The quilt patch titled
Subject: mm: wrap __find_buddy_pfn() with a necessary buddy page validation
has been removed from the -mm tree. Its filename was
mm-wrap-__find_buddy_pfn-with-a-necessary-buddy-page-validation.patch
This patch was dropped because it was merged into mm-stable
------------------------------------------------------
From: Zi Yan <ziy@xxxxxxxxxx>
Subject: mm: wrap __find_buddy_pfn() with a necessary buddy page validation
Whenever the buddy of a page is found from __find_buddy_pfn(),
page_is_buddy() should be used to check its validity. Add a helper
function find_buddy_page_pfn() to find the buddy page and do the check
together.
[ziy@xxxxxxxxxx: updates per David]
Link: https://lkml.kernel.org/r/20220401230804.1658207-2-zi.yan@xxxxxxxx
Link: https://lore.kernel.org/linux-mm/CAHk-=wji_AmYygZMTsPMdJ7XksMt7kOur8oDfDdniBRMjm4VkQ@xxxxxxxxxxxxxx/
Link: https://lkml.kernel.org/r/7236E7CA-B5F1-4C04-AB85-E86FA3E9A54B@xxxxxxxxxx
Suggested-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Zi Yan <ziy@xxxxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
Acked-by: David Hildenbrand <david@xxxxxxxxxx>
Cc: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: Mike Rapoport <rppt@xxxxxxxxxx>
Cc: Oscar Salvador <osalvador@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/internal.h | 117 ++++++++++++++++++++++++++++++++----------
mm/page_alloc.c | 52 ++----------------
mm/page_isolation.c | 9 +--
3 files changed, 101 insertions(+), 77 deletions(-)
--- a/mm/internal.h~mm-wrap-__find_buddy_pfn-with-a-necessary-buddy-page-validation
+++ a/mm/internal.h
@@ -212,6 +212,67 @@ struct alloc_context {
};
/*
+ * This function returns the order of a free page in the buddy system. In
+ * general, page_zone(page)->lock must be held by the caller to prevent the
+ * page from being allocated in parallel and returning garbage as the order.
+ * If a caller does not hold page_zone(page)->lock, it must guarantee that the
+ * page cannot be allocated or merged in parallel. Alternatively, it must
+ * handle invalid values gracefully, and use buddy_order_unsafe() below.
+ */
+static inline unsigned int buddy_order(struct page *page)
+{
+ /* PageBuddy() must be checked by the caller */
+ return page_private(page);
+}
+
+/*
+ * Like buddy_order(), but for callers who cannot afford to hold the zone lock.
+ * PageBuddy() should be checked first by the caller to minimize race window,
+ * and invalid values must be handled gracefully.
+ *
+ * READ_ONCE is used so that if the caller assigns the result into a local
+ * variable and e.g. tests it for valid range before using, the compiler cannot
+ * decide to remove the variable and inline the page_private(page) multiple
+ * times, potentially observing different values in the tests and the actual
+ * use of the result.
+ */
+#define buddy_order_unsafe(page) READ_ONCE(page_private(page))
+
+/*
+ * This function checks whether a page is free && is the buddy
+ * we can coalesce a page and its buddy if
+ * (a) the buddy is not in a hole (check before calling!) &&
+ * (b) the buddy is in the buddy system &&
+ * (c) a page and its buddy have the same order &&
+ * (d) a page and its buddy are in the same zone.
+ *
+ * For recording whether a page is in the buddy system, we set PageBuddy.
+ * Setting, clearing, and testing PageBuddy is serialized by zone->lock.
+ *
+ * For recording page's order, we use page_private(page).
+ */
+static inline bool page_is_buddy(struct page *page, struct page *buddy,
+ unsigned int order)
+{
+ if (!page_is_guard(buddy) && !PageBuddy(buddy))
+ return false;
+
+ if (buddy_order(buddy) != order)
+ return false;
+
+ /*
+ * zone check is done late to avoid uselessly calculating
+ * zone/node ids for pages that could never merge.
