Re: [PATCH] xfs_io: allow passing an open file to copy_range

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

On Wed, May 29, 2019 at 01:13:30PM +0300, Amir Goldstein wrote:
> Commit 1a05efba ("io: open pipes in non-blocking mode")
> addressed a specific copy_range issue with pipes by always opening
> pipes in non-blocking mode.
> 
> This change takes a different approach and allows passing any
> open file as the source file to copy_range.  Besides providing
> more flexibility to the copy_range command, this allows xfstests
> to check if xfs_io supports passing an open file to copy_range.
> 
> The intended usage is:
> $ mkfifo fifo
> $ xfs_io -f -n -r -c "open -f dst" -C "copy_range -f 0" fifo
> 
> Signed-off-by: Amir Goldstein <amir73il@gmail.com>
> ---
> 
> Darrick,
> 
> Folowing our discussion on the copy_range bounds test [1],
> what do you think about using copy_range -f in the copy_range
> fifo test with a fifo that was explicitly opened non-blocking,
> instead of trying to figure out if copy_range is going to hang
> or not?
> 
> This option is already available with sendfile command and
> we can make it available for reflink and dedupe commands if
> we want to. Too bad that these 4 commands have 3 different
> usage patterns to begin with...

I wonder if there's any sane way to overload the src_file argument such
that we can pass filetable[] offsets without having to burn more getopt
flags...?

(Oh wait, I bet you're using the '-f' flag to figure out if xfs_io is
new enough not to block on fifos, right? :))

But otherwise this seems like a reasonable approach.

> Thanks,
> Amir.
> 
> [1] https://marc.info/?l=fstests&m=155910786017989&w=2
> 
>  io/copy_file_range.c | 30 ++++++++++++++++++++++++------
>  man/man8/xfs_io.8    | 10 +++++++---
>  2 files changed, 31 insertions(+), 9 deletions(-)
> 
> diff --git a/io/copy_file_range.c b/io/copy_file_range.c
> index d069e5bb..1f0d2713 100644
> --- a/io/copy_file_range.c
> +++ b/io/copy_file_range.c
> @@ -26,6 +26,8 @@ copy_range_help(void)
>  					       file at offset 200\n\
>   'copy_range some_file' - copies all bytes from some_file into the open file\n\
>                            at position 0\n\
> + 'copy_range -f 2' - copies all bytes from open file 2 into the current open file\n\
> +                          at position 0\n\
>  "));
>  }
>  
> @@ -82,11 +84,12 @@ copy_range_f(int argc, char **argv)
>  	int opt;
>  	int ret;
>  	int fd;
> +	int src_file_arg = 1;
>  	size_t fsblocksize, fssectsize;
>  
>  	init_cvtnum(&fsblocksize, &fssectsize);
>  
> -	while ((opt = getopt(argc, argv, "s:d:l:")) != -1) {
> +	while ((opt = getopt(argc, argv, "s:d:l:f:")) != -1) {
>  		switch (opt) {
>  		case 's':
>  			src = cvtnum(fsblocksize, fssectsize, optarg);
> @@ -109,15 +112,30 @@ copy_range_f(int argc, char **argv)
>  				return 0;
>  			}
>  			break;
> +		case 'f':
> +			fd = atoi(argv[1]);
> +			if (fd < 0 || fd >= filecount) {
> +				printf(_("value %d is out of range (0-%d)\n"),
> +					fd, filecount-1);
> +				return 0;
> +			}
> +			fd = filetable[fd].fd;
> +			/* Expect no src_file arg */
> +			src_file_arg = 0;
> +			break;
>  		}
>  	}
>  
> -	if (optind != argc - 1)
> +	if (optind != argc - src_file_arg) {
> +		fprintf(stderr, "optind=%d, argc=%d, src_file_arg=%d\n", optind, argc, src_file_arg);
>  		return command_usage(&copy_range_cmd);
> +	}
>  
> -	fd = openfile(argv[optind], NULL, IO_READONLY, 0, NULL);
> -	if (fd < 0)
> -		return 0;
> +	if (src_file_arg) {

I wonder if it would be easier to declare "int fd = -1" and the only do
the openfile here if fd < 0?

Otherwise it seems fine to me...

--D

> +		fd = openfile(argv[optind], NULL, IO_READONLY, 0, NULL);
> +		if (fd < 0)
> +			return 0;
> +	}
>  
>  	if (src == 0 && dst == 0 && len == 0) {
>  		off64_t	sz;
> @@ -150,7 +168,7 @@ copy_range_init(void)
>  	copy_range_cmd.argmin = 1;
>  	copy_range_cmd.argmax = 7;
>  	copy_range_cmd.flags = CMD_NOMAP_OK | CMD_FOREIGN_OK;
> -	copy_range_cmd.args = _("[-s src_off] [-d dst_off] [-l len] src_file");
> +	copy_range_cmd.args = _("[-s src_off] [-d dst_off] [-l len] src_file | -f N");
>  	copy_range_cmd.oneline = _("Copy a range of data between two files");
>  	copy_range_cmd.help = copy_range_help;
>  
> diff --git a/man/man8/xfs_io.8 b/man/man8/xfs_io.8
> index 980dcfd3..6e064bdd 100644
> --- a/man/man8/xfs_io.8
> +++ b/man/man8/xfs_io.8
> @@ -660,12 +660,16 @@ Do not print timing statistics at all.
>  .RE
>  .PD
>  .TP
> -.BI "copy_range [ -s " src_offset " ] [ -d " dst_offset " ] [ -l " length " ] src_file"
> +.BI "copy_range [ -s " src_offset " ] [ -d " dst_offset " ] [ -l " length " ] src_file | \-f " N
>  On filesystems that support the
>  .BR copy_file_range (2)
> -system call, copies data from the
> +system call, copies data from the source file into the current open file.
> +The source must be specified either by path
> +.RB ( src_file )
> +or as another open file
> +.RB ( \-f ).
> +If
>  .I src_file
> -into the open file.  If
>  .IR src_offset ,
>  .IR dst_offset ,
>  and
> -- 
> 2.17.1
>