From: Joao Martins <joao.m.martins@xxxxxxxxxx> Subject: device-dax: ensure dev_dax->pgmap is valid for dynamic devices Right now, only static dax regions have a valid @pgmap pointer in its struct dev_dax. Dynamic dax case however, do not. In preparation for device-dax compound devmap support, make sure that dev_dax pgmap field is set after it has been allocated and initialized. dynamic dax device have the @pgmap is allocated at probe() and it's managed by devm (contrast to static dax region which a pgmap is provided and dax core kfrees it). So in addition to ensure a valid @pgmap, clear the pgmap when the dynamic dax device is released to avoid the same pgmap ranges to be re-requested across multiple region device reconfigs. Add a static_dev_dax() and use that helper in dev_dax_probe() to ensure the initialization differences between dynamic and static regions are more explicit. While at it, consolidate the ranges initialization when we allocate the @pgmap for the dynamic dax region case. Also take the opportunity to document the differences between static and dynamic da regions. Link: https://lkml.kernel.org/r/20211202204422.26777-8-joao.m.martins@xxxxxxxxxx Suggested-by: Dan Williams <dan.j.williams@xxxxxxxxx> Signed-off-by: Joao Martins <joao.m.martins@xxxxxxxxxx> Cc: Christoph Hellwig <hch@xxxxxx> Cc: Dave Jiang <dave.jiang@xxxxxxxxx> Cc: Jane Chu <jane.chu@xxxxxxxxxx> Cc: Jason Gunthorpe <jgg@xxxxxxxxxx> Cc: Jason Gunthorpe <jgg@xxxxxxxx> Cc: John Hubbard <jhubbard@xxxxxxxxxx> Cc: Jonathan Corbet <corbet@xxxxxxx> Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx> Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx> Cc: Muchun Song <songmuchun@xxxxxxxxxxxxx> Cc: Naoya Horiguchi <naoya.horiguchi@xxxxxxx> Cc: Vishal Verma <vishal.l.verma@xxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- drivers/dax/bus.c | 32 ++++++++++++++++++++++++++++++++ drivers/dax/bus.h | 1 + drivers/dax/device.c | 29 +++++++++++++++++++++-------- 3 files changed, 54 insertions(+), 8 deletions(-) --- a/drivers/dax/bus.c~device-dax-ensure-dev_dax-pgmap-is-valid-for-dynamic-devices +++ a/drivers/dax/bus.c @@ -129,11 +129,35 @@ ATTRIBUTE_GROUPS(dax_drv); static int dax_bus_match(struct device *dev, struct device_driver *drv); +/* + * Static dax regions are regions created by an external subsystem + * nvdimm where a single range is assigned. Its boundaries are by the external + * subsystem and are usually limited to one physical memory range. For example, + * for PMEM it is usually defined by NVDIMM Namespace boundaries (i.e. a + * single contiguous range) + * + * On dynamic dax regions, the assigned region can be partitioned by dax core + * into multiple subdivisions. A subdivision is represented into one + * /dev/daxN.M device composed by one or more potentially discontiguous ranges. + * + * When allocating a dax region, drivers must set whether it's static + * (IORESOURCE_DAX_STATIC). On static dax devices, the @pgmap is pre-assigned + * to dax core when calling devm_create_dev_dax(), whereas in dynamic dax + * devices it is NULL but afterwards allocated by dax core on device ->probe(). + * Care is needed to make sure that dynamic dax devices are torn down 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; } +bool static_dev_dax(struct dev_dax *dev_dax) +{ + return is_static(dev_dax->region); +} +EXPORT_SYMBOL_GPL(static_dev_dax); + static u64 dev_dax_size(struct dev_dax *dev_dax) { u64 size = 0; @@ -363,6 +387,14 @@ void kill_dev_dax(struct dev_dax *dev_da kill_dax(dax_dev); unmap_mapping_range(inode->i_mapping, 0, 0, 1); + + /* + * Dynamic dax region have the pgmap allocated via dev_kzalloc() + * and thus freed by devm. Clear the pgmap to not have stale pgmap + * ranges on probe() from previous reconfigurations of region devices. + */ + if (!static_dev_dax(dev_dax)) + dev_dax->pgmap = NULL; } EXPORT_SYMBOL_GPL(kill_dev_dax); --- a/drivers/dax/bus.h~device-dax-ensure-dev_dax-pgmap-is-valid-for-dynamic-devices +++ a/drivers/dax/bus.h @@ -48,6 +48,7 @@ int __dax_driver_register(struct dax_dev __dax_driver_register(driver, THIS_MODULE, KBUILD_MODNAME) void dax_driver_unregister(struct dax_device_driver *dax_drv); void kill_dev_dax(struct dev_dax *dev_dax); +bool static_dev_dax(struct dev_dax *dev_dax); #if IS_ENABLED(CONFIG_DEV_DAX_PMEM_COMPAT) int dev_dax_probe(struct dev_dax *dev_dax); --- a/drivers/dax/device.c~device-dax-ensure-dev_dax-pgmap-is-valid-for-dynamic-devices +++ a/drivers/dax/device.c @@ -398,18 +398,34 @@ int dev_dax_probe(struct dev_dax *dev_da void *addr; int rc, i; - pgmap = dev_dax->pgmap; - if (dev_WARN_ONCE(dev, pgmap && dev_dax->nr_range > 1, - "static pgmap / multi-range device conflict\n")) - return -EINVAL; + if (static_dev_dax(dev_dax)) { + if (dev_dax->nr_range > 1) { + dev_warn(dev, + "static pgmap / multi-range device conflict\n"); + return -EINVAL; + } + + pgmap = dev_dax->pgmap; + } else { + if (dev_dax->pgmap) { + dev_warn(dev, + "dynamic-dax with pre-populated page map\n"); + return -EINVAL; + } - if (!pgmap) { pgmap = devm_kzalloc(dev, struct_size(pgmap, ranges, dev_dax->nr_range - 1), GFP_KERNEL); if (!pgmap) return -ENOMEM; + pgmap->nr_range = dev_dax->nr_range; + dev_dax->pgmap = pgmap; + + for (i = 0; i < dev_dax->nr_range; i++) { + struct range *range = &dev_dax->ranges[i].range; + pgmap->ranges[i] = *range; + } } for (i = 0; i < dev_dax->nr_range; i++) { @@ -421,9 +437,6 @@ int dev_dax_probe(struct dev_dax *dev_da i, range->start, range->end); return -EBUSY; } - /* don't update the range for static pgmap */ - if (!dev_dax->pgmap) - pgmap->ranges[i] = *range; } pgmap->type = MEMORY_DEVICE_GENERIC; _
