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

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
......@@ -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,
......
......@@ -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,
......
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