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remove PageReserved

PATCH In review Nick Piggin 3 participants 13 messages Jul 26, 2005 – Jul 28, 2005

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Nick Piggin

author
#0 lore raw

cover remove PageReserved

Hi Andrew,

If you're feeling like -mm is getting too stable, then you might consider giving these patches a spin? (unless anyone else raises an objection).

Ben thought I should get moving with them soon.

Not much change from last time. A bit of ppc64 input from Ben, and some rmap.c input from Hugh. Boots and runs on a few machines I have lying around here.

The only remaining places that *test* PageReserved are swsusp, a trivial useage in drivers/char/agp/amd64-agp.c, and arch/ code.

Most of the arch code is just reserved memory reporting, which isn't very interesting and could easily be removed. Some arch users are a bit more subtle, however they *should not* break, because all the places that set and clear PageReserved are basically intact.

We can phase PageReserved out of the tree completely when the core becomes stable.

Now the main problems we might have are the introduction of some tighter checks introduced by this patchset - for example 'bad_page' is triggered on PG_reserved.

The other thing is - MAP_PRIVATE of VM_RESERVED regions becomes disallowed. Any program that attempts such a thing prints a warning. Hugh has some code which handles this case but he suggested that we should first see whether it is even required.

Any thoughts? Comments?

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author
#1 lore raw

PATCH 1/6 mm: comment rmap

1/6

Just be clear that VM_RESERVED pages here are a bug, and the test is not there because they are expected.

Signed-off-by Nick Piggin <[email protected]>
mm/rmap.c +2 -0
Index: linux-2.6/mm/rmap.c
===================================================================
@@ -532,6 +532,8 @@ static int try_to_unmap_one(struct page 
 	 * If the page is mlock()d, we cannot swap it out.
 	 * If it's recently referenced (perhaps page_referenced
 	 * skipped over this mm) then we should reactivate it.
+	 *
+	 * Pages belonging to VM_RESERVED regions should not happen here.
 	 */
 	if ((vma->vm_flags & (VM_LOCKED|VM_RESERVED)) ||
 			ptep_clear_flush_young(vma, address, pte)) {
author
#2 lore raw

PATCH 2/6 mm: micro-optimise rmap

2/6

Microoptimise page_add_anon_rmap. Although these expressions are used only in the taken branch of the if() statement, the compiler can't reorder them inside because atomic_inc_and_test is a barrier.

Signed-off-by Nick Piggin <[email protected]>
mm/rmap.c +11 -10
Index: linux-2.6/mm/rmap.c
===================================================================
@@ -442,22 +442,23 @@ int page_referenced(struct page *page, i
 void page_add_anon_rmap(struct page *page,
 	struct vm_area_struct *vma, unsigned long address)
 {
-	struct anon_vma *anon_vma = vma->anon_vma;
-	pgoff_t index;
-
 	BUG_ON(PageReserved(page));
-	BUG_ON(!anon_vma);
 
 	inc_mm_counter(vma->vm_mm, anon_rss);
 
-	anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
-	index = (address - vma->vm_start) >> PAGE_SHIFT;
-	index += vma->vm_pgoff;
-	index >>= PAGE_CACHE_SHIFT - PAGE_SHIFT;
-
 	if (atomic_inc_and_test(&page->_mapcount)) {
-		page->index = index;
+		struct anon_vma *anon_vma = vma->anon_vma;
+		pgoff_t index;
+
+		BUG_ON(!anon_vma);
+		anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
 		page->mapping = (struct address_space *) anon_vma;
+
+		index = (address - vma->vm_start) >> PAGE_SHIFT;
+		index += vma->vm_pgoff;
+		index >>= PAGE_CACHE_SHIFT - PAGE_SHIFT;
+		page->index = index;
+
 		inc_page_state(nr_mapped);
 	}
 	/* else checking page index and mapping is racy */
author
#3 lore raw

PATCH 3/6 mm: cleanup rmap

3/6

Thanks to Bill Irwin for pointing this out.

Signed-off-by Nick Piggin <[email protected]>
mm/rmap.c +1 -5
Index: linux-2.6/mm/rmap.c
===================================================================
@@ -448,16 +448,12 @@ void page_add_anon_rmap(struct page *pag
 
 	if (atomic_inc_and_test(&page->_mapcount)) {
 		struct anon_vma *anon_vma = vma->anon_vma;
-		pgoff_t index;
 
 		BUG_ON(!anon_vma);
 		anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
 		page->mapping = (struct address_space *) anon_vma;
 
-		index = (address - vma->vm_start) >> PAGE_SHIFT;
-		index += vma->vm_pgoff;
-		index >>= PAGE_CACHE_SHIFT - PAGE_SHIFT;
-		page->index = index;
+		page->index = linear_page_index(vma, address);
 
 		inc_page_state(nr_mapped);
 	}
author
#4 lore raw

PATCH 4/6 mm: remove atomic

4/6

OK, these first 4 patches don't have much to do with removing PageReserved, but I put them in this series because that's how I have them arranged.

This bitop does not need to be atomic because it is performed when there will be no references to the page (ie. the page is being freed).

Signed-off-by Nick Piggin <[email protected]>
mm/page_alloc.c +1 -1
Index: linux-2.6/mm/page_alloc.c
===================================================================
@@ -329,7 +329,7 @@ static inline void free_pages_check(cons
 			1 << PG_writeback )))
 		bad_page(function, page);
 	if (PageDirty(page))
-		ClearPageDirty(page);
+		__ClearPageDirty(page);
 }
 
 /*
include/linux/page-flags.h +1 -0
Index: linux-2.6/include/linux/page-flags.h
===================================================================
@@ -194,6 +194,7 @@ extern void __mod_page_state(unsigned lo
 #define SetPageDirty(page)	set_bit(PG_dirty, &(page)->flags)
 #define TestSetPageDirty(page)	test_and_set_bit(PG_dirty, &(page)->flags)
 #define ClearPageDirty(page)	clear_bit(PG_dirty, &(page)->flags)
+#define __ClearPageDirty(page)	__clear_bit(PG_dirty, &(page)->flags)
 #define TestClearPageDirty(page) test_and_clear_bit(PG_dirty, &(page)->flags)
 
 #define SetPageLRU(page)	set_bit(PG_lru, &(page)->flags)
author
#5 lore raw

PATCH 5/6 mm: remap ZERO_PAGE mappings

5/6

Remap ZERO_PAGE ptes when remapping memory. This is currently just an optimisation for MIPS, which is the only architecture with multiple zero pages - it now retains the mapping it needs for good cache performance, and as well do_wp_page is now able to always correctly detect and optimise zero page COW faults.

This change is required in order to be able to detect whether a pte points to a ZERO_PAGE using only its (pte, vaddr) pair.

