rbd: flush dcache after zeroing page data

Neither zero_bio_chain() nor zero_pages() contains a call to flush
caches after zeroing a portion of a page.  This can cause problems
on architectures that have caches that allow virtual address
aliasing.

This resolves:
    http://tracker.ceph.com/issues/4777

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index 291802c52c65..cb728a01a19f 100644
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -1126,6 +1126,7 @@ static void zero_bio_chain(struct bio *chain, int start_ofs)
                                 buf = bvec_kmap_irq(bv, &flags);
                                 memset(buf + remainder, 0,
                                        bv->bv_len - remainder);
+                                flush_dcache_page(bv->bv_page);
                                 bvec_kunmap_irq(buf, &flags);
                         }
                         pos += bv->bv_len;
@@ -1158,6 +1159,7 @@ static void zero_pages(struct page **pages, u64 offset, u64 end)
                 local_irq_save(flags);
                 kaddr = kmap_atomic(*page);
                 memset(kaddr + page_offset, 0, length);
+                flush_dcache_page(*page);
                 kunmap_atomic(kaddr);
                 local_irq_restore(flags);