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| author | Johannes Weiner <hannes@cmpxchg.org> | 2009-06-16 15:32:33 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2009-06-16 19:47:39 -0700 |
| commit | f8ad0f499fad5cdbcaaa2d97542b2db869b5a770 (patch) | |
| tree | f1b5e91072238c2a303940bd522485484dc22105 /mm/memory.c | |
| parent | e9bb35df6f813ca46f8e6273add657643c7df73f (diff) | |
| download | lwn-f8ad0f499fad5cdbcaaa2d97542b2db869b5a770.tar.gz lwn-f8ad0f499fad5cdbcaaa2d97542b2db869b5a770.zip | |
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: Johannes Weiner <hannes@cmpxchg.org>
Cc: Christoph Hellwig <hch@infradead.org>
Acked-by: Magnus 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/memory.c')
| -rw-r--r-- | mm/memory.c | 37 |
1 files changed, 37 insertions, 0 deletions
diff --git a/mm/memory.c b/mm/memory.c index 891bad0613f4..7135d6b25995 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3103,6 +3103,43 @@ int in_gate_area_no_task(unsigned long addr) #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 int follow_phys(struct vm_area_struct *vma, unsigned long address, unsigned int flags, |