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authorJohannes Weiner <hannes@cmpxchg.org>2009-06-16 15:32:35 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-06-16 19:47:40 -0700
commit3b6748e2dd69906af3835db4dc9d1c8a3ee4c68c (patch)
tree5d5476844f8e29e31684ce8ccf7e163ab3182ad6 /mm/memory.c
parent03668a4debf4f50de55c34b6e66dae63e1c73716 (diff)
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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: 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.c29
1 files changed, 29 insertions, 0 deletions
diff --git a/mm/memory.c b/mm/memory.c
index 24ff20480bb..d5d1653d60a 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3140,6 +3140,35 @@ out:
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,