diff mbox series

[v2,3/6] module: extract patient module check into helper

Message ID 20230405022702.753323-4-mcgrof@kernel.org (mailing list archive)
State New
Headers show
Series module: avoid userspace pressure on unwanted allocations | expand

Commit Message

Luis Chamberlain April 5, 2023, 2:26 a.m. UTC
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

David Hildenbrand April 5, 2023, 5:11 p.m. UTC | #1
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.
Luis Chamberlain April 5, 2023, 7:45 p.m. UTC | #2
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
diff mbox series

Patch

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) {
+		/* 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;
 }