I've constructed a test patch that is currently addressing all the
issues on my system.

The portion of Openmotif that was having issues with page faults works
correctly with this patch, and gcc-4.4.5 builds without issue.

I extracted only the portion of the first patch that corrects the
handling of dirty_pages when copied==0, and incorporated the second
patch that falls back to one-page-at-a-time if there are troubles with
page faults.

--- fs/btrfs/file.c     2011-03-05 07:34:43.025131607 -0600
+++ /usr/src/linux/fs/btrfs/file.c      2011-03-05 07:41:45.001260294 -0600
@@ -1023,8 +1023,20 @@

                copied = btrfs_copy_from_user(pos, num_pages,
                                           write_bytes, pages, &i);
-               dirty_pages = (copied + offset + PAGE_CACHE_SIZE - 1) >>
-                               PAGE_CACHE_SHIFT;
+
+               /*
+                * if we have trouble faulting in the pages, fall
+                * back to one page at a time
+                */
+               if (copied < write_bytes)
+                       nrptrs = 1;
+
+               if (copied == 0)
+                       dirty_pages = 0;
+               else
+                       dirty_pages = (copied + offset +
+                                      PAGE_CACHE_SIZE - 1) >>
+                                      PAGE_CACHE_SHIFT;

                if (num_pages > dirty_pages) {
                        if (copied > 0)
--
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