[PATCH for-next v2 0/2] rw link fixes

[PATCH for-next v2 0/2] rw link fixes

[Pavel Begunkov]

1/2 fixes an unexpected link breakage issue with reads.
2/2 makes pre-retry setup fails a bit nicer.

v2: rebase and add tested-by

Pavel Begunkov (2):
  io_uring/rw: fix unexpected link breakage
  io_uring/rw: don't lose short results on io_setup_async_rw()

 io_uring/rw.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

-- 
2.37.2

[PATCH for-next v2 1/2] io_uring/rw: fix unexpected link breakage

[Pavel Begunkov]

req->cqe.res is set in io_read() to the amount of bytes left to be done,
which is used to figure out whether to fail a read or not. However,
io_read() may do another without returning, and we stash the previous
value into ->bytes_done but forget to update cqe.res. Then we ask a read
to do strictly less than cqe.res but expect the return to be exactly
cqe.res.

Fix the bug by updating cqe.res for retries.

Cc: stable@vger.kernel.org
Reported-and-Tested-by: Beld Zhang <beldzhang@gmail.com>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 io_uring/rw.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/io_uring/rw.c b/io_uring/rw.c
index 59c92a4616b8..ed14322aadb9 100644
--- a/io_uring/rw.c
+++ b/io_uring/rw.c
@@ -793,6 +793,7 @@ int io_read(struct io_kiocb *req, unsigned int issue_flags)
 			return -EAGAIN;
 		}
 
+		req->cqe.res = iov_iter_count(&s->iter);
 		/*
 		 * Now retry read with the IOCB_WAITQ parts set in the iocb. If
 		 * we get -EIOCBQUEUED, then we'll get a notification when the
-- 
2.37.2

[PATCH for-next v2 2/2] io_uring/rw: don't lose short results on io_setup_async_rw()

[Pavel Begunkov]

If a retry io_setup_async_rw() fails we lose result from the first
io_iter_do_read(), which is a problem mostly for streams/sockets.

Cc: stable@vger.kernel.org
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 io_uring/rw.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/io_uring/rw.c b/io_uring/rw.c
index ed14322aadb9..1ae1e52ab4cb 100644
--- a/io_uring/rw.c
+++ b/io_uring/rw.c
@@ -764,10 +764,12 @@ int io_read(struct io_kiocb *req, unsigned int issue_flags)
 	iov_iter_restore(&s->iter, &s->iter_state);
 
 	ret2 = io_setup_async_rw(req, iovec, s, true);
-	if (ret2)
-		return ret2;
-
 	iovec = NULL;
+	if (ret2) {
+		ret = ret > 0 ? ret : ret2;
+		goto done;
+	}
+
 	io = req->async_data;
 	s = &io->s;
 	/*
-- 
2.37.2

Re: [PATCH for-next v2 0/2] rw link fixes

[Jens Axboe]

On Tue, 27 Sep 2022 00:44:38 +0100, Pavel Begunkov wrote:
> 1/2 fixes an unexpected link breakage issue with reads.
> 2/2 makes pre-retry setup fails a bit nicer.
> 
> v2: rebase and add tested-by
> 
> Pavel Begunkov (2):
>   io_uring/rw: fix unexpected link breakage
>   io_uring/rw: don't lose short results on io_setup_async_rw()
> 
> [...]

Applied, thanks!

[1/2] io_uring/rw: fix unexpected link breakage
      commit: bf68b5b34311ee57ed40749a1257a30b46127556
[2/2] io_uring/rw: don't lose short results on io_setup_async_rw()
      commit: c278d9f8ac0db5590909e6d9e85b5ca2b786704f

Best regards,
-- 
Jens Axboe