[PATCH 4/9 next] fs/io_uring Don't use the return value from import_iovec().

This is the only code that relies on import_iovec() returning
iter.count on success.
This allows a better interface to import_iovec().

Signed-off-by: David Laight <redacted>
---
 fs/io_uring.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 3790c7fe9fee..0df43882e4b3 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c

@@ -2824,7 +2824,7 @@ static ssize_t __io_import_iovec(int rw, struct io_kiocb *req,
 
 		ret = import_single_range(rw, buf, sqe_len, *iovec, iter);
 		*iovec = NULL;
-		return ret < 0 ? ret : sqe_len;
+		return ret;
 	}
 
 	if (req->flags & REQ_F_BUFFER_SELECT) {

@@ -2853,7 +2853,7 @@ static ssize_t io_import_iovec(int rw, struct io_kiocb *req,
 	if (!req->io)
 		return __io_import_iovec(rw, req, iovec, iter, needs_lock);
 	*iovec = NULL;
-	return iov_iter_count(&req->io->rw.iter);
+	return 0;
 }
 
 static inline loff_t *io_kiocb_ppos(struct kiocb *kiocb)

@@ -3123,7 +3123,7 @@ static int io_read(struct io_kiocb *req, bool force_nonblock,
 	if (ret < 0)
 		return ret;
 	iov_count = iov_iter_count(iter);
-	io_size = ret;
+	io_size = iov_count;
 	req->result = io_size;
 	ret = 0;
 

@@ -3246,7 +3246,7 @@ static int io_write(struct io_kiocb *req, bool force_nonblock,
 	if (ret < 0)
 		return ret;
 	iov_count = iov_iter_count(iter);
-	io_size = ret;
+	io_size = iov_count;
 	req->result = io_size;
 
 	/* Ensure we clear previously set non-block flag */

-- 
2.25.1

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)

On Tue, Sep 15, 2020 at 02:55:20PM +0000, David Laight wrote:

This is the only code that relies on import_iovec() returning
iter.count on success.
This allows a better interface to import_iovec().

This looks generall sane, but a comment below:

I tink the local iov_count variable can go away in both functions,
as io_size only changes after the last use of iov_count (io_read) or
not at all (io_write).

From: Christoph Hellwig

Sent: 21 September 2020 15:15

On Tue, Sep 15, 2020 at 02:55:20PM +0000, David Laight wrote:

quoted

This is the only code that relies on import_iovec() returning
iter.count on success.
This allows a better interface to import_iovec().

This looks generall sane, but a comment below:

quoted

@@ -3123,7 +3123,7 @@ static int io_read(struct io_kiocb *req, bool force_nonblock,
 	if (ret < 0)
 		return ret;
 	iov_count = iov_iter_count(iter);
-	io_size = ret;
+	io_size = iov_count;
 	req->result = io_size;
 	ret = 0;

@@ -3246,7 +3246,7 @@ static int io_write(struct io_kiocb *req, bool force_nonblock,
 	if (ret < 0)
 		return ret;
 	iov_count = iov_iter_count(iter);
-	io_size = ret;
+	io_size = iov_count;
 	req->result = io_size;

I tink the local iov_count variable can go away in both functions,
as io_size only changes after the last use of iov_count (io_read) or
not at all (io_write).

Yes, the compiler will probably make that optimisation.
I did a minimal change because my head hurts whenever I look at io_uring.c.

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)

On 21/09/2020 17:38, David Laight wrote:

From: Christoph Hellwig

quoted

Sent: 21 September 2020 15:15

On Tue, Sep 15, 2020 at 02:55:20PM +0000, David Laight wrote:

quoted

This is the only code that relies on import_iovec() returning
iter.count on success.
This allows a better interface to import_iovec().

Reviewed-by: Pavel Begunkov <asml.silence@gmail.com>

quoted

This looks generall sane, but a comment below:

quoted

@@ -3123,7 +3123,7 @@ static int io_read(struct io_kiocb *req, bool force_nonblock,
 	if (ret < 0)
 		return ret;
 	iov_count = iov_iter_count(iter);
-	io_size = ret;
+	io_size = iov_count;
 	req->result = io_size;
 	ret = 0;

@@ -3246,7 +3246,7 @@ static int io_write(struct io_kiocb *req, bool force_nonblock,
 	if (ret < 0)
 		return ret;
 	iov_count = iov_iter_count(iter);
-	io_size = ret;
+	io_size = iov_count;
 	req->result = io_size;

I tink the local iov_count variable can go away in both functions,
as io_size only changes after the last use of iov_count (io_read) or
not at all (io_write).

Yes, iov_count should be killed, now or later.

Yes, the compiler will probably make that optimisation.
I did a minimal change because my head hurts whenever I look at io_uring.c.

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)

-- 
Pavel Begunkov

On 15/09/2020 15:55, David Laight wrote:

This is the only code that relies on import_iovec() returning
iter.count on success.
This allows a better interface to import_iovec().

Seems this got nowhere. I'll pick it and send with some other
patches to Jens.

-- 
Pavel Begunkov