um: Remove unnecessary faulted check in uaccess.c

It is not necessary to check if a fault has occured or not
after disabling pagefaults. kmap_atomic does that in all
cases and we can disable it for 64 bit where kmap is not needed
and a simple page_address would suffice.

dd if=/dev/zero of=/dev/null bs=1M count=1M
Before: 3.1GB/s. After: 3.5GB/s

There is a noticeable difference for file disk read and write
as well as less noticeable difference for network IO.

Signed-off-by: Anton Ivanov <anton.ivanov@cambridgegreys.com>
Signed-off-by: Richard Weinberger <richard@nod.at>

1 files changed, 12 insertions, 11 deletions

diff --git a/arch/um/kernel/skas/uaccess.c b/arch/um/kernel/skas/uaccess.c
index d450797a3a7c..7f06fdbc7ee1 100644
--- a/arch/um/kernel/skas/uaccess.c
+++ b/arch/um/kernel/skas/uaccess.c
@@ -62,27 +62,28 @@ static int do_op_one_page(unsigned long addr, int len, int is_write,
         jmp_buf buf;
         struct page *page;
         pte_t *pte;
-        int n, faulted;
+        int n;
 
         pte = maybe_map(addr, is_write);
         if (pte == NULL)
                 return -1;
 
         page = pte_page(*pte);
+#ifdef CONFIG_64BIT
+        pagefault_disable();
+        addr = (unsigned long) page_address(page) +
+                (addr & ~PAGE_MASK);
+#else
         addr = (unsigned long) kmap_atomic(page) +
                 (addr & ~PAGE_MASK);
+#endif
+        n = (*op)(addr, len, arg);
 
-        current->thread.fault_catcher = &buf;
-
-        faulted = UML_SETJMP(&buf);
-        if (faulted == 0)
-                n = (*op)(addr, len, arg);
-        else
-                n = -1;
-
-        current->thread.fault_catcher = NULL;
-
+#ifdef CONFIG_64BIT
+        pagefault_enable();
+#else
         kunmap_atomic((void *)addr);
+#endif
 
         return n;
 }