cxl/pmem: Refactor nvdimm device registration, delete the workqueue

The three objects 'struct cxl_nvdimm_bridge', 'struct cxl_nvdimm', and
'struct cxl_pmem_region' manage CXL persistent memory resources. The
bridge represents base platform resources, the nvdimm represents one or
more endpoints, and the region is a collection of nvdimms that
contribute to an assembled address range.

Their relationship is such that a region is torn down if any component
endpoints are removed. All regions and endpoints are torn down if the
foundational bridge device goes down.

A workqueue was deployed to manage these interdependencies, but it is
difficult to reason about, and fragile. A recent attempt to take the CXL
root device lock in the cxl_mem driver was reported by lockdep as
colliding with the flush_work() in the cxl_pmem flows.

Instead of the workqueue, arrange for all pmem/nvdimm devices to be torn
down immediately and hierarchically. A similar change is made to both
the 'cxl_nvdimm' and 'cxl_pmem_region' objects. For bisect-ability both
changes are made in the same patch which unfortunately makes the patch
bigger than desired.

Arrange for cxl_memdev and cxl_region to register a cxl_nvdimm and
cxl_pmem_region as a devres release action of the bridge device.
Additionally, include a devres release action of the cxl_memdev or
cxl_region device that triggers the bridge's release action if an endpoint
exits before the bridge. I.e. this allows either unplugging the bridge,
or unplugging and endpoint to result in the same cleanup actions.

To keep the patch smaller the cleanup of the now defunct workqueue
infrastructure is saved for a follow-on patch.

Tested-by: Robert Richter <rrichter@amd.com>
Link: https://lore.kernel.org/r/166993041773.1882361.16444301376147207609.stgit@dwillia2-xfh.jf.intel.com
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

1 files changed, 35 insertions, 86 deletions

diff --git a/drivers/cxl/pmem.c b/drivers/cxl/pmem.c
index 652f00fc68ca..76cf54eeb310 100644
--- a/drivers/cxl/pmem.c
+++ b/drivers/cxl/pmem.c
@@ -34,26 +34,16 @@ static int cxl_nvdimm_probe(struct device *dev)
 {
 	struct cxl_nvdimm *cxl_nvd = to_cxl_nvdimm(dev);
 	struct cxl_memdev *cxlmd = cxl_nvd->cxlmd;
+	struct cxl_nvdimm_bridge *cxl_nvb = cxlmd->cxl_nvb;
 	unsigned long flags = 0, cmd_mask = 0;
 	struct cxl_dev_state *cxlds = cxlmd->cxlds;
-	struct cxl_nvdimm_bridge *cxl_nvb;
 	struct nvdimm *nvdimm;
 	int rc;
 
-	cxl_nvb = cxl_find_nvdimm_bridge(dev);
-	if (!cxl_nvb)
-		return -ENXIO;
-
-	device_lock(&cxl_nvb->dev);
-	if (!cxl_nvb->nvdimm_bus) {
-		rc = -ENXIO;
-		goto out;
-	}
-
 	set_exclusive_cxl_commands(cxlds, exclusive_cmds);
 	rc = devm_add_action_or_reset(dev, clear_exclusive, cxlds);
 	if (rc)
-		goto out;
+		return rc;
 
 	set_bit(NDD_LABELING, &flags);
 	set_bit(ND_CMD_GET_CONFIG_SIZE, &cmd_mask);
@@ -61,19 +51,11 @@ static int cxl_nvdimm_probe(struct device *dev)
 	set_bit(ND_CMD_SET_CONFIG_DATA, &cmd_mask);
 	nvdimm = nvdimm_create(cxl_nvb->nvdimm_bus, cxl_nvd, NULL, flags,
 			       cmd_mask, 0, NULL);
-	if (!nvdimm) {
-		rc = -ENOMEM;
-		goto out;
-	}
+	if (!nvdimm)
+		return -ENOMEM;
 