Signed-off-by Nick Piggin <[email protected]>
mm/mremap.c +4 -0
Index: linux-2.6/mm/mremap.c
===================================================================
@@ -141,6 +141,10 @@ move_one_page(struct vm_area_struct *vma
 			if (dst) {
 				pte_t pte;
 				pte = ptep_clear_flush(vma, old_addr, src);
+				/* ZERO_PAGE can be dependant on virtual addr */
+				if (pfn_valid(pte_pfn(pte)) &&
+					pte_page(pte) == ZERO_PAGE(old_addr))
+					pte = pte_wrprotect(mk_pte(ZERO_PAGE(new_addr), new_vma->vm_page_prot));
 				set_pte_at(mm, new_addr, dst, pte);
 			} else
 				error = -ENOMEM;
author
#6 lore raw

PATCH 6/6 mm: core remove PageReserved

6/6

Remove PageReserved() calls from core code by tightening VM_RESERVED handling in mm/ to cover PageReserved functionality.

PageReserved special casing is removed from get_page and put_page.

All setting and clearning of PageReserved is retained, and it is now flagged in the page_alloc checks to help ensure we don't introduce any refcount based freeing of Reserved pages.

MAP_PRIVATE, PROT_WRITE of VM_RESERVED regions is tentatively being deprecated. We never completely handled it correctly anyway, and is difficult to handle nicely - difficult but not impossible, it could be reintroduced in future if required (Hugh has a proof of concept).

Once PageReserved() calls are removed from kernel/power/swsusp.c, and all arch/ and driver code, the Set and Clear calls, and the PG_reserved bit can be trivially removed.

Last real user of PageReserved is swsusp, which uses PageReserved to determine whether a struct page points to valid memory or not. This still needs to be addressed.

Many thanks to Hugh Dickins for input.

Signed-off-by Nick Piggin <[email protected]>
include/linux/mm.h +4 -2
Index: linux-2.6/include/linux/mm.h
===================================================================
@@ -156,7 +156,8 @@ extern unsigned int kobjsize(const void 
 
 #define VM_DONTCOPY	0x00020000      /* Do not copy this vma on fork */
 #define VM_DONTEXPAND	0x00040000	/* Cannot expand with mremap() */
-#define VM_RESERVED	0x00080000	/* Don't unmap it from swap_out */
+#define VM_RESERVED	0x00080000	/* Pages and ptes in region aren't managed with regular pagecache or rmap routines */
+
 #define VM_ACCOUNT	0x00100000	/* Is a VM accounted object */
 #define VM_HUGETLB	0x00400000	/* Huge TLB Page VM */
 #define VM_NONLINEAR	0x00800000	/* Is non-linear (remap_file_pages) */

@@ -337,7 +338,7 @@ static inline void get_page(struct page 
 
 static inline void put_page(struct page *page)
 {
-	if (!PageReserved(page) && put_page_testzero(page))
+	if (put_page_testzero(page))
 		__page_cache_release(page);
 }
 

@@ -711,6 +712,7 @@ void install_arg_page(struct vm_area_str
 
 int get_user_pages(struct task_struct *tsk, struct mm_struct *mm, unsigned long start,
 		int len, int write, int force, struct page **pages, struct vm_area_struct **vmas);
+void print_invalid_pfn(const char *, pte_t, unsigned long, unsigned long);
 
 int __set_page_dirty_buffers(struct page *page);
 int __set_page_dirty_nobuffers(struct page *page);
mm/madvise.c +1 -1
Index: linux-2.6/mm/madvise.c
===================================================================
@@ -126,7 +126,7 @@ static long madvise_dontneed(struct vm_a
 			     unsigned long start, unsigned long end)
 {
 	*prev = vma;
-	if ((vma->vm_flags & VM_LOCKED) || is_vm_hugetlb_page(vma))
+	if ((vma->vm_flags & (VM_LOCKED|VM_RESERVED)) || is_vm_hugetlb_page(vma))
 		return -EINVAL;
 
 	if (unlikely(vma->vm_flags & VM_NONLINEAR)) {
mm/memory.c +79 -46

267 lines not on this page · raw message

mm/page_alloc.c +8 -6
Index: linux-2.6/mm/page_alloc.c
===================================================================
@@ -113,7 +113,8 @@ static void bad_page(const char *functio
 			1 << PG_reclaim |
 			1 << PG_slab    |
 			1 << PG_swapcache |
-			1 << PG_writeback);
+			1 << PG_writeback |
+			1 << PG_reserved );
 	set_page_count(page, 0);
 	reset_page_mapcount(page);
 	page->mapping = NULL;

@@ -243,7 +244,6 @@ static inline int page_is_buddy(struct p
 {
        if (PagePrivate(page)           &&
            (page_order(page) == order) &&
-           !PageReserved(page)         &&
             page_count(page) == 0)
                return 1;
        return 0;

@@ -326,7 +326,8 @@ static inline void free_pages_check(cons
 			1 << PG_reclaim	|
 			1 << PG_slab	|
 			1 << PG_swapcache |
-			1 << PG_writeback )))
+			1 << PG_writeback |
+			1 << PG_reserved )))
 		bad_page(function, page);
 	if (PageDirty(page))
 		__ClearPageDirty(page);

@@ -454,7 +455,8 @@ static void prep_new_page(struct page *p
 			1 << PG_reclaim	|
 			1 << PG_slab    |
 			1 << PG_swapcache |
-			1 << PG_writeback )))
+			1 << PG_writeback |
+			1 << PG_reserved )))
 		bad_page(__FUNCTION__, page);
 
 	page->flags &= ~(1 << PG_uptodate | 1 << PG_error |

@@ -1011,7 +1013,7 @@ void __pagevec_free(struct pagevec *pvec
 
 fastcall void __free_pages(struct page *page, unsigned int order)
 {
-	if (!PageReserved(page) && put_page_testzero(page)) {
+	if (put_page_testzero(page)) {
 		if (order == 0)
 			free_hot_page(page);
 		else

@@ -1654,7 +1656,7 @@ void __init memmap_init_zone(unsigned lo
 			continue;
 		page = pfn_to_page(pfn);
 		set_page_links(page, zone, nid, pfn);
-		set_page_count(page, 0);
+		set_page_count(page, 1);
 		reset_page_mapcount(page);
 		SetPageReserved(page);
 		INIT_LIST_HEAD(&page->lru);
mm/swap.c +2 -2
Index: linux-2.6/mm/swap.c
===================================================================
@@ -48,7 +48,7 @@ void put_page(struct page *page)
 		}
 		return;
 	}
-	if (!PageReserved(page) && put_page_testzero(page))
+	if (put_page_testzero(page))
 		__page_cache_release(page);
 }
 EXPORT_SYMBOL(put_page);

