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Commit 238f58d8 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Support strange discontiguous PFN remappings 



These get created by some drivers that don't generally even want a pfn
remapping at all, but would really mostly prefer to just map pages
they've allocated individually instead.

For now, create a helper function that turns such an incomplete PFN
remapping call into a loop that does that explicit mapping.  In the long
run we almost certainly want to export a totally different interface for
that, though.

Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent eca35133

include/linux/mm.h

+1 −0
Original line number Original line Diff line number Diff line
@@ -163,6 +163,7 @@ extern unsigned int kobjsize(const void *objp); 
#define VM_HUGETLB	0x00400000	/* Huge TLB Page VM */

#define VM_HUGETLB	0x00400000	/* Huge TLB Page VM */

#define VM_NONLINEAR	0x00800000	/* Is non-linear (remap_file_pages) */

#define VM_NONLINEAR	0x00800000	/* Is non-linear (remap_file_pages) */

#define VM_MAPPED_COPY	0x01000000	/* T if mapped copy of data (nommu mmap) */

#define VM_MAPPED_COPY	0x01000000	/* T if mapped copy of data (nommu mmap) */

#define VM_INCOMPLETE	0x02000000	/* Strange partial PFN mapping marker */





#ifndef VM_STACK_DEFAULT_FLAGS		/* arch can override this */

#ifndef VM_STACK_DEFAULT_FLAGS		/* arch can override this */

#define VM_STACK_DEFAULT_FLAGS VM_DATA_DEFAULT_FLAGS

#define VM_STACK_DEFAULT_FLAGS VM_DATA_DEFAULT_FLAGS

mm/memory.c

+92 −0
Original line number Original line Diff line number Diff line
@@ -1146,6 +1146,95 @@ int zeromap_page_range(struct vm_area_struct *vma, 
	return err;

	return err;

}

}





/*

 * This is the old fallback for page remapping.

 *

 * For historical reasons, it only allows reserved pages. Only

 * old drivers should use this, and they needed to mark their

 * pages reserved for the old functions anyway.

 */

static int insert_page(struct mm_struct *mm, unsigned long addr, struct page *page, pgprot_t prot)

{

	int retval;

	pgd_t * pgd;

	pud_t * pud;

	pmd_t * pmd;  

	pte_t * pte;

	spinlock_t *ptl;  



	retval = -EINVAL;

	if (PageAnon(page) || !PageReserved(page))

		goto out;

	retval = -ENOMEM;

	flush_dcache_page(page);

	pgd = pgd_offset(mm, addr);

	pud = pud_alloc(mm, pgd, addr);

	if (!pud)

		goto out;

	pmd = pmd_alloc(mm, pud, addr);

	if (!pmd)

		goto out;

	pte = pte_alloc_map_lock(mm, pmd, addr, &ptl);

	if (!pte)

		goto out;

	retval = -EBUSY;

	if (!pte_none(*pte))

		goto out_unlock;



	/* Ok, finally just insert the thing.. */

	get_page(page);

	inc_mm_counter(mm, file_rss);

	page_add_file_rmap(page);

	set_pte_at(mm, addr, pte, mk_pte(page, prot));



	retval = 0;

out_unlock:

	pte_unmap_unlock(pte, ptl);

out:

	return retval;

}



/*

 * Somebody does a pfn remapping that doesn't actually work as a vma.

 *

 * Do it as individual pages instead, and warn about it. It's bad form,

 * and very inefficient.

 */

static int incomplete_pfn_remap(struct vm_area_struct *vma,

		unsigned long start, unsigned long end,

		unsigned long pfn, pgprot_t prot)

{

	static int warn = 10;

	struct page *page;

	int retval;



	if (!(vma->vm_flags & VM_INCOMPLETE)) {

		if (warn) {

			warn--;

			printk("%s does an incomplete pfn remapping", current->comm);

			dump_stack();

		}

	}

	vma->vm_flags |= VM_INCOMPLETE | VM_IO | VM_RESERVED;



	if (start < vma->vm_start || end > vma->vm_end)

		return -EINVAL;



	if (!pfn_valid(pfn))

		return -EINVAL;



	retval = 0;

	page = pfn_to_page(pfn);

	while (start < end) {

		retval = insert_page(vma->vm_mm, start, page, prot);

		if (retval < 0)

			break;

		start += PAGE_SIZE;

		page++;

	}

	return retval;

}



/*

/*

 * maps a range of physical memory into the requested pages. the old

 * maps a range of physical memory into the requested pages. the old

 * mappings are removed. any references to nonexistent pages results

 * mappings are removed. any references to nonexistent pages results
@@ -1220,6 +1309,9 @@ int remap_pfn_range(struct vm_area_struct *vma, unsigned long addr, 
	struct mm_struct *mm = vma->vm_mm;

	struct mm_struct *mm = vma->vm_mm;

	int err;

	int err;





	if (addr != vma->vm_start || end != vma->vm_end)

		return incomplete_pfn_remap(vma, addr, end, pfn, prot);



	/*

	/*

	 * Physically remapped pages are special. Tell the

	 * Physically remapped pages are special. Tell the

	 * rest of the world about it:

	 * rest of the world about it: