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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@nvidia.com: updates per David]
Link: https://lkml.kernel.org/r/20220401230804.1658207-2-zi.yan@sent.com
Link: https://lore.kernel.org/linux-mm/CAHk-=wji_AmYygZMTsPMdJ7XksMt7kOur8oDfDdniBRMjm4VkQ@mail.gmail.com/
Link: https://lkml.kernel.org/r/7236E7CA-B5F1-4C04-AB85-E86FA3E9A54B@nvidia.com
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Zi Yan <ziy@nvidia.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Steven Rostedt (Google) <rostedt@goodmis.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Oscar Salvador <osalvador@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Zi Yan 2022-04-28 23:16:01 -07:00 committed by akpm
parent bb0e28eb5b
commit 8170ac4700
3 changed files with 101 additions and 77 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

117
mm/internal.h
View File

@ -211,6 +211,67 @@ struct alloc_context {
bool spread_dirty_pages;
};
/*
* 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, unsigned int order)
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);
@ -336,33 +426,6 @@ isolate_migratepages_range(struct compact_control *cc,
int find_suitable_fallback(struct free_area *area, unsigned int order,
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.
*/

52
mm/page_alloc.c
View File

@ -867,40 +867,6 @@ static inline void set_buddy_order(struct page *page, unsigned int order)
__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(struct page *page,
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)) {

9
mm/page_isolation.c
View File

@ -70,7 +70,6 @@ static void unset_migratetype_isolate(struct page *page, unsigned migratetype)
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(struct page *page, unsigned migratetype)
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