linux-kernel - Re: [PATCH 2/2] [PATCH 2/2] proc-vmcore: wrong data type casting fix

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Message-ID: <20160311074827.GA8337@dhcp-128-65.nay.redhat.com>
Date:	Fri, 11 Mar 2016 15:48:27 +0800
From:	Dave Young <dyoung@...hat.com>
To:	Minfei Huang <mhuang@...hat.com>
Cc:	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	d.hatayama@...fujitsu.com, bhe@...hat.com, vgoyal@...hat.com,
	kexec@...ts.infradead.org
Subject: Re: [PATCH 2/2] [PATCH 2/2] proc-vmcore: wrong data type casting fix

Hi, Minfei

On 03/11/16 at 03:19pm, Minfei Huang wrote:
> On 03/11/16 at 02:21pm, dyoung@...hat.com wrote:
> > @@ -231,7 +231,8 @@ static ssize_t __read_vmcore(char *buffe
> >  
> >  	list_for_each_entry(m, &vmcore_list, list) {
> >  		if (*fpos < m->offset + m->size) {
> > -			tsz = min_t(size_t, m->offset + m->size - *fpos, buflen);
> > +			tsz = (size_t)min_lt(m->offset + m->size - *fpos,
> > +					    buflen);
> >  			start = m->paddr + *fpos - m->offset;
> >  			tmp = read_from_oldmem(buffer, tsz, &start, userbuf);
> >  			if (tmp < 0)
> > @@ -461,7 +462,7 @@ static int mmap_vmcore(struct file *file
> >  		if (start < m->offset + m->size) {
> >  			u64 paddr = 0;
> >  
> > -			tsz = min_t(size_t, m->offset + m->size - start, size);
> > +			tsz = (size_t)min_lt(m->offset + m->size - start, size);
> >  			paddr = m->paddr + start - m->offset;
> >  			if (vmcore_remap_oldmem_pfn(vma, vma->vm_start + len,
> >  						    paddr >> PAGE_SHIFT, tsz,
> 
> Hi, Dave.
> 
> Seems the previous parameter is unsigned long long, and the later one is
> size_t. The size of both these types doesn't change in running time, why
> not use min_t(unsigned long long, a, b) instead?

Just want a common macro so it can benefit other users so that we can simply
use it without knowning type details and avoid such similar bugs also.

Thanks
Dave