diff mbox series

[v5,07/11] iov_iter: Add a kernel-type iterator-only iteration function

Message ID 20230920222231.686275-8-dhowells@redhat.com (mailing list archive)
State New
Headers show
Series iov_iter: Convert the iterator macros into inline funcs | expand

Commit Message

David Howells Sept. 20, 2023, 10:22 p.m. UTC
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 | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

Comments

Simon Horman Sept. 22, 2023, 9:34 a.m. UTC | #1
On Wed, Sep 20, 2023 at 11:22:27PM +0100, David Howells wrote:
> 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 | 31 +++++++++++++++++++++++++++++++
>  1 file changed, 31 insertions(+)
> 
> diff --git a/include/linux/iov_iter.h b/include/linux/iov_iter.h
> index 270454a6703d..a94d605d7386 100644
> --- a/include/linux/iov_iter.h
> +++ b/include/linux/iov_iter.h
> @@ -271,4 +271,35 @@ 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.

nit: an entry for @priv2 belongs here

> + * @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)
> +{

...
diff mbox series

Patch

diff --git a/include/linux/iov_iter.h b/include/linux/iov_iter.h
index 270454a6703d..a94d605d7386 100644
--- a/include/linux/iov_iter.h
+++ b/include/linux/iov_iter.h
@@ -271,4 +271,35 @@  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)
+{
+	if (unlikely(iter->count < len))
+		len = iter->count;
+	if (unlikely(!len))
+		return 0;
+
+	if (iov_iter_is_bvec(iter))
+		return iterate_bvec(iter, len, priv, priv2, step);
+	if (iov_iter_is_kvec(iter))
+		return iterate_kvec(iter, len, priv, priv2, step);
+	if (iov_iter_is_xarray(iter))
+		return iterate_xarray(iter, len, priv, priv2, step);
+	if (iov_iter_is_discard(iter))
+		return iterate_discard(iter, len, priv, priv2, step);
+	WARN_ON_ONCE(1);
+	return 0;
+}
+
 #endif /* _LINUX_IOV_ITER_H */