Introduce DM_UEVENT_GENERATED_FLAG in dm ioctl return and let user space
program know whether a uevent was generated or not. This helps the ioctl
caller to determine proper actions that should be taken while awaiting the
uevent.

Signed-off-by: Peter Rajnoha <prajnoha@redhat.com>
---

diff -purN linux-2.6.33-rc8.orig/drivers/md/dm.c linux-2.6.33-rc8/drivers/md/dm.c
--- linux-2.6.33-rc8.orig/drivers/md/dm.c 2010-02-26 22:36:11.276554991 +0100
+++ linux-2.6.33-rc8/drivers/md/dm.c 2010-02-26 22:35:15.591552363 +0100
@@ -2618,18 +2618,19 @@ out:
/*-----------------------------------------------------------------
* Event notification.
*---------------------------------------------------------------*/
-void dm_kobject_uevent(struct mapped_device *md, enum kobject_action action,
+int dm_kobject_uevent(struct mapped_device *md, enum kobject_action action,
unsigned cookie)
{
char udev_cookie[DM_COOKIE_LENGTH];
char *envp[] = { udev_cookie, NULL };

if (!cookie)
- kobject_uevent(&disk_to_dev(md->disk)->kobj, action);
+ return kobject_uevent(&disk_to_dev(md->disk)->kobj, action);
else {
snprintf(udev_cookie, DM_COOKIE_LENGTH, "%s=%u",
DM_COOKIE_ENV_VAR_NAME, cookie);
- kobject_uevent_env(&disk_to_dev(md->disk)->kobj, action, envp);
+ return kobject_uevent_env(&disk_to_dev(md->disk)->kobj,
+ action, envp);
}
}

diff -purN linux-2.6.33-rc8.orig/drivers/md/dm.h linux-2.6.33-rc8/drivers/md/dm.h
--- linux-2.6.33-rc8.orig/drivers/md/dm.h 2010-02-26 22:30:46.635549737 +0100
+++ linux-2.6.33-rc8/drivers/md/dm.h 2010-02-26 22:35:15.592552351 +0100
@@ -125,8 +125,8 @@ void dm_stripe_exit(void);
int dm_open_count(struct mapped_device *md);
int dm_lock_for_deletion(struct mapped_device *md);

-void dm_kobject_uevent(struct mapped_device *md, enum kobject_action action,
- unsigned cookie);
+int dm_kobject_uevent(struct mapped_device *md, enum kobject_action action,
+ unsigned cookie);

int dm_io_init(void);
void dm_io_exit(void);
diff -purN linux-2.6.33-rc8.orig/drivers/md/dm-ioctl.c linux-2.6.33-rc8/drivers/md/dm-ioctl.c
--- linux-2.6.33-rc8.orig/drivers/md/dm-ioctl.c 2010-02-26 22:36:11.296550413 +0100
+++ linux-2.6.33-rc8/drivers/md/dm-ioctl.c 2010-02-28 19:40:20.737790992 +0100
@@ -285,7 +285,8 @@ retry:
up_write(&_hash_lock);
}

-static int dm_hash_rename(uint32_t cookie, const char *old, const char *new)
+static int dm_hash_rename(uint32_t cookie, uint32_t *flags, const char *old,
+ const char *new)
{
char *new_name, *old_name;
struct hash_cell *hc;
@@ -344,7 +345,8 @@ static int dm_hash_rename(uint32_t cooki
dm_table_put(table);
}

- dm_kobject_uevent(hc->md, KOBJ_CHANGE, cookie);
+ if (!dm_kobject_uevent(hc->md, KOBJ_CHANGE, cookie))
+ *flags |= DM_UEVENT_GENERATED_FLAG;

dm_put(hc->md);
up_write(&_hash_lock);
@@ -736,10 +738,10 @@ static int dev_remove(struct dm_ioctl *p
__hash_remove(hc);
up_write(&_hash_lock);

