From ea308da1198f8ca9de6e4ff7f22120e27d4e6338 Mon Sep 17 00:00:00 2001 From: John Ogness Date: Mon, 9 Jan 2023 11:13:59 +0106 Subject: [PATCH] printk: use printk_buffers for devkmsg 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 Reviewed-by: Petr Mladek Signed-off-by: Petr Mladek Link: https://lore.kernel.org/r/20230109100800.1085541-8-john.ogness@linutronix.de --- 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 @@ out: return len; } +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; }; 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 = file->private_data; - struct printk_record *r = &user->record; - size_t len; + char *outbuf = &user->pbufs.outbuf[0]; + struct printk_message pmsg = { + .pbufs = &user->pbufs, + }; ssize_t ret; if (!user) @@ -797,7 +798,7 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf, if (ret) return ret; - if (!prb_read_valid(prb, atomic64_read(&user->seq), r)) { + if (!printk_get_next_message(&pmsg, atomic64_read(&user->seq), true, false)) { if (file->f_flags & O_NONBLOCK) { ret = -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 = 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; } - if (r->info->seq != 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 = -EPIPE; goto out; } - len = info_print_ext_header(user->buf, sizeof(user->buf), r->info); - len += 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); - if (len > count) { + if (pmsg.outbuf_len > count) { ret = -EINVAL; goto out; } - if (copy_to_user(buf, user->buf, len)) { + if (copy_to_user(buf, outbuf, pmsg.outbuf_len)) { ret = -EFAULT; goto out; } - ret = len; + ret = pmsg.outbuf_len; out: mutex_unlock(&user->lock); return ret; @@ -937,9 +933,6 @@ static int devkmsg_open(struct inode *inode, struct file *file) mutex_init(&user->lock); - 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)); file->private_data = user; @@ -2762,12 +2755,14 @@ static void console_prepend_dropped(struct printk_message *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; @@ -2810,7 +2805,7 @@ static bool printk_get_next_message(struct printk_message *pmsg, u64 seq, } /* 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; if (is_extended) { @@ -2853,7 +2848,7 @@ static bool console_emit_next_record(struct console *con, bool *handover, int co *handover = false; - if (!printk_get_next_message(&pmsg, con->seq, is_extended)) + if (!printk_get_next_message(&pmsg, con->seq, is_extended, true)) return false; con->dropped += pmsg.dropped; -- 2.25.1