 	dev_set_drvdata(dev, nvdimm);
-	cxl_nvd->bridge = cxl_nvb;
-	rc = devm_add_action_or_reset(dev, unregister_nvdimm, nvdimm);
-out:
-	device_unlock(&cxl_nvb->dev);
-	put_device(&cxl_nvb->dev);
-
-	return rc;
+	return devm_add_action_or_reset(dev, unregister_nvdimm, nvdimm);
 }
 
 static struct cxl_driver cxl_nvdimm_driver = {
@@ -200,6 +182,15 @@ static int cxl_pmem_ctl(struct nvdimm_bus_descriptor *nd_desc,
 	return cxl_pmem_nvdimm_ctl(nvdimm, cmd, buf, buf_len);
 }
 
+static void unregister_nvdimm_bus(void *_cxl_nvb)
+{
+	struct cxl_nvdimm_bridge *cxl_nvb = _cxl_nvb;
+	struct nvdimm_bus *nvdimm_bus = cxl_nvb->nvdimm_bus;
+
+	cxl_nvb->nvdimm_bus = NULL;
+	nvdimm_bus_unregister(nvdimm_bus);
+}
+
 static bool online_nvdimm_bus(struct cxl_nvdimm_bridge *cxl_nvb)
 {
 	if (cxl_nvb->nvdimm_bus)
@@ -303,23 +294,21 @@ static int cxl_nvdimm_bridge_probe(struct device *dev)
 {
 	struct cxl_nvdimm_bridge *cxl_nvb = to_cxl_nvdimm_bridge(dev);
 
-	if (cxl_nvb->state == CXL_NVB_DEAD)
-		return -ENXIO;
+	cxl_nvb->nd_desc = (struct nvdimm_bus_descriptor) {
+		.provider_name = "CXL",
+		.module = THIS_MODULE,
+		.ndctl = cxl_pmem_ctl,
+	};
 
-	if (cxl_nvb->state == CXL_NVB_NEW) {
-		cxl_nvb->nd_desc = (struct nvdimm_bus_descriptor) {
-			.provider_name = "CXL",
-			.module = THIS_MODULE,
-			.ndctl = cxl_pmem_ctl,
-		};
+	cxl_nvb->nvdimm_bus =
+		nvdimm_bus_register(&cxl_nvb->dev, &cxl_nvb->nd_desc);
 
-		INIT_WORK(&cxl_nvb->state_work, cxl_nvb_update_state);
-	}
+	if (!cxl_nvb->nvdimm_bus)
+		return -ENOMEM;
 
-	cxl_nvb->state = CXL_NVB_ONLINE;
-	cxl_nvdimm_bridge_state_work(cxl_nvb);
+	INIT_WORK(&cxl_nvb->state_work, cxl_nvb_update_state);
 
-	return 0;
+	return devm_add_action_or_reset(dev, unregister_nvdimm_bus, cxl_nvb);
 }
 
 static struct cxl_driver cxl_nvdimm_bridge_driver = {
@@ -332,11 +321,6 @@ static struct cxl_driver cxl_nvdimm_bridge_driver = {
 	},
 };
 
-static int match_cxl_nvdimm(struct device *dev, void *data)
-{
-	return is_cxl_nvdimm(dev);
-}
-
 static void unregister_nvdimm_region(void *nd_region)
 {
 	nvdimm_region_delete(nd_region);
@@ -357,8 +341,8 @@ static int cxl_pmem_region_probe(struct device *dev)
 	struct nd_mapping_desc mappings[CXL_DECODER_MAX_INTERLEAVE];
 	struct cxl_pmem_region *cxlr_pmem = to_cxl_pmem_region(dev);
 	struct cxl_region *cxlr = cxlr_pmem->cxlr;
+	struct cxl_nvdimm_bridge *cxl_nvb = cxlr->cxl_nvb;
 	struct cxl_pmem_region_info *info = NULL;
-	struct cxl_nvdimm_bridge *cxl_nvb;
 	struct nd_interleave_set *nd_set;
 	struct nd_region_desc ndr_desc;
 	struct cxl_nvdimm *cxl_nvd;
@@ -366,28 +350,12 @@ static int cxl_pmem_region_probe(struct device *dev)
 	struct resource *res;
 	int rc, i = 0;
 
