Subject: Re: [RFC PATCH v2 11/22] devlink: add functions to take snapshot while locked

From: Jiri Pirko <[email-masked]>
Date: Mon, 2 Mar 2020 18:43:55 +0100

Sat, Feb 15, 2020 at 12:22:10AM CET, [email-masked] wrote:
>A future change is going to add a new devlink command to request
>a snapshot on demand. This function will want to call the
>devlink_region_snapshot_id_get and devlink_region_snapshot_create
>functions while already holding the devlink instance lock.
>
>Extract the logic of these two functions into static functions prefixed
>by `__` to indicate they are internal helper functions. Modify the
>original functions to be implemented in terms of the new locked
>functions.
>
>Signed-off-by: Jacob Keller <[email-masked]>

Reviewed-by: Jiri Pirko <[email-masked]>

>---
> net/core/devlink.c | 93 ++++++++++++++++++++++++++++++----------------
> 1 file changed, 61 insertions(+), 32 deletions(-)
>
>diff --git a/net/core/devlink.c b/net/core/devlink.c
>index fef93f48028c..0e94887713f4 100644
>--- a/net/core/devlink.c
>+++ b/net/core/devlink.c
>@@ -3760,6 +3760,65 @@ static void devlink_nl_region_notify(struct devlink_region *region,
> 	nlmsg_free(msg);
> }
> 
>+/**
>+ *	__devlink_region_snapshot_id_get - get snapshot ID
>+ *	@devlink: devlink instance
>+ *
>+ *	Returns a new snapshot id. Must be called while holding the
>+ *	devlink instance lock.
>+ */

You don't need this docu comment for static functions.

>+static u32 __devlink_region_snapshot_id_get(struct devlink *devlink)
>+{
>+	lockdep_assert_held(&devlink->lock);
>+	return ++devlink->snapshot_id;
>+}
>+
>+/**
>+ *	__devlink_region_snapshot_create - create a new snapshot
>+ *	This will add a new snapshot of a region. The snapshot
>+ *	will be stored on the region struct and can be accessed
>+ *	from devlink. This is useful for future analyses of snapshots.
>+ *	Multiple snapshots can be created on a region.
>+ *	The @snapshot_id should be obtained using the getter function.
>+ *
>+ *	Must be called only while holding the devlink instance lock.
>+ *
>+ *	@region: devlink region of the snapshot
>+ *	@data: snapshot data
>+ *	@snapshot_id: snapshot id to be created
>+ */
>+static int
>+__devlink_region_snapshot_create(struct devlink_region *region,
>+				 u8 *data, u32 snapshot_id)
>+{
>+	struct devlink *devlink = region->devlink;
>+	struct devlink_snapshot *snapshot;
>+
>+	lockdep_assert_held(&devlink->lock);
>+
>+	/* check if region can hold one more snapshot */
>+	if (region->cur_snapshots == region->max_snapshots)
>+		return -ENOMEM;
>+
>+	if (devlink_region_snapshot_get_by_id(region, snapshot_id))
>+		return -EEXIST;
>+
>+	snapshot = kzalloc(sizeof(*snapshot), GFP_KERNEL);
>+	if (!snapshot)
>+		return -ENOMEM;
>+
>+	snapshot->id = snapshot_id;
>+	snapshot->region = region;
>+	snapshot->data = data;
>+
>+	list_add_tail(&snapshot->list, &region->snapshot_list);
>+
>+	region->cur_snapshots++;
>+
>+	devlink_nl_region_notify(region, snapshot, DEVLINK_CMD_REGION_NEW);
>+	return 0;
>+}
>+
> static void devlink_region_snapshot_del(struct devlink_region *region,
> 					struct devlink_snapshot *snapshot)
> {
>@@ -7618,7 +7677,7 @@ u32 devlink_region_snapshot_id_get(struct devlink *devlink)
> 	u32 id;
> 
> 	mutex_lock(&devlink->lock);
>-	id = ++devlink->snapshot_id;
>+	id = __devlink_region_snapshot_id_get(devlink);
> 	mutex_unlock(&devlink->lock);
> 
> 	return id;
>@@ -7641,42 +7700,12 @@ int devlink_region_snapshot_create(struct devlink_region *region,
> 				   u8 *data, u32 snapshot_id)
> {
> 	struct devlink *devlink = region->devlink;
>-	struct devlink_snapshot *snapshot;
> 	int err;
> 
> 	mutex_lock(&devlink->lock);
>-
>-	/* check if region can hold one more snapshot */
>-	if (region->cur_snapshots == region->max_snapshots) {
>-		err = -ENOMEM;
>-		goto unlock;
>-	}
>-
>-	if (devlink_region_snapshot_get_by_id(region, snapshot_id)) {
>-		err = -EEXIST;
>-		goto unlock;
>-	}
>-
>-	snapshot = kzalloc(sizeof(*snapshot), GFP_KERNEL);
>-	if (!snapshot) {
>-		err = -ENOMEM;
>-		goto unlock;
>-	}
>-
>-	snapshot->id = snapshot_id;
>-	snapshot->region = region;
>-	snapshot->data = data;
>-
>-	list_add_tail(&snapshot->list, &region->snapshot_list);
>-
>-	region->cur_snapshots++;
>-
>-	devlink_nl_region_notify(region, snapshot, DEVLINK_CMD_REGION_NEW);
>+	err = __devlink_region_snapshot_create(region, data, snapshot_id);
> 	mutex_unlock(&devlink->lock);
>-	return 0;
> 
>-unlock:
>-	mutex_unlock(&devlink->lock);
> 	return err;
> }
> EXPORT_SYMBOL_GPL(devlink_region_snapshot_create);
>-- 
>2.25.0.368.g28a2d05eebfb
>