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gpio: virtuser: lock up configfs that an instantiated device depends on

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Once a virtuser device is instantiated and actively used, allowing rmdir
for its configfs serves no purpose and can be confusing. Userspace
interacts with the virtual consumer at arbitrary times, meaning it
depends on its existence.

Make the subsystem itself depend on the configfs entry for a virtuser
device while it is in active use.

Signed-off-by: Koichiro Den <koichiro.den@canonical.com>
Link: https://lore.kernel.org/r/20250103141829.430662-4-koichiro.den@canonical.com
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
This commit is contained in:
Koichiro Den 2025-01-03 23:18:28 +09:00 committed by Bartosz Golaszewski
parent 656cc2e892
commit c7c434c1db
1 changed files with 41 additions and 8 deletions
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49
drivers/gpio/gpio-virtuser.c
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@ -1546,6 +1546,30 @@ gpio_virtuser_device_deactivate(struct gpio_virtuser_device *dev)
dev->pdev = NULL;
}
static void
gpio_virtuser_device_lockup_configfs(struct gpio_virtuser_device *dev, bool lock)
{
struct configfs_subsystem *subsys = dev->group.cg_subsys;
struct gpio_virtuser_lookup_entry *entry;
struct gpio_virtuser_lookup *lookup;
/*
* The device only needs to depend on leaf lookup entries. This is
* sufficient to lock up all the configfs entries that the
* instantiated, alive device depends on.
*/
list_for_each_entry(lookup, &dev->lookup_list, siblings) {
list_for_each_entry(entry, &lookup->entry_list, siblings) {
if (lock)
WARN_ON(configfs_depend_item_unlocked(
subsys, &entry->group.cg_item));
else
configfs_undepend_item_unlocked(
&entry->group.cg_item);
}
}
}
static ssize_t
gpio_virtuser_device_config_live_store(struct config_item *item,
const char *page, size_t count)
@ -1558,15 +1582,24 @@ gpio_virtuser_device_config_live_store(struct config_item *item,
if (ret)
return ret;
guard(mutex)(&dev->lock);
if (live == gpio_virtuser_device_is_live(dev))
return -EPERM;
if (live)
ret = gpio_virtuser_device_activate(dev);
else
gpio_virtuser_device_deactivate(dev);
gpio_virtuser_device_lockup_configfs(dev, true);
scoped_guard(mutex, &dev->lock) {
if (live == gpio_virtuser_device_is_live(dev))
ret = -EPERM;
else if (live)
ret = gpio_virtuser_device_activate(dev);
else
gpio_virtuser_device_deactivate(dev);
}
/*
* Undepend is required only if device disablement (live == 0)
* succeeds or if device enablement (live == 1) fails.
*/
if (live == !!ret)
gpio_virtuser_device_lockup_configfs(dev, false);
return ret ?: count;
}