Re: [dpdk-dev] [PATCH] eal: fix check number of bytes from read function

["Jastrzebski, MichalX K" <michalx.k.jastrzebski@intel.com>]

> -----Original Message-----
> From: Thomas Monjalon [mailto:thomas.monjalon@6wind.com]
> Sent: Thursday, July 21, 2016 4:36 PM
> To: Jastrzebski, MichalX K <michalx.k.jastrzebski@intel.com>
> Cc: dev@dpdk.org; Richardson, Bruce <bruce.richardson@intel.com>;
> Kobylinski, MichalX <michalx.kobylinski@intel.com>; Gonzalez Monroy,
> Sergio <sergio.gonzalez.monroy@intel.com>; david.marchand@6wind.com
> Subject: Re: [dpdk-dev] [PATCH] eal: fix check number of bytes from read
> function
> 
> Hi,
> 
> 2016-07-20 16:24, Michal Jastrzebski:
> > -	if (read(fd, &page, sizeof(uint64_t)) < 0) {
> > +
> > +	retval = read(fd, &page, sizeof(uint64_t));
> > +	if (retval < 0) {
> >  		RTE_LOG(ERR, EAL, "%s(): cannot read /proc/self/pagemap:
> %s\n",
> >  				__func__, strerror(errno));
> >  		close(fd);
> >  		return RTE_BAD_PHYS_ADDR;
> > +	}	else if (retval >= 0 && retval < (int)sizeof(uint64_t))	{
> 

Hi Thomas,

> I have 4 comments about the above line:
That's too much for one line. I should improve next time:)

> - the check retval >= 0 is not needed because implied by else
> - why not checking retval != sizeof(uint64_t) as it is the exact expected
> value?

Yes, it is better solution,

> - (int)sizeof(uint64_t) can be replaced by 8 but it's shorter ;)

I didn't want to change all invokes of read() function here. 
I can use some macro:
#define PFN_MASK_SIZE	8
How do You think?

> - only 1 space is required between } and else
> 
> > +		RTE_LOG(ERR, EAL, "%s(): read %d bytes from
> /proc/self/pagemap "
> > +				"but expected %d: %s\n",
> > +				__func__, retval, (int)sizeof(uint64_t),
> strerror(errno));
> 
> Are you sure errno is meaningful here?

I think it is not. Will send v2.
> 
> > +		close(fd);
> > +		return RTE_BAD_PHYS_ADDR;
> >  	}

Thanks for a review
Michal.