iv/linux
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

printk: use printk_buffers for devkmsg

Browse Source 
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 <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20230109100800.1085541-8-john.ogness@linutronix.de
This commit is contained in:
John Ogness 2023-01-09 11:13:59 +01:06 committed by Petr Mladek
parent c4fcc617e1
commit ea308da119
1 changed files with 22 additions and 27 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

49
kernel/printk/printk.c
View File

@ -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, pmsg.seq + 1);
atomic64_set(&user->seq, r->info->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;