Re: [PATCH 1/3] Add support for pwritev2()

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Thu, Sep 28, 2017 at 01:54:24PM -0500, Goldwyn Rodrigues wrote:
> From: Goldwyn Rodrigues <rgoldwyn@suse.com>
> 
> Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
> ---
>  io/Makefile |  2 +-
>  io/pwrite.c | 36 +++++++++++++++++++++++-------------
>  2 files changed, 24 insertions(+), 14 deletions(-)
> 
> diff --git a/io/Makefile b/io/Makefile
> index 62bc03b8..87649dc6 100644
> --- a/io/Makefile
> +++ b/io/Makefile
> @@ -87,7 +87,7 @@ endif
>  
>  # Also implies PWRITEV
>  ifeq ($(HAVE_PREADV),yes)
> -LCFLAGS += -DHAVE_PREADV -DHAVE_PWRITEV
> +LCFLAGS += -DHAVE_PREADV -DHAVE_PWRITEV -DHAVE_PWRITEV2

Uh..... preadv doesn't imply pwritev2.  Separate configure test, please.

>  endif
>  
>  ifeq ($(HAVE_READDIR),yes)
> diff --git a/io/pwrite.c b/io/pwrite.c
> index 67631ce5..82eaf827 100644
> --- a/io/pwrite.c
> +++ b/io/pwrite.c
> @@ -62,7 +62,8 @@ do_pwritev(
>  	int		fd,
>  	off64_t		offset,
>  	ssize_t		count,
> -	ssize_t		buffer_size)
> +	ssize_t		buffer_size,
> +	int 		pwritev2_flags)
>  {
>  	int vecs = 0;
>  	ssize_t oldlen = 0;
> @@ -81,7 +82,11 @@ do_pwritev(
>  	} else {
>  		vecs = vectors;
>  	}
> +#ifdef HAVE_PWRITEV2
> +	bytes = pwritev2(fd, iov, vectors, offset, pwritev2_flags);

If HAVE_PWRITEV2 is defined on the system that built xfs_io but the
system that runs xfs_io doesn't support this syscall, why do we not fall
back to pwritev if !pwritev2_flags?

--D

> +#else
>  	bytes = pwritev(fd, iov, vectors, offset);
> +#endif
>  
>  	/* restore trimmed iov */
>  	if (oldlen)
> @@ -98,12 +103,13 @@ do_pwrite(
>  	int		fd,
>  	off64_t		offset,
>  	ssize_t		count,
> -	ssize_t		buffer_size)
> +	ssize_t		buffer_size,
> +	int 		pwritev2_flags)
>  {
>  	if (!vectors)
>  		return pwrite64(fd, buffer, min(count, buffer_size), offset);
>  
> -	return do_pwritev(fd, offset, count, buffer_size);
> +	return do_pwritev(fd, offset, count, buffer_size, pwritev2_flags);
>  }
>  
>  static int
> @@ -111,7 +117,8 @@ write_random(
>  	off64_t		offset,
>  	long long	count,
>  	unsigned int	seed,
> -	long long	*total)
> +	long long	*total,
> +	int 		pwritev2_flags)
>  {
>  	off64_t		off, range;
>  	ssize_t		bytes;
> @@ -133,7 +140,7 @@ write_random(
>  				buffersize;
>  		else
>  			off = offset;
> -		bytes = do_pwrite(file->fd, off, buffersize, buffersize);
> +		bytes = do_pwrite(file->fd, off, buffersize, buffersize, pwritev2_flags);
>  		if (bytes == 0)
>  			break;
>  		if (bytes < 0) {
> @@ -153,7 +160,8 @@ static int
>  write_backward(
>  	off64_t		offset,
>  	long long	*count,
> -	long long	*total)
> +	long long	*total,
> +	int		pwritev2_flags)
>  {
>  	off64_t		end, off = offset;
>  	ssize_t		bytes = 0, bytes_requested;
> @@ -171,7 +179,7 @@ write_backward(
>  	if ((bytes_requested = (off % buffersize))) {
>  		bytes_requested = min(cnt, bytes_requested);
>  		off -= bytes_requested;
> -		bytes = do_pwrite(file->fd, off, bytes_requested, buffersize);
> +		bytes = do_pwrite(file->fd, off, bytes_requested, buffersize, pwritev2_flags);
>  		if (bytes == 0)
>  			return ops;
>  		if (bytes < 0) {
> @@ -189,7 +197,7 @@ write_backward(
>  	while (cnt > end) {
>  		bytes_requested = min(cnt, buffersize);
>  		off -= bytes_requested;
> -		bytes = do_pwrite(file->fd, off, cnt, buffersize);
> +		bytes = do_pwrite(file->fd, off, cnt, buffersize, pwritev2_flags);
>  		if (bytes == 0)
>  			break;
>  		if (bytes < 0) {
> @@ -212,7 +220,8 @@ write_buffer(
>  	size_t		bs,
>  	int		fd,
>  	off64_t		skip,
> -	long long	*total)
> +	long long	*total,
> +	int		pwritev2_flags)
>  {
>  	ssize_t		bytes;
>  	long long	bar = min(bs, count);
> @@ -224,7 +233,7 @@ write_buffer(
>  			if (read_buffer(fd, skip + *total, bs, &bar, 0, 1) < 0)
>  				break;
>  		}
> -		bytes = do_pwrite(file->fd, offset, count, bar);
> +		bytes = do_pwrite(file->fd, offset, count, bar, pwritev2_flags);
>  		if (bytes == 0)
>  			break;
>  		if (bytes < 0) {
> @@ -258,6 +267,7 @@ pwrite_f(
>  	int		Cflag, qflag, uflag, dflag, wflag, Wflag;
>  	int		direction = IO_FORWARD;
>  	int		c, fd = -1;
> +	int		pwritev2_flags = 0;
>  
>  	Cflag = qflag = uflag = dflag = wflag = Wflag = 0;
>  	init_cvtnum(&fsblocksize, &fssectsize);
> @@ -365,13 +375,13 @@ pwrite_f(
>  	case IO_RANDOM:
>  		if (!zeed)	/* srandom seed */
>  			zeed = time(NULL);
> -		c = write_random(offset, count, zeed, &total);
> +		c = write_random(offset, count, zeed, &total, pwritev2_flags);
>  		break;
>  	case IO_FORWARD:
> -		c = write_buffer(offset, count, bsize, fd, skip, &total);
> +		c = write_buffer(offset, count, bsize, fd, skip, &total, pwritev2_flags);
>  		break;
>  	case IO_BACKWARD:
> -		c = write_backward(offset, &count, &total);
> +		c = write_backward(offset, &count, &total, pwritev2_flags);
>  		break;
>  	default:
>  		total = 0;
> -- 
> 2.14.1
> 
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