Commit b5810039 authored by Nick Piggin's avatar Nick Piggin Committed by Linus Torvalds
Browse files

[PATCH] core remove PageReserved 



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 clearing 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 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 (a generic page_is_ram() should work).

A last caveat: the ZERO_PAGE is now refcounted and managed with rmap (and
thus mapcounted and count towards shared rss).  These writes to the struct
page could cause excessive cacheline bouncing on big systems.  There are a
number of ways this could be addressed if it is an issue.

Signed-off-by: default avatarNick Piggin <npiggin@suse.de>

Refcount bug fix for filemap_xip.c

Signed-off-by: default avatarCarsten Otte <cotte@de.ibm.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent f9c98d02

arch/ppc64/kernel/vdso.c

+7 −5
Original line number Diff line number Diff line
@@ -176,13 +176,13 @@ static struct page * vdso_vma_nopage(struct vm_area_struct * vma, 
		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);



	get_page(pg);

	DBG(" ->page count: %d\n", page_count(pg));
@@ -259,7 +259,7 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int executable_stack) 
	 * gettimeofday will be totally dead. It's fine to use that for setting

	 * breakpoints in the vDSO code pages though

	 */

	vma->vm_flags = VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;

	vma->vm_flags = VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC | VM_RESERVED;

	vma->vm_flags |= mm->def_flags;

	vma->vm_page_prot = protection_map[vma->vm_flags & 0x7];

	vma->vm_ops = &vdso_vmops;
@@ -603,6 +603,8 @@ 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)

arch/sparc/mm/generic.c

+3 −0
Original line number Diff line number Diff line
@@ -73,6 +73,9 @@ int io_remap_pfn_range(struct vm_area_struct *vma, unsigned long from, 
	int space = GET_IOSPACE(pfn);

	unsigned long offset = GET_PFN(pfn) << PAGE_SHIFT;



	/* See comment in mm/memory.c remap_pfn_range */

	vma->vm_flags |= VM_IO | VM_RESERVED;



	prot = __pgprot(pg_iobits);

	offset -= from;

	dir = pgd_offset(mm, from);

arch/sparc64/mm/generic.c

+3 −0
Original line number Diff line number Diff line
@@ -127,6 +127,9 @@ int io_remap_pfn_range(struct vm_area_struct *vma, unsigned long from, 
	int space = GET_IOSPACE(pfn);

	unsigned long offset = GET_PFN(pfn) << PAGE_SHIFT;



	/* See comment in mm/memory.c remap_pfn_range */

	vma->vm_flags |= VM_IO | VM_RESERVED;



	prot = __pgprot(pg_iobits);

	offset -= from;

	dir = pgd_offset(mm, from);

drivers/scsi/sg.c

+8 −4
Original line number Diff line number Diff line
@@ -1886,13 +1886,17 @@ st_unmap_user_pages(struct scatterlist *sgl, const unsigned int nr_pages, 
	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
Original line number Diff line number Diff line
@@ -4526,12 +4526,16 @@ static int sgl_unmap_user_pages(struct scatterlist *sgl, const unsigned int nr_p 
	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;

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