On code.haskell.org, which is using reiserfs and kernel "Linux 
nun.haskell.org 2.6.18-028stab064.7 #1 SMP Wed Aug 26 13:11:07 MSD 2009 
i686 GNU/Linux"

Darcs 2.4.1, built against mmap 0.4.1

Make a non-empty old-fashioned repo, run darcs optimize --upgrade:

darcs-2.4.1: mmap of './_darcs/tentative_pristine' failed: invalid 
argument (Invalid argument)

Reported by Sergei Trofimovich and Lennart Kolmodin after they 
encountered a problem with their gentoo-haskell repository.

Also on the same machine, same darcs, with an empty old-fashioned repo:

ganesh@nun:~/temp/foo$ darcs optimize --upgrade
Checking repository in case of corruption...
Invalid repository:  /home/ganesh/temp/foo
darcs-2.4.1: _darcs/pristine.hashed: removeFile: does not exist (No such 
file or directory)

One important note I've forgot to mention:
darcs was built with quite old ghc-6.8.2
trying to build it gainst ghc-6.12.1 fixed problem

I think I've once again was biten by
http://hackage.haskell.org/trac/ghc/ticket/2093

lack of AC_SYS_LARGEFILE in unix package broke stat(2) (and, maybe,
mmap(2)) in our case.

Sorry for the noise.

I think this is still an issue because GHC 6.8.2 is nominally a supported 
compiler, but it's clearly now much less important.

Where did the GHC 6.8.2 come from? The one in Debian lenny ought to have 
the AC_SYS_LARGEFILE patch in, and thus not have the problem.

It was built on a gentoo stable box with unstable packages for darcs.
Stable ghc there is still ghc-6.8.2

Unstable gentoo has fixed ghc-6.8.3 and ghc-6.10.4.
As darcs-2.4.x is still unstable it's not a problem here too.

As I said before using newer ghc on this stable box allowed me to build
perfectly working binary, which I placed on code.haskell.org:
/home/slyfox/bin/darcs-2.4.1-ghc-6.12.1

Resolved by (a) dropping GHC 6.8 support for the 2.5 release and (b)
supporting GHC >= 6.8.3 on the 2.4 line?