staging: lustre: mdc: fix NULL pointer dereference in mdc_adjust_dirpages

The function mdc_adjust_dirpages is only called on platforms which
don't have pages 4K in size which is why kbuild only reported this
for platforms like the Alpha. The problem was a typo in ordering of
variables in the beginning of a while loop. We were accessing the
dp pointer before it was kmapped.
Signed-off-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/lustre/lustre/mdc/mdc_request.c

@@ -1133,9 +1133,9 @@ static void mdc_adjust_dirpages(struct page **pages, int cfs_pgs, int lu_pgs)
 	int i;
 
 	for (i = 0; i < cfs_pgs; i++) {
+		struct lu_dirpage *dp = kmap(pages[i]);
 		__u64 hash_end = le64_to_cpu(dp->ldp_hash_end);
 		__u32 flags = le32_to_cpu(dp->ldp_flags);
-		struct lu_dirpage *dp = kmap(pages[i]);
 		struct lu_dirpage *first = dp;
 		struct lu_dirent *end_dirent = NULL;
 		struct lu_dirent *ent;