[PATCH] xfs: prevent NMI timeouts in cmn_err

[Christoph Hellwig]

On Fri, Dec 03, 2010 at 03:38:46PM +1100, Dave Chinner wrote:
> FWIW, while these macros are the best way to make a simple backport
> is possible, I just discovered that mainline has a %pV format
> operator that allows an implementation like:
> 
> void
> xfs_fs_cmn_err(
> 	const char              *lvl,
> 	struct xfs_mount        *mp,
> 	const char              *fmt,
> 	...)
> {
> 	struct va_format        vaf;
> 	va_list                 args;
> 
> 	va_start(args, fmt);
> 	vaf.fmt = fmt;
> 	vaf.va = &args;
> 
> 	printk("%sFilesystem %s: %pV", lvl, mp->m_fsname, &vaf);
> 	va_end(args);
> 
> 	BUG_ON(strncmp(lvl, KERN_EMERG, strlen(KERN_EMERG)) == 0);
> }

With this we can also keep the existing integer-based CE_ values
and do trivial array lookup.  That also avoids having to do a strcmp for
every message printed.