From nobody Tue Sep 16 01:25:52 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8CDE8C678D9 for ; Mon, 9 Jan 2023 10:09:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234256AbjAIKJZ (ORCPT ); Mon, 9 Jan 2023 05:09:25 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57990 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236885AbjAIKIv (ORCPT ); Mon, 9 Jan 2023 05:08:51 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1D5B3B1C1 for ; Mon, 9 Jan 2023 02:08:49 -0800 (PST) From: John Ogness DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1673258926; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=PJqnYxHgAm5zPWQPXQ8w2S1sD7jcnMKX3VIFczAZH38=; b=1EByRzQzhb8tbRlrbFCbzD5+nrEU7ae34iNdqti1AKJsCvff+F8EJIdQKnShLXRjNtCyMk pzFgLfbQe4s268Hu/bbClmRcSoW2mxIet/PgIqMGHRJUDKPe7xwiMgRgtDCXo93ugKUoCA x4U2kVPQ/Yhzu6YHEmMl+cr7mv+TGcQmzIynuOic3tuyJtS7hX+mrEmZUAIvW2kCPTi6x8 cYSC2gWk61+8r8gddLm9JBPOQtbuqkdoEzNt2WE5uWfXqnl5h+ibCj00NQLwk94J8Ueb+I gvB37aNHy802lVSChD96146Ln3NCZcd+MdfejcBvRTU9HfaIZd0yOa6KGW3vBA== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1673258926; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=PJqnYxHgAm5zPWQPXQ8w2S1sD7jcnMKX3VIFczAZH38=; b=IAQ1RJhglgrijsFvOo0DaKvloLt3um1/8neEecwhxvE1oNmhiHOEx7HpZl4r7r/RwkrLS3 jZivOpfaIOa5lyCg== To: Petr Mladek Cc: Sergey Senozhatsky , Steven Rostedt , Thomas Gleixner , linux-kernel@vger.kernel.org Subject: [PATCH printk v5 7/8] printk: use printk_buffers for devkmsg Date: Mon, 9 Jan 2023 11:13:59 +0106 Message-Id: <20230109100800.1085541-8-john.ogness@linutronix.de> In-Reply-To: <20230109100800.1085541-1-john.ogness@linutronix.de> References: <20230109100800.1085541-1-john.ogness@linutronix.de> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Replace the buffers in struct devkmsg_user with a struct printk_buffers. This reduces the number of buffers to keep track of. As a side-effect, @text_buf was 8kB large, even though it only needed to be the max size of a ringbuffer record. By switching to struct printk_buffers, ~7kB less memory is allocated when opening /dev/kmsg. And since struct printk_buffers will be used now, reduce duplicate code by calling printk_get_next_message() to handle the record reading and formatting. Note that since /dev/kmsg never suppresses records based on loglevel, printk_get_next_message() is extended with an extra bool argument to specify if suppression is allowed. Signed-off-by: John Ogness --- kernel/printk/printk.c | 49 +++++++++++++++++++----------------------- 1 file changed, 22 insertions(+), 27 deletions(-) diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 80a49ec6f42b..a72904890a5f 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -695,16 +695,15 @@ static ssize_t msg_print_ext_body(char *buf, size_t s= ize, return len; } =20 +static bool printk_get_next_message(struct printk_message *pmsg, u64 seq, + bool is_extended, bool may_supress); + /* /dev/kmsg - userspace message inject/listen interface */ struct devkmsg_user { atomic64_t seq; struct ratelimit_state rs; struct mutex lock; - char buf[CONSOLE_EXT_LOG_MAX]; - - struct printk_info info; - char text_buf[CONSOLE_EXT_LOG_MAX]; - struct printk_record record; + struct printk_buffers pbufs; }; =20 static __printf(3, 4) __cold @@ -786,8 +785,10 @@ static ssize_t devkmsg_read(struct file *file, char __= user *buf, size_t count, loff_t *ppos) { struct devkmsg_user *user =3D file->private_data; - struct printk_record *r =3D &user->record; - size_t len; + char *outbuf =3D &user->pbufs.outbuf[0]; + struct printk_message pmsg =3D { + .pbufs =3D &user->pbufs, + }; ssize_t ret; =20 if (!user) @@ -797,7 +798,7 @@ static ssize_t devkmsg_read(struct file *file, char __u= ser *buf, if (ret) return ret; =20 - if (!prb_read_valid(prb, atomic64_read(&user->seq), r)) { + if (!printk_get_next_message(&pmsg, atomic64_read(&user->seq), true, fals= e)) { if (file->f_flags & O_NONBLOCK) { ret =3D -EAGAIN; goto out; @@ -814,36 +815,31 @@ static ssize_t devkmsg_read(struct file *file, char _= _user *buf, * This pairs with __wake_up_klogd:A. */ ret =3D wait_event_interruptible(log_wait, - prb_read_valid(prb, - atomic64_read(&user->seq), r)); /* LMM(devkmsg_read:A) */ + printk_get_next_message(&pmsg, atomic64_read(&user->seq), true, + false)); /* LMM(devkmsg_read:A) */ if (ret) goto out; } =20 - if (r->info->seq !=3D atomic64_read(&user->seq)) { + if (pmsg.dropped) { /* our last seen message is gone, return error and reset */ - atomic64_set(&user->seq, r->info->seq); + atomic64_set(&user->seq, pmsg.seq); ret =3D -EPIPE; goto out; } =20 - len =3D info_print_ext_header(user->buf, sizeof(user->buf), r->info); - len +=3D msg_print_ext_body(user->buf + len, sizeof(user->buf) - len, - &r->text_buf[0], r->info->text_len, - &r->info->dev_info); - - atomic64_set(&user->seq, r->info->seq + 1); + atomic64_set(&user->seq, pmsg.seq + 1); =20 - if (len > count) { + if (pmsg.outbuf_len > count) { ret =3D -EINVAL; goto out; } =20 - if (copy_to_user(buf, user->buf, len)) { + if (copy_to_user(buf, outbuf, pmsg.outbuf_len)) { ret =3D -EFAULT; goto out; } - ret =3D len; + ret =3D pmsg.outbuf_len; out: mutex_unlock(&user->lock); return ret; @@ -937,9 +933,6 @@ static int devkmsg_open(struct inode *inode, struct fil= e *file) =20 mutex_init(&user->lock); =20 - prb_rec_init_rd(&user->record, &user->info, - &user->text_buf[0], sizeof(user->text_buf)); - atomic64_set(&user->seq, prb_first_valid_seq(prb)); =20 file->private_data =3D user; @@ -2762,12 +2755,14 @@ static void console_prepend_dropped(struct printk_m= essage *pmsg, unsigned long d * @is_extended specifies if the message should be formatted for extended * console output. * + * @may_supress specifies if records may be skipped based on loglevel. + * * Returns false if no record is available. Otherwise true and all fields * of @pmsg are valid. (See the documentation of struct printk_message * for information about the @pmsg fields.) */ static bool printk_get_next_message(struct printk_message *pmsg, u64 seq, - bool is_extended) + bool is_extended, bool may_suppress) { static int panic_console_dropped; =20 @@ -2810,7 +2805,7 @@ static bool printk_get_next_message(struct printk_mes= sage *pmsg, u64 seq, } =20 /* Skip record that has level above the console loglevel. */ - if (suppress_message_printing(r.info->level)) + if (may_suppress && suppress_message_printing(r.info->level)) goto out; =20 if (is_extended) { @@ -2853,7 +2848,7 @@ static bool console_emit_next_record(struct console *= con, bool *handover, int co =20 *handover =3D false; =20 - if (!printk_get_next_message(&pmsg, con->seq, is_extended)) + if (!printk_get_next_message(&pmsg, con->seq, is_extended, true)) return false; =20 con->dropped +=3D pmsg.dropped; --=20 2.30.2