This patch broke NFS for nommu kernels because of the use of vm_map_ram()/vm_unmap_ram() which don't exist for nommu.
Author: Bryan Schumaker <firstname.lastname@example.org>
Date: Wed Oct 20 15:44:37 2010 -0400
NFS: readdir with vmapped pages
When trying to boot from an NFS root, I hit:
BUG: failure at /linux-2.6/mm/nommu.c:419/vm_map_ram()!
First-Bad-Commit : 56e4ebf877b6043c289bda32a5a7385b80c17dee
Created attachment 42952 [details]
NFS: Don't use vm_map_ram() in readdir
vm_map_ram() is not available on NOMMU platforms, and causes trouble
on incoherrent architectures such as ARM when we access the page data
through both the direct and the virtual mapping.
The alternative is to use the direct mapping to access page data
for the case when we are not crossing a page boundary, but to copy
the data into a linear scratch buffer when we are accessing data
that spans page boundaries.
The above patch has been merged into mainline as commit 6650239a4b01077e80d5a4468562756d77afaa59, with Cc: email@example.com
Marking this bug as resolved for now. Please tell me if this is not the case.