Description of problem:
Map expiry doesn't work with file maps. File maps are only re-read if the
requested key is not found in the current map and the map has been modified
since the map was initially read. This doesn't account for changed entries, only
added/removed ones.

Version-Release number of selected component (if applicable):
autofs-4.1.3-47

How reproducible:
Always

Steps to Reproduce:
1. Set two entries in /etc/auto.misc with same key but different mounts
2. Comment one of them out
3. access the mountpoint
4. manually umount the mntpoint
5. uncomment the commented one, comment the uncommented one (switch them) in
auto.misc
6. access the mountpoint
  
Actual results:
You'll get the same mount as the first time even though the map has changed

Expected results:
Second access gets new mount

Additional info:
This is broken off of 137206. Here's a potentially relevant remark from that bug:

Comment #16 From Dave Lehman (dlehman)  	 on 2005-02-04 12:11 EST  
[reply]  	 Private

Jeff, expiry with file maps doesn't work.

The thing is that NIS maps get queried with every request, so the cache is
updated every time, effectively eliminating the benefit of caching the NIS maps
AFAICT. File maps, OTOH, are only re-read if a) the requested key/entry is not
found *and* b) the file has been modified since it was initialized.

I started putting a patch together to re-read the file maps whenever the file
has been modified, but I found that there's no good way to update the timestamp
in the lookup_context struct defined in modules/lookup_file.c. What this means
is that if the map has been modified at all since the automounter initialized
the map (daemon startup or SIGHUP) it will be re-read for every request. Again,
this voids the cache.

Let me know if you want me to upload the patch.