[PATCH 3/8] devmem: fix kmem write bug on memory holes

[Wu Fengguang]

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.

CC: Kelly Bowa <kmb@xxxxxxxxxx>
CC: Andi Kleen <andi@xxxxxxxxxxxxxx>
CC: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
CC: Christoph Lameter <cl@xxxxxxxxxxxxxxxxxxxx>
CC: Ingo Molnar <mingo@xxxxxxx>
CC: Tejun Heo <tj@xxxxxxxxxx>
CC: Nick Piggin <npiggin@xxxxxxx>
CC: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
CC: <stable@xxxxxxxxxx>
Signed-off-by: Wu Fengguang <fengguang.wu@xxxxxxxxx>
---
 drivers/char/mem.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- linux-mm.orig/drivers/char/mem.c	2010-01-11 10:32:32.000000000 +0800
+++ linux-mm/drivers/char/mem.c	2010-01-11 10:32:34.000000000 +0800
@@ -555,7 +555,7 @@ static ssize_t write_kmem(struct file * 
 				err = -EFAULT;
 				break;
 			}
-			sz = vwrite(kbuf, (char *)p, sz);
+			vwrite(kbuf, (char *)p, sz);
 			count -= sz;
 			buf += sz;
 			virtr += sz;


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