Subject: [PATCH v1 1/7] mm/memory_hotplug: Simplify and fix check_hotplug_memory_range()

From: David Hildenbrand <[email-masked]>
Date: Wed, 24 Apr 2019 12:25:05 +0200

By converting start and size to page granularity, we actually ignore
unaligned parts within a page instead of properly bailing out with an
error.

Cc: Andrew Morton <[email-masked]>
Cc: Oscar Salvador <[email-masked]>
Cc: Michal Hocko <[email-masked]>
Cc: David Hildenbrand <[email-masked]>
Cc: Pavel Tatashin <[email-masked]>
Cc: Qian Cai <[email-masked]>
Cc: Wei Yang <[email-masked]>
Cc: Arun KS <[email-masked]>
Cc: Mathieu Malaterre <[email-masked]>
Signed-off-by: David Hildenbrand <[email-masked]>
---
 mm/memory_hotplug.c | 11 +++--------
 1 file changed, 3 insertions(+), 8 deletions(-)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 328878b6799d..202febe88b58 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1050,16 +1050,11 @@ int try_online_node(int nid)
 
 static int check_hotplug_memory_range(u64 start, u64 size)
 {
-	unsigned long block_sz = memory_block_size_bytes();
-	u64 block_nr_pages = block_sz >> PAGE_SHIFT;
-	u64 nr_pages = size >> PAGE_SHIFT;
-	u64 start_pfn = PFN_DOWN(start);
-
 	/* memory range must be block size aligned */
-	if (!nr_pages || !IS_ALIGNED(start_pfn, block_nr_pages) ||
-	    !IS_ALIGNED(nr_pages, block_nr_pages)) {
+	if (!size || !IS_ALIGNED(start, memory_block_size_bytes()) ||
+	    !IS_ALIGNED(size, memory_block_size_bytes())) {
 		pr_err("Block size [%#lx] unaligned hotplug range: start %#llx, size %#llx",
-		       block_sz, start, size);
+		       memory_block_size_bytes(), start, size);
 		return -EINVAL;
 	}
 
-- 
2.20.1