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SubjectRe: [PATCH] printk: remove unnecessary kmalloc() from syslog during clear
On Wed 2018-06-20 19:26:19, Namit Gupta wrote:
> When the request is only for clearing logs, there is no need for
> allocation/deallocation. Only the indexes need to be reset and returned.
> Rest of the patch is mostly made up of changes because of indention.
>
> Signed-off-by: Namit Gupta <gupta.namit@samsung.com>
> Signed-off-by: Himanshu Maithani <himanshu.m@samsung.com>

> ---
> kernel/printk/printk.c | 111 ++++++++++++++++++++++++++-----------------------
> 1 file changed, 60 insertions(+), 51 deletions(-)
>
> diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
> index 512f7c2..53952ce 100644
> --- a/kernel/printk/printk.c
> +++ b/kernel/printk/printk.c
> @@ -1348,71 +1348,80 @@ static int syslog_print_all(char __user *buf, int size, bool clear)
> {
> char *text;
> int len = 0;
> + u64 next_seq;
> + u64 seq;
> + u32 idx;
> +
> + if (!buf) {
> + if (clear) {
> + logbuf_lock_irq();
> + clear_seq = log_next_seq;
> + clear_idx = log_next_idx;
> + logbuf_unlock_irq();

I pushed a bit different version into printk.git, branch for-4.19,
see below. It removes the code duplication. Also it keeps the original
indentation. IMHO, it helped to better distinguish the code for printing
and clearing.

It is rather a cosmetic change, so I do not want you to resend
Reviewed-by tags. But feel free to disagree and ask me to use
the original variant.


This is in printk.git now:

From 41cb6dcedd9257d51fd310bf9b2958d11d93aa2b Mon Sep 17 00:00:00 2001
From: Namit Gupta <gupta.namit@samsung.com>
Date: Mon, 25 Jun 2018 14:58:05 +0200
Subject: [PATCH] printk: remove unnecessary kmalloc() from syslog during

When the request is only for clearing logs, there is no need for
allocation/deallocation. Only the indexes need to be reset and returned.
Rest of the patch is mostly made up of changes because of indention.

Link: http://lkml.kernel.org/r/20180620135951epcas5p3bd2a8f25ec689ca333bce861b527dba2~54wyKcT0_3155531555epcas5p3y@epcas5p3.samsung.com
Cc: linux-kernel@vger.kernel.org
Cc: pankaj.m@samsung.com
Cc: a.sahrawat@samsung.com
Signed-off-by: Namit Gupta <gupta.namit@samsung.com>
Signed-off-by: Himanshu Maithani <himanshu.m@samsung.com>
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
[pmladek@suse.com: Removed code duplication.]
Signed-off-by: Petr Mladek <pmladek@suse.com>
---
kernel/printk/printk.c | 13 ++++++++-----
1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 247808333ba4..0fa2ca6fd8f9 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -1350,12 +1350,14 @@ static int syslog_print(char __user *buf, int size)

static int syslog_print_all(char __user *buf, int size, bool clear)
{
- char *text;
+ char *text = NULL;
int len = 0;

- text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
- if (!text)
- return -ENOMEM;
+ if (buf) {
+ text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
+ if (!text)
+ return -ENOMEM;
+ }

logbuf_lock_irq();
if (buf) {
@@ -1426,7 +1428,8 @@ static int syslog_print_all(char __user *buf, int size, bool clear)
}
logbuf_unlock_irq();

- kfree(text);
+ if (text)
+ kfree(text);
return len;
}

--
2.13.7
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