Prepare the memory hot-{add,remove} paths for handling sub-section
ranges by plumbing the starting page frame and number of pages being
handled through arch_{add,remove}_memory() to
sparse_{add,remove}_one_section().

This is simply plumbing, small cleanups, and some identifier renames. No
intended functional changes.

Cc: Andrew Morton <a...@linux-foundation.org>
Cc: Mel Gorman <mgor...@techsingularity.net>
Cc: Vlastimil Babka <vba...@suse.cz>
Cc: Johannes Weiner <han...@cmpxchg.org>
Cc: Logan Gunthorpe <log...@deltatee.com>
Cc: Stephen Bates <stephen.ba...@microsemi.com>
Signed-off-by: Dan Williams <dan.j.willi...@intel.com>
---
 arch/x86/mm/init_64.c          |   11 +++++
 include/linux/memory_hotplug.h |    6 ++-
 mm/memory_hotplug.c            |   89 +++++++++++++++++++++-------------------
 mm/sparse.c                    |    6 ++-
 4 files changed, 66 insertions(+), 46 deletions(-)

diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index e3fb2b1be060..02ffdccaa861 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -660,6 +660,17 @@ int arch_add_memory(int nid, u64 start, u64 size, bool 
for_device)
        unsigned long nr_pages = size >> PAGE_SHIFT;
        int ret;
 
+       /*
+        * Only allow partial section hotplug for ZONE_DEVICE ranges,
+        * since register_new_memory() requires section alignment, and
+        * CONFIG_SPARSEMEM_VMEMMAP=n requires sections to be fully
+        * populated.
+        */
+       if ((!IS_ENABLED(CONFIG_SPARSEMEM_VMEMMAP) || !for_device)
+                       && ((start & ~PA_SECTION_MASK)
+                               || (size & ~PA_SECTION_MASK)))
+               return -EINVAL;
+
        init_memory_mapping(start, start + size);
 
        ret = __add_pages(nid, zone, start_pfn, nr_pages);
diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
index 01033fadea47..a6ac3c975d5d 100644
--- a/include/linux/memory_hotplug.h
+++ b/include/linux/memory_hotplug.h
@@ -279,8 +279,10 @@ extern int arch_add_memory(int nid, u64 start, u64 size, 
bool for_device);
 extern int offline_pages(unsigned long start_pfn, unsigned long nr_pages);
 extern bool is_memblock_offlined(struct memory_block *mem);
 extern void remove_memory(int nid, u64 start, u64 size);
-extern int sparse_add_one_section(struct zone *zone, unsigned long start_pfn);
-extern void sparse_remove_one_section(struct zone *zone, struct mem_section 
*ms,
+extern int sparse_add_section(struct zone *zone, unsigned long pfn,
+               unsigned long nr_pages);
+extern void sparse_remove_section(struct zone *zone, struct mem_section *ms,
+               unsigned long pfn, unsigned long nr_pages,
                unsigned long map_offset);
 extern struct page *sparse_decode_mem_map(unsigned long coded_mem_map,
                                          unsigned long pnum);
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index c8b1a4926fb7..d11c56b22572 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -466,10 +466,10 @@ static void __meminit grow_pgdat_span(struct pglist_data 
*pgdat, unsigned long s
                                        pgdat->node_start_pfn;
 }
 
-static int __meminit __add_zone(struct zone *zone, unsigned long 
phys_start_pfn)
+static int __meminit __add_zone(struct zone *zone, unsigned long 
phys_start_pfn,
+               unsigned long nr_pages)
 {
        struct pglist_data *pgdat = zone->zone_pgdat;
-       int nr_pages = PAGES_PER_SECTION;
        int nid = pgdat->node_id;
        int zone_type;
        unsigned long flags, pfn;
@@ -499,24 +499,21 @@ static int __meminit __add_zone(struct zone *zone, 
unsigned long phys_start_pfn)
 }
 
 static int __meminit __add_section(int nid, struct zone *zone,
-                                       unsigned long phys_start_pfn)
+               unsigned long pfn, unsigned long nr_pages)
 {
        int ret;
 
-       if (pfn_valid(phys_start_pfn))
-               return -EEXIST;
-
-       ret = sparse_add_one_section(zone, phys_start_pfn);
+       ret = sparse_add_section(zone, pfn, nr_pages);
 
        if (ret < 0)
                return ret;
 
