drivers/base/memory.c: don't store end_section_nr in memory blocks

Each memory block spans the same amount of sections/pages/bytes.  The size
is determined before the first memory block is created.  No need to store
what we can easily calculate - and the calculations even look simpler now.

Michal brought up the idea of variable-sized memory blocks.  However, if
we ever implement something like this, we will need an API compatibility
switch and reworks at various places (most code assumes a fixed memory
block size).  So let's cleanup what we have right now.

While at it, fix the variable naming in register_mem_sect_under_node() -
we no longer talk about a single section.

Link: http://lkml.kernel.org/r/20190809110200.2746-1-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Oscar Salvador <osalvador@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

4 files changed, 6 insertions, 8 deletions

diff --git a/drivers/base/memory.c b/drivers/base/memory.c
index 763154c82eb3..6bea4f3f8040 100644
--- a/drivers/base/memory.c
+++ b/drivers/base/memory.c
@@ -656,7 +656,6 @@ static int init_memory_block(struct memory_block **memory,
                 return -ENOMEM;
 
         mem->start_section_nr = block_id * sections_per_block;
-        mem->end_section_nr = mem->start_section_nr + sections_per_block - 1;
         mem->state = state;
         start_pfn = section_nr_to_pfn(mem->start_section_nr);
         mem->phys_device = arch_get_memory_phys_device(start_pfn);
diff --git a/drivers/base/node.c b/drivers/base/node.c
index 840c95baa1d8..257449cf061f 100644
--- a/drivers/base/node.c
+++ b/drivers/base/node.c
@@ -756,13 +756,13 @@ static int __ref get_nid_for_pfn(unsigned long pfn)
 static int register_mem_sect_under_node(struct memory_block *mem_blk,
                                          void *arg)
 {
+        unsigned long memory_block_pfns = memory_block_size_bytes() / PAGE_SIZE;
+        unsigned long start_pfn = section_nr_to_pfn(mem_blk->start_section_nr);
+        unsigned long end_pfn = start_pfn + memory_block_pfns - 1;
         int ret, nid = *(int *)arg;
-        unsigned long pfn, sect_start_pfn, sect_end_pfn;
+        unsigned long pfn;
 
-        sect_start_pfn = section_nr_to_pfn(mem_blk->start_section_nr);
-        sect_end_pfn = section_nr_to_pfn(mem_blk->end_section_nr);
-        sect_end_pfn += PAGES_PER_SECTION - 1;
-        for (pfn = sect_start_pfn; pfn <= sect_end_pfn; pfn++) {
+        for (pfn = start_pfn; pfn <= end_pfn; pfn++) {
                 int page_nid;
 
                 /*
diff --git a/include/linux/memory.h b/include/linux/memory.h
index b3d9df060626..0ebb105eb261 100644
--- a/include/linux/memory.h
+++ b/include/linux/memory.h
@@ -25,7 +25,6 @@
 
 struct memory_block {
         unsigned long start_section_nr;
-        unsigned long end_section_nr;
         unsigned long state;            /* serialized by the dev->lock */
         int section_count;              /* serialized by mem_sysfs_mutex */
         int online_type;                /* for passing data to online routine */
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 5b8811945bbb..3706a137d880 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1654,7 +1654,7 @@ static int check_memblock_offlined_cb(struct memory_block *mem, void *arg)
                 phys_addr_t beginpa, endpa;
 
                 beginpa = PFN_PHYS(section_nr_to_pfn(mem->start_section_nr));
-                endpa = PFN_PHYS(section_nr_to_pfn(mem->end_section_nr + 1))-1;
+                endpa = beginpa + memory_block_size_bytes() - 1;
                 pr_warn("removing memory fails, because memory [%pa-%pa] is onlined\n",
                         &beginpa, &endpa);