Hi,
I am not able to find the implementation of directory delegation,
either. Similarly, the callback functions CB_NOTIFY is not
implemented, either. I find that in preprocss_nfs41_op() in
callback_xdr.c, whenever a CB_NOTIFY is encountered, an
NFS4ERR_NOTSUPP is returned directly.
Am I missing something? Or they are just not supported in the current version?
Thanks a lot!
best,
Yudong
On Mon, Aug 2, 2010 at 5:17 PM, Yudong Gao <[email protected]> wrote:
> Hi,
>
> I am looking at the delegation implementation in the source code of
> NFS 4.1 in kernel 2.6.32.15. I can find the code for read delegation,
> which is working and can serve the read requests locally. But I can
> never find the code about write delegation, which is supposed to cache
> the write update locally. I try to look at the functions including
> nfs_writepage(s), nfs_file_flush() but none of them checks or uses the
> write delegation.
>
> Is write delegation currently implemented in NFS 4.1?
>
> Thanks!
>
> best,
>
> Yudong
>
On Wed, 2010-08-04 at 14:40 -0700, Yudong Gao wrote:
> I see. But according to the spec, the write delegation is supposed to
> break the close-to-open consistency so that the client can avoid
> flushing dirty page to server when closing the file. Is this part
> implemented? I can not find it in the source code...
No. We didn't do that. The main reason for continuing to flush the
writes on close is to avoid slow delegation recalls.
> Another question is how the nfs file write interacts with fscache? I
> was not able to find the code that update the page copy in fscache
> when the page in memory is modified.
AFAIK fscache is read-only at this point. I think David has plans to
make it read/write, but I don't know whether he will ever do so for NFS.
Trond
> Thanks a lot!
>
> best,
>
> Yudong
>
> On Wed, Aug 4, 2010 at 2:22 PM, Trond Myklebust
> <[email protected]> wrote:
> > On Wed, 2010-08-04 at 14:11 -0700, Yudong Gao wrote:
> >> Thanks for the reply, Andy!
> >>
> >> So the write delegation can only reduce the unnecessary open/close and
> >> lock/locku. But if a client modify the same page for multiple times,
> >> e.g. editing the file in a editor, is there any optimization to
> >> prevent the client from sending the half-updated pages? Ideally only
> >> the final update need to be put on the wire.
> >>
> >
> > Yes. However that optimisation is not linked to whether or not we hold a
> > write delegation. The NFS client assumes close-to-open cache
> > consistency, and so will cache writes until either the VM tries to
> > reclaim memory by writing out dirty page, or the application calls one
> > of fcntl(F_UNLCK), fsync() or close().
> >
> > Trond
> >
> >> Thanks!
> >>
> >> best,
> >>
> >> Yudong
> >>
> >> On Wed, Aug 4, 2010 at 1:59 PM, Andy Adamson <[email protected]> wrote:
> >> >
> >> > On Aug 4, 2010, at 3:21 PM, Yudong Gao wrote:
> >> >
> >> >> Hi,
> >> >>
> >> >> I am not able to find the implementation of directory delegation,
> >> >> either. Similarly, the callback functions CB_NOTIFY is not
> >> >> implemented, either. I find that in preprocss_nfs41_op() in
> >> >> callback_xdr.c, whenever a CB_NOTIFY is encountered, an
> >> >> NFS4ERR_NOTSUPP is returned directly.
> >> >
> >> > CB_NOTIFY is not currently supported on the Linux NFS client.
> >> >
> >> >>
> >> >> Am I missing something? Or they are just not supported in the current version?
> >> >>
> >> >> Thanks a lot!
> >> >>
> >> >> best,
> >> >>
> >> >> Yudong
> >> >>
> >> >> On Mon, Aug 2, 2010 at 5:17 PM, Yudong Gao <[email protected]> wrote:
> >> >>> Hi,
> >> >>>
> >> >>> I am looking at the delegation implementation in the source code of
> >> >>> NFS 4.1 in kernel 2.6.32.15. I can find the code for read delegation,
> >> >>> which is working and can serve the read requests locally. But I can
> >> >>> never find the code about write delegation, which is supposed to cache
> >> >>> the write update locally. I try to look at the functions including
> >> >>> nfs_writepage(s), nfs_file_flush() but none of them checks or uses the
> >> >>> write delegation.
> >> >>>
> >> >>> Is write delegation currently implemented in NFS 4.1?
> >> >
> >> > Write delegation is supported but I don't think write behavior changes - writes are still cached and flushed as without a write delegation. The write delegation does prevent open/close and lock/locku from being put on the wire.
> >> >
> >> > -->Andy
> >> >
> >> >>>
> >> >>> Thanks!
