Don't use GFP_KERNEL in netfilter hook (softirq)

According to this email
netfilter hooks might be called from softirq context. Therefore, we must
not sleep and must avoid GFP_KERNEL.

Call kmem_cache_alloc() with GFP_NOWAIT instead of GFP_KERNEL. We could
use GFP_ATOMIC but that implies GFP_HIGH which might not be necessary
here because it's acceptable for this call to fail.

We previously saw this error message: "BUG: scheduling while atomic"

Change-Id: I770ba9b82ba3a6f192b92c035383adb4d7c34e8d
1 file changed