-       ret = __add_zone(zone, phys_start_pfn);
+       ret = __add_zone(zone, pfn, nr_pages);
 
        if (ret < 0)
                return ret;
 
-       return register_new_memory(zone, nid, __pfn_to_section(phys_start_pfn));
+       return register_new_memory(zone, nid, __pfn_to_section(pfn));
 }
 
 /*
@@ -525,26 +522,20 @@ static int __meminit __add_section(int nid, struct zone 
*zone,
  * call this function after deciding the zone to which to
  * add the new pages.
  */
-int __ref __add_pages(int nid, struct zone *zone, unsigned long phys_start_pfn,
+int __ref __add_pages(int nid, struct zone *zone, unsigned long pfn,
                        unsigned long nr_pages)
 {
-       unsigned long i;
-       int err = 0;
-       int start_sec, end_sec;
        struct vmem_altmap *altmap;
+       int err = 0, start_sec, end_sec, i;
 
        clear_zone_contiguous(zone);
 
-       /* during initialize mem_map, align hot-added range to section */
-       start_sec = pfn_to_section_nr(phys_start_pfn);
-       end_sec = pfn_to_section_nr(phys_start_pfn + nr_pages - 1);
-
-       altmap = to_vmem_altmap((unsigned long) pfn_to_page(phys_start_pfn));
+       altmap = to_vmem_altmap((unsigned long) pfn_to_page(pfn));
        if (altmap) {
                /*
                 * Validate altmap is within bounds of the total request
                 */
-               if (altmap->base_pfn != phys_start_pfn
+               if (altmap->base_pfn != pfn
                                || vmem_altmap_offset(altmap) > nr_pages) {
                        pr_warn_once("memory add fail, invalid altmap\n");
                        err = -EINVAL;
@@ -553,8 +544,16 @@ int __ref __add_pages(int nid, struct zone *zone, unsigned 
long phys_start_pfn,
                altmap->alloc = 0;
        }
 
+       start_sec = pfn_to_section_nr(pfn);
+       end_sec = pfn_to_section_nr(pfn + nr_pages - 1);
        for (i = start_sec; i <= end_sec; i++) {
-               err = __add_section(nid, zone, section_nr_to_pfn(i));
+               unsigned long pfns;
+
+               pfns = min(nr_pages, PAGES_PER_SECTION
+                               - (pfn & ~PAGE_SECTION_MASK));
+               err = __add_section(nid, zone, pfn, pfns);
+               pfn += pfns;
+               nr_pages -= pfns;
 
                /*
                 * EEXIST is finally dealt with by ioresource collision
@@ -760,10 +759,10 @@ static void shrink_pgdat_span(struct pglist_data *pgdat,
        pgdat->node_spanned_pages = 0;
 }
 
-static void __remove_zone(struct zone *zone, unsigned long start_pfn)
+static void __remove_zone(struct zone *zone, unsigned long start_pfn,
+               unsigned long nr_pages)
 {
        struct pglist_data *pgdat = zone->zone_pgdat;
-       int nr_pages = PAGES_PER_SECTION;
        int zone_type;
        unsigned long flags;
 
@@ -775,11 +774,10 @@ static void __remove_zone(struct zone *zone, unsigned 
long start_pfn)
        pgdat_resize_unlock(zone->zone_pgdat, &flags);
 }
 
-static int __remove_section(struct zone *zone, struct mem_section *ms,
-               unsigned long map_offset)
+static int __remove_section(struct zone *zone, unsigned long pfn,
+               unsigned long nr_pages, unsigned long map_offset)
 {
-       unsigned long start_pfn;
-       int scn_nr;
+       struct mem_section *ms = __nr_to_section(pfn_to_section_nr(pfn));
        int ret = -EINVAL;
 
        if (!valid_section(ms))
@@ -789,11 +787,9 @@ static int __remove_section(struct zone *zone, struct 
mem_section *ms,
        if (ret)
                return ret;
 
-       scn_nr = __section_nr(ms);
-       start_pfn = section_nr_to_pfn(scn_nr);
-       __remove_zone(zone, start_pfn);
+       __remove_zone(zone, pfn, nr_pages);
 
