Re: [PATCH v2 2/4] btrfs: make __btrfs_dump_space_info() output better formatted

[Boris Burkov <boris@bur.io>]

On Tue, Jul 26, 2022 at 11:39:28PM +0200, David Sterba wrote:
> On Tue, Jul 26, 2022 at 01:53:33PM -0700, Boris Burkov wrote:
> > > Yes we shold care about readability but kernel printk output lines can
> > > be interleaved, single line is much easier to grep for and all the
> > > values are from one event. The format where it's a series of "key=value"
> > > is common and I think we're used to it from tracepoints too. There are
> > > lines that do not put "=" between keys and values we could unify that
> > > eventually.
> > 
> > Agreed that a long line is OK, and preferable to full on splitting.
> > 
> > What about making some btrfs printing macros that use KERN_CONT? I think
> > that would do what Qu wants without splitting the lines or being bad for
> > ratelimiting.
> 
> IIRC I've read some discussions about KERN_CONT suggesting not to use
> it, I'll ask what's the status.

I just saw a comment at its definition that reads:

/*
 * Annotation for a "continued" line of log printout (only done after a
 * line that had no enclosing \n). Only to be used by core/arch code
 * during early bootup (a continued line is not SMP-safe otherwise).
 */
#define KERN_CONT       KERN_SOH "c"

So that's not an encouraging sign. OTOH, I found some code in
ext4/super.c that prints its errors with KERN_CONT here:
'ext4: super.c: Update logging style using KERN_CONT'