It's illegal to call flush_dcache_page on slab pages on a number
of architectures. So this patch avoids doing so if PageSlab is
true.
In future we can move the flush_dcache_page call to those page
cache users that actually need it.
Reported-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