+ */
+ if (page_zone_id(page) != page_zone_id(buddy))
+ return false;
+
+ VM_BUG_ON_PAGE(page_count(buddy) != 0, buddy);
+
+ return true;
+}
+
+/*
* Locate the struct page for both the matching buddy in our
* pair (buddy1) and the combined O(n+1) page they form (page).
*
@@ -234,6 +295,35 @@ __find_buddy_pfn(unsigned long page_pfn,
return page_pfn ^ (1 << order);
}
+/*
+ * Find the buddy of @page and validate it.
+ * @page: The input page
+ * @pfn: The pfn of the page, it saves a call to page_to_pfn() when the
+ * function is used in the performance-critical __free_one_page().
+ * @order: The order of the page
+ * @buddy_pfn: The output pointer to the buddy pfn, it also saves a call to
+ * page_to_pfn().
+ *
+ * The found buddy can be a non PageBuddy, out of @page's zone, or its order is
+ * not the same as @page. The validation is necessary before use it.
+ *
+ * Return: the found buddy page or NULL if not found.
+ */
+static inline struct page *find_buddy_page_pfn(struct page *page,
+ unsigned long pfn, unsigned int order, unsigned long *buddy_pfn)
+{
+ unsigned long __buddy_pfn = __find_buddy_pfn(pfn, order);
+ struct page *buddy;
+
+ buddy = page + (__buddy_pfn - pfn);
+ if (buddy_pfn)
+ *buddy_pfn = __buddy_pfn;
+
+ if (page_is_buddy(page, buddy, order))
+ return buddy;
+ return NULL;
+}
+
extern struct page *__pageblock_pfn_to_page(unsigned long start_pfn,
unsigned long end_pfn, struct zone *zone);
@@ -337,33 +427,6 @@ int find_suitable_fallback(struct free_a
int migratetype, bool only_stealable, bool *can_steal);
/*
- * This function returns the order of a free page in the buddy system. In
- * general, page_zone(page)->lock must be held by the caller to prevent the
- * page from being allocated in parallel and returning garbage as the order.
- * If a caller does not hold page_zone(page)->lock, it must guarantee that the
- * page cannot be allocated or merged in parallel. Alternatively, it must
- * handle invalid values gracefully, and use buddy_order_unsafe() below.
- */
-static inline unsigned int buddy_order(struct page *page)
-{
- /* PageBuddy() must be checked by the caller */
- return page_private(page);
-}
-
-/*
- * Like buddy_order(), but for callers who cannot afford to hold the zone lock.
- * PageBuddy() should be checked first by the caller to minimize race window,
- * and invalid values must be handled gracefully.
- *
- * READ_ONCE is used so that if the caller assigns the result into a local
- * variable and e.g. tests it for valid range before using, the compiler cannot
- * decide to remove the variable and inline the page_private(page) multiple
- * times, potentially observing different values in the tests and the actual
- * use of the result.
- */
-#define buddy_order_unsafe(page) READ_ONCE(page_private(page))
-
-/*
* These three helpers classifies VMAs for virtual memory accounting.
*/
--- a/mm/page_alloc.c~mm-wrap-__find_buddy_pfn-with-a-necessary-buddy-page-validation
+++ a/mm/page_alloc.c
@@ -867,40 +867,6 @@ static inline void set_buddy_order(struc
__SetPageBuddy(page);
}
-/*
- * This function checks whether a page is free && is the buddy
- * we can coalesce a page and its buddy if
- * (a) the buddy is not in a hole (check before calling!) &&
- * (b) the buddy is in the buddy system &&
- * (c) a page and its buddy have the same order &&
- * (d) a page and its buddy are in the same zone.
- *
- * For recording whether a page is in the buddy system, we set PageBuddy.
- * Setting, clearing, and testing PageBuddy is serialized by zone->lock.
- *
- * For recording page's order, we use page_private(page).