@@ -215,7 +215,7 @@ void release_pages(struct page **pages, 
 		struct page *page = pages[i];
 		struct zone *pagezone;
 
-		if (PageReserved(page) || !put_page_testzero(page))
+		if (!put_page_testzero(page))
 			continue;
 
 		pagezone = page_zone(page);
mm/fremap.c +16 -9
Index: linux-2.6/mm/fremap.c
===================================================================
@@ -29,18 +29,21 @@ static inline void zap_pte(struct mm_str
 		return;
 	if (pte_present(pte)) {
 		unsigned long pfn = pte_pfn(pte);
+		struct page *page;
 
 		flush_cache_page(vma, addr, pfn);
 		pte = ptep_clear_flush(vma, addr, ptep);
-		if (pfn_valid(pfn)) {
-			struct page *page = pfn_to_page(pfn);
-			if (!PageReserved(page)) {
-				if (pte_dirty(pte))
-					set_page_dirty(page);
-				page_remove_rmap(page);
-				page_cache_release(page);
-				dec_mm_counter(mm, rss);
-			}
+		if (unlikely(!pfn_valid(pfn))) {
+			print_invalid_pfn("zap_pte", pte, vma->vm_flags, addr);
+			return;
+		}
+		page = pfn_to_page(pfn);
+		if (page != ZERO_PAGE(addr)) {
+			if (pte_dirty(pte))
+				set_page_dirty(page);
+			page_remove_rmap(page);
+			dec_mm_counter(mm, rss);
+			page_cache_release(page);
 		}
 	} else {
 		if (!pte_file(pte))

@@ -65,6 +68,8 @@ int install_page(struct mm_struct *mm, s
 	pgd_t *pgd;
 	pte_t pte_val;
 
+	BUG_ON(vma->vm_flags & VM_RESERVED);
+
 	pgd = pgd_offset(mm, addr);
 	spin_lock(&mm->page_table_lock);
 	

@@ -122,6 +127,8 @@ int install_file_pte(struct mm_struct *m
 	pgd_t *pgd;
 	pte_t pte_val;
 
+	BUG_ON(vma->vm_flags & VM_RESERVED);
+
 	pgd = pgd_offset(mm, addr);
 	spin_lock(&mm->page_table_lock);
mm/msync.c +7 -3
Index: linux-2.6/mm/msync.c
===================================================================
@@ -37,11 +37,12 @@ static void sync_pte_range(struct vm_are
 		if (!pte_maybe_dirty(*pte))
 			continue;
 		pfn = pte_pfn(*pte);
-		if (!pfn_valid(pfn))
+		if (unlikely(!pfn_valid(pfn))) {
+			print_invalid_pfn("sync_pte_range", *pte,
+							vma->vm_flags, addr);
 			continue;
+		}
 		page = pfn_to_page(pfn);
-		if (PageReserved(page))
-			continue;
 
 		if (ptep_clear_flush_dirty(vma, addr, pte) ||
 		    page_test_and_clear_dirty(page))

@@ -149,6 +150,9 @@ static int msync_interval(struct vm_area
 	if ((flags & MS_INVALIDATE) && (vma->vm_flags & VM_LOCKED))
 		return -EBUSY;
 
+	if (vma->vm_flags & VM_RESERVED)
+		return -EINVAL;
+
 	if (file && (vma->vm_flags & VM_SHARED)) {
 		filemap_sync(vma, addr, end);
mm/rmap.c +5 -10
Index: linux-2.6/mm/rmap.c
===================================================================
@@ -442,8 +442,6 @@ int page_referenced(struct page *page, i
 void page_add_anon_rmap(struct page *page,
 	struct vm_area_struct *vma, unsigned long address)
 {
-	BUG_ON(PageReserved(page));
-
 	inc_mm_counter(vma->vm_mm, anon_rss);
 
 	if (atomic_inc_and_test(&page->_mapcount)) {

@@ -469,8 +467,7 @@ void page_add_anon_rmap(struct page *pag
 void page_add_file_rmap(struct page *page)
 {
 	BUG_ON(PageAnon(page));
-	if (!pfn_valid(page_to_pfn(page)) || PageReserved(page))
-		return;
+	BUG_ON(!pfn_valid(page_to_pfn(page)));
 
 	if (atomic_inc_and_test(&page->_mapcount))
 		inc_page_state(nr_mapped);

@@ -484,8 +481,6 @@ void page_add_file_rmap(struct page *pag
  */
 void page_remove_rmap(struct page *page)
 {
-	BUG_ON(PageReserved(page));
-
 	if (atomic_add_negative(-1, &page->_mapcount)) {
 		BUG_ON(page_mapcount(page) < 0);
 		/*

@@ -643,13 +638,14 @@ static void try_to_unmap_cluster(unsigne
 			continue;
 
 		pfn = pte_pfn(*pte);
-		if (!pfn_valid(pfn))
+		if (unlikely(!pfn_valid(pfn))) {
+			print_invalid_pfn("try_to_unmap_cluster", *pte,
+							vma->vm_flags, address);
 			continue;
+		}
 
 		page = pfn_to_page(pfn);
 		BUG_ON(PageAnon(page));
-		if (PageReserved(page))
-			continue;
 
 		if (ptep_clear_flush_young(vma, address, pte))
 			continue;

@@ -812,7 +808,6 @@ int try_to_unmap(struct page *page)
 {
 	int ret;
 
-	BUG_ON(PageReserved(page));
 	BUG_ON(!PageLocked(page));
 
 	if (PageAnon(page))
drivers/scsi/sg.c +8 -4
Index: linux-2.6/drivers/scsi/sg.c
===================================================================
@@ -1887,13 +1887,17 @@ st_unmap_user_pages(struct scatterlist *
 	int i;
 
 	for (i=0; i < nr_pages; i++) {
-		if (dirtied && !PageReserved(sgl[i].page))
-			SetPageDirty(sgl[i].page);
-		/* unlock_page(sgl[i].page); */
+		struct page *page = sgl[i].page;
+
+		/* XXX: just for debug. Remove when PageReserved is removed */
+		BUG_ON(PageReserved(page));
+		if (dirtied)
+			SetPageDirty(page);
+		/* unlock_page(page); */
 		/* FIXME: cache flush missing for rw==READ
 		 * FIXME: call the correct reference counting function
 		 */
-		page_cache_release(sgl[i].page);
+		page_cache_release(page);
 	}
 
 	return 0;
drivers/scsi/st.c +7 -3
Index: linux-2.6/drivers/scsi/st.c
===================================================================
@@ -4435,12 +4435,16 @@ static int sgl_unmap_user_pages(struct s
 	int i;
 
