sh: get_user_pages_fast() must flush cache the way

Hi Andrew, could you please apply?

-=-=-=-=-=-=-=-=-=# Don't remove this line #=-=-=-=-=-=-=-=-=- This patch avoids fuse hangs on sh4 by flushing the cache on get_user_pages_fast(). This is not necessary a good thing to do, but get_user_pages() does this, so get_user_pages_fast() should too.

Please note the patch for mips arch that addresses the similar problem:
https://kernel.googlesource.com/pub/scm/linux/kernel/git/ralf/linux/+/linux-3.4.50%5E!/#F0
They basically simply disable get_user_pages_fast() at all, using a fall-back to get_user_pages(). But my fix is different, it adds an explicit cache flushes.

---
 arch/sh/mm/gup.c | 2 ++
 1 file changed, 2 insertions(+)

index bf8daf9..37458f3 100644
@@ -105,6 +105,8 @@ static noinline int gup_pte_range(pmd_t pmd,

unsigned long addr,

         VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
         page = pte_page(pte);
         get_page(page);
+        __flush_anon_page(page, addr);
+        flush_dcache_page(page);
         pages[*nr] = page;
         (*nr)++;

1.7.11.7