-	cxl_nvb = cxl_find_nvdimm_bridge(&cxlr_pmem->mapping[0].cxlmd->dev);
-	if (!cxl_nvb) {
-		dev_dbg(dev, "bridge not found\n");
-		return -ENXIO;
-	}
-	cxlr_pmem->bridge = cxl_nvb;
-
-	device_lock(&cxl_nvb->dev);
-	if (!cxl_nvb->nvdimm_bus) {
-		dev_dbg(dev, "nvdimm bus not found\n");
-		rc = -ENXIO;
-		goto out_nvb;
-	}
-
 	memset(&mappings, 0, sizeof(mappings));
 	memset(&ndr_desc, 0, sizeof(ndr_desc));
 
 	res = devm_kzalloc(dev, sizeof(*res), GFP_KERNEL);
-	if (!res) {
-		rc = -ENOMEM;
-		goto out_nvb;
-	}
+	if (!res)
+		return -ENOMEM;
 
 	res->name = "Persistent Memory";
 	res->start = cxlr_pmem->hpa_range.start;
@@ -397,11 +365,11 @@ static int cxl_pmem_region_probe(struct device *dev)
 
 	rc = insert_resource(&iomem_resource, res);
 	if (rc)
-		goto out_nvb;
+		return rc;
 
 	rc = devm_add_action_or_reset(dev, cxlr_pmem_remove_resource, res);
 	if (rc)
-		goto out_nvb;
+		return rc;
 
 	ndr_desc.res = res;
 	ndr_desc.provider_data = cxlr_pmem;
@@ -415,39 +383,23 @@ static int cxl_pmem_region_probe(struct device *dev)
 	}
 
 	nd_set = devm_kzalloc(dev, sizeof(*nd_set), GFP_KERNEL);
-	if (!nd_set) {
-		rc = -ENOMEM;
-		goto out_nvb;
-	}
+	if (!nd_set)
+		return -ENOMEM;
 
 	ndr_desc.memregion = cxlr->id;
 	set_bit(ND_REGION_CXL, &ndr_desc.flags);
 	set_bit(ND_REGION_PERSIST_MEMCTRL, &ndr_desc.flags);
 
 	info = kmalloc_array(cxlr_pmem->nr_mappings, sizeof(*info), GFP_KERNEL);
-	if (!info) {
-		rc = -ENOMEM;
-		goto out_nvb;
-	}
+	if (!info)
+		return -ENOMEM;
 
 	for (i = 0; i < cxlr_pmem->nr_mappings; i++) {
 		struct cxl_pmem_region_mapping *m = &cxlr_pmem->mapping[i];
 		struct cxl_memdev *cxlmd = m->cxlmd;
 		struct cxl_dev_state *cxlds = cxlmd->cxlds;
-		struct device *d;
 
-		d = device_find_child(&cxlmd->dev, NULL, match_cxl_nvdimm);
-		if (!d) {
-			dev_dbg(dev, "[%d]: %s: no cxl_nvdimm found\n", i,
-				dev_name(&cxlmd->dev));
-			rc = -ENODEV;
-			goto out_nvd;
-		}
-
-		/* safe to drop ref now with bridge lock held */
-		put_device(d);
-
-		cxl_nvd = to_cxl_nvdimm(d);
+		cxl_nvd = cxlmd->cxl_nvd;
 		nvdimm = dev_get_drvdata(&cxl_nvd->dev);
 		if (!nvdimm) {
 			dev_dbg(dev, "[%d]: %s: no nvdimm found\n", i,
@@ -488,9 +440,6 @@ static int cxl_pmem_region_probe(struct device *dev)
 				      cxlr_pmem->nd_region);
 out_nvd:
 	kfree(info);
-out_nvb:
-	device_unlock(&cxl_nvb->dev);
-	put_device(&cxl_nvb->dev);
 
 	return rc;
 }