linux-kernel - Re: [PATCH] kmsg: Use vmalloc instead of kmalloc when writing

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Message-ID: <20120330234306.GC21328@kroah.com>
Date:	Fri, 30 Mar 2012 16:43:06 -0700
From:	Greg KH <gregkh@...uxfoundation.org>
To:	Sasha Levin <levinsasha928@...il.com>
Cc:	Arnd Bergmann <arnd@...db.de>,
	Thomas Gleixner <tglx@...utronix.de>, viro@...iv.linux.org.uk,
	davej@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kmsg: Use vmalloc instead of kmalloc when writing

On Sat, Mar 31, 2012 at 12:02:39AM +0200, Sasha Levin wrote:
> On Fri, Mar 30, 2012 at 11:17 PM, Greg KH <gregkh@...uxfoundation.org> wrote:
> > On Fri, Mar 30, 2012 at 09:05:52PM +0000, Arnd Bergmann wrote:
> >> On Friday 30 March 2012, Thomas Gleixner wrote:
> >> > I think so. This is an interface to inject stuff into dmesg. Limiting
> >> > that to a reasonable size makes sense. We can probably limit it to
> >> > something small like 1024, but I don't know about the "ideas" of those
> >> > folks who think that it's a great idea to do it at all.
> >>
> >> I guess a page would be a reasonable size, similar to what we do for
> >> sysfs.
> >
> > Ok. Sasha, as you seem to have noticed this, care to dig in syslog and
> > systemd to get an idea of the buffer sizes they are expecting to pass
> > into kmsg, and if they can handle a short write properly?  If so,
> > restricting it to a page is fine with me, otherwise we might want to
> > make it a bit bigger.
> 
> systemd seems to use posix LINE_MAX sized buffers, syslog-ng uses
> dynamic strings, but it chews them one line at the time.

Ok, care to update this patch with a max size?

And again, does systemd and syslog-ng handle short writes properly?

thanks,

greg k-h
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