[RESEND PATCH v2] memory-hotplug: fix store_mem_state() return value

[Reza Arbab <arbab@linux.vnet.ibm.com>]

Attempting to online memory which is already online will cause this:

1. store_mem_state() called with buf="online"
2. device_online() returns 1 because device is already online
3. store_mem_state() returns 1
4. calling code interprets this as 1-byte buffer read
5. store_mem_state() called again with buf="nline"
6. store_mem_state() returns -EINVAL

Example:

$ cat /sys/devices/system/memory/memory0/state
online
$ echo online > /sys/devices/system/memory/memory0/state
-bash: echo: write error: Invalid argument

Fix the return value of store_mem_state() so this doesn't happen.

Signed-off-by: Reza Arbab <arbab@linux.vnet.ibm.com>
---
Andrew et al, Greg asked that this come in through the -mm tree, as
you know this code better than him.

 drivers/base/memory.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/base/memory.c b/drivers/base/memory.c
index 1cea0ba..8e385ea 100644
--- a/drivers/base/memory.c
+++ b/drivers/base/memory.c
@@ -359,7 +359,7 @@ store_mem_state(struct device *dev,
 err:
 	unlock_device_hotplug();
 
-	if (ret)
+	if (ret < 0)
 		return ret;
 	return count;
 }
-- 
1.8.3.1

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