 	for (i=0; i < nr_pages; i++) {
-		if (dirtied && !PageReserved(sgl[i].page))
-			SetPageDirty(sgl[i].page);
+		struct page *page = sgl[i].page;
+
+		/* XXX: just for debug. Remove when PageReserved is removed */
+		BUG_ON(PageReserved(page));
+		if (dirtied)
+			SetPageDirty(page);
 		/* FIXME: cache flush missing for rw==READ
 		 * FIXME: call the correct reference counting function
 		 */
-		page_cache_release(sgl[i].page);
+		page_cache_release(page);
 	}
 
 	return 0;
sound/core/pcm_native.c +3 -6
Index: linux-2.6/sound/core/pcm_native.c
===================================================================
@@ -2944,8 +2944,7 @@ static struct page * snd_pcm_mmap_status
 		return NOPAGE_OOM;
 	runtime = substream->runtime;
 	page = virt_to_page(runtime->status);
-	if (!PageReserved(page))
-		get_page(page);
+	get_page(page);
 	if (type)
 		*type = VM_FAULT_MINOR;
 	return page;

@@ -2987,8 +2986,7 @@ static struct page * snd_pcm_mmap_contro
 		return NOPAGE_OOM;
 	runtime = substream->runtime;
 	page = virt_to_page(runtime->control);
-	if (!PageReserved(page))
-		get_page(page);
+	get_page(page);
 	if (type)
 		*type = VM_FAULT_MINOR;
 	return page;

@@ -3061,8 +3059,7 @@ static struct page *snd_pcm_mmap_data_no
 		vaddr = runtime->dma_area + offset;
 		page = virt_to_page(vaddr);
 	}
-	if (!PageReserved(page))
-		get_page(page);
+	get_page(page);
 	if (type)
 		*type = VM_FAULT_MINOR;
 	return page;
mm/mmap.c +11 -0
Index: linux-2.6/mm/mmap.c
===================================================================
@@ -1073,6 +1073,17 @@ munmap_back:
 		error = file->f_op->mmap(file, vma);
 		if (error)
 			goto unmap_and_free_vma;
+		if ((vma->vm_flags & (VM_SHARED | VM_WRITE | VM_RESERVED))
+						== (VM_WRITE | VM_RESERVED)) {
+			printk(KERN_WARNING "program %s is using MAP_PRIVATE, "
+				"PROT_WRITE mmap of VM_RESERVED memory, which "
+				"is deprecated. Please report this to "
+				"[email protected]\n",current->comm);
+			if (vma->vm_ops && vma->vm_ops->close)
+				vma->vm_ops->close(vma);
+			error = -EACCES;
+			goto unmap_and_free_vma;
+		}
 	} else if (vm_flags & VM_SHARED) {
 		error = shmem_zero_setup(vma);
 		if (error)
mm/mprotect.c +8 -0
Index: linux-2.6/mm/mprotect.c
===================================================================
@@ -131,6 +131,14 @@ mprotect_fixup(struct vm_area_struct *vm
 				return -ENOMEM;
 			newflags |= VM_ACCOUNT;
 		}
+		if (oldflags & VM_RESERVED) {
+			BUG_ON(oldflags & VM_WRITE);
+			printk(KERN_WARNING "program %s is using MAP_PRIVATE, "
+				"PROT_WRITE mprotect of VM_RESERVED memory, "
+				"which is deprecated. Please report this to "
+				"[email protected]\n",current->comm);
+			return -EACCES;
+		}
 	}
 
 	newprot = protection_map[newflags & 0xf];
mm/bootmem.c +1 -0
Index: linux-2.6/mm/bootmem.c
===================================================================
@@ -297,6 +297,7 @@ static unsigned long __init free_all_boo
 				if (j + 16 < BITS_PER_LONG)
 					prefetchw(page + j + 16);
 				__ClearPageReserved(page + j);
+				set_page_count(page + j, 0);
 			}
 			__free_pages(page, order);
 			i += BITS_PER_LONG;
mm/mempolicy.c +5 -1
Index: linux-2.6/mm/mempolicy.c
===================================================================
@@ -253,8 +253,10 @@ static int check_pte_range(struct mm_str
 		if (!pte_present(*pte))
 			continue;
 		pfn = pte_pfn(*pte);
-		if (!pfn_valid(pfn))
+		if (unlikely(!pfn_valid(pfn))) {
+			print_invalid_pfn("check_pte_range", *pte, -1UL, addr);
 			continue;
+		}
 		nid = pfn_to_nid(pfn);
 		if (!test_bit(nid, nodes))
 			break;

@@ -326,6 +328,8 @@ check_range(struct mm_struct *mm, unsign
 	first = find_vma(mm, start);
 	if (!first)
 		return ERR_PTR(-EFAULT);
+	if (first->vm_flags & VM_RESERVED)
+		return ERR_PTR(-EACCES);
 	prev = NULL;
 	for (vma = first; vma && vma->vm_start < end; vma = vma->vm_next) {
 		if (!vma->vm_next && vma->vm_end < end)
arch/ppc64/kernel/vdso.c +6 -4
Index: linux-2.6/arch/ppc64/kernel/vdso.c
===================================================================
@@ -176,13 +176,13 @@ static struct page * vdso_vma_nopage(str
 		return NOPAGE_SIGBUS;
 
 	/*
-	 * Last page is systemcfg, special handling here, no get_page() a
-	 * this is a reserved page
+	 * Last page is systemcfg.
 	 */
 	if ((vma->vm_end - address) <= PAGE_SIZE)
-		return virt_to_page(systemcfg);
+		pg = virt_to_page(systemcfg);
+	else
+		pg = virt_to_page(vbase + offset);
 
-	pg = virt_to_page(vbase + offset);
 	get_page(pg);
 	DBG(" ->page count: %d\n", page_count(pg));
 

@@ -600,6 +600,8 @@ void __init vdso_init(void)
 		ClearPageReserved(pg);
 		get_page(pg);
 	}
+
+	get_page(virt_to_page(systemcfg));
 }
 
 int in_gate_area_no_task(unsigned long addr)
kernel/power/swsusp.c +16 -9
Index: linux-2.6/kernel/power/swsusp.c
===================================================================
@@ -434,15 +434,23 @@ static int save_highmem_zone(struct zone
 			continue;
 		page = pfn_to_page(pfn);
 		/*
-		 * This condition results from rvmalloc() sans vmalloc_32()
-		 * and architectural memory reservations. This should be
-		 * corrected eventually when the cases giving rise to this
-		 * are better understood.
+		 * PageReserved results from rvmalloc() sans vmalloc_32()
+		 * and architectural memory reservations.
+		 *
+		 * rvmalloc should not cause this, because all implementations
+		 * appear to always be using vmalloc_32 on architectures with
+		 * highmem. This is a good thing, because we would like to save
+		 * rvmalloc pages.
+		 *
+		 * It appears to be triggered by pages which do not point to
+		 * valid memory (see arch/i386/mm/init.c:one_highpage_init(),
+		 * which sets PageReserved if the page does not point to valid
+		 * RAM.
+		 *
+		 * XXX: must remove usage of PageReserved!
 		 */
-		if (PageReserved(page)) {
-			printk("highmem reserved page?!\n");
+		if (PageReserved(page))
 			continue;
-		}
 		BUG_ON(PageNosave(page));
 		if (PageNosaveFree(page))
 			continue;

