On Wed, 2011-01-05 at 10:14 -0500, Trond Myklebust wrote: 

OK. So,the new behaviour in 2.6.37 is that we're writing to a series of
pages via the usual kmap_atomic()/kunmap_atomic() and kmap()/kunmap()
interfaces, but we can end up reading them via a virtual address range
that gets set up via vm_map_ram() (that range gets set up before the
write occurs).

Do we perhaps need an invalidate_kernel_vmap_range() before we can read
the data on ARM in this kind of scenario?

IOW: Does something like the following patch fix the problem?

------------------------------------------------------------------------------- 
From: Trond Myklebust <redacted>
NFS: Ensure we clean the TLB cache in nfs_readdir_xdr_to_array
    
After calling nfs_readdir_xdr_filler(), we need a call to
invalidate_kernel_vmap_range() before we can proceed to read
the data back through the virtual address range.
    
Signed-off-by: Trond Myklebust <redacted>
---

diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index 996dd89..4640470 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c

@@ -587,6 +587,9 @@ int nfs_readdir_xdr_to_array(nfs_readdir_descriptor_t *desc, struct page *page,
 		if (status < 0)
 			break;
 		pglen = status;
+
+		invalidate_kernel_vmap_range(pages_ptr, pglen);
+
 		status = nfs_readdir_page_filler(desc, &entry, pages_ptr, page, pglen);
 		if (status < 0) {
 			if (status == -ENOSPC)

-- 
Trond Myklebust
Linux NFS client maintainer

NetApp
Trond.Myklebust@netapp.com
www.netapp.com