[v2,3/6] module: extract patient module check into helper
Commit Message
The patient module check inside add_unformed_module() is large
enough as we need it. It is a bit hard to read too, so just
move it to a helper and do the inverse checks first to help
shift the code and make it easier to read. The new helper then
is module_patient_check_exists().
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
---
kernel/module/main.c | 71 +++++++++++++++++++++++++-------------------
1 file changed, 40 insertions(+), 31 deletions(-)
Comments
On 05.04.23 04:26, Luis Chamberlain wrote:
> The patient module check inside add_unformed_module() is large
> enough as we need it. It is a bit hard to read too, so just
> move it to a helper and do the inverse checks first to help
> shift the code and make it easier to read. The new helper then
> is module_patient_check_exists().
>
> Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
> ---
> kernel/module/main.c | 71 +++++++++++++++++++++++++-------------------
> 1 file changed, 40 insertions(+), 31 deletions(-)
>
> diff --git a/kernel/module/main.c b/kernel/module/main.c
> index 98c261928325..8f382580195b 100644
> --- a/kernel/module/main.c
> +++ b/kernel/module/main.c
> @@ -2638,6 +2638,43 @@ static bool finished_loading(const char *name)
> return ret;
> }
>
> +/* Must be called with module_mutex held */
> +static int module_patient_check_exists(const char *name)
> +{
> + struct module *old;
> + int err = 0;
> +
> + old = find_module_all(name, strlen(name), true);
> + if (old == NULL)
> + return 0;
> +
> + if (old->state == MODULE_STATE_COMING
> + || old->state == MODULE_STATE_UNFORMED) {
I never understood why people prefer to prefix the || on a newline. But
it seems to be a thing in the module/ world :)
> + /* Wait in case it fails to load. */
> + mutex_unlock(&module_mutex);
> + err = wait_event_interruptible(module_wq,
> + finished_loading(name));
> + if (err)
> + return err;
You return with the mutex unlocked. The caller will unlock again ...
> +
> + /* The module might have gone in the meantime. */
> + mutex_lock(&module_mutex);
> + old = find_module_all(name, strlen(name), true);
> + }
> +
> + /*
> + * We are here only when the same module was being loaded. Do
> + * not try to load it again right now. It prevents long delays
> + * caused by serialized module load failures. It might happen
> + * when more devices of the same type trigger load of
> + * a particular module.
> + */
> + if (old && old->state == MODULE_STATE_LIVE)
> + return -EEXIST;
> + else
> + return -EBUSY;
You can drop the else and return right away.
> +}
> +
> /*
> * We try to place it in the list now to make sure it's unique before
Besides, LGTM.
On Wed, Apr 05, 2023 at 07:11:24PM +0200, David Hildenbrand wrote:
> On 05.04.23 04:26, Luis Chamberlain wrote:
> > The patient module check inside add_unformed_module() is large
> > enough as we need it. It is a bit hard to read too, so just
> > move it to a helper and do the inverse checks first to help
> > shift the code and make it easier to read. The new helper then
> > is module_patient_check_exists().
> >
> > Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
> > ---
> > kernel/module/main.c | 71 +++++++++++++++++++++++++-------------------
> > 1 file changed, 40 insertions(+), 31 deletions(-)
> >
> > diff --git a/kernel/module/main.c b/kernel/module/main.c
> > index 98c261928325..8f382580195b 100644
> > --- a/kernel/module/main.c
> > +++ b/kernel/module/main.c
> > @@ -2638,6 +2638,43 @@ static bool finished_loading(const char *name)
> > return ret;
> > }
> > +/* Must be called with module_mutex held */
> > +static int module_patient_check_exists(const char *name)
> > +{
> > + struct module *old;
> > + int err = 0;
> > +
> > + old = find_module_all(name, strlen(name), true);
> > + if (old == NULL)
> > + return 0;
> > +
> > + if (old->state == MODULE_STATE_COMING
> > + || old->state == MODULE_STATE_UNFORMED) {
>
> I never understood why people prefer to prefix the || on a newline. But it
> seems to be a thing in the module/ world :)
Yeah the other way seems better, I'll make it pretty.
