From f42158fe6785dd366073c7fd00f159a65c631597 Mon Sep 17 00:00:00 2001
From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Date: Tue, 30 Apr 2013 15:27:01 -0700
Subject: zcache/tmem: Better error checking on frontswap_register_ops return
 value.

In the past it either used to be NULL or the "older" backend. Now we
also return -Exx error codes.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Bob Liu <lliubbo@gmail.com>
Cc: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Cc: Andor Daam <andor.daam@googlemail.com>
Cc: Dan Magenheimer <dan.magenheimer@oracle.com>
Cc: Florian Schmaus <fschmaus@gmail.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Stefan Hengelein <ilendir@googlemail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
 drivers/xen/tmem.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

(limited to 'drivers/xen')

diff --git a/drivers/xen/tmem.c b/drivers/xen/tmem.c
index 8adde8e8428..e3600be4e7f 100644
--- a/drivers/xen/tmem.c
+++ b/drivers/xen/tmem.c
@@ -397,8 +397,11 @@ static int xen_tmem_init(void)
 			frontswap_register_ops(&tmem_frontswap_ops);
 
 		tmem_frontswap_poolid = -1;
-		if (old_ops)
+		if (IS_ERR(old_ops) || old_ops) {
+			if (IS_ERR(old_ops))
+				return PTR_ERR(old_ops);
 			s = " (WARNING: frontswap_ops overridden)";
+		}
 		printk(KERN_INFO "frontswap enabled, RAM provided by "
 				 "Xen Transcendent Memory%s\n", s);
 	}
-- 
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