new primitive: iov_iter_for_each_range()

For kvec and bvec: feeds segments to given callback as long as it
returns 0.  For iovec and pipe: fails.

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

diff --git a/include/linux/uio.h b/include/linux/uio.h
index 5885dae..e67e12a 100644 (file)
--- a/include/linux/uio.h
+++ b/include/linux/uio.h
@@ -244,4 +244,8 @@ int compat_import_iovec(int type, const struct compat_iovec __user * uvector,
 int import_single_range(int type, void __user *buf, size_t len,
                 struct iovec *iov, struct iov_iter *i);
 
+int iov_iter_for_each_range(struct iov_iter *i, size_t bytes,
+                           int (*f)(struct kvec *vec, void *context),
+                           void *context);
+
 #endif

diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index 1c1c06d..9702126 100644 (file)
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -1446,3 +1446,25 @@ int import_single_range(int rw, void __user *buf, size_t len,
        return 0;
 }
 EXPORT_SYMBOL(import_single_range);
+
+int iov_iter_for_each_range(struct iov_iter *i, size_t bytes,
+                           int (*f)(struct kvec *vec, void *context),
+                           void *context)
+{
+       struct kvec w;
+       int err = -EINVAL;
+       if (!bytes)
+               return 0;
+
+       iterate_all_kinds(i, bytes, v, -EINVAL, ({
+               w.iov_base = kmap(v.bv_page) + v.bv_offset;
+               w.iov_len = v.bv_len;
+               err = f(&w, context);
+               kunmap(v.bv_page);
+               err;}), ({
+               w = v;
+               err = f(&w, context);})
+       )
+       return err;
+}
+EXPORT_SYMBOL(iov_iter_for_each_range);