Re: [dpdk-dev] [PATCH v7 04/10] vhost: add two new messages to support a shared buffer

[Tiwei Bie <tiwei.bie@intel.com>]

On Thu, Sep 26, 2019 at 11:06:22PM +0800, Yu, Jin wrote:
> > >
> > > +static int
> > > +mem_create(const char *name, unsigned int flags) { #ifdef
> > > +MEMFD_SUPPORTED
> > > +	return memfd_create(name, flags);
> > > +#else
> > > +	RTE_LOG(ERR, VHOST_CONFIG,
> > > +		"doesn't support memfd--name:%s and flag:%x\n",
> > > +		name, flags);
> > 
> > You probably don't want to always print an error when memfd isn't available.
> I saw below error message from ci/Intel-compilation. 
> ../lib/librte_vhost/vhost_user.c:1202:24: error: unused parameter ‘name’ [-Werror=unused-parameter]
>  mem_create(const char *name, unsigned int flags)
>                         ^~~~
> ../lib/librte_vhost/vhost_user.c:1202:43: error: unused parameter ‘flags’ [-Werror=unused-parameter]
>  mem_create(const char *name, unsigned int flags)
> 
> That's why I add this print.Should I ignore this?

Looks better to do it like this (compile test only):

static void *
inflight_mem_alloc(const char *name, size_t size, int *fd)
{
	char fname[20] = "/tmp/memfd-XXXXXX";
	int mfd = -1;
	void *addr;

#ifdef MEMFD_SUPPORTED
	mfd = memfd_create(name, MFD_CLOEXEC);
#else
	RTE_SET_USED(name);
#endif
	if (mfd == -1) {
		mfd = mkstemp(fname);
		if (mfd == -1) {
			RTE_LOG(ERR, VHOST_CONFIG,
				"failed to create memory file for inflight buffer\n");
			return NULL;
		}
		unlink(fname);
	}

	if (ftruncate(mfd, size) == -1) {
		RTE_LOG(ERR, VHOST_CONFIG,
			"failed to truncate memory file for inflight buffer\n");
		close(mfd);
		return NULL;
	}

	addr = mmap(0, size, PROT_READ | PROT_WRITE, MAP_SHARED, mfd, 0);
	if (addr == MAP_FAILED) {
		RTE_LOG(ERR, VHOST_CONFIG,
			"failed to map memory file for inflight buffer\n");
		close(mfd);
		return NULL;
	}

	*fd = mfd;
	return addr;
}

And you don't need to define CLOEXEC by yourself.


> Thanks.
> 
> > 
> > > +	return -1;
> > > +#endif
> > > +}
> > > +
> > > +static void *
> > > +inflight_mem_alloc(const char *name, size_t size, int *fd) {
> > > +	void *ptr;
> > > +	int mfd = -1;
> > > +	char fname[20] = "/tmp/memfd-XXXXXX";
> > > +
> > > +	*fd = -1;
> > > +	mfd = mem_create(name, CLOEXEC);
> > > +	if (mfd != -1) {
> > > +		if (ftruncate(mfd, size) == -1) {
> > > +			RTE_LOG(ERR, VHOST_CONFIG,
> > > +				"ftruncate fail for alloc inflight buffer\n");
> > > +			close(mfd);
> > > +			return NULL;
> > > +		}
> > > +	} else {
> > > +		mfd = mkstemp(fname);
> > > +		unlink(fname);
> > > +
> > > +		if (mfd == -1) {
> > > +			RTE_LOG(ERR, VHOST_CONFIG,
> > > +				"mkstemp fail for alloc inflight buffer\n");
> > > +			return NULL;
> > > +		}
> > > +
> > > +		if (ftruncate(mfd, size) == -1) {
> > > +			RTE_LOG(ERR, VHOST_CONFIG,
> > > +				"ftruncate fail for alloc inflight buffer\n");
> > > +			close(mfd);
> > > +			return NULL;
> > > +		}
> > > +	}
> > > +
> > > +	ptr = mmap(0, size, PROT_READ | PROT_WRITE, MAP_SHARED, mfd, 0);
> > > +	if (ptr == MAP_FAILED) {
> > > +		RTE_LOG(ERR, VHOST_CONFIG,
> > > +			"mmap fail for alloc inflight buffer\n");
> > > +		close(mfd);
> > > +		return NULL;
> > > +	}
> > > +
> > > +	*fd = mfd;
> > > +	return ptr;
> > > +}