> >> >>>
> >> >>> best,
> >> >>>
> >> >>> Yudong
> >> >>>
> >> >> --
> >> >> To unsubscribe from this list: send the line "unsubscribe linux-nfs" in
> >> >> the body of a message to [email protected]
> >> >> 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 [email protected]
> >> More majordomo info at http://vger.kernel.org/majordomo-info.html
> >
> >
> >
> >
I see. That makes sense. I think in most case the file open delegation
will be enough. It seems to me that the directory data is at least as
critical as the file meta data such as file attributes. This kind of
data, in most cases, should be propagated to the server as soon as
possible. Not sure whether this argument makes sense. :P
Thanks!
best,
Yudong
On Wed, Aug 4, 2010 at 2:09 PM, Trond Myklebust
<[email protected]> wrote:
> On Wed, 2010-08-04 at 12:21 -0700, Yudong Gao wrote:
>> Hi,
>>
>> I am not able to find the implementation of directory delegation,
>> either. Similarly, the callback functions CB_NOTIFY is not
>> implemented, either. I find that in preprocss_nfs41_op() in
>> callback_xdr.c, whenever a CB_NOTIFY is encountered, an
>> NFS4ERR_NOTSUPP is returned directly.
>>
>> Am I missing something? Or they are just not supported in the current version?
>
> The client currently does not request any directory delegations or
> notifications, so there is no reason for it to support CB_NOTIFY.
>
> Maybe we will add support for directory delegations and notifications at
> some time in the future, but before that happens, somebody needs to
> convince me that they are useful. Currently there is very little
> documentation to support any assertion that they are...
>
> Cheers
> ?Trond
>
>
On Wed, 2010-08-04 at 14:11 -0700, Yudong Gao wrote:
> Thanks for the reply, Andy!
>
> So the write delegation can only reduce the unnecessary open/close and
> lock/locku. But if a client modify the same page for multiple times,
> e.g. editing the file in a editor, is there any optimization to
> prevent the client from sending the half-updated pages? Ideally only
> the final update need to be put on the wire.
>
Yes. However that optimisation is not linked to whether or not we hold a
write delegation. The NFS client assumes close-to-open cache
consistency, and so will cache writes until either the VM tries to
reclaim memory by writing out dirty page, or the application calls one
of fcntl(F_UNLCK), fsync() or close().
Trond
> Thanks!
>
> best,
>
> Yudong
>
> On Wed, Aug 4, 2010 at 1:59 PM, Andy Adamson <[email protected]> wrote:
> >
> > On Aug 4, 2010, at 3:21 PM, Yudong Gao wrote:
> >
> >> Hi,
> >>
> >> I am not able to find the implementation of directory delegation,
> >> either. Similarly, the callback functions CB_NOTIFY is not
> >> implemented, either. I find that in preprocss_nfs41_op() in
> >> callback_xdr.c, whenever a CB_NOTIFY is encountered, an
> >> NFS4ERR_NOTSUPP is returned directly.
> >
> > CB_NOTIFY is not currently supported on the Linux NFS client.
> >
> >>
> >> Am I missing something? Or they are just not supported in the current version?
> >>
> >> Thanks a lot!
> >>
> >> best,
> >>
> >> Yudong
> >>
> >> On Mon, Aug 2, 2010 at 5:17 PM, Yudong Gao <[email protected]> wrote:
> >>> Hi,
> >>>
> >>> I am looking at the delegation implementation in the source code of
> >>> NFS 4.1 in kernel 2.6.32.15. I can find the code for read delegation,
> >>> which is working and can serve the read requests locally. But I can
> >>> never find the code about write delegation, which is supposed to cache
> >>> the write update locally. I try to look at the functions including
> >>> nfs_writepage(s), nfs_file_flush() but none of them checks or uses the
> >>> write delegation.
> >>>
> >>> Is write delegation currently implemented in NFS 4.1?
> >
> > Write delegation is supported but I don't think write behavior changes - writes are still cached and flushed as without a write delegation. The write delegation does prevent open/close and lock/locku from being put on the wire.
> >
> > -->Andy
> >
> >>>
> >>> Thanks!
> >>>
> >>> best,
> >>>
> >>> Yudong
> >>>
> >> --
> >> To unsubscribe from this list: send the line "unsubscribe linux-nfs" in
> >> the body of a message to [email protected]
> >> 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 [email protected]
> More majordomo info at http://vger.kernel.org/majordomo-info.html
On Wed, 2010-08-04 at 12:21 -0700, Yudong Gao wrote:
> Hi,
>
> I am not able to find the implementation of directory delegation,
> either. Similarly, the callback functions CB_NOTIFY is not
> implemented, either. I find that in preprocss_nfs41_op() in
> callback_xdr.c, whenever a CB_NOTIFY is encountered, an
> NFS4ERR_NOTSUPP is returned directly.
>
> Am I missing something? Or they are just not supported in the current version?
