Is there anything that prevents PageDirty from theoretically being
speculatively loaded before page_count here? (see patch)

It would result in pagecache corruption in the following situation:

1                                2
find_get_page();
write to page                    write_lock(tree_lock);
SetPageDirty();                  if (page_count != 2
put_page();                          || PageDirty())

Now I'm worried that 2 might see PageDirty *before* SetPageDirty in
1, and page_count *after* put_page in 1.

Or am I seeing things that aren't there?

Thanks,

-- 
SUSE Labs, Novell Inc.