linux-kernel - [PATCH RFC 1/3] mm/memory_hotplug: Simplify and fix check_hotplug_memory

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Date:   Mon,  8 Apr 2019 12:12:24 +0200
From:   David Hildenbrand <david@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Andrew Banman <andrew.banman@....com>, mike.travis@....com,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        Oscar Salvador <osalvador@...e.de>,
        Michal Hocko <mhocko@...e.com>,
        Pavel Tatashin <pavel.tatashin@...rosoft.com>,
        Wei Yang <richard.weiyang@...il.com>, Qian Cai <cai@....pw>,
        Arun KS <arunks@...eaurora.org>,
        Mathieu Malaterre <malat@...ian.org>, linux-mm@...ck.org,
        dan.j.williams@...el.com, David Hildenbrand <david@...hat.com>
Subject: [PATCH RFC 1/3] mm/memory_hotplug: Simplify and fix check_hotplug_memory_range()

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

Signed-off-by: David Hildenbrand <david@...hat.com>
---
 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 f206b8b66af1..680dcc67f9d5 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1070,16 +1070,11 @@ 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;
 	}
 
-- 
2.17.2