[PATCH] printk: Remove no longer used LOG_PREFIX.

[PATCH] printk: Remove no longer used LOG_PREFIX.

[Tetsuo Handa]

When commit 5becfb1df5ac8e49 ("kmsg: merge continuation records while
printing") introduced LOG_PREFIX, we used KERN_DEFAULT etc. as a flag
for setting LOG_PREFIX in order to tell whether to call cont_add()
(i.e. whether to append the message to "struct cont").

But since commit 4bcc595ccd80decb ("printk: reinstate KERN_CONT for
printing continuation lines") inverted the behavior (i.e. don't append
the message to "struct cont" unless KERN_CONT is specified) and commit
5aa068ea4082b39e ("printk: remove games with previous record flags")
removed the last LOG_PREFIX check, setting LOG_PREFIX via KERN_DEFAULT
etc. is no longer meaningful.

Therefore, we can remove LOG_PREFIX and make KERN_DEFAULT empty string.

Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
---
 include/linux/kern_levels.h | 2 +-
 include/linux/printk.h      | 1 -
 kernel/printk/printk.c      | 6 +-----
 3 files changed, 2 insertions(+), 7 deletions(-)

diff --git a/include/linux/kern_levels.h b/include/linux/kern_levels.h
index d237fe8..bf2389c 100644
--- a/include/linux/kern_levels.h
+++ b/include/linux/kern_levels.h
@@ -14,7 +14,7 @@
 #define KERN_INFO	KERN_SOH "6"	/* informational */
 #define KERN_DEBUG	KERN_SOH "7"	/* debug-level messages */
 
-#define KERN_DEFAULT	KERN_SOH "d"	/* the default kernel loglevel */
+#define KERN_DEFAULT	""		/* the default kernel loglevel */
 
 /*
  * Annotation for a "continued" line of log printout (only done after a
diff --git a/include/linux/printk.h b/include/linux/printk.h
index 77740a5..9fe6c9e 100644
--- a/include/linux/printk.h
+++ b/include/linux/printk.h
@@ -18,7 +18,6 @@ static inline int printk_get_level(const char *buffer)
 	if (buffer[0] == KERN_SOH_ASCII && buffer[1]) {
 		switch (buffer[1]) {
 		case '0' ... '7':
-		case 'd':	/* KERN_DEFAULT */
 		case 'c':	/* KERN_CONT */
 			return buffer[1];
 		}
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index d3d1703..3e4a735 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -344,7 +344,6 @@ enum con_msg_format_flags {
 
 enum log_flags {
 	LOG_NEWLINE	= 2,	/* text ended with a newline */
-	LOG_PREFIX	= 4,	/* text started with a prefix */
 	LOG_CONT	= 8,	/* text is a fragment of a continuation line */
 };
 
@@ -1867,9 +1866,6 @@ int vprintk_store(int facility, int level,
 			case '0' ... '7':
 				if (level == LOGLEVEL_DEFAULT)
 					level = kern_level - '0';
-				/* fallthrough */
-			case 'd':	/* KERN_DEFAULT */
-				lflags |= LOG_PREFIX;
 				break;
 			case 'c':	/* KERN_CONT */
 				lflags |= LOG_CONT;
@@ -1884,7 +1880,7 @@ int vprintk_store(int facility, int level,
 		level = default_message_loglevel;
 
 	if (dict)
-		lflags |= LOG_PREFIX|LOG_NEWLINE;
+		lflags |= LOG_NEWLINE;
 
 	return log_output(facility, level, lflags,
 			  dict, dictlen, text, text_len);
-- 
1.8.3.1

Re: [PATCH] printk: Remove no longer used LOG_PREFIX.

[Tetsuo Handa]

Can this patch go to Linux 5.1?

On 2019/02/22 18:59, Tetsuo Handa wrote:
> When commit 5becfb1df5ac8e49 ("kmsg: merge continuation records while
> printing") introduced LOG_PREFIX, we used KERN_DEFAULT etc. as a flag
> for setting LOG_PREFIX in order to tell whether to call cont_add()
> (i.e. whether to append the message to "struct cont").
> 
> But since commit 4bcc595ccd80decb ("printk: reinstate KERN_CONT for
> printing continuation lines") inverted the behavior (i.e. don't append
> the message to "struct cont" unless KERN_CONT is specified) and commit
> 5aa068ea4082b39e ("printk: remove games with previous record flags")
> removed the last LOG_PREFIX check, setting LOG_PREFIX via KERN_DEFAULT
> etc. is no longer meaningful.
> 
> Therefore, we can remove LOG_PREFIX and make KERN_DEFAULT empty string.
> 
> Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
> ---
>  include/linux/kern_levels.h | 2 +-
>  include/linux/printk.h      | 1 -
>  kernel/printk/printk.c      | 6 +-----
>  3 files changed, 2 insertions(+), 7 deletions(-)

Re: [PATCH] printk: Remove no longer used LOG_PREFIX.

[Petr Mladek]

On Fri 2019-03-01 19:31:59, Tetsuo Handa wrote:
> Can this patch go to Linux 5.1?

I am going to look at it the following week. I do not think that
it is necessary to hurry a clean up of old stuff up into 5.1.

I believe that it is correct. But it is not a typo fix. For example,
I want to double check what was the history of KERN_DEFAULT defined
as "d". It existed since ages...

