@@ -258,4 +258,39 @@ size_t iterate_and_advance(struct iov_iter *iter, size_t len, void *priv,
return iterate_and_advance2(iter, len, priv, NULL, ustep, step);
}
+/**
+ * iterate_and_advance_kernel - Iterate over a kernel iterator
+ * @iter: The iterator to iterate over.
+ * @len: The amount to iterate over.
+ * @priv: Data for the step functions.
+ * @step: Processing function; given kernel addresses.
+ *
+ * Like iterate_and_advance2(), but rejected UBUF and IOVEC iterators and does
+ * not take a user-step function.
+ */
+static __always_inline
+size_t iterate_and_advance_kernel(struct iov_iter *iter, size_t len, void *priv,
+ void *priv2, iov_step_f step)
+{
+ size_t progress;
+
+ if (unlikely(iter->count < len))
+ len = iter->count;
+ if (unlikely(!len))
+ return 0;
+
+ if (iov_iter_is_bvec(iter))
+ progress = iterate_bvec(iter, len, priv, priv2, step);
+ else if (iov_iter_is_kvec(iter))
+ progress = iterate_kvec(iter, len, priv, priv2, step);
+ else if (iov_iter_is_xarray(iter))
+ progress = iterate_xarray(iter, len, priv, priv2, step);
+ else if (WARN_ON_ONCE(unlikely(iter_is_ubuf(iter) || iter_is_iovec(iter))))
+ progress = 0;
+ else
+ progress = len;
+ iter->count -= progress;
+ return progress;
+}
+
#endif /* _LINUX_IOV_ITER_H */
Add an iteration function that can only iterate over kernel internal-type iterators (ie. BVEC, KVEC, XARRAY) and not user-backed iterators (ie. UBUF and IOVEC). This allows for smaller iterators to be built when it is known the caller won't have a user-backed iterator. Signed-off-by: David Howells <dhowells@redhat.com> cc: Alexander Viro <viro@zeniv.linux.org.uk> cc: Jens Axboe <axboe@kernel.dk> cc: Christoph Hellwig <hch@lst.de> cc: Christian Brauner <christian@brauner.io> cc: Matthew Wilcox <willy@infradead.org> cc: Linus Torvalds <torvalds@linux-foundation.org> cc: David Laight <David.Laight@ACULAB.COM> cc: linux-block@vger.kernel.org cc: linux-fsdevel@vger.kernel.org cc: linux-mm@kvack.org --- include/linux/iov_iter.h | 35 +++++++++++++++++++++++++++++++++++ 1 file changed, 35 insertions(+)