Re: [PATCH v1] mm/memory_hotplug: drop valid_start/valid_end from test_pages_in_a_zone()

From: Andrew Morton
Date: Thu Jan 30 2020 - 23:42:34 EST


On Fri, 10 Jan 2020 19:33:08 +0100 David Hildenbrand <david@xxxxxxxxxx> wrote:

> The callers are only interested in the actual zone, they don't care
> about boundaries. Return the zone instead to simplify.
>

Any reviewers for this one?

From: David Hildenbrand <david@xxxxxxxxxx>
Subject: mm/memory_hotplug: drop valid_start/valid_end from test_pages_in_a_zone()

The callers are only interested in the actual zone, they don't care about
boundaries. Return the zone instead to simplify.

Link: http://lkml.kernel.org/r/20200110183308.11849-1-david@xxxxxxxxxx
Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: "Rafael J. Wysocki" <rafael@xxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Oscar Salvador <osalvador@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---

drivers/base/memory.c | 9 ++++-----
include/linux/memory_hotplug.h | 4 ++--
mm/memory_hotplug.c | 31 +++++++++----------------------
3 files changed, 15 insertions(+), 29 deletions(-)

--- a/drivers/base/memory.c~mm-memory_hotplug-drop-valid_start-valid_end-from-test_pages_in_a_zone
+++ a/drivers/base/memory.c
@@ -376,7 +376,6 @@ static ssize_t valid_zones_show(struct d
struct memory_block *mem = to_memory_block(dev);
unsigned long start_pfn = section_nr_to_pfn(mem->start_section_nr);
unsigned long nr_pages = PAGES_PER_SECTION * sections_per_block;
- unsigned long valid_start_pfn, valid_end_pfn;
struct zone *default_zone;
int nid;

@@ -389,11 +388,11 @@ static ssize_t valid_zones_show(struct d
* The block contains more than one zone can not be offlined.
* This can happen e.g. for ZONE_DMA and ZONE_DMA32
*/
- if (!test_pages_in_a_zone(start_pfn, start_pfn + nr_pages,
- &valid_start_pfn, &valid_end_pfn))
+ default_zone = test_pages_in_a_zone(start_pfn,
+ start_pfn + nr_pages);
+ if (!default_zone)
return sprintf(buf, "none\n");
- start_pfn = valid_start_pfn;
- strcat(buf, page_zone(pfn_to_page(start_pfn))->name);
+ strcat(buf, default_zone->name);
goto out;
}

--- a/include/linux/memory_hotplug.h~mm-memory_hotplug-drop-valid_start-valid_end-from-test_pages_in_a_zone
+++ a/include/linux/memory_hotplug.h
@@ -95,8 +95,8 @@ extern int zone_grow_waitqueues(struct z
extern int add_one_highpage(struct page *page, int pfn, int bad_ppro);
/* VM interface that may be used by firmware interface */
extern int online_pages(unsigned long, unsigned long, int);
-extern int test_pages_in_a_zone(unsigned long start_pfn, unsigned long end_pfn,
- unsigned long *valid_start, unsigned long *valid_end);
+extern struct zone *test_pages_in_a_zone(unsigned long start_pfn,
+ unsigned long end_pfn);
extern unsigned long __offline_isolated_pages(unsigned long start_pfn,
unsigned long end_pfn);

--- a/mm/memory_hotplug.c~mm-memory_hotplug-drop-valid_start-valid_end-from-test_pages_in_a_zone
+++ a/mm/memory_hotplug.c
@@ -1206,14 +1206,13 @@ bool is_mem_section_removable(unsigned l
}

/*
- * Confirm all pages in a range [start, end) belong to the same zone.
- * When true, return its valid [start, end).
+ * Confirm all pages in a range [start, end) belong to the same zone (skipping
+ * memory holes). When true, return the zone.
*/
-int test_pages_in_a_zone(unsigned long start_pfn, unsigned long end_pfn,
- unsigned long *valid_start, unsigned long *valid_end)
+struct zone *test_pages_in_a_zone(unsigned long start_pfn,
+ unsigned long end_pfn)
{
unsigned long pfn, sec_end_pfn;
- unsigned long start, end;
struct zone *zone = NULL;
struct page *page;
int i;
@@ -1234,24 +1233,15 @@ int test_pages_in_a_zone(unsigned long s
continue;
/* Check if we got outside of the zone */
if (zone && !zone_spans_pfn(zone, pfn + i))
- return 0;
+ return NULL;
page = pfn_to_page(pfn + i);
if (zone && page_zone(page) != zone)
- return 0;
- if (!zone)
- start = pfn + i;
+ return NULL;
zone = page_zone(page);
- end = pfn + MAX_ORDER_NR_PAGES;
}
}

- if (zone) {
- *valid_start = start;
- *valid_end = min(end, end_pfn);
- return 1;
- } else {
- return 0;
- }
+ return zone;
}

/*
@@ -1496,7 +1486,6 @@ static int __ref __offline_pages(unsigne
unsigned long offlined_pages = 0;
int ret, node, nr_isolate_pageblock;
unsigned long flags;
- unsigned long valid_start, valid_end;
struct zone *zone;
struct memory_notify arg;
char *reason;
@@ -1521,14 +1510,12 @@ static int __ref __offline_pages(unsigne

/* This makes hotplug much easier...and readable.
we assume this for now. .*/
- if (!test_pages_in_a_zone(start_pfn, end_pfn, &valid_start,
- &valid_end)) {
+ zone = test_pages_in_a_zone(start_pfn, end_pfn);
+ if (!zone) {
ret = -EINVAL;
reason = "multizone range";
goto failed_removal;
}
-
- zone = page_zone(pfn_to_page(valid_start));
node = zone_to_nid(zone);

/* set above range as isolated */
_