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Commit 3b6748e2 authored by Johannes Weiner's avatar Johannes Weiner Committed by Linus Torvalds
Browse files

mm: introduce follow_pfn() 



Analoguous to follow_phys(), add a helper that looks up the PFN at a
user virtual address in an IO mapping or a raw PFN mapping.

Signed-off-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Cc: Christoph Hellwig <hch@infradead.org>
Acked-by: default avatarMagnus Damm <magnus.damm@gmail.com>
Cc: Hans Verkuil <hverkuil@xs4all.nl>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 03668a4d

include/linux/mm.h

+2 −0
Original line number Diff line number Diff line
@@ -792,6 +792,8 @@ int copy_page_range(struct mm_struct *dst, struct mm_struct *src, 
			struct vm_area_struct *vma);

void unmap_mapping_range(struct address_space *mapping,

		loff_t const holebegin, loff_t const holelen, int even_cows);

int follow_pfn(struct vm_area_struct *vma, unsigned long address,

	unsigned long *pfn);

int follow_phys(struct vm_area_struct *vma, unsigned long address,

		unsigned int flags, unsigned long *prot, resource_size_t *phys);

int generic_access_phys(struct vm_area_struct *vma, unsigned long addr,

mm/memory.c

+29 −0
Original line number Diff line number Diff line
@@ -3140,6 +3140,35 @@ static int follow_pte(struct mm_struct *mm, unsigned long address, 
	return -EINVAL;

}



/**

 * follow_pfn - look up PFN at a user virtual address

 * @vma: memory mapping

 * @address: user virtual address

 * @pfn: location to store found PFN

 *

 * Only IO mappings and raw PFN mappings are allowed.

 *

 * Returns zero and the pfn at @pfn on success, -ve otherwise.

 */

int follow_pfn(struct vm_area_struct *vma, unsigned long address,

	unsigned long *pfn)

{

	int ret = -EINVAL;

	spinlock_t *ptl;

	pte_t *ptep;



	if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)))

		return ret;



	ret = follow_pte(vma->vm_mm, address, &ptep, &ptl);

	if (ret)

		return ret;

	*pfn = pte_pfn(*ptep);

	pte_unmap_unlock(ptep, ptl);

	return 0;

}

EXPORT_SYMBOL(follow_pfn);



#ifdef CONFIG_HAVE_IOREMAP_PROT

int follow_phys(struct vm_area_struct *vma,

		unsigned long address, unsigned int flags,