@@ -528,10 +536,9 @@ static int saveable(struct zone * zone, 
 		return 0;
 
 	page = pfn_to_page(pfn);
-	BUG_ON(PageReserved(page) && PageNosave(page));
 	if (PageNosave(page))
 		return 0;
-	if (PageReserved(page) && pfn_is_nosave(pfn)) {
+	if (pfn_is_nosave(pfn)) {
 		pr_debug("[nosave pfn 0x%lx]", pfn);
 		return 0;
 	}
mm/shmem.c +2 -1
Index: linux-2.6/mm/shmem.c
===================================================================
@@ -1523,7 +1523,8 @@ static void do_shmem_file_read(struct fi
 		index += offset >> PAGE_CACHE_SHIFT;
 		offset &= ~PAGE_CACHE_MASK;
 
-		page_cache_release(page);
+		if (page != ZERO_PAGE(0))
+			page_cache_release(page);
 		if (ret != nr || !desc->count)
 			break;
author
#7 lore raw

PATCH 6/6 mm: core remove PageReserved (take 2)

Quoted 2 lines · Nick Piggin

6/6

Actually I think Hugh gave me some feedback about the introduced print_invalid_pfn function, which I ignored.

So here is patch 6 again, with print_invalid_pfn renamed invalid_pfn, and using a macro to alleviate the requirement of passing in the function name by hand.

Remove PageReserved() calls from core code by tightening VM_RESERVED handling in mm/ to cover PageReserved functionality.

PageReserved special casing is removed from get_page and put_page.

All setting and clearning of PageReserved is retained, and it is now flagged in the page_alloc checks to help ensure we don't introduce any refcount based freeing of Reserved pages.

MAP_PRIVATE, PROT_WRITE of VM_RESERVED regions is tentatively being deprecated. We never completely handled it correctly anyway, and is difficult to handle nicely - difficult but not impossible, it could be reintroduced in future if required (Hugh has a proof of concept).

Once PageReserved() calls are removed from kernel/power/swsusp.c, and all arch/ and driver code, the Set and Clear calls, and the PG_reserved bit can be trivially removed.

Last real user of PageReserved is swsusp, which uses PageReserved to determine whether a struct page points to valid memory or not. This still needs to be addressed.

Many thanks to Hugh Dickins for input.

Signed-off-by Nick Piggin <[email protected]>
include/linux/mm.h +6 -2
Index: linux-2.6/include/linux/mm.h
===================================================================
@@ -156,7 +156,8 @@ extern unsigned int kobjsize(const void 
 
 #define VM_DONTCOPY	0x00020000      /* Do not copy this vma on fork */
 #define VM_DONTEXPAND	0x00040000	/* Cannot expand with mremap() */
-#define VM_RESERVED	0x00080000	/* Don't unmap it from swap_out */
+#define VM_RESERVED	0x00080000	/* Pages and ptes in region aren't managed with regular pagecache or rmap routines */
+
 #define VM_ACCOUNT	0x00100000	/* Is a VM accounted object */
 #define VM_HUGETLB	0x00400000	/* Huge TLB Page VM */
 #define VM_NONLINEAR	0x00800000	/* Is non-linear (remap_file_pages) */

@@ -337,7 +338,7 @@ static inline void get_page(struct page 
 
 static inline void put_page(struct page *page)
 {
-	if (!PageReserved(page) && put_page_testzero(page))
+	if (put_page_testzero(page))
 		__page_cache_release(page);
 }
 

@@ -711,6 +712,9 @@ void install_arg_page(struct vm_area_str
 
 int get_user_pages(struct task_struct *tsk, struct mm_struct *mm, unsigned long start,
 		int len, int write, int force, struct page **pages, struct vm_area_struct **vmas);
+#define invalid_pfn(pte, vm_flags, vaddr)		\
+		__invalid_pfn(__FUNCTION__, pte, vm_flags, vaddr)
+void __invalid_pfn(const char *, pte_t, unsigned long, unsigned long);
 
 int __set_page_dirty_buffers(struct page *page);
 int __set_page_dirty_nobuffers(struct page *page);
mm/madvise.c +1 -1
Index: linux-2.6/mm/madvise.c
===================================================================
@@ -126,7 +126,7 @@ static long madvise_dontneed(struct vm_a
 			     unsigned long start, unsigned long end)
 {
 	*prev = vma;
-	if ((vma->vm_flags & VM_LOCKED) || is_vm_hugetlb_page(vma))
+	if ((vma->vm_flags & (VM_LOCKED|VM_RESERVED)) || is_vm_hugetlb_page(vma))
 		return -EINVAL;
 
 	if (unlikely(vma->vm_flags & VM_NONLINEAR)) {
mm/memory.c +78 -46

266 lines not on this page · raw message

mm/page_alloc.c +8 -6
Index: linux-2.6/mm/page_alloc.c
===================================================================
@@ -113,7 +113,8 @@ static void bad_page(const char *functio
 			1 << PG_reclaim |
 			1 << PG_slab    |
 			1 << PG_swapcache |
-			1 << PG_writeback);
+			1 << PG_writeback |
+			1 << PG_reserved );
 	set_page_count(page, 0);
 	reset_page_mapcount(page);
 	page->mapping = NULL;

@@ -243,7 +244,6 @@ static inline int page_is_buddy(struct p
 {
        if (PagePrivate(page)           &&
            (page_order(page) == order) &&
-           !PageReserved(page)         &&
             page_count(page) == 0)
                return 1;
        return 0;

@@ -326,7 +326,8 @@ static inline void free_pages_check(cons
 			1 << PG_reclaim	|
 			1 << PG_slab	|
 			1 << PG_swapcache |
-			1 << PG_writeback )))
+			1 << PG_writeback |
+			1 << PG_reserved )))
 		bad_page(function, page);
 	if (PageDirty(page))
 		__ClearPageDirty(page);

