libnvdimm fixes for 6.2

- Resolve the conflict between KMSAN and NVDIMM with respect to
   reserving pmem namespace / volume capacity for larger
   sizeof(struct page)
 
 - Fix a lockdep warning in the the NFIT code
 
 - Fix a kernel-doc build warning
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Merge tag 'libnvdimm-fixes-6.2' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm

Pull libnvdimm fixes from Dan Williams:
 "A fix for an issue that could causes users to inadvertantly reserve
  too much capacity when debugging the KMSAN and persistent memory
  namespace, a lockdep fix, and a kernel-doc build warning:

   - Resolve the conflict between KMSAN and NVDIMM with respect to
     reserving pmem namespace / volume capacity for larger sizeof(struct
     page)

   - Fix a lockdep warning in the the NFIT code

   - Fix a kernel-doc build warning"

* tag 'libnvdimm-fixes-6.2' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm:
  nvdimm: Support sizeof(struct page) > MAX_STRUCT_PAGE_SIZE
  ACPI: NFIT: fix a potential deadlock during NFIT teardown
  dax: super.c: fix kernel-doc bad line warning

drivers/acpi/nfit/core.c

@@ -3297,8 +3297,8 @@ void acpi_nfit_shutdown(void *data)
 
 	mutex_lock(&acpi_desc->init_mutex);
 	set_bit(ARS_CANCEL, &acpi_desc->scrub_flags);
-	cancel_delayed_work_sync(&acpi_desc->dwork);
 	mutex_unlock(&acpi_desc->init_mutex);
+	cancel_delayed_work_sync(&acpi_desc->dwork);
 
 	/*
 	 * Bounce the nvdimm bus lock to make sure any in-flight

drivers/dax/super.c

@@ -475,7 +475,7 @@ EXPORT_SYMBOL_GPL(put_dax);
 /**
  * dax_holder() - obtain the holder of a dax device
  * @dax_dev: a dax_device instance
-
+ *
  * Return: the holder's data which represents the holder if registered,
  * otherwize NULL.
  */

drivers/nvdimm/Kconfig

@@ -102,6 +102,25 @@ config NVDIMM_KEYS
 	depends on ENCRYPTED_KEYS
 	depends on (LIBNVDIMM=ENCRYPTED_KEYS) || LIBNVDIMM=m
 
+config NVDIMM_KMSAN
+	bool
+	depends on KMSAN
+	help
+	  KMSAN, and other memory debug facilities, increase the size of
+	  'struct page' to contain extra metadata. This collides with
+	  the NVDIMM capability to store a potentially
+	  larger-than-"System RAM" size 'struct page' array in a
+	  reservation of persistent memory rather than limited /
+	  precious DRAM. However, that reservation needs to persist for
+	  the life of the given NVDIMM namespace. If you are using KMSAN
+	  to debug an issue unrelated to NVDIMMs or DAX then say N to this
+	  option. Otherwise, say Y but understand that any namespaces
+	  (with the page array stored pmem) created with this build of
+	  the kernel will permanently reserve and strand excess
+	  capacity compared to the CONFIG_KMSAN=n case.
+
+	  Select N if unsure.
+
 config NVDIMM_TEST_BUILD
 	tristate "Build the unit test core"
 	depends on m

drivers/nvdimm/nd.h

@@ -652,7 +652,7 @@ void devm_namespace_disable(struct device *dev,
 		struct nd_namespace_common *ndns);
 #if IS_ENABLED(CONFIG_ND_CLAIM)
 /* max struct page size independent of kernel config */
-#define MAX_STRUCT_PAGE_SIZE 128
+#define MAX_STRUCT_PAGE_SIZE 64
 int nvdimm_setup_pfn(struct nd_pfn *nd_pfn, struct dev_pagemap *pgmap);
 #else
 static inline int nvdimm_setup_pfn(struct nd_pfn *nd_pfn,

drivers/nvdimm/pfn_devs.c

@@ -13,6 +13,8 @@
 #include "pfn.h"
 #include "nd.h"
 
