Commit 8666925c authored by Vlastimil Babka's avatar Vlastimil Babka Committed by Andrew Morton
Browse files

mm, page_alloc: use check_pages_enabled static key to check tail pages 

Commit 700d2e9a ("mm, page_alloc: reduce page alloc/free sanity
checks") has introduced a new static key check_pages_enabled to control
when struct pages are sanity checked during allocation and freeing.  Mel
Gorman suggested that free_tail_pages_check() could use this static key as
well, instead of relying on CONFIG_DEBUG_VM.  That makes sense, so do
that.  Also rename the function to free_tail_page_prepare() because it
works on a single tail page and has a struct page preparation component as
well as the optional checking component.

Also remove some unnecessary unlikely() within static_branch_unlikely()
statements that Mel pointed out for commit 700d2e9a.

Link: https://lkml.kernel.org/r/20230405142840.11068-1-vbabka@suse.cz


Signed-off-by: default avatarVlastimil Babka <vbabka@suse.cz>
Suggested-by: default avatarMel Gorman <mgorman@techsingularity.net>
Acked-by: default avatarMel Gorman <mgorman@techsingularity.net>
Cc: Alexander Halbuer <halbuer@sra.uni-hannover.de>
Cc: Kees Cook <keescook@chromium.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 27da93d8

mm/hugetlb_vmemmap.c

+1 −1
Original line number Diff line number Diff line
@@ -264,7 +264,7 @@ static void vmemmap_remap_pte(pte_t *pte, unsigned long addr, 
 * How many struct page structs need to be reset. When we reuse the head

 * struct page, the special metadata (e.g. page->flags or page->mapping)

 * cannot copy to the tail struct page structs. The invalid value will be

 * checked in the free_tail_pages_check(). In order to avoid the message

 * checked in the free_tail_page_prepare(). In order to avoid the message

 * of "corrupted mapping in tail page". We need to reset at least 3 (one

 * head struct page struct and two tail struct page structs) struct page

 * structs.

mm/page_alloc.c

+5 −5
Original line number Diff line number Diff line
@@ -1131,7 +1131,7 @@ static inline bool free_page_is_bad(struct page *page) 
	return true;

}



static int free_tail_pages_check(struct page *head_page, struct page *page)

static int free_tail_page_prepare(struct page *head_page, struct page *page)

{

	struct folio *folio = (struct folio *)head_page;

	int ret = 1;
@@ -1142,7 +1142,7 @@ static int free_tail_pages_check(struct page *head_page, struct page *page) 
	 */

	BUILD_BUG_ON((unsigned long)LIST_POISON1 & 1);



	if (!IS_ENABLED(CONFIG_DEBUG_VM)) {

	if (!static_branch_unlikely(&check_pages_enabled)) {

		ret = 0;

		goto out;

	}
@@ -1276,9 +1276,9 @@ static __always_inline bool free_pages_prepare(struct page *page, 
			ClearPageHasHWPoisoned(page);

		for (i = 1; i < (1 << order); i++) {

			if (compound)

				bad += free_tail_pages_check(page, page + i);

				bad += free_tail_page_prepare(page, page + i);

			if (is_check_pages_enabled()) {

				if (unlikely(free_page_is_bad(page + i))) {

				if (free_page_is_bad(page + i)) {

					bad++;

					continue;

				}
@@ -1627,7 +1627,7 @@ static inline bool check_new_pages(struct page *page, unsigned int order) 
		for (int i = 0; i < (1 << order); i++) {

			struct page *p = page + i;



			if (unlikely(check_new_page(p)))

			if (check_new_page(p))

				return true;

		}

	}