@@ -454,7 +455,8 @@ static void prep_new_page(struct page *p
 			1 << PG_reclaim	|
 			1 << PG_slab    |
 			1 << PG_swapcache |
-			1 << PG_writeback )))
+			1 << PG_writeback |
+			1 << PG_reserved )))
 		bad_page(__FUNCTION__, page);
 
 	page->flags &= ~(1 << PG_uptodate | 1 << PG_error |

@@ -1011,7 +1013,7 @@ void __pagevec_free(struct pagevec *pvec
 
 fastcall void __free_pages(struct page *page, unsigned int order)
 {
-	if (!PageReserved(page) && put_page_testzero(page)) {
+	if (put_page_testzero(page)) {
 		if (order == 0)
 			free_hot_page(page);
 		else

@@ -1654,7 +1656,7 @@ void __init memmap_init_zone(unsigned lo
 			continue;
 		page = pfn_to_page(pfn);
 		set_page_links(page, zone, nid, pfn);
-		set_page_count(page, 0);
+		set_page_count(page, 1);
 		reset_page_mapcount(page);
 		SetPageReserved(page);
 		INIT_LIST_HEAD(&page->lru);
mm/swap.c +2 -2
Index: linux-2.6/mm/swap.c
===================================================================
@@ -48,7 +48,7 @@ void put_page(struct page *page)
 		}
 		return;
 	}
-	if (!PageReserved(page) && put_page_testzero(page))
+	if (put_page_testzero(page))
 		__page_cache_release(page);
 }
 EXPORT_SYMBOL(put_page);

@@ -215,7 +215,7 @@ void release_pages(struct page **pages, 
 		struct page *page = pages[i];
 		struct zone *pagezone;
 
-		if (PageReserved(page) || !put_page_testzero(page))
+		if (!put_page_testzero(page))
 			continue;
 
 		pagezone = page_zone(page);
mm/fremap.c +16 -9
Index: linux-2.6/mm/fremap.c
===================================================================
@@ -29,18 +29,21 @@ static inline void zap_pte(struct mm_str
 		return;
 	if (pte_present(pte)) {
 		unsigned long pfn = pte_pfn(pte);
+		struct page *page;
 
 		flush_cache_page(vma, addr, pfn);
 		pte = ptep_clear_flush(vma, addr, ptep);
-		if (pfn_valid(pfn)) {
-			struct page *page = pfn_to_page(pfn);
-			if (!PageReserved(page)) {
-				if (pte_dirty(pte))
-					set_page_dirty(page);
-				page_remove_rmap(page);
-				page_cache_release(page);
-				dec_mm_counter(mm, rss);
-			}
+		if (unlikely(!pfn_valid(pfn))) {
+			invalid_pfn(pte, vma->vm_flags, addr);
+			return;
+		}
+		page = pfn_to_page(pfn);
+		if (page != ZERO_PAGE(addr)) {
+			if (pte_dirty(pte))
+				set_page_dirty(page);
+			page_remove_rmap(page);
+			dec_mm_counter(mm, rss);
+			page_cache_release(page);
 		}
 	} else {
 		if (!pte_file(pte))

@@ -65,6 +68,8 @@ int install_page(struct mm_struct *mm, s
 	pgd_t *pgd;
 	pte_t pte_val;
 
+	BUG_ON(vma->vm_flags & VM_RESERVED);
+
 	pgd = pgd_offset(mm, addr);
 	spin_lock(&mm->page_table_lock);
 	

@@ -122,6 +127,8 @@ int install_file_pte(struct mm_struct *m
 	pgd_t *pgd;
 	pte_t pte_val;
 
+	BUG_ON(vma->vm_flags & VM_RESERVED);
+
 	pgd = pgd_offset(mm, addr);
 	spin_lock(&mm->page_table_lock);
mm/msync.c +6 -3
Index: linux-2.6/mm/msync.c
===================================================================
@@ -37,11 +37,11 @@ static void sync_pte_range(struct vm_are
 		if (!pte_maybe_dirty(*pte))
 			continue;
 		pfn = pte_pfn(*pte);
-		if (!pfn_valid(pfn))
+		if (unlikely(!pfn_valid(pfn))) {
+			invalid_pfn(*pte, vma->vm_flags, addr);
 			continue;
+		}
 		page = pfn_to_page(pfn);
-		if (PageReserved(page))
-			continue;
 
 		if (ptep_clear_flush_dirty(vma, addr, pte) ||
 		    page_test_and_clear_dirty(page))

@@ -149,6 +149,9 @@ static int msync_interval(struct vm_area
 	if ((flags & MS_INVALIDATE) && (vma->vm_flags & VM_LOCKED))
 		return -EBUSY;
 
+	if (vma->vm_flags & VM_RESERVED)
+		return -EINVAL;
+
 	if (file && (vma->vm_flags & VM_SHARED)) {
 		filemap_sync(vma, addr, end);
mm/rmap.c +4 -10
Index: linux-2.6/mm/rmap.c
===================================================================
@@ -442,8 +442,6 @@ int page_referenced(struct page *page, i
 void page_add_anon_rmap(struct page *page,
 	struct vm_area_struct *vma, unsigned long address)
 {
-	BUG_ON(PageReserved(page));
-
 	inc_mm_counter(vma->vm_mm, anon_rss);
 
 	if (atomic_inc_and_test(&page->_mapcount)) {

@@ -469,8 +467,7 @@ void page_add_anon_rmap(struct page *pag
 void page_add_file_rmap(struct page *page)
 {
 	BUG_ON(PageAnon(page));
-	if (!pfn_valid(page_to_pfn(page)) || PageReserved(page))
-		return;
+	BUG_ON(!pfn_valid(page_to_pfn(page)));
 
 	if (atomic_inc_and_test(&page->_mapcount))
 		inc_page_state(nr_mapped);

@@ -484,8 +481,6 @@ void page_add_file_rmap(struct page *pag
  */
 void page_remove_rmap(struct page *page)
 {
-	BUG_ON(PageReserved(page));
-
 	if (atomic_add_negative(-1, &page->_mapcount)) {
 		BUG_ON(page_mapcount(page) < 0);
 		/*

@@ -643,13 +638,13 @@ static void try_to_unmap_cluster(unsigne
 			continue;
 
 		pfn = pte_pfn(*pte);
-		if (!pfn_valid(pfn))
+		if (unlikely(!pfn_valid(pfn))) {
+			invalid_pfn(*pte, vma->vm_flags, address);
 			continue;
+		}
 
 		page = pfn_to_page(pfn);
 		BUG_ON(PageAnon(page));
-		if (PageReserved(page))
-			continue;
 
 		if (ptep_clear_flush_young(vma, address, pte))
 			continue;

@@ -812,7 +807,6 @@ int try_to_unmap(struct page *page)
 {
 	int ret;
 
