[PATCH 14/15] zcache/tmem: Better error checking on frontswap_register_ops return value.

[Konrad Rzeszutek Wilk]

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.w...@oracle.com>
---
 drivers/staging/zcache/zcache-main.c | 5 ++++-
 drivers/xen/tmem.c                   | 5 ++++-
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/staging/zcache/zcache-main.c 
b/drivers/staging/zcache/zcache-main.c
index 288c841..79c10af 100644
--- a/drivers/staging/zcache/zcache-main.c
+++ b/drivers/staging/zcache/zcache-main.c
@@ -1826,8 +1826,11 @@ static int zcache_init(void)
                        namestr, frontswap_has_exclusive_gets,
                        !disable_frontswap_ignore_nonactive);
 #endif
-               if (old_ops != NULL)
+               if (IS_ERR(old_ops) || old_ops) {
+                       if (IS_ERR(old_ops))
+                               return PTR_RET(old_ops);
                        pr_warn("%s: frontswap_ops overridden\n", namestr);
+               }
        }
        if (ramster_enabled)
                ramster_init(!disable_cleancache, !disable_frontswap,
diff --git a/drivers/xen/tmem.c b/drivers/xen/tmem.c
index 9a4a9ec..2f939e5 100644
--- a/drivers/xen/tmem.c
+++ b/drivers/xen/tmem.c
@@ -395,8 +395,11 @@ 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\n");
        }
-- 
1.7.11.7

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