> > + /* Wait in case it fails to load. */
> > + mutex_unlock(&module_mutex);
> > + err = wait_event_interruptible(module_wq,
> > + finished_loading(name));
> > + if (err)
> > + return err;
>
> You return with the mutex unlocked. The caller will unlock again ...
Fixed now by moving the mutex below up after the wait_event_interruptible(),
thanks.
> > +
> > + /* The module might have gone in the meantime. */
> > + mutex_lock(&module_mutex);
> > + old = find_module_all(name, strlen(name), true);
> > + }
> > +
> > + /*
> > + * We are here only when the same module was being loaded. Do
> > + * not try to load it again right now. It prevents long delays
> > + * caused by serialized module load failures. It might happen
> > + * when more devices of the same type trigger load of
> > + * a particular module.
> > + */
> > + if (old && old->state == MODULE_STATE_LIVE)
> > + return -EEXIST;
> > + else
> > + return -EBUSY;
>
> You can drop the else and return right away.
Will make it pretty like that, thanks.
Luis
@@ -2638,6 +2638,43 @@ static bool finished_loading(const char *name)
return ret;
}
+/* Must be called with module_mutex held */
+static int module_patient_check_exists(const char *name)
+{
+ struct module *old;
+ int err = 0;
+
+ old = find_module_all(name, strlen(name), true);
+ if (old == NULL)
+ return 0;
+
+ if (old->state == MODULE_STATE_COMING
+ || old->state == MODULE_STATE_UNFORMED) {
+ /* Wait in case it fails to load. */
+ mutex_unlock(&module_mutex);
+ err = wait_event_interruptible(module_wq,
+ finished_loading(name));
+ if (err)
+ return err;
+
+ /* The module might have gone in the meantime. */
+ mutex_lock(&module_mutex);
+ old = find_module_all(name, strlen(name), true);
+ }
+
+ /*
+ * We are here only when the same module was being loaded. Do
+ * not try to load it again right now. It prevents long delays
+ * caused by serialized module load failures. It might happen
+ * when more devices of the same type trigger load of
+ * a particular module.
+ */
+ if (old && old->state == MODULE_STATE_LIVE)
+ return -EEXIST;
+ else
+ return -EBUSY;
+}
+
/*
* We try to place it in the list now to make sure it's unique before
* we dedicate too many resources. In particular, temporary percpu
@@ -2646,41 +2683,14 @@ static bool finished_loading(const char *name)
static int add_unformed_module(struct module *mod)
{
int err;
- struct module *old;
mod->state = MODULE_STATE_UNFORMED;
mutex_lock(&module_mutex);
- old = find_module_all(mod->name, strlen(mod->name), true);
- if (old != NULL) {
- if (old->state == MODULE_STATE_COMING
- || old->state == MODULE_STATE_UNFORMED) {
- /* Wait in case it fails to load. */
- mutex_unlock(&module_mutex);
- err = wait_event_interruptible(module_wq,
- finished_loading(mod->name));
- if (err)
- goto out_unlocked;
-
- /* The module might have gone in the meantime. */
- mutex_lock(&module_mutex);
- old = find_module_all(mod->name, strlen(mod->name),
- true);
- }
-
- /*
- * We are here only when the same module was being loaded. Do
- * not try to load it again right now. It prevents long delays
- * caused by serialized module load failures. It might happen
- * when more devices of the same type trigger load of
- * a particular module.
- */
- if (old && old->state == MODULE_STATE_LIVE)
- err = -EEXIST;
- else
- err = -EBUSY;
+ err = module_patient_check_exists(mod->name);
+ if (err)
goto out;
- }
+
mod_update_bounds(mod);
list_add_rcu(&mod->list, &modules);
mod_tree_insert(mod);
@@ -2688,7 +2698,6 @@ static int add_unformed_module(struct module *mod)
out:
mutex_unlock(&module_mutex);
-out_unlocked:
return err;
}