new helper: dup_iter()

Copy iter and kmemdup the underlying array for the copy.  Returns
a pointer to result of kmemdup() to be kfree()'d later.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 15 insertions, 0 deletions

diff --git a/mm/iov_iter.c b/mm/iov_iter.c
index 827732047da1..9d96e283520c 100644
--- a/mm/iov_iter.c
+++ b/mm/iov_iter.c
@@ -751,3 +751,18 @@ int iov_iter_npages(const struct iov_iter *i, int maxpages)
         return npages;
 }
 EXPORT_SYMBOL(iov_iter_npages);
+
+const void *dup_iter(struct iov_iter *new, struct iov_iter *old, gfp_t flags)
+{
+        *new = *old;
+        if (new->type & ITER_BVEC)
+                return new->bvec = kmemdup(new->bvec,
+                                    new->nr_segs * sizeof(struct bio_vec),
+                                    flags);
+        else
+                /* iovec and kvec have identical layout */
+                return new->iov = kmemdup(new->iov,
+                                   new->nr_segs * sizeof(struct iovec),
+                                   flags);
+}
+EXPORT_SYMBOL(dup_iter);