-	BUG_ON(PageReserved(page));
 	BUG_ON(!PageLocked(page));
 
 	if (PageAnon(page))
drivers/scsi/sg.c +8 -4
Index: linux-2.6/drivers/scsi/sg.c
===================================================================
@@ -1887,13 +1887,17 @@ st_unmap_user_pages(struct scatterlist *
 	int i;
 
 	for (i=0; i < nr_pages; i++) {
-		if (dirtied && !PageReserved(sgl[i].page))
-			SetPageDirty(sgl[i].page);
-		/* unlock_page(sgl[i].page); */
+		struct page *page = sgl[i].page;
+
+		/* XXX: just for debug. Remove when PageReserved is removed */
+		BUG_ON(PageReserved(page));
+		if (dirtied)
+			SetPageDirty(page);
+		/* unlock_page(page); */
 		/* FIXME: cache flush missing for rw==READ
 		 * FIXME: call the correct reference counting function
 		 */
-		page_cache_release(sgl[i].page);
+		page_cache_release(page);
 	}
 
 	return 0;
drivers/scsi/st.c +7 -3
Index: linux-2.6/drivers/scsi/st.c
===================================================================
@@ -4435,12 +4435,16 @@ static int sgl_unmap_user_pages(struct s
 	int i;
 
 	for (i=0; i < nr_pages; i++) {
-		if (dirtied && !PageReserved(sgl[i].page))
-			SetPageDirty(sgl[i].page);
+		struct page *page = sgl[i].page;
+
+		/* XXX: just for debug. Remove when PageReserved is removed */
+		BUG_ON(PageReserved(page));
+		if (dirtied)
+			SetPageDirty(page);
 		/* FIXME: cache flush missing for rw==READ
 		 * FIXME: call the correct reference counting function
 		 */
-		page_cache_release(sgl[i].page);
+		page_cache_release(page);
 	}
 
 	return 0;
sound/core/pcm_native.c +3 -6
Index: linux-2.6/sound/core/pcm_native.c
===================================================================
@@ -2944,8 +2944,7 @@ static struct page * snd_pcm_mmap_status
 		return NOPAGE_OOM;
 	runtime = substream->runtime;
 	page = virt_to_page(runtime->status);
-	if (!PageReserved(page))
-		get_page(page);
+	get_page(page);
 	if (type)
 		*type = VM_FAULT_MINOR;
 	return page;

@@ -2987,8 +2986,7 @@ static struct page * snd_pcm_mmap_contro
 		return NOPAGE_OOM;
 	runtime = substream->runtime;
 	page = virt_to_page(runtime->control);
-	if (!PageReserved(page))
-		get_page(page);
+	get_page(page);
 	if (type)
 		*type = VM_FAULT_MINOR;
 	return page;

@@ -3061,8 +3059,7 @@ static struct page *snd_pcm_mmap_data_no
 		vaddr = runtime->dma_area + offset;
 		page = virt_to_page(vaddr);
 	}
-	if (!PageReserved(page))
-		get_page(page);
+	get_page(page);
 	if (type)
 		*type = VM_FAULT_MINOR;
 	return page;
mm/mmap.c +11 -0
Index: linux-2.6/mm/mmap.c
===================================================================
@@ -1073,6 +1073,17 @@ munmap_back:
 		error = file->f_op->mmap(file, vma);
 		if (error)
 			goto unmap_and_free_vma;
+		if ((vma->vm_flags & (VM_SHARED | VM_WRITE | VM_RESERVED))
+						== (VM_WRITE | VM_RESERVED)) {
+			printk(KERN_WARNING "program %s is using MAP_PRIVATE, "
+				"PROT_WRITE mmap of VM_RESERVED memory, which "
+				"is deprecated. Please report this to "
+				"[email protected]\n",current->comm);
+			if (vma->vm_ops && vma->vm_ops->close)
+				vma->vm_ops->close(vma);
+			error = -EACCES;
+			goto unmap_and_free_vma;
+		}
 	} else if (vm_flags & VM_SHARED) {
 		error = shmem_zero_setup(vma);
 		if (error)
mm/mprotect.c +8 -0
Index: linux-2.6/mm/mprotect.c
===================================================================
@@ -131,6 +131,14 @@ mprotect_fixup(struct vm_area_struct *vm
 				return -ENOMEM;
 			newflags |= VM_ACCOUNT;
 		}
+		if (oldflags & VM_RESERVED) {
+			BUG_ON(oldflags & VM_WRITE);
+			printk(KERN_WARNING "program %s is using MAP_PRIVATE, "
+				"PROT_WRITE mprotect of VM_RESERVED memory, "
+				"which is deprecated. Please report this to "
+				"[email protected]\n",current->comm);
+			return -EACCES;
+		}
 	}
 
 	newprot = protection_map[newflags & 0xf];
mm/bootmem.c +1 -0
Index: linux-2.6/mm/bootmem.c
===================================================================
@@ -297,6 +297,7 @@ static unsigned long __init free_all_boo
 				if (j + 16 < BITS_PER_LONG)
 					prefetchw(page + j + 16);
 				__ClearPageReserved(page + j);
+				set_page_count(page + j, 0);
 			}
 			__free_pages(page, order);
 			i += BITS_PER_LONG;
mm/mempolicy.c +5 -1
Index: linux-2.6/mm/mempolicy.c
===================================================================
@@ -253,8 +253,10 @@ static int check_pte_range(struct mm_str
 		if (!pte_present(*pte))
 			continue;
 		pfn = pte_pfn(*pte);
-		if (!pfn_valid(pfn))
+		if (unlikely(!pfn_valid(pfn))) {
+			invalid_pfn(*pte, -1UL, addr);
 			continue;
+		}
 		nid = pfn_to_nid(pfn);
 		if (!test_bit(nid, nodes))
 			break;

@@ -326,6 +328,8 @@ check_range(struct mm_struct *mm, unsign
 	first = find_vma(mm, start);
 	if (!first)
 		return ERR_PTR(-EFAULT);
+	if (first->vm_flags & VM_RESERVED)
+		return ERR_PTR(-EACCES);
 	prev = NULL;
 	for (vma = first; vma && vma->vm_start < end; vma = vma->vm_next) {
 		if (!vma->vm_next && vma->vm_end < end)
arch/ppc64/kernel/vdso.c +6 -4
Index: linux-2.6/arch/ppc64/kernel/vdso.c
===================================================================
@@ -176,13 +176,13 @@ static struct page * vdso_vma_nopage(str
 		return NOPAGE_SIGBUS;
 
 	/*
-	 * Last page is systemcfg, special handling here, no get_page() a
-	 * this is a reserved page
+	 * Last page is systemcfg.
 	 */
 	if ((vma->vm_end - address) <= PAGE_SIZE)
-		return virt_to_page(systemcfg);
+		pg = virt_to_page(systemcfg);
+	else
+		pg = virt_to_page(vbase + offset);
 
