memremap: replace the altmap_valid field with a PGMAP_ALTMAP_VALID flag

Add a flags field to struct dev_pagemap to replace the altmap_valid
boolean to be a little more extensible.  Also add a pgmap_altmap() helper
to find the optional altmap and clean up the code using the altmap using
it.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Tested-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

9 files changed, 29 insertions, 43 deletions

diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
index 2540d3b2588c..a2923c5c1982 100644
--- a/arch/powerpc/mm/mem.c
+++ b/arch/powerpc/mm/mem.c
@@ -131,17 +131,9 @@ void __ref arch_remove_memory(int nid, u64 start, u64 size,
 {
         unsigned long start_pfn = start >> PAGE_SHIFT;
         unsigned long nr_pages = size >> PAGE_SHIFT;
-        struct page *page;
+        struct page *page = pfn_to_page(start_pfn) + vmem_altmap_offset(altmap);
         int ret;
 
-        /*
-         * If we have an altmap then we need to skip over any reserved PFNs
-         * when querying the zone.
-         */
-        page = pfn_to_page(start_pfn);
-        if (altmap)
-                page += vmem_altmap_offset(altmap);
-
         __remove_pages(page_zone(page), start_pfn, nr_pages, altmap);
 
         /* Remove htab bolted mappings for this section of memory */
diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 0f01c7b1d217..08bbf648827b 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -1213,13 +1213,9 @@ void __ref arch_remove_memory(int nid, u64 start, u64 size,
 {
         unsigned long start_pfn = start >> PAGE_SHIFT;
         unsigned long nr_pages = size >> PAGE_SHIFT;
-        struct page *page = pfn_to_page(start_pfn);
-        struct zone *zone;
+        struct page *page = pfn_to_page(start_pfn) + vmem_altmap_offset(altmap);
+        struct zone *zone = page_zone(page);
 
-        /* With altmap the first mapped page is offset from @start */
-        if (altmap)
-                page += vmem_altmap_offset(altmap);
-        zone = page_zone(page);
         __remove_pages(zone, start_pfn, nr_pages, altmap);
         kernel_physical_mapping_remove(start, start + size);
 }
diff --git a/drivers/nvdimm/pfn_devs.c b/drivers/nvdimm/pfn_devs.c
index 0f81fc56bbfd..55fb6b7433ed 100644
--- a/drivers/nvdimm/pfn_devs.c
+++ b/drivers/nvdimm/pfn_devs.c
@@ -622,7 +622,6 @@ static int __nvdimm_setup_pfn(struct nd_pfn *nd_pfn, struct dev_pagemap *pgmap)
                 if (offset < reserve)
                         return -EINVAL;
                 nd_pfn->npfns = le64_to_cpu(pfn_sb->npfns);
-                pgmap->altmap_valid = false;
         } else if (nd_pfn->mode == PFN_MODE_PMEM) {
                 nd_pfn->npfns = PFN_SECTION_ALIGN_UP((resource_size(res)
                                         - offset) / PAGE_SIZE);
@@ -634,7 +633,7 @@ static int __nvdimm_setup_pfn(struct nd_pfn *nd_pfn, struct dev_pagemap *pgmap)
                 memcpy(altmap, &__altmap, sizeof(*altmap));
                 altmap->free = PHYS_PFN(offset - reserve);
                 altmap->alloc = 0;
-                pgmap->altmap_valid = true;
+                pgmap->flags |= PGMAP_ALTMAP_VALID;
         } else
                 return -ENXIO;
 
diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index 093408ce40ad..e7d8cc9f41e8 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -412,7 +412,6 @@ static int pmem_attach_disk(struct device *dev,
                 bb_res.start += pmem->data_offset;
         } else if (pmem_should_map_pages(dev)) {
                 memcpy(&pmem->pgmap.res, &nsio->res, sizeof(pmem->pgmap.res));
-                pmem->pgmap.altmap_valid = false;
                 pmem->pgmap.type = MEMORY_DEVICE_FS_DAX;
                 pmem->pgmap.ops = &fsdax_pagemap_ops;
                 addr = devm_memremap_pages(dev, &pmem->pgmap);
diff --git a/include/linux/memremap.h b/include/linux/memremap.h
index 336eca601dad..e25685b878e9 100644
--- a/include/linux/memremap.h
+++ b/include/linux/memremap.h
@@ -88,6 +88,8 @@ struct dev_pagemap_ops {
         vm_fault_t (*migrate_to_ram)(struct vm_fault *vmf);
 };
 
+#define PGMAP_ALTMAP_VALID      (1 << 0)
+
 /**
  * struct dev_pagemap - metadata for ZONE_DEVICE mappings
  * @altmap: pre-allocated/reserved memory for vmemmap allocations
@@ -96,19 +98,27 @@ struct dev_pagemap_ops {
  * @dev: host device of the mapping for debug
  * @data: private data pointer for page_free()
  * @type: memory type: see MEMORY_* in memory_hotplug.h
+ * @flags: PGMAP_* flags to specify defailed behavior
  * @ops: method table
  */
 struct dev_pagemap {
         struct vmem_altmap altmap;
-        bool altmap_valid;
         struct resource res;
         struct percpu_ref *ref;
         struct device *dev;
         enum memory_type type;
+        unsigned int flags;
         u64 pci_p2pdma_bus_offset;
         const struct dev_pagemap_ops *ops;
 };
 
