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Commit fe896d18 authored by Joonsoo Kim's avatar Joonsoo Kim Committed by Linus Torvalds
Browse files

mm: introduce page reference manipulation functions 



The success of CMA allocation largely depends on the success of
migration and key factor of it is page reference count.  Until now, page
reference is manipulated by direct calling atomic functions so we cannot
follow up who and where manipulate it.  Then, it is hard to find actual
reason of CMA allocation failure.  CMA allocation should be guaranteed
to succeed so finding offending place is really important.

In this patch, call sites where page reference is manipulated are
converted to introduced wrapper function.  This is preparation step to
add tracepoint to each page reference manipulation function.  With this
facility, we can easily find reason of CMA allocation failure.  There is
no functional change in this patch.

In addition, this patch also converts reference read sites.  It will
help a second step that renames page._count to something else and
prevents later attempt to direct access to it (Suggested by Andrew).

Signed-off-by: default avatarJoonsoo Kim <iamjoonsoo.kim@lge.com>
Acked-by: default avatarMichal Nazarewicz <mina86@mina86.com>
Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 444eb2a4

arch/mips/mm/gup.c

+1 −1
Original line number Diff line number Diff line
@@ -64,7 +64,7 @@ static inline void get_head_page_multiple(struct page *page, int nr) 
{

	VM_BUG_ON(page != compound_head(page));

	VM_BUG_ON(page_count(page) == 0);

	atomic_add(nr, &page->_count);

	page_ref_add(page, nr);

	SetPageReferenced(page);

}

arch/powerpc/mm/mmu_context_hash64.c

+1 −2
Original line number Diff line number Diff line
@@ -118,8 +118,7 @@ static void destroy_pagetable_page(struct mm_struct *mm) 
	/* drop all the pending references */

	count = ((unsigned long)pte_frag & ~PAGE_MASK) >> PTE_FRAG_SIZE_SHIFT;

	/* We allow PTE_FRAG_NR fragments from a PTE page */

	count = atomic_sub_return(PTE_FRAG_NR - count, &page->_count);

	if (!count) {

	if (page_ref_sub_and_test(page, PTE_FRAG_NR - count)) {

		pgtable_page_dtor(page);

		free_hot_cold_page(page, 0);

	}

arch/powerpc/mm/pgtable_64.c

+1 −1
Original line number Diff line number Diff line
@@ -403,7 +403,7 @@ static pte_t *__alloc_for_cache(struct mm_struct *mm, int kernel) 
	 * count.

	 */

	if (likely(!mm->context.pte_frag)) {

		atomic_set(&page->_count, PTE_FRAG_NR);

		set_page_count(page, PTE_FRAG_NR);

		mm->context.pte_frag = ret + PTE_FRAG_SIZE;

	}

	spin_unlock(&mm->page_table_lock);

arch/powerpc/platforms/512x/mpc512x_shared.c

+1 −1
Original line number Diff line number Diff line
@@ -188,7 +188,7 @@ static struct fsl_diu_shared_fb __attribute__ ((__aligned__(8))) diu_shared_fb; 
static inline void mpc512x_free_bootmem(struct page *page)

{

	BUG_ON(PageTail(page));

	BUG_ON(atomic_read(&page->_count) > 1);

	BUG_ON(page_ref_count(page) > 1);

	free_reserved_page(page);

}

arch/x86/mm/gup.c

+1 −1
Original line number Diff line number Diff line
@@ -131,7 +131,7 @@ static inline void get_head_page_multiple(struct page *page, int nr) 
{

	VM_BUG_ON_PAGE(page != compound_head(page), page);

	VM_BUG_ON_PAGE(page_count(page) == 0, page);

	atomic_add(nr, &page->_count);

	page_ref_add(page, nr);

	SetPageReferenced(page);

}