Re: [PATCH] xfs_io: copy_range don't truncate dst_file, and add smart length.

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

On Fri, Sep 06, 2019 at 01:39:27PM +0800, Jianhong.Yin wrote:
> 1. copy_range should be a simple wrapper for copy_file_range(2)
> and nothing else. and there's already -t option for truncate.
> so here we remove the truncate action in copy_range.
> see: https://patchwork.kernel.org/comment/22863587/#1
> 
> 2. improve the default length value generation:
> if -l option is omitted use the length that from src_offset to end
> (src_file's size - src_offset) instead.
> if src_offset is greater than file size, length is 0.
> 
> 3. update manpage
> 
> and have confirmed that this change will not affect xfstests.
> 
> Signed-off-by: Jianhong Yin <yin-jianhong@163.com>
> ---
>  io/copy_file_range.c | 22 +++++-----------------
>  man/man8/xfs_io.8    |  9 +++------
>  2 files changed, 8 insertions(+), 23 deletions(-)
> 
> diff --git a/io/copy_file_range.c b/io/copy_file_range.c
> index b7b9fd88..02d50e53 100644
> --- a/io/copy_file_range.c
> +++ b/io/copy_file_range.c
> @@ -66,21 +66,13 @@ copy_src_filesize(int fd)
>  	return st.st_size;
>  }
>  
> -static int
> -copy_dst_truncate(void)
> -{
> -	int ret = ftruncate(file->fd, 0);
> -	if (ret < 0)
> -		perror("ftruncate");
> -	return ret;
> -}
> -
>  static int
>  copy_range_f(int argc, char **argv)
>  {
>  	long long src = 0;
>  	long long dst = 0;
>  	size_t len = 0;
> +	int len_ommited = 1;

Nit: The correct spelling is "omitted", not "ommited".  As in,

bool len_omitted = true;

(You could also call it "len_specified" since it's a little odd to
declare that it's ommitted before we even parse the arguments but now
we're just splitting hairs...)

>  	int opt;
>  	int ret;
>  	int fd;
> @@ -112,6 +104,7 @@ copy_range_f(int argc, char **argv)
>  				printf(_("invalid length -- %s\n"), optarg);
>  				return 0;
>  			}
> +			len_ommited = 0;
>  			break;
>  		case 'f':
>  			src_file_nr = atoi(argv[1]);
> @@ -137,7 +130,7 @@ copy_range_f(int argc, char **argv)
>  		fd = filetable[src_file_nr].fd;
>  	}
>  
> -	if (src == 0 && dst == 0 && len == 0) {
> +	if (len_ommited) {
>  		off64_t	sz;
>  
>  		sz = copy_src_filesize(fd);
> @@ -145,13 +138,8 @@ copy_range_f(int argc, char **argv)
>  			ret = 1;
>  			goto out;
>  		}
> -		len = sz;
> -
> -		ret = copy_dst_truncate();
> -		if (ret < 0) {
> -			ret = 1;
> -			goto out;
> -		}
> +		if (sz > src)
> +			len = sz - src;
>  	}
>  
>  	ret = copy_file_range_cmd(fd, &src, &dst, len);
> diff --git a/man/man8/xfs_io.8 b/man/man8/xfs_io.8
> index 6e064bdd..8bfaeeba 100644
> --- a/man/man8/xfs_io.8
> +++ b/man/man8/xfs_io.8
> @@ -669,13 +669,10 @@ The source must be specified either by path
>  or as another open file
>  .RB ( \-f ).
>  If
> -.I src_file
> -.IR src_offset ,
> -.IR dst_offset ,
> -and
>  .I length
> -are omitted the contents of src_file will be copied to the beginning of the
> -open file, overwriting any data already there.
> +is omitted will use ( src_size - 
> +.I src_offset
> +) instead.

"If length is not specified, this command copies data from src_offset to
the end of the src_file into the dst_file at dst_offset." ?

--D

>  .RS 1.0i
>  .PD 0
>  .TP 0.4i
> -- 
> 2.21.0
>