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Commit f8ad0f49 authored by Johannes Weiner's avatar Johannes Weiner Committed by Linus Torvalds
Browse files

mm: introduce follow_pte() 



A generic readonly page table lookup helper to map an address space and an
address from it to a pte.

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 e9bb35df

mm/memory.c

+37 −0
Original line number Original line Diff line number Diff line
@@ -3103,6 +3103,43 @@ int in_gate_area_no_task(unsigned long addr) 




#endif	/* __HAVE_ARCH_GATE_AREA */

#endif	/* __HAVE_ARCH_GATE_AREA */





static int follow_pte(struct mm_struct *mm, unsigned long address,

		pte_t **ptepp, spinlock_t **ptlp)

{

	pgd_t *pgd;

	pud_t *pud;

	pmd_t *pmd;

	pte_t *ptep;



	pgd = pgd_offset(mm, address);

	if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))

		goto out;



	pud = pud_offset(pgd, address);

	if (pud_none(*pud) || unlikely(pud_bad(*pud)))

		goto out;



	pmd = pmd_offset(pud, address);

	if (pmd_none(*pmd) || unlikely(pmd_bad(*pmd)))

		goto out;



	/* We cannot handle huge page PFN maps. Luckily they don't exist. */

	if (pmd_huge(*pmd))

		goto out;



	ptep = pte_offset_map_lock(mm, pmd, address, ptlp);

	if (!ptep)

		goto out;

	if (!pte_present(*ptep))

		goto unlock;

	*ptepp = ptep;

	return 0;

unlock:

	pte_unmap_unlock(ptep, *ptlp);

out:

	return -EINVAL;

}



#ifdef CONFIG_HAVE_IOREMAP_PROT

#ifdef CONFIG_HAVE_IOREMAP_PROT

int follow_phys(struct vm_area_struct *vma,

int follow_phys(struct vm_area_struct *vma,

		unsigned long address, unsigned int flags,

		unsigned long address, unsigned int flags,