The client currently does not request any directory delegations or
notifications, so there is no reason for it to support CB_NOTIFY.
Maybe we will add support for directory delegations and notifications at
some time in the future, but before that happens, somebody needs to
convince me that they are useful. Currently there is very little
documentation to support any assertion that they are...
Cheers
Trond
On Aug 4, 2010, at 3:21 PM, Yudong Gao wrote:
> Hi,
>
> I am not able to find the implementation of directory delegation,
> either. Similarly, the callback functions CB_NOTIFY is not
> implemented, either. I find that in preprocss_nfs41_op() in
> callback_xdr.c, whenever a CB_NOTIFY is encountered, an
> NFS4ERR_NOTSUPP is returned directly.
CB_NOTIFY is not currently supported on the Linux NFS client.
>
> Am I missing something? Or they are just not supported in the current version?
>
> Thanks a lot!
>
> best,
>
> Yudong
>
> On Mon, Aug 2, 2010 at 5:17 PM, Yudong Gao <[email protected]> wrote:
>> Hi,
>>
>> I am looking at the delegation implementation in the source code of
>> NFS 4.1 in kernel 2.6.32.15. I can find the code for read delegation,
>> which is working and can serve the read requests locally. But I can
>> never find the code about write delegation, which is supposed to cache
>> the write update locally. I try to look at the functions including
>> nfs_writepage(s), nfs_file_flush() but none of them checks or uses the
>> write delegation.
>>
>> Is write delegation currently implemented in NFS 4.1?
Write delegation is supported but I don't think write behavior changes - writes are still cached and flushed as without a write delegation. The write delegation does prevent open/close and lock/locku from being put on the wire.
-->Andy
>>
>> Thanks!
>>
>> best,
>>
>> Yudong
>>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-nfs" in
> the body of a message to [email protected]
> More majordomo info at http://vger.kernel.org/majordomo-info.html
On Wed, Aug 4, 2010 at 5:52 PM, Trond Myklebust
<[email protected]> wrote:
> On Wed, 2010-08-04 at 14:40 -0700, Yudong Gao wrote:
>> I see. But according to the spec, the write delegation is supposed to
>> break the close-to-open consistency so that the client can avoid
>> flushing dirty page to server when closing the file. Is this part
>> implemented? I can not find it in the source code...
>
> No. We didn't do that. The main reason for continuing to flush the
> writes on close is to avoid slow delegation recalls.
>
This makes sense! Thanks for clarifying!
>> Another question is how the nfs file write interacts with fscache? I
>> was not able to find the code that update the page copy in fscache
>> when the page in memory is modified.
>
> AFAIK fscache is read-only at this point. I think David has plans to
> make it read/write, but I don't know whether he will ever do so for NFS.
>
I think fscache itself support writing. We can find the
fscache_write_page() definition in both the api document and the
source code. I check the source code and it seems fully implemented.
But for the integration with NFS, it is confusing. The
fscache_write_page() is called only in one place:
nfs_readpage_release(). So a NFS page is only written to fscache after
it is read from the server in nfs_readpage. So my question is, if a
page is locally modified, when its data is propagated to fscache? I
check the nfs_write_begin() and nfs_write_end() but cannot find any
relative implementation.
Thanks!
best,
Yudong
> Trond
>
>> Thanks a lot!
>>
>> best,
>>
>> Yudong
>>
>> On Wed, Aug 4, 2010 at 2:22 PM, Trond Myklebust
>> <[email protected]> wrote:
>> > On Wed, 2010-08-04 at 14:11 -0700, Yudong Gao wrote:
>> >> Thanks for the reply, Andy!
>> >>
>> >> So the write delegation can only reduce the unnecessary open/close and
>> >> lock/locku. But if a client modify the same page for multiple times,
>> >> e.g. editing the file in a editor, is there any optimization to
>> >> prevent the client from sending the half-updated pages? Ideally only
>> >> the final update need to be put on the wire.
>> >>
>> >
>> > Yes. However that optimisation is not linked to whether or not we hold a
>> > write delegation. The NFS client assumes close-to-open cache
>> > consistency, and so will cache writes until either the VM tries to
>> > reclaim memory by writing out dirty page, or the application calls one
>> > of fcntl(F_UNLCK), fsync() or close().
>> >
>> > Trond
>> >
>> >> Thanks!
>> >>
>> >> best,
>> >>
>> >> Yudong
>> >>
>> >> On Wed, Aug 4, 2010 at 1:59 PM, Andy Adamson <[email protected]> wrote:
>> >> >
>> >> > On Aug 4, 2010, at 3:21 PM, Yudong Gao wrote:
>> >> >
>> >> >> Hi,
>> >> >>
>> >> >> I am not able to find the implementation of directory delegation,
>> >> >> either. Similarly, the callback functions CB_