Commit 5556cfe8 authored by Vlastimil Babka's avatar Vlastimil Babka Committed by Linus Torvalds
Browse files

mm, page_owner: fix off-by-one error in __set_page_owner_handle() 

Patch series "followups to debug_pagealloc improvements through
page_owner", v3.

These are followups to [1] which made it to Linus meanwhile.  Patches 1
and 3 are based on Kirill's review, patch 2 on KASAN request [2].  It
would be nice if all of this made it to 5.4 with [1] already there (or
at least Patch 1).

This patch (of 3):

As noted by Kirill, commit 7e2f2a0c ("mm, page_owner: record page
owner for each subpage") has introduced an off-by-one error in
__set_page_owner_handle() when looking up page_ext for subpages.  As a
result, the head page page_owner info is set twice, while for the last
tail page, it's not set at all.

Fix this and also make the code more efficient by advancing the page_ext
pointer we already have, instead of calling lookup_page_ext() for each
subpage.  Since the full size of struct page_ext is not known at compile
time, we can't use a simple page_ext++ statement, so introduce a
page_ext_next() inline function for that.

Link: http://lkml.kernel.org/r/20190930122916.14969-2-vbabka@suse.cz


Fixes: 7e2f2a0c ("mm, page_owner: record page owner for each subpage")
Signed-off-by: default avatarVlastimil Babka <vbabka@suse.cz>
Reported-by: default avatarKirill A. Shutemov <kirill@shutemov.name>
Reported-by: default avatarMiles Chen <miles.chen@mediatek.com>
Acked-by: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Walter Wu <walter-zh.wu@mediatek.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 2abd839a

include/linux/page_ext.h

+8 −0
Original line number Diff line number Diff line
@@ -36,6 +36,7 @@ struct page_ext { 
	unsigned long flags;

};



extern unsigned long page_ext_size;

extern void pgdat_page_ext_init(struct pglist_data *pgdat);



#ifdef CONFIG_SPARSEMEM
@@ -52,6 +53,13 @@ static inline void page_ext_init(void) 


struct page_ext *lookup_page_ext(const struct page *page);



static inline struct page_ext *page_ext_next(struct page_ext *curr)

{

	void *next = curr;

	next += page_ext_size;

	return next;

}



#else /* !CONFIG_PAGE_EXTENSION */

struct page_ext;

mm/page_ext.c

+9 −14
Original line number Diff line number Diff line
@@ -67,8 +67,9 @@ static struct page_ext_operations *page_ext_ops[] = { 
#endif

};



unsigned long page_ext_size = sizeof(struct page_ext);



static unsigned long total_usage;

static unsigned long extra_mem;



static bool __init invoke_need_callbacks(void)

{
@@ -78,9 +79,8 @@ static bool __init invoke_need_callbacks(void) 


	for (i = 0; i < entries; i++) {

		if (page_ext_ops[i]->need && page_ext_ops[i]->need()) {

			page_ext_ops[i]->offset = sizeof(struct page_ext) +

						extra_mem;

			extra_mem += page_ext_ops[i]->size;

			page_ext_ops[i]->offset = page_ext_size;

			page_ext_size += page_ext_ops[i]->size;

			need = true;

		}

	}
@@ -99,14 +99,9 @@ static void __init invoke_init_callbacks(void) 
	}

}



static unsigned long get_entry_size(void)

{

	return sizeof(struct page_ext) + extra_mem;

}



static inline struct page_ext *get_entry(void *base, unsigned long index)

{

	return base + get_entry_size() * index;

	return base + page_ext_size * index;

}



#if !defined(CONFIG_SPARSEMEM)
@@ -156,7 +151,7 @@ static int __init alloc_node_page_ext(int nid) 
		!IS_ALIGNED(node_end_pfn(nid), MAX_ORDER_NR_PAGES))

		nr_pages += MAX_ORDER_NR_PAGES;



	table_size = get_entry_size() * nr_pages;

	table_size = page_ext_size * nr_pages;



	base = memblock_alloc_try_nid(

			table_size, PAGE_SIZE, __pa(MAX_DMA_ADDRESS),
@@ -234,7 +229,7 @@ static int __meminit init_section_page_ext(unsigned long pfn, int nid) 
	if (section->page_ext)

		return 0;



	table_size = get_entry_size() * PAGES_PER_SECTION;

	table_size = page_ext_size * PAGES_PER_SECTION;

	base = alloc_page_ext(table_size, nid);



	/*
@@ -254,7 +249,7 @@ static int __meminit init_section_page_ext(unsigned long pfn, int nid) 
	 * we need to apply a mask.

	 */

	pfn &= PAGE_SECTION_MASK;

	section->page_ext = (void *)base - get_entry_size() * pfn;

	section->page_ext = (void *)base - page_ext_size * pfn;

	total_usage += table_size;

	return 0;

}
@@ -267,7 +262,7 @@ static void free_page_ext(void *addr) 
		struct page *page = virt_to_page(addr);

		size_t table_size;



		table_size = get_entry_size() * PAGES_PER_SECTION;

		table_size = page_ext_size * PAGES_PER_SECTION;



		BUG_ON(PageReserved(page));

		kmemleak_free(addr);

mm/page_owner.c

+7 −8
Original line number Diff line number Diff line
@@ -156,10 +156,10 @@ void __reset_page_owner(struct page *page, unsigned int order) 
		handle = save_stack(GFP_NOWAIT | __GFP_NOWARN);

#endif



	for (i = 0; i < (1 << order); i++) {

		page_ext = lookup_page_ext(page + i);

	page_ext = lookup_page_ext(page);

	if (unlikely(!page_ext))

			continue;

		return;

	for (i = 0; i < (1 << order); i++) {

		__clear_bit(PAGE_EXT_OWNER_ACTIVE, &page_ext->flags);

#ifdef CONFIG_DEBUG_PAGEALLOC

		if (debug_pagealloc_enabled()) {
@@ -167,6 +167,7 @@ void __reset_page_owner(struct page *page, unsigned int order) 
			page_owner->free_handle = handle;

		}

#endif

		page_ext = page_ext_next(page_ext);

	}

}
@@ -186,7 +187,7 @@ static inline void __set_page_owner_handle(struct page *page, 
		__set_bit(PAGE_EXT_OWNER, &page_ext->flags);

		__set_bit(PAGE_EXT_OWNER_ACTIVE, &page_ext->flags);



		page_ext = lookup_page_ext(page + i);

		page_ext = page_ext_next(page_ext);

	}

}
@@ -224,12 +225,10 @@ void __split_page_owner(struct page *page, unsigned int order) 
	if (unlikely(!page_ext))

		return;



	for (i = 0; i < (1 << order); i++) {

		page_owner = get_page_owner(page_ext);

		page_owner->order = 0;

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

		page_ext = lookup_page_ext(page + i);

		page_owner = get_page_owner(page_ext);

		page_owner->order = 0;

		page_ext = page_ext_next(page_ext);

	}

}

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