Best Regards,
Petr

> On 2019/02/22 18:59, Tetsuo Handa wrote:
> > When commit 5becfb1df5ac8e49 ("kmsg: merge continuation records while
> > printing") introduced LOG_PREFIX, we used KERN_DEFAULT etc. as a flag
> > for setting LOG_PREFIX in order to tell whether to call cont_add()
> > (i.e. whether to append the message to "struct cont").
> > 
> > But since commit 4bcc595ccd80decb ("printk: reinstate KERN_CONT for
> > printing continuation lines") inverted the behavior (i.e. don't append
> > the message to "struct cont" unless KERN_CONT is specified) and commit
> > 5aa068ea4082b39e ("printk: remove games with previous record flags")
> > removed the last LOG_PREFIX check, setting LOG_PREFIX via KERN_DEFAULT
> > etc. is no longer meaningful.
> > 
> > Therefore, we can remove LOG_PREFIX and make KERN_DEFAULT empty string.
> > 
> > Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
> > ---
> >  include/linux/kern_levels.h | 2 +-
> >  include/linux/printk.h      | 1 -
> >  kernel/printk/printk.c      | 6 +-----
> >  3 files changed, 2 insertions(+), 7 deletions(-)

Re: [PATCH] printk: Remove no longer used LOG_PREFIX.

[Joe Perches]

On Fri, 2019-03-01 at 13:48 +0100, Petr Mladek wrote:
> I want to double check what was the history of KERN_DEFAULT defined
> as "d". It existed since ages...

There less than 100 uses of KERN_DEFAULT.

Relatively speaking, KERN_DEFAULT hasn't existed all
that long actually.

commit e28d713704117bca0820c732210df6075b09f13b
Author: Linus Torvalds <torvalds@linux-foundation.org>
Date:   Tue Jun 16 11:02:28 2009 -0700

    printk: Add KERN_DEFAULT printk log-level

    This adds a KERN_DEFAULT loglevel marker, for when you cannot decide
    which loglevel you want, and just want to keep an existing printk
    with the default loglevel.
    
    The difference between having KERN_DEFAULT and having no log-level
    marker at all is two-fold:
    
     - having the log-level marker will now force a new-line if the
       previous printout had not added one (perhaps because it forgot,
       but perhaps because it expected a continuation)
    
     - having a log-level marker is required if you are printing out a
       message that otherwise itself could perhaps otherwise be mistaken
       for a log-level.
    
    Signed-of-by: Linus Torvalds <torvalds@linux-foundation.org>

Ever since Linus changed the default logging mechanism
for printks and KERN_CONT uses in

commit 4bcc595ccd80decb4245096e3d1258989c50ed41
Author: Linus Torvalds <torvalds@linux-foundation.org>
Date:   Sat Oct 8 20:32:40 2016 -0700

    printk: reinstate KERN_CONT for printing continuation lines
    
the listed reasons in commit e28d713704117bca0820c732210df6075b09f13b
for the use of KERN_DEFAULT are no longer necessary.

I still think it'd be better to remove KERN_DEFAULT altogether.

Re: [PATCH] printk: Remove no longer used LOG_PREFIX.

[Sergey Senozhatsky]

On (02/22/19 18:59), Tetsuo Handa wrote:
> When commit 5becfb1df5ac8e49 ("kmsg: merge continuation records while
> printing") introduced LOG_PREFIX, we used KERN_DEFAULT etc. as a flag
> for setting LOG_PREFIX in order to tell whether to call cont_add()
> (i.e. whether to append the message to "struct cont").
> 
> But since commit 4bcc595ccd80decb ("printk: reinstate KERN_CONT for
> printing continuation lines") inverted the behavior (i.e. don't append
> the message to "struct cont" unless KERN_CONT is specified) and commit
> 5aa068ea4082b39e ("printk: remove games with previous record flags")
> removed the last LOG_PREFIX check, setting LOG_PREFIX via KERN_DEFAULT
> etc. is no longer meaningful.
> 
> Therefore, we can remove LOG_PREFIX and make KERN_DEFAULT empty string.
> 
> Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>

Looks good to me. Well, at least I don't see any problems with the patch.
We can do a tree-wide KERN_DEFAULT removal later.

Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>

	-ss

Re: [PATCH] printk: Remove no longer used LOG_PREFIX.

[Petr Mladek]

On Mon 2019-03-04 11:22:29, Sergey Senozhatsky wrote:
> On (02/22/19 18:59), Tetsuo Handa wrote:
> > When commit 5becfb1df5ac8e49 ("kmsg: merge continuation records while
> > printing") introduced LOG_PREFIX, we used KERN_DEFAULT etc. as a flag
> > for setting LOG_PREFIX in order to tell whether to call cont_add()
> > (i.e. whether to append the message to "struct cont").
> > 
> > But since commit 4bcc595ccd80decb ("printk: reinstate KERN_CONT for
> > printing continuation lines") inverted the behavior (i.e. don't append
> > the message to "struct cont" unless KERN_CONT is specified) and commit
> > 5aa068ea4082b39e ("printk: remove games with previous record flags")
> > removed the last LOG_PREFIX check, setting LOG_PREFIX via KERN_DEFAULT
> > etc. is no longer meaningful.
> > 
> > Therefore, we can remove LOG_PREFIX and make KERN_DEFAULT empty string.
> > 
> > Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
> 
> Looks good to me. Well, at least I don't see any problems with the patch.
> We can do a tree-wide KERN_DEFAULT removal later.

Yup.

> Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>

With a fresh head after the weekend, the patch looks fine and
pretty safe to me.

I have pushed it into for-5.1 branch.

Best Regards,
Petr