+static const bool page_struct_override = IS_ENABLED(CONFIG_NVDIMM_KMSAN);
+
 static void nd_pfn_release(struct device *dev)
 {
 	struct nd_region *nd_region = to_nd_region(dev->parent);
@@ -758,12 +760,6 @@ static int nd_pfn_init(struct nd_pfn *nd_pfn)
 		return -ENXIO;
 	}
 
-	/*
-	 * Note, we use 64 here for the standard size of struct page,
-	 * debugging options may cause it to be larger in which case the
-	 * implementation will limit the pfns advertised through
-	 * ->direct_access() to those that are included in the memmap.
-	 */
 	start = nsio->res.start;
 	size = resource_size(&nsio->res);
 	npfns = PHYS_PFN(size - SZ_8K);
@@ -782,20 +778,33 @@ static int nd_pfn_init(struct nd_pfn *nd_pfn)
 	}
 	end_trunc = start + size - ALIGN_DOWN(start + size, align);
 	if (nd_pfn->mode == PFN_MODE_PMEM) {
+		unsigned long page_map_size = MAX_STRUCT_PAGE_SIZE * npfns;
+
 		/*
 		 * The altmap should be padded out to the block size used
 		 * when populating the vmemmap. This *should* be equal to
 		 * PMD_SIZE for most architectures.
 		 *
-		 * Also make sure size of struct page is less than 128. We
-		 * want to make sure we use large enough size here so that
-		 * we don't have a dynamic reserve space depending on
-		 * struct page size. But we also want to make sure we notice
-		 * when we end up adding new elements to struct page.
+		 * Also make sure size of struct page is less than
+		 * MAX_STRUCT_PAGE_SIZE. The goal here is compatibility in the
+		 * face of production kernel configurations that reduce the
+		 * 'struct page' size below MAX_STRUCT_PAGE_SIZE. For debug
+		 * kernel configurations that increase the 'struct page' size
+		 * above MAX_STRUCT_PAGE_SIZE, the page_struct_override allows
+		 * for continuing with the capacity that will be wasted when
+		 * reverting to a production kernel configuration. Otherwise,
+		 * those configurations are blocked by default.
 		 */
-		BUILD_BUG_ON(sizeof(struct page) > MAX_STRUCT_PAGE_SIZE);
-		offset = ALIGN(start + SZ_8K + MAX_STRUCT_PAGE_SIZE * npfns, align)
-			- start;
+		if (sizeof(struct page) > MAX_STRUCT_PAGE_SIZE) {
+			if (page_struct_override)
+				page_map_size = sizeof(struct page) * npfns;
+			else {
+				dev_err(&nd_pfn->dev,
+					"Memory debug options prevent using pmem for the page map\n");
+				return -EINVAL;
+			}
+		}
+		offset = ALIGN(start + SZ_8K + page_map_size, align) - start;
 	} else if (nd_pfn->mode == PFN_MODE_RAM)
 		offset = ALIGN(start + SZ_8K, align) - start;
 	else
@@ -818,7 +827,10 @@ static int nd_pfn_init(struct nd_pfn *nd_pfn)
 	pfn_sb->version_minor = cpu_to_le16(4);
 	pfn_sb->end_trunc = cpu_to_le32(end_trunc);
 	pfn_sb->align = cpu_to_le32(nd_pfn->align);
-	pfn_sb->page_struct_size = cpu_to_le16(MAX_STRUCT_PAGE_SIZE);
+	if (sizeof(struct page) > MAX_STRUCT_PAGE_SIZE && page_struct_override)
+		pfn_sb->page_struct_size = cpu_to_le16(sizeof(struct page));
+	else
+		pfn_sb->page_struct_size = cpu_to_le16(MAX_STRUCT_PAGE_SIZE);
 	pfn_sb->page_size = cpu_to_le32(PAGE_SIZE);
 	checksum = nd_sb_checksum((struct nd_gen_sb *) pfn_sb);
 	pfn_sb->checksum = cpu_to_le64(checksum);