On Fri, Dec 04, 2015 at 12:05:05PM -0500, Anna Schumaker wrote:
> On 12/04/2015 11:49 AM, J. Bruce Fields wrote:
> > On Fri, Dec 04, 2015 at 10:49:24AM -0500, Anna Schumaker wrote:
> >> On 12/04/2015 10:45 AM, J. Bruce Fields wrote:
> >>> On Thu, Dec 03, 2015 at 03:55:35PM -0500, Anna Schumaker wrote:
> >>>> @@ -498,6 +499,22 @@ __be32 nfsd4_set_nfs4_label(struct svc_rqst *rqstp, struct svc_fh *fhp,
> >>>> }
> >>>> #endif
> >>>>
> >>>> +ssize_t nfsd_copy_range(struct file *src, u64 src_pos,
> >>>> + struct file *dst, u64 dst_pos,
> >>>> + u64 count)
> >>>> +{
> >>>> + ssize_t bytes;
> >>>> + u64 limit = 0x10000000;
> >>>
> >>> Why that value? Could I get a comment here?
> >>
> >> Whoops! I had a comment there at one point, but I must have deleted it :(. That value is to cap copies to 256MB.
> >
> > Could you include some justification for the choice of that particular
> > value?
>
> Yeah, I can run tests with different values and include the results in v2.
>
> >
> >>>> + if (count > limit)
> >>>> + count = limit;
> >>>> +
> >>>> + bytes = vfs_copy_file_range(src, src_pos, dst, dst_pos, count, 0);
> >>>
> >>> Sorry, I lost track of the copy discussions: does this only work on
> >>> filesystems with special support, or does it fall back on doing the copy
> >>> by hand? Which filesystems (of the exportable filesystems) support
> >>> this?
> >>
> >> The system call falls back on doing the copy by hand if there is no filesystem acceleration.
> >
> > Is this practical? It means a huge range in possible latency of the
> > single COPY call depending on filesystem.
>
> That's why I'm breaking copies into smaller chunks, rather than doing everything at once.
>
> >
> > I guess I can live with it and we can see if people run into problems in
> > practice. But let's make sure this is documented.
>
> Okay. I'll add documentation about this!
OK, thanks. I think those are my only concerns, good to see that this
is all the new code we need now.--b.
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