[PATCH] xfs_io: actually issue 0 size writes

[Felix Blyakher]

On Aug 13, 2009, at 5:15 PM, Eric Sandeen wrote:

> While testing some stuff in generic_write_checks() in the
> kernel I realized that you can't actually use xfs_io to send
> a 0-byte write in.  This is actually a condition worth testing:
>
>       If  count  is zero and fd refers to a regular file,
>       then write() may return a failure status if one  of
>       the  errors  below  is  detected.  If no errors are
>       detected, 0 will be returned  without  causing  any
>       other  effect.

As I understand the desire to be able to issue 0 size writes
from xfs_io is to test the possibility of writing to a given fd.
What kind of errors would you expect to test for?

Otherwise looks good.

Felix

>
>
> So fix that up.
>
> Signed-off-by: Eric Sandeen <sandeen at sandeen.net>
> ---
>
> iff --git a/io/pwrite.c b/io/pwrite.c
> index 54c3f78..26a7850 100644
> --- a/io/pwrite.c
> +++ b/io/pwrite.c
> @@ -163,7 +163,7 @@ write_buffer(
> 	int		ops = 0;
>
> 	*total = 0;
> -	while (count > 0) {
> +	while (count >= 0) {
> 		if (fd > 0) {	/* input file given, read buffer first */
> 			if (read_buffer(fd, skip + *total, bs, &bar, 0, 1) < 0)
> 				break;
> @@ -182,6 +182,8 @@ write_buffer(
> 			break;
> 		offset += bytes;
> 		count -= bytes;
> +		if (count == 0)
> +			break;
> 	}
> 	return ops;
> }
>
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