Re: [PATCH v5 7/8] device-dax: ensure dev_dax->pgmap is valid for dynamic devices
From: Joao Martins <hidden>
Date: 2021-11-17 10:16:28
Also in:
linux-mm, nvdimm
Subsystem:
device direct access (dax), the rest · Maintainers:
Dan Williams, Vishal Verma, Dave Jiang, Linus Torvalds
On 11/17/21 10:37, Christoph Hellwig wrote:
quoted
+bool static_dev_dax(struct dev_dax *dev_dax) +{ + return is_static(dev_dax->region); +} +EXPORT_SYMBOL_GPL(static_dev_dax);This function would massively benefit from documentic what a static DAX region is and why someone would want to care. Because even as someone occasionally dabbling with the DAX code I have no idea at all what that means.
Good idea. Maybe something like this:
diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c
index 19dd83d3f3ea..8be6ec1ba193 100644
--- a/drivers/dax/bus.c
+++ b/drivers/dax/bus.c@@ -129,6 +129,19 @@ ATTRIBUTE_GROUPS(dax_drv); static int dax_bus_match(struct device *dev, struct device_driver *drv); +/* + * Static dax regions (PMEM) are regions partitioned by an external entity like + * nvdimm where a single range is assigned and which boundaries are + * defined by NVDIMM Namespace boundaries (e.g. need to be contiguous). + * Dynamic dax regions (HMEM), the assigned region can be subdivided by dax + * core into multiple devices (i.e. "partitions") which are composed with 1 or + * more discontiguous ranges. + * When allocating a dax region, drivers must set whether it's static. + * On static dax devices, the @pgmap is pre-assigned to dax when calling + * devm_create_dev_dax(), whereas in dynamic dax devices it is allocated + * on device ->probe(). Care is needed to make sure that non static devices + * are killed with a cleared @pgmap field (see kill_dev_dax()). + */ static bool is_static(struct dax_region *dax_region) { return (dax_region->res.flags & IORESOURCE_DAX_STATIC) != 0;