- dm_kobject_uevent(md, KOBJ_REMOVE, param->event_nr);
+ if (!dm_kobject_uevent(md, KOBJ_REMOVE, param->event_nr))
+ param->flags |= DM_UEVENT_GENERATED_FLAG;

dm_put(md);
- param->data_size = 0;
return 0;
}

@@ -773,7 +775,8 @@ static int dev_rename(struct dm_ioctl *p
return r;

param->data_size = 0;
- return dm_hash_rename(param->event_nr, param->name, new_name);
+ return dm_hash_rename(param->event_nr, &param->flags,
+ param->name, new_name);
}

static int dev_set_geometry(struct dm_ioctl *param, size_t param_size)
@@ -899,8 +902,8 @@ static int do_resume(struct dm_ioctl *pa

if (dm_suspended_md(md)) {
r = dm_resume(md);
- if (!r)
- dm_kobject_uevent(md, KOBJ_CHANGE, param->event_nr);
+ if (!r && !dm_kobject_uevent(md, KOBJ_CHANGE, param->event_nr))
+ param->flags |= DM_UEVENT_GENERATED_FLAG;
}

if (old_map)
diff -purN linux-2.6.33-rc8.orig/include/linux/dm-ioctl.h linux-2.6.33-rc8/include/linux/dm-ioctl.h
--- linux-2.6.33-rc8.orig/include/linux/dm-ioctl.h 2010-02-26 22:30:47.168549633 +0100
+++ linux-2.6.33-rc8/include/linux/dm-ioctl.h 2010-02-28 19:42:35.197553190 +0100
@@ -266,9 +266,9 @@ enum {
#define DM_DEV_SET_GEOMETRY _IOWR(DM_IOCTL, DM_DEV_SET_GEOMETRY_CMD, struct dm_ioctl)

#define DM_VERSION_MAJOR 4
-#define DM_VERSION_MINOR 16
+#define DM_VERSION_MINOR 17
#define DM_VERSION_PATCHLEVEL 0
-#define DM_VERSION_EXTRA "-ioctl (2009-11-05)"
+#define DM_VERSION_EXTRA "-ioctl (2010-03-01)"

/* Status bits */
#define DM_READONLY_FLAG (1 << 0) /* In/Out */
@@ -316,4 +316,9 @@ enum {
*/
#define DM_QUERY_INACTIVE_TABLE_FLAG (1 << 12) /* In */

+/*
+ * Indicates whether a uevent was generated.
+ */
+#define DM_UEVENT_GENERATED_FLAG (1 << 13) /* Out */
+
#endif /* _LINUX_DM_IOCTL_H */

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On Mon, Mar 01, 2010 at 09:27:17AM +0100, Peter Rajnoha wrote:
> diff -purN linux-2.6.33-rc8.orig/drivers/md/dm-ioctl.c linux-2.6.33-rc8/drivers/md/dm-ioctl.c

> @@ -736,10 +738,10 @@ static int dev_remove(struct dm_ioctl *p

> dm_put(md);
> - param->data_size = 0;
> return 0;

Why is that line removed?

Alasdair

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On Mon, Mar 01, 2010 at 09:27:17AM +0100, Peter Rajnoha wrote:
> + if (!dm_kobject_uevent(hc->md, KOBJ_CHANGE, cookie))
> + *flags |= DM_UEVENT_GENERATED_FLAG;

If userspace set this flag before the call, where is it cleared?
It needs to have a defined state on *every* call.
I'll add this to the top of validate_params.

Alasdair

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On 03/05/2010 08:32 PM, Alasdair G Kergon wrote:
> On Mon, Mar 01, 2010 at 09:27:17AM +0100, Peter Rajnoha wrote:
>> diff -purN linux-2.6.33-rc8.orig/drivers/md/dm-ioctl.c linux-2.6.33-rc8/drivers/md/dm-ioctl.c
>
>> @@ -736,10 +738,10 @@ static int dev_remove(struct dm_ioctl *p
>
>> dm_put(md);
>> - param->data_size = 0;
>> return 0;
>
> Why is that line removed?

That's because of the copy_to_user in the outer ctl_ioctl fn
so it copies back the result (with the new flag). We had nothing
in return before...

Peter

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On 03/05/2010 08:38 PM, Alasdair G Kergon wrote:
> On Mon, Mar 01, 2010 at 09:27:17AM +0100, Peter Rajnoha wrote:
>> + if (!dm_kobject_uevent(hc->md, KOBJ_CHANGE, cookie))
>> + *flags |= DM_UEVENT_GENERATED_FLAG;
>
> If userspace set this flag before the call, where is it cleared?
> It needs to have a defined state on *every* call.
> I'll add this to the top of validate_params.

Yes, you're right, we shouldn't rely on userspace to do this.
Indeed, it needs to be cleared directly. Thanks!

Peter

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