Re: [PATCH] edd: fix error paths in module_init

On Sat, May 24, 2008 at 12:22:05AM -0500, Matt Domsch wrote:
On Sat, May 24, 2008 at 11:03:23AM +0900, Akinobu Mita wrote:
This patch fixes error handlings when kzalloc() or edd_device_register()
failed in module_init. It needs to clean registered edd_devices before
return error.

Also this patch fixes return value of module_init. module_init should not
return positive value.

Thanks for these. You caught me on holiday; I'll take a more thorough
look when I'm back next week.

Thanks!

--- 2.6-git.orig/drivers/firmware/edd.c
+++ 2.6-git/drivers/firmware/edd.c
@@ -718,8 +718,7 @@ edd_device_register(struct edd_device *e
{
int error;

- if (!edev)
- return 1;
+ BUG_ON(!edev);

Wouldn't WARN_ON() and return failure be sufficient? I hate crashing
the system when loading a driver if I can avoid it.

OK.

@@ -753,29 +752,36 @@ edd_init(void)

if (!edd_num_devices()) {
printk(KERN_INFO "EDD information not available.\n");
- return 1;
+ return -ENODEV;
}

edd_kset = kset_create_and_add("edd", NULL, firmware_kobj);
if (!edd_kset)
return -ENOMEM;

- for (i = 0; i < edd_num_devices() && !rc; i++) {
+ for (i = 0; i < edd_num_devices(); i++) {
edev = kzalloc(sizeof (*edev), GFP_KERNEL);
- if (!edev)
- return -ENOMEM;
+ if (!edev) {
+ rc = -ENOMEM;
+ goto out;
+ }

rc = edd_device_register(edev, i);
if (rc) {
kfree(edev);
- break;
+ goto out;
}
edd_devices[i] = edev;
}

- if (rc)
- kset_unregister(edd_kset);
- return rc;
+ return 0;
+out:
+ while (--i >= 0)
+ edd_device_unregister(edd_devices[i]);
+
+ kset_unregister(edd_kset);
+
+ return rc;

I didn't really like my initial approach, but the question was: when
you hit a failure, do you try to back completely out (unregister
everything that had successfully registered until now), or do you
leave the things that have succeeded, and only fail the current and
future devices? For my purposes, having even the first device be
reported, even if the others couldn't be, is useful. Hence why I
didn't undo all the registrations on failure.

OK. This is update patch.

From: Akinobu Mita <akinobu.mita@xxxxxxxxx>
Subject: edd: fix error paths in module_init

If kzalloc() or edd_device_register() failed in module_init, it returns
error without cleanup the devices already registered.

Rather than fixing it to back completely out (unregister everything that had
successfully registered until now) and return error, This patch makes it
have succeeded. Because having even the first device be reported, even if
the others couldn't be, is useful.

Also this patch fixes return value of module_init. module_init should not
return positive value.

Signed-off-by: Akinobu Mita <akinobu.mita@xxxxxxxxx>
Cc: Matt Domsch <Matt_Domsch@xxxxxxxx>
---
drivers/firmware/edd.c | 20 +++++++++-----------
1 file changed, 9 insertions(+), 11 deletions(-)

Index: 2.6-git/drivers/firmware/edd.c
===================================================================
--- 2.6-git.orig/drivers/firmware/edd.c
+++ 2.6-git/drivers/firmware/edd.c
@@ -718,8 +718,8 @@ edd_device_register(struct edd_device *e
{
int error;

- if (!edev)
- return 1;
+ if (WARN_ON(!edev))
+ return -EINVAL;
edd_dev_set_info(edev, i);
edev->kobj.kset = edd_kset;
error = kobject_init_and_add(&edev->kobj, &edd_ktype, NULL,
@@ -744,8 +744,8 @@ static inline int edd_num_devices(void)
static int __init
edd_init(void)
{
- unsigned int i;
- int rc=0;
+ int i;
+ int rc;
struct edd_device *edev;

printk(KERN_INFO "BIOS EDD facility v%s %s, %d devices found\n",
@@ -753,29 +753,27 @@ edd_init(void)

if (!edd_num_devices()) {
printk(KERN_INFO "EDD information not available.\n");
- return 1;
+ return -ENODEV;
}

edd_kset = kset_create_and_add("edd", NULL, firmware_kobj);
if (!edd_kset)
return -ENOMEM;

- for (i = 0; i < edd_num_devices() && !rc; i++) {
+ for (i = 0; i < edd_num_devices(); i++) {
edev = kzalloc(sizeof (*edev), GFP_KERNEL);
if (!edev)
- return -ENOMEM;
+ continue;

rc = edd_device_register(edev, i);
if (rc) {
kfree(edev);
- break;
+ continue;
}
edd_devices[i] = edev;
}

- if (rc)
- kset_unregister(edd_kset);
- return rc;
+ return 0;
}

static void __exit
--
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