devmem: fix kmem write bug on memory holes

commit c85e9a97c4102ce2e83112da850d838cfab5ab13 upstream

devmem: fix kmem write bug on memory holes

[ cebbert@redhat.com : backport to 2.6.32 ]

write_kmem() used to assume vwrite() always return the full buffer length.
However now vwrite() could return 0 to indicate memory hole.  This
creates a bug that "buf" is not advanced accordingly.

Fix it to simply ignore the return value, hence the memory hole.

Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Tejun Heo <tj@kernel.org>
Cc: Nick Piggin <npiggin@suse.de>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Chuck Ebbert <cebbert@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index 96b2586d2bec58aaa4568b0a7c908afda4be7337..aef3fb42150e5e75e902ac04d582179aa33b8370 100644 (file)
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -593,7 +593,7 @@ static ssize_t write_kmem(struct file * file, const char __user * buf,
                                        break;
                                }
                        }
-                       len = vwrite(kbuf, (char *)p, len);
+                       vwrite(kbuf, (char *)p, len);
                        count -= len;
                        buf += len;
                        virtr += len;