linux-kernel - [PATCH] printk: Fix unnecessary returning broken pipe error from devkmsg

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Date:   Wed, 18 Sep 2019 21:31:43 +0800
From:   <zhe.he@...driver.com>
To:     <pmladek@...e.com>, <sergey.senozhatsky@...il.com>,
        <rostedt@...dmis.org>, <linux-kernel@...r.kernel.org>,
        <zhe.he@...driver.com>
Subject: [PATCH] printk: Fix unnecessary returning broken pipe error from devkmsg_read

From: He Zhe <zhe.he@...driver.com>

When users read the buffer from start, there is no need to return -EPIPE
since the possible overflows will not affect the output.

Signed-off-by: He Zhe <zhe.he@...driver.com>
---
 kernel/printk/printk.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 1888f6a..4a6a129 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -886,7 +886,9 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf,
 		logbuf_lock_irq();
 	}
 
-	if (user->seq < log_first_seq) {
+	if (user->seq == 0) {
+		user->seq = log_first_seq;
+	} else if (user->seq < log_first_seq) {
 		/* our last seen message is gone, return error and reset */
 		user->idx = log_first_idx;
 		user->seq = log_first_seq;
-- 
2.7.4