+static inline struct vmem_altmap *pgmap_altmap(struct dev_pagemap *pgmap)
+{
+        if (pgmap->flags & PGMAP_ALTMAP_VALID)
+                return &pgmap->altmap;
+        return NULL;
+}
+
 #ifdef CONFIG_ZONE_DEVICE
 void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap);
 void devm_memunmap_pages(struct device *dev, struct dev_pagemap *pgmap);
diff --git a/kernel/memremap.c b/kernel/memremap.c
index 6c3dbb692037..eee490e7d7e1 100644
--- a/kernel/memremap.c
+++ b/kernel/memremap.c
@@ -54,14 +54,8 @@ static void pgmap_array_delete(struct resource *res)
 
 static unsigned long pfn_first(struct dev_pagemap *pgmap)
 {
-        const struct resource *res = &pgmap->res;
-        struct vmem_altmap *altmap = &pgmap->altmap;
-        unsigned long pfn;
-
-        pfn = res->start >> PAGE_SHIFT;
-        if (pgmap->altmap_valid)
-                pfn += vmem_altmap_offset(altmap);
-        return pfn;
+        return (pgmap->res.start >> PAGE_SHIFT) +
+                vmem_altmap_offset(pgmap_altmap(pgmap));
 }
 
 static unsigned long pfn_end(struct dev_pagemap *pgmap)
@@ -109,7 +103,7 @@ static void devm_memremap_pages_release(void *data)
                                 align_size >> PAGE_SHIFT, NULL);
         } else {
                 arch_remove_memory(nid, align_start, align_size,
-                                pgmap->altmap_valid ? &pgmap->altmap : NULL);
+                                pgmap_altmap(pgmap));
                 kasan_remove_zero_shadow(__va(align_start), align_size);
         }
         mem_hotplug_done();
@@ -129,8 +123,8 @@ static void devm_memremap_pages_release(void *data)
  * 1/ At a minimum the res, ref and type and ops members of @pgmap must be
  *    initialized by the caller before passing it to this function
  *
- * 2/ The altmap field may optionally be initialized, in which case altmap_valid
- *    must be set to true
+ * 2/ The altmap field may optionally be initialized, in which case
+ *    PGMAP_ALTMAP_VALID must be set in pgmap->flags.
  *
  * 3/ pgmap->ref must be 'live' on entry and will be killed and reaped
  *    at devm_memremap_pages_release() time, or if this routine fails.
@@ -142,15 +136,13 @@ static void devm_memremap_pages_release(void *data)
 void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap)
 {
         resource_size_t align_start, align_size, align_end;
-        struct vmem_altmap *altmap = pgmap->altmap_valid ?
-                        &pgmap->altmap : NULL;
         struct resource *res = &pgmap->res;
         struct dev_pagemap *conflict_pgmap;
         struct mhp_restrictions restrictions = {
                 /*
                  * We do not want any optional features only our own memmap
                 */
-                .altmap = altmap,
+                .altmap = pgmap_altmap(pgmap),
         };
         pgprot_t pgprot = PAGE_KERNEL;
         int error, nid, is_ram;
@@ -274,7 +266,7 @@ void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap)
 
                 zone = &NODE_DATA(nid)->node_zones[ZONE_DEVICE];
                 move_pfn_range_to_zone(zone, align_start >> PAGE_SHIFT,
-                                align_size >> PAGE_SHIFT, altmap);
+                                align_size >> PAGE_SHIFT, pgmap_altmap(pgmap));
         }
 
         mem_hotplug_done();
@@ -319,7 +311,9 @@ EXPORT_SYMBOL_GPL(devm_memunmap_pages);
 unsigned long vmem_altmap_offset(struct vmem_altmap *altmap)
 {
         /* number of pfns from base where pfn_to_page() is valid */
-        return altmap->reserve + altmap->free;
+        if (altmap)
+                return altmap->reserve + altmap->free;
+        return 0;
 }
 
 void vmem_altmap_free(struct vmem_altmap *altmap, unsigned long nr_pfns)
diff --git a/mm/hmm.c b/mm/hmm.c
index 36e25cdbdac1..e4470462298f 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -1442,7 +1442,6 @@ struct hmm_devmem *hmm_devmem_add(const struct hmm_devmem_ops *ops,
         devmem->pagemap.type = MEMORY_DEVICE_PRIVATE;
         devmem->pagemap.res = *devmem->resource;
         devmem->pagemap.ops = &hmm_pagemap_ops;
-        devmem->pagemap.altmap_valid = false;
         devmem->pagemap.ref = &devmem->ref;
 
         result = devm_memremap_pages(devmem->device, &devmem->pagemap);
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index e096c987d261..6166ba5a15f3 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -557,10 +557,8 @@ void __remove_pages(struct zone *zone, unsigned long phys_start_pfn,
         int sections_to_remove;
 
         /* In the ZONE_DEVICE case device driver owns the memory region */
-        if (is_dev_zone(zone)) {
-                if (altmap)
-                        map_offset = vmem_altmap_offset(altmap);
-        }
+        if (is_dev_zone(zone))
+                map_offset = vmem_altmap_offset(altmap);
 
         clear_zone_contiguous(zone);
 
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index d66bc8abe0af..17a39d40a556 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5853,6 +5853,7 @@ void __ref memmap_init_zone_device(struct zone *zone,
 {
         unsigned long pfn, end_pfn = start_pfn + size;
         struct pglist_data *pgdat = zone->zone_pgdat;
+        struct vmem_altmap *altmap = pgmap_altmap(pgmap);
         unsigned long zone_idx = zone_idx(zone);
         unsigned long start = jiffies;
         int nid = pgdat->node_id;
@@ -5865,9 +5866,7 @@ void __ref memmap_init_zone_device(struct zone *zone,
          * of the pages reserved for the memmap, so we can just jump to
          * the end of that region and start processing the device pages.
          */
-        if (pgmap->altmap_valid) {
-                struct vmem_altmap *altmap = &pgmap->altmap;
-
+        if (altmap) {
                 start_pfn = altmap->base_pfn + vmem_altmap_offset(altmap);
                 size = end_pfn - start_pfn;
         }