linux-kernel - Re: [PATCH v4] lib: add size unit t/p/e to memparse

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Message-ID: <1402977569.5755.3.camel@localhost.localdomain>
Date:	Tue, 17 Jun 2014 11:59:29 +0800
From:	Gui Hecheng <guihc.fnst@...fujitsu.com>
To:	David Rientjes <rientjes@...gle.com>
CC:	<linux-kernel@...r.kernel.org>, <linux-btrfs@...r.kernel.org>,
	<akpm@...ux-foundation.org>
Subject: Re: [PATCH v4] lib: add size unit t/p/e to memparse

On Mon, 2014-06-16 at 18:29 -0700, David Rientjes wrote:
> On Tue, 17 Jun 2014, Gui Hecheng wrote:
> 
> > > > diff --git a/lib/cmdline.c b/lib/cmdline.c
> > > > index d4932f7..76a712e 100644
> > > > --- a/lib/cmdline.c
> > > > +++ b/lib/cmdline.c
> > > > @@ -121,11 +121,7 @@ EXPORT_SYMBOL(get_options);
> > > >   *	@retptr: (output) Optional pointer to next char after parse completes
> > > >   *
> > > >   *	Parses a string into a number.  The number stored at @ptr is
> > > > - *	potentially suffixed with %K (for kilobytes, or 1024 bytes),
> > > > - *	%M (for megabytes, or 1048576 bytes), or %G (for gigabytes, or
> > > > - *	1073741824).  If the number is suffixed with K, M, or G, then
> > > > - *	the return value is the number multiplied by one kilobyte, one
> > > > - *	megabyte, or one gigabyte, respectively.
> > > > + *	potentially suffixed with K, M, G, T, P, E.
> > > >   */
> > > >  
> > > >  unsigned long long memparse(const char *ptr, char **retptr)
> > > > @@ -135,6 +131,15 @@ unsigned long long memparse(const char *ptr, char **retptr)
> > > >  	unsigned long long ret = simple_strtoull(ptr, &endptr, 0);
> > > >  
> > > >  	switch (*endptr) {
> > > > +	case 'E':
> > > > +	case 'e':
> > > > +		ret <<= 10;
> > > > +	case 'P':
> > > > +	case 'p':
> > > > +		ret <<= 10;
> > > > +	case 'T':
> > > > +	case 't':
> > > > +		ret <<= 10;
> > > >  	case 'G':
> > > >  	case 'g':
> > > >  		ret <<= 10;
> > > 
> > > Seems fine since unsigned long long is always at least 64 bits, but 
> > > perhaps also change simple_strtoull() to use kstrtoull() at the same time 
> > > since the former is deprecated?
> > 
> > Yes, that is a point. But the deprecated function is a separate problem
> > and may not be included in this patch.
> > Also, I find that simple_strtoull is used in many places in the kernel
> > code, it is better to replace it globally?
> > 
> 
> If you're going to have a go at replacing the simple_strto*() functions 
> throughout the kernel, it's probably better to do it per subsystem (as 
> defined by the separate sections of MAINTAINERS) and propose the patches 
> individually to those maintainers.  Once it has been removed entirely, you 
> can submit a patch to remove the functions themselves.
> 
> Be aware that there are many callers to the deprecated functions so it may 
> take a significant amount of time.

Hmmmm...It may really take a long time. But I am not sure whether this
is really a good idea to do this big replacement. Let's see whether
anyone would like to share his opinions.

-Gui

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