Re: [PATCH V3 04/20] nvdimm/label: Update mutex_lock() with guard(mutex)()

Ira Weiny
2025-09-20T17:42:14Z

Dave Jiang wrote:

[snip]

> > @@ -998,9 +998,8 @@ static int init_labels(struct nd_mapping *nd_mapping, int num_labels)
> > label_ent = kzalloc(sizeof(*label_ent), GFP_KERNEL);
> > if (!label_ent)
> > return -ENOMEM;
> > - mutex_lock(&nd_mapping->lock);
> > + guard(mutex)(&nd_mapping->lock);
> > list_add_tail(&label_ent->list, &nd_mapping->labels);
> > - mutex_unlock(&nd_mapping->lock);
>
> I would not mix and match old and new locking flow in a function. If you are going to convert, then do the whole function. I think earlier in this function you may need a scoped_guard() call.
>

FWIW I would limit the changes to __pmem_label_update() because that is
the function which benefits from these changes.

> > }
> >
> > if (ndd->ns_current == -1 || ndd->ns_next == -1)
> > @@ -1039,7 +1038,7 @@ static int del_labels(struct nd_mapping *nd_mapping, uuid_t *uuid)
> > if (!preamble_next(ndd, &nsindex, &free, &nslot))
> > return 0;
> >
> > - mutex_lock(&nd_mapping->lock);
> > + guard(mutex)(&nd_mapping->lock);
>
> So this change now includes nd_label_write_index() in the lock context as well compare to the old code. So either you should use a scoped_guard() or create a helper function and move the block of code being locked to the helper function with guard() to avoid changing the original code flow.
>

Sure you could do this but again I don't think these updates are worth
this amount of work right now.

Ira

> DJ
>
> > list_for_each_entry_safe(label_ent, e, &nd_mapping->labels, list) {
> > struct nd_namespace_label *nd_label = label_ent->label;
> >
> > @@ -1061,7 +1060,6 @@ static int del_labels(struct nd_mapping *nd_mapping, uuid_t *uuid)
> > nd_mapping_free_labels(nd_mapping);
> > dev_dbg(ndd->dev, "no more active labels\n");
> > }
> > - mutex_unlock(&nd_mapping->lock);
> >
> > return nd_label_write_index(ndd, ndd->ns_next,
> > nd_inc_seq(__le32_to_cpu(nsindex->seq)), 0);
>
>