On 2/15/2017 04:07, Mora, Jorge wrote:
> Hello,
>
> The NFSv4.2 spec (RFC 7862) on section 15.2.3 (COPY description) says the following:
>
> If the source offset or the source offset plus count is greater than
> the size of the source file, the operation MUST fail with
> NFS4ERR_INVAL.
>
> I can understand failing with NFS4ERR_INVAL when the source offset is beyond the end of the file,
Yes, that's right.
> but do you think failing with NFS4ERR_INVAL is too strict when the source offset plus the count is beyond the end of the file?
> What is the rationalization for failing on this specific instance?
> Why not return a short copy instead?
The man-pages of copy_file_range description as,
EINVAL Requested range extends beyond the end of the source file; or
the flags argument is not 0.
So, the specific instance you said isn't allowed.
> Can the COPY return a count less than what it requested (a short copy)?
Yes, the return value of copy_file_range is,
RETURN VALUE
Upon successful completion, copy_file_range() will return the number of
bytes copied between files. This could be less than the length origi‐
nally requested.
>
> As of right now, the implementation on the Linux server adheres to the spec but copy_file_range succeeds
> when it is called against the local file system, NFSv4.x or NFSv3.
NFSv3 doesn't support copy_file_range, and only NFSv4.2 supports copy_file_range.
> For the local file system, NFSv4.x or NFSv3 copy_file_range falls back to regular copy by
> reading from the source file and then writing to the destination file but I do believe the
> syscall should be consistent regardless of the underlying file system.
>
>
> --Jorge
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