linux-kernel - Re: [PATCH 13/13] libnvdimm, namespace: Publish page structure init state / control

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Date:   Thu, 5 Jul 2018 12:49:36 -0700
From:   Matthew Wilcox <willy@...radead.org>
To:     Dan Williams <dan.j.williams@...el.com>
Cc:     Johannes Thumshirn <jthumshirn@...e.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Ross Zwisler <ross.zwisler@...ux.intel.com>,
        Vishal Verma <vishal.l.verma@...el.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Jeff Moyer <jmoyer@...hat.com>, Christoph Hellwig <hch@....de>,
        linux-nvdimm <linux-nvdimm@...ts.01.org>,
        Linux MM <linux-mm@...ck.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 13/13] libnvdimm, namespace: Publish page structure init
 state / control

On Thu, Jul 05, 2018 at 07:46:05AM -0700, Dan Williams wrote:
> On Thu, Jul 5, 2018 at 1:29 AM, Johannes Thumshirn <jthumshirn@...e.de> wrote:
> > On Wed, Jul 04, 2018 at 11:50:13PM -0700, Dan Williams wrote:
> >> +static ssize_t memmap_state_store(struct device *dev,
> >> +             struct device_attribute *attr, const char *buf, size_t len)
> >> +{
> >> +     int i;
> >> +     struct nd_pfn *nd_pfn = to_nd_pfn_safe(dev);
> >> +     struct memmap_async_state *async = &nd_pfn->async;
> >> +
> >> +     if (strcmp(buf, "sync") == 0)
> >> +             /* pass */;
> >> +     else if (strcmp(buf, "sync\n") == 0)
> >> +             /* pass */;
> >> +     else
> >> +             return -EINVAL;
> >
> > Hmm what about:
> >
> >         if (strncmp(buf, "sync", 4))
> >            return -EINVAL;
> >
> > This collapses 6 lines into 4.
> 
> ...but that also allows 'echo "syncAndThenSomeGarbage" >
> /sys/.../memmap_state' to succeed.

	if (strncmp(buf, "sync", 4))
		return -EINVAL;
	if (buf[4] != '\0' && buf[4] != '\n')
		return -EINVAL;