-	pg = virt_to_page(vbase + offset);
 	get_page(pg);
 	DBG(" ->page count: %d\n", page_count(pg));
 

@@ -600,6 +600,8 @@ void __init vdso_init(void)
 		ClearPageReserved(pg);
 		get_page(pg);
 	}
+
+	get_page(virt_to_page(systemcfg));
 }
 
 int in_gate_area_no_task(unsigned long addr)
kernel/power/swsusp.c +16 -9
Index: linux-2.6/kernel/power/swsusp.c
===================================================================
@@ -434,15 +434,23 @@ static int save_highmem_zone(struct zone
 			continue;
 		page = pfn_to_page(pfn);
 		/*
-		 * This condition results from rvmalloc() sans vmalloc_32()
-		 * and architectural memory reservations. This should be
-		 * corrected eventually when the cases giving rise to this
-		 * are better understood.
+		 * PageReserved results from rvmalloc() sans vmalloc_32()
+		 * and architectural memory reservations.
+		 *
+		 * rvmalloc should not cause this, because all implementations
+		 * appear to always be using vmalloc_32 on architectures with
+		 * highmem. This is a good thing, because we would like to save
+		 * rvmalloc pages.
+		 *
+		 * It appears to be triggered by pages which do not point to
+		 * valid memory (see arch/i386/mm/init.c:one_highpage_init(),
+		 * which sets PageReserved if the page does not point to valid
+		 * RAM.
+		 *
+		 * XXX: must remove usage of PageReserved!
 		 */
-		if (PageReserved(page)) {
-			printk("highmem reserved page?!\n");
+		if (PageReserved(page))
 			continue;
-		}
 		BUG_ON(PageNosave(page));
 		if (PageNosaveFree(page))
 			continue;

@@ -528,10 +536,9 @@ static int saveable(struct zone * zone, 
 		return 0;
 
 	page = pfn_to_page(pfn);
-	BUG_ON(PageReserved(page) && PageNosave(page));
 	if (PageNosave(page))
 		return 0;
-	if (PageReserved(page) && pfn_is_nosave(pfn)) {
+	if (pfn_is_nosave(pfn)) {
 		pr_debug("[nosave pfn 0x%lx]", pfn);
 		return 0;
 	}
mm/shmem.c +2 -1
Index: linux-2.6/mm/shmem.c
===================================================================
@@ -1523,7 +1523,8 @@ static void do_shmem_file_read(struct fi
 		index += offset >> PAGE_CACHE_SHIFT;
 		offset &= ~PAGE_CACHE_MASK;
 
-		page_cache_release(page);
+		if (page != ZERO_PAGE(0))
+			page_cache_release(page);
 		if (ret != nr || !desc->count)
 			break;
#8 lore raw

Re: [patch 2/6] mm: micro-optimise rmap

In reply to Nick Piggin

[Nick, your mail bounced while sending this privately so reply-all this time]

Quoted 25 lines

Index: linux-2.6/mm/rmap.c
===================================================================

mm/rmap.c +2 -10
@@ -442,22 +442,23 @@ int page_referenced(struct page *page, i
 void page_add_anon_rmap(struct page *page,
 	struct vm_area_struct *vma, unsigned long address)
 {
-	struct anon_vma *anon_vma = vma->anon_vma;
-	pgoff_t index;
-
 	BUG_ON(PageReserved(page));
-	BUG_ON(!anon_vma);
 
 	inc_mm_counter(vma->vm_mm, anon_rss);
 
-	anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
-	index = (address - vma->vm_start) >> PAGE_SHIFT;
-	index += vma->vm_pgoff;
-	index >>= PAGE_CACHE_SHIFT - PAGE_SHIFT;
-
 	if (atomic_inc_and_test(&page->_mapcount)) {
-		page->index = index;
+		struct anon_vma *anon_vma = vma->anon_vma;
+		pgoff_t index;

mm/rmap.c int page_referenced(struct page *page, i · line 461

Quoted 10 lines
mm/rmap.c +9 -0
+
+		BUG_ON(!anon_vma);
+		anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
 		page->mapping = (struct address_space *) anon_vma;
+
+		index = (address - vma->vm_start) >> PAGE_SHIFT;
+		index += vma->vm_pgoff;
+		index >>= PAGE_CACHE_SHIFT - PAGE_SHIFT;
+		page->index = index;
+

linear_page_index() here too?

author
#9 lore raw

Re: [patch 2/6] mm: micro-optimise rmap

Quoted 5 lines · Alexander Nyberg
Quoted 1 line

void page_add_anon_rmap(struct page *page,

linear_page_index() here too?

Hi Alexander,

Yes, that's what patch 3/6 did :)

Signature · 3 lines
SUSE Labs, Novell Inc.

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author
#10 lore raw
In reply to Nick Piggin
Quoted 6 lines · Nick Piggin

Hi Andrew,

If you're feeling like -mm is getting too stable, then you might consider giving these patches a spin? (unless anyone else raises an objection).

Patches are against 2.6.13-rc3-git7

Signature · 3 lines
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#11 lore raw
In reply to Nick Piggin
Quoted 12 lines · Nick Piggin

Hi Andrew,

If you're feeling like -mm is getting too stable, then you might consider giving these patches a spin? (unless anyone else raises an objection).

Ben thought I should get moving with them soon.

Not much change from last time. A bit of ppc64 input from Ben, and some rmap.c input from Hugh. Boots and runs on a few machines I have lying around here.

Quoted 7 lines

The only remaining places that *test* PageReserved are swsusp, a trivial useage in drivers/char/agp/amd64-agp.c, and arch/ code.

Most of the arch code is just reserved memory reporting, which isn't very interesting and could easily be removed. Some arch users are a bit more subtle, however they *should not* break, because all the places that set and clear PageReserved are basically intact.

What is the desired fix look like for arch users?

- kumar

author
#12 lore raw
Quoted 9 lines · Kumar Gala
Quoted 5 lines

Most of the arch code is just reserved memory reporting, which isn't very interesting and could easily be removed. Some arch users are a bit more subtle, however they *should not* break, because all the places that set and clear PageReserved are basically intact.

What is the desired fix look like for arch users?

It really depends on how it is used.

Firstly, we want to retain all the places that do SetPageReserved and ClearPageReserved to ensure that remaining places that test PageReserved will continue to work.

So users of PageReserved need to be removed. For example, on i386 this is simply reserved memory accounting - which isn't very meaningful and can probably be simply deleted. i386 ioremap also tests PageReserved to ensure it isn't remapping usable RAM, which is a similar need to swsusp's, so one solution would likely cover that ioremap and swsusp.

For now, the main thing to keep in mind is to not add a new user of PageReserved. We can start looking at how to cut down existing users when the core patch gets into -mm or further upstream.

Nick

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