linux-kernel - [PATCH 5.10 128/199] io_uring: fix short read retries for non-reg files

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Message-Id: <20210125183221.617294291@linuxfoundation.org>
Date:   Mon, 25 Jan 2021 19:39:10 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Jens Axboe <axboe@...nel.dk>,
        Pavel Begunkov <asml.silence@...il.com>
Subject: [PATCH 5.10 128/199] io_uring: fix short read retries for non-reg files

From: Pavel Begunkov <asml.silence@...il.com>

commit 9a173346bd9e16ab19c7addb8862d95a5cea9feb upstream.

Sockets and other non-regular files may actually expect short reads to
happen, don't retry reads for them. Because non-reg files don't set
FMODE_BUF_RASYNC and so it won't do second/retry do_read, we can filter
out those cases after first do_read() attempt with ret>0.

Cc: stable@...r.kernel.org # 5.9+
Suggested-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Pavel Begunkov <asml.silence@...il.com>
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/io_uring.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -3461,7 +3461,7 @@ static int io_read(struct io_kiocb *req,
 
 	/* read it all, or we did blocking attempt. no retry. */
 	if (!iov_iter_count(iter) || !force_nonblock ||
-	    (req->file->f_flags & O_NONBLOCK))
+	    (req->file->f_flags & O_NONBLOCK) || !(req->flags & REQ_F_ISREG))
 		goto done;
 
 	io_size -= ret;