sh: get_user_pages_fast() must flush cache

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.

Signed-off-by: Stas Sergeev <stsp@users.sourceforge.net>
Cc: Geert Uytterhoeven <geert+renesas@glider.be>
Cc: Kamal Dasu <kdasu.kdev@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/arch/sh/mm/gup.c b/arch/sh/mm/gup.c
index bf8daf9d9c9b..37458f38b220 100644
--- a/arch/sh/mm/gup.c
+++ b/arch/sh/mm/gup.c
@@ -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)++;