-       sparse_remove_one_section(zone, ms, map_offset);
+       sparse_remove_section(zone, ms, pfn, nr_pages, map_offset);
        return 0;
 }
 
@@ -808,16 +804,15 @@ static int __remove_section(struct zone *zone, struct 
mem_section *ms,
  * sure that pages are marked reserved and zones are adjust properly by
  * calling offline_pages().
  */
-int __remove_pages(struct zone *zone, unsigned long phys_start_pfn,
+int __remove_pages(struct zone *zone, unsigned long pfn,
                 unsigned long nr_pages)
 {
-       unsigned long i;
        unsigned long map_offset = 0;
-       int sections_to_remove, ret = 0;
+       int i, start_sec, end_sec, ret = 0;
 
        /* In the ZONE_DEVICE case device driver owns the memory region */
        if (is_dev_zone(zone)) {
-               struct page *page = pfn_to_page(phys_start_pfn);
+               struct page *page = pfn_to_page(pfn);
                struct vmem_altmap *altmap;
 
                altmap = to_vmem_altmap((unsigned long) page);
@@ -826,7 +821,7 @@ int __remove_pages(struct zone *zone, unsigned long 
phys_start_pfn,
        } else {
                resource_size_t start, size;
 
-               start = phys_start_pfn << PAGE_SHIFT;
+               start = pfn << PAGE_SHIFT;
                size = nr_pages * PAGE_SIZE;
 
                ret = release_mem_region_adjustable(&iomem_resource, start,
@@ -842,16 +837,26 @@ int __remove_pages(struct zone *zone, unsigned long 
phys_start_pfn,
        clear_zone_contiguous(zone);
 
        /*
-        * We can only remove entire sections
+        * Only ZONE_DEVICE memory is enabled to remove
+        * section-unaligned ranges. See register_new_memory() which
+        * assumes section alignment and is skipped for ZONE_DEVICE
+        * ranges.
         */
-       BUG_ON(phys_start_pfn & ~PAGE_SECTION_MASK);
-       BUG_ON(nr_pages % PAGES_PER_SECTION);
+       if (!is_dev_zone(zone) && ((pfn | nr_pages) & ~PAGE_SECTION_MASK)) {
+               WARN(1, "section unaligned removal not supported\n");
+               return -EINVAL;
+       }
 
-       sections_to_remove = nr_pages / PAGES_PER_SECTION;
-       for (i = 0; i < sections_to_remove; i++) {
-               unsigned long pfn = phys_start_pfn + i*PAGES_PER_SECTION;
+       start_sec = pfn_to_section_nr(pfn);
+       end_sec = pfn_to_section_nr(pfn + nr_pages - 1);
+       for (i = start_sec; i <= end_sec; i++) {
+               unsigned long pfns;
 
-               ret = __remove_section(zone, __pfn_to_section(pfn), map_offset);
+               pfns = min(nr_pages, PAGES_PER_SECTION
+                               - (pfn & ~PAGE_SECTION_MASK));
+               ret = __remove_section(zone, pfn, pfns, map_offset);
+               pfn += pfns;
+               nr_pages -= pfns;
                map_offset = 0;
                if (ret)
                        break;
diff --git a/mm/sparse.c b/mm/sparse.c
index 97f91770e3d0..a8358d15a90d 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -753,7 +753,8 @@ static void free_map_bootmem(struct page *memmap)
 #endif /* CONFIG_MEMORY_HOTREMOVE */
 #endif /* CONFIG_SPARSEMEM_VMEMMAP */
 
-int __meminit sparse_add_one_section(struct zone *zone, unsigned long 
start_pfn)
+int __meminit sparse_add_section(struct zone *zone, unsigned long start_pfn,
+               unsigned long nr_pages)
 {
        unsigned long section_nr = pfn_to_section_nr(start_pfn);
        struct pglist_data *pgdat = zone->zone_pgdat;
@@ -855,7 +856,8 @@ static void free_section_usage(struct page *memmap,
                free_map_bootmem(memmap);
 }
 
-void sparse_remove_one_section(struct zone *zone, struct mem_section *ms,
+void sparse_remove_section(struct zone *zone, struct mem_section *ms,
+               unsigned long pfn, unsigned long nr_pages,
                unsigned long map_offset)
 {
        unsigned long flags;

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