- */
-static inline bool page_is_buddy(struct page *page, struct page *buddy,
- unsigned int order)
-{
- if (!page_is_guard(buddy) && !PageBuddy(buddy))
- return false;
-
- if (buddy_order(buddy) != order)
- return false;
-
- /*
- * zone check is done late to avoid uselessly calculating
- * zone/node ids for pages that could never merge.
- */
- if (page_zone_id(page) != page_zone_id(buddy))
- return false;
-
- VM_BUG_ON_PAGE(page_count(buddy) != 0, buddy);
-
- return true;
-}
-
#ifdef CONFIG_COMPACTION
static inline struct capture_control *task_capc(struct zone *zone)
{
@@ -1009,18 +975,17 @@ static inline bool
buddy_merge_likely(unsigned long pfn, unsigned long buddy_pfn,
struct page *page, unsigned int order)
{
- struct page *higher_page, *higher_buddy;
- unsigned long combined_pfn;
+ unsigned long higher_page_pfn;
+ struct page *higher_page;
if (order >= MAX_ORDER - 2)
return false;
- combined_pfn = buddy_pfn & pfn;
- higher_page = page + (combined_pfn - pfn);
- buddy_pfn = __find_buddy_pfn(combined_pfn, order + 1);
- higher_buddy = higher_page + (buddy_pfn - combined_pfn);
+ higher_page_pfn = buddy_pfn & pfn;
+ higher_page = page + (higher_page_pfn - pfn);
- return page_is_buddy(higher_page, higher_buddy, order + 1);
+ return find_buddy_page_pfn(higher_page, higher_page_pfn, order + 1,
+ NULL) != NULL;
}
/*
@@ -1074,10 +1039,9 @@ static inline void __free_one_page(struc
migratetype);
return;
}
- buddy_pfn = __find_buddy_pfn(pfn, order);
- buddy = page + (buddy_pfn - pfn);
- if (!page_is_buddy(page, buddy, order))
+ buddy = find_buddy_page_pfn(page, pfn, order, &buddy_pfn);
+ if (!buddy)
goto done_merging;
if (unlikely(order >= pageblock_order)) {
--- a/mm/page_isolation.c~mm-wrap-__find_buddy_pfn-with-a-necessary-buddy-page-validation
+++ a/mm/page_isolation.c
@@ -70,7 +70,6 @@ static void unset_migratetype_isolate(st
unsigned long flags, nr_pages;
bool isolated_page = false;
unsigned int order;
- unsigned long pfn, buddy_pfn;
struct page *buddy;
zone = page_zone(page);
@@ -89,11 +88,9 @@ static void unset_migratetype_isolate(st
if (PageBuddy(page)) {
order = buddy_order(page);
if (order >= pageblock_order && order < MAX_ORDER - 1) {
- pfn = page_to_pfn(page);
- buddy_pfn = __find_buddy_pfn(pfn, order);
- buddy = page + (buddy_pfn - pfn);
-
- if (!is_migrate_isolate_page(buddy)) {
+ buddy = find_buddy_page_pfn(page, page_to_pfn(page),
+ order, NULL);
+ if (buddy && !is_migrate_isolate_page(buddy)) {
isolated_page = !!__isolate_free_page(page, order);
/*
* Isolating a free page in an isolated pageblock
_
Patches currently in -mm which might be from ziy@xxxxxxxxxx are
mm-page_isolation-move-has_unmovable_pages-to-mm-page_isolationc.patch
mm-page_isolation-check-specified-range-for-unmovable-pages.patch
mm-make-alloc_contig_range-work-at-pageblock-granularity.patch
mm-make-alloc_contig_range-work-at-pageblock-granularity-fix.patch
mm-page_isolation-enable-arbitrary-range-page-isolation.patch
mm-cma-use-pageblock_order-as-the-single-alignment.patch
drivers-virtio_mem-use-pageblock-size-as-the-minimum-virtio_mem-size.patch
