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!
Anna
>
> --b.
> --
> To unsubscribe from this list: send the line "unsubscribe linux-nfs" in
> the body of a message to majordomo@xxxxxxxxxxxxxxx
> More majordomo info at http://vger.kernel.org/majordomo-info.html
>
--
To unsubscribe from this list: send the line "unsubscribe linux-nfs" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
