netdev - [PATCH v6 06/13] iov_iter: Derive user-backedness from the iterator type

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Date: Fri, 22 Sep 2023 13:02:20 +0100
From: David Howells <dhowells@...hat.com>
To: Jens Axboe <axboe@...nel.dk>
Cc: David Howells <dhowells@...hat.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Christoph Hellwig <hch@....de>,
	Christian Brauner <christian@...uner.io>,
	David Laight <David.Laight@...LAB.COM>,
	Matthew Wilcox <willy@...radead.org>,
	Jeff Layton <jlayton@...nel.org>,
	linux-fsdevel@...r.kernel.org,
	linux-block@...r.kernel.org,
	linux-mm@...ck.org,
	netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH v6 06/13] iov_iter: Derive user-backedness from the iterator type

Use the iterator type to determine whether an iterator is user-backed or
not rather than using a special flag for it.  Now that ITER_UBUF and
ITER_IOVEC are 0 and 1, they can be checked with a single comparison.

Signed-off-by: David Howells <dhowells@...hat.com>
cc: Alexander Viro <viro@...iv.linux.org.uk>
cc: Jens Axboe <axboe@...nel.dk>
cc: Christoph Hellwig <hch@....de>
cc: Christian Brauner <christian@...uner.io>
cc: Matthew Wilcox <willy@...radead.org>
cc: Linus Torvalds <torvalds@...ux-foundation.org>
cc: David Laight <David.Laight@...LAB.COM>
cc: linux-block@...r.kernel.org
cc: linux-fsdevel@...r.kernel.org
cc: linux-mm@...ck.org
---
 include/linux/uio.h | 4 +---
 lib/iov_iter.c      | 1 -
 2 files changed, 1 insertion(+), 4 deletions(-)

diff --git a/include/linux/uio.h b/include/linux/uio.h
index bef8e56aa45c..65d9143f83c8 100644
--- a/include/linux/uio.h
+++ b/include/linux/uio.h
@@ -43,7 +43,6 @@ struct iov_iter {
 	bool copy_mc;
 	bool nofault;
 	bool data_source;
-	bool user_backed;
 	size_t iov_offset;
 	/*
 	 * Hack alert: overlay ubuf_iovec with iovec + count, so
@@ -140,7 +139,7 @@ static inline unsigned char iov_iter_rw(const struct iov_iter *i)
 
 static inline bool user_backed_iter(const struct iov_iter *i)
 {
-	return i->user_backed;
+	return iter_is_ubuf(i) || iter_is_iovec(i);
 }
 
 /*
@@ -380,7 +379,6 @@ static inline void iov_iter_ubuf(struct iov_iter *i, unsigned int direction,
 	*i = (struct iov_iter) {
 		.iter_type = ITER_UBUF,
 		.copy_mc = false,
-		.user_backed = true,
 		.data_source = direction,
 		.ubuf = buf,
 		.count = count,
diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index 27234a820eeb..227c9f536b94 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -290,7 +290,6 @@ void iov_iter_init(struct iov_iter *i, unsigned int direction,
 		.iter_type = ITER_IOVEC,
 		.copy_mc = false,
 		.nofault = false,
-		.user_backed = true,
 		.data_source = direction,
 		.__iov = iov,
 		.nr_segs = nr_segs,