linux-kernel - [PATCH 04/15] tty: n_tty: invert the condition in copy_from_read

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Date:   Tue, 19 Sep 2023 10:51:45 +0200
From:   "Jiri Slaby (SUSE)" <jirislaby@...nel.org>
To:     gregkh@...uxfoundation.org
Cc:     linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org,
        "Jiri Slaby (SUSE)" <jirislaby@...nel.org>
Subject: [PATCH 04/15] tty: n_tty: invert the condition in copy_from_read_buf()

Make "no numbers available" a fast quit from the function. And do the
heavy work outside the 'if'. This makes the code more understandable and
conforming to the common kernel coding style.

Signed-off-by: Jiri Slaby (SUSE) <jirislaby@...nel.org>
---
 drivers/tty/n_tty.c | 38 ++++++++++++++++++++------------------
 1 file changed, 20 insertions(+), 18 deletions(-)

diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
index 6a112910c058..922fb61b587a 100644
--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c
@@ -1966,24 +1966,26 @@ static bool copy_from_read_buf(const struct tty_struct *tty, u8 **kbp,
 	size_t tail = MASK(ldata->read_tail);
 
 	n = min3(head - ldata->read_tail, N_TTY_BUF_SIZE - tail, *nr);
-	if (n) {
-		u8 *from = read_buf_addr(ldata, tail);
-		memcpy(*kbp, from, n);
-		is_eof = n == 1 && *from == EOF_CHAR(tty);
-		tty_audit_add_data(tty, from, n);
-		zero_buffer(tty, from, n);
-		smp_store_release(&ldata->read_tail, ldata->read_tail + n);
-		/* Turn single EOF into zero-length read */
-		if (L_EXTPROC(tty) && ldata->icanon && is_eof &&
-		    (head == ldata->read_tail))
-			return false;
-		*kbp += n;
-		*nr -= n;
-
-		/* If we have more to copy, let the caller know */
-		return head != ldata->read_tail;
-	}
-	return false;
+	if (!n)
+		return false;
+
+	u8 *from = read_buf_addr(ldata, tail);
+	memcpy(*kbp, from, n);
+	is_eof = n == 1 && *from == EOF_CHAR(tty);
+	tty_audit_add_data(tty, from, n);
+	zero_buffer(tty, from, n);
+	smp_store_release(&ldata->read_tail, ldata->read_tail + n);
+
+	/* Turn single EOF into zero-length read */
+	if (L_EXTPROC(tty) && ldata->icanon && is_eof &&
+	    head == ldata->read_tail)
+		return false;
+
+	*kbp += n;
+	*nr -= n;
+
+	/* If we have more to copy, let the caller know */
+	return head != ldata->read_tail;
 }
 
 /**
-- 
2.42.0