On 7/2/20 5:44 AM, Greg Kroah-Hartman wrote:

On Mon, Jun 29, 2020 at 08:50:08AM +0200, Bartosz Golaszewski wrote:

quoted

From: Bartosz Golaszewski <redacted>

Shrink pmbus code by using devm_hwmon_device_register_with_groups()
and devm_krealloc() instead of their non-managed variants.

Signed-off-by: Bartosz Golaszewski <redacted>
---
 drivers/hwmon/pmbus/pmbus_core.c | 28 +++++++++-------------------
 1 file changed, 9 insertions(+), 19 deletions(-)

diff --git a/drivers/hwmon/pmbus/pmbus_core.c b/drivers/hwmon/pmbus/pmbus_core.c
index a420877ba533..225d0ac162c7 100644
--- a/drivers/hwmon/pmbus/pmbus_core.c
+++ b/drivers/hwmon/pmbus/pmbus_core.c

@@ -1022,9 +1022,9 @@ static int pmbus_add_attribute(struct pmbus_data *data, struct attribute *attr)
 {
 	if (data->num_attributes >= data->max_attributes - 1) {
 		int new_max_attrs = data->max_attributes + PMBUS_ATTR_ALLOC_SIZE;
-		void *new_attrs = krealloc(data->group.attrs,
-					   new_max_attrs * sizeof(void *),
-					   GFP_KERNEL);
+		void *new_attrs = devm_krealloc(data->dev, data->group.attrs,
+						new_max_attrs * sizeof(void *),
+						GFP_KERNEL);

dynamic sysfs attributes in a devm-allocated chunk of memory?  What
could go wrong...

You mean that the memory might be removed before the attributes
are removed ? Hmm, but that isn't different to the current implementation.
The hwmon device is removed first (removing the sysfs attributes),
followed by the kfree. Are you saying this is not safe ?
Pretty much all code which allocates memory for struct attribute
is doing the same, so that would be a problem throughout the kernel.

Anyway, is this the only in-kernel user that you could find for this
function?  If so, it feels like it's a lot of extra work for no real
gain.

And I was so happy that I'd be able to get rid of pmbus_do_remove()
subsequently. But then I can also use devm_add_action() and have it
call kfree(), with the same result. Given that, if hwmon would really
be the only user, we can live without it.

Guenter