devmem: Handle class_create() failure

I hit this when we had a bug in IDR for a few days. Basically sysfs would fail to create new inodes since it uses an IDR and therefore class_create would fail.

While we are unlikely to see this fail we may as well handle it instead of oopsing.

---

Index: linux-2.6/drivers/char/mem.c
===================================================================
@@ -901,6 +901,9 @@ static int __init chr_dev_init(void)
 		printk("unable to get major %d for memory devs\n", MEM_MAJOR);
 
 	mem_class = class_create(THIS_MODULE, "mem");
+	if (IS_ERR(mem_class))
+		return PTR_ERR(mem_class);
+
 	mem_class->devnode = mem_devnode;
 	for (minor = 1; minor < ARRAY_SIZE(devlist); minor++) {
 		if (!devlist[minor].name)

Looks good to me. Thanks!

Is this something that we need for .34? How were you getting this to fail in the first place?

thanks,

greg k-h

Hi Greg,

I hit this when we broke the IDR allocator for a few days. The bug got introduced in commit 859ddf09743a8cc680af33f7259ccd0fd36bfe9d (idr: fix a critical misallocation bug), and was backed out a few days later in commit 6f14a668f1a8b715a6e855f4e32705e54a6e86a1 (idr: revert misallocation bug fix).

The sysfs inode allocator which uses IDR was getting back a bogus ENOSPC return code. I think the chances of seeing this fail otherwise would be pretty remote, you'd have to use up 2^31 sysfs inodes before hitting the real IDR limit.

Anton