:1: Error in sourced command file:
No symbol table is loaded.  Use the "file" command.
Reading symbols from /home/mtjm/apr/src/apr-1.4.6/test/testall...done.
(gdb) b mmap64
Function "mmap64" not defined.
Make breakpoint pending on future shared library load? (y or [n]) y
Breakpoint 1 (mmap64) pending.
(gdb) r testlfs
Starting program: /home/mtjm/apr/src/apr-1.4.6/test/testall testlfs
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/libthread_db.so.1".
testlfs             : -
Breakpoint 1, 0x77e92a00 in mmap64 () from /lib/libc.so.6
(gdb) frame 1
#1  0x77f99ea8 in apr_mmap_create (new=0x7fff2c74, file=0x100b0528, offset=8589869056, size=65536, flag=1, cont=0x100b00a0) at mmap/unix/mmap.c:133
133         mm = mmap(NULL, size, native_flags, MAP_SHARED, file->filedes, offset);
(gdb) print size
$1 = 65536
(gdb) print offset
$2 = 8589869056
(gdb) n
Single stepping until exit from function mmap64,
which has no line number information.
apr_mmap_create (new=0x7fff2c74, file=0x100b0528, offset=8589869056, size=65536, flag=1, cont=0x100b00a0) at mmap/unix/mmap.c:135
135         if (mm == (void *)-1) {
(gdb) print mm
$3 = (void *) 0xffffffff
(gdb) print errno
$4 = 22

The thread of https://mail-archives.apache.org/mod_mbox/apr-dev/200806.mbox/%3Cacf3f2e60806170925t6685556v5660b9be9f627cd3@mail.gmail.com%3E suggested this being caused by offset not divisible by page size, but it is divisible here (16K pages).

Changing the offset to 0 or 65536 makes the mmap succeed (and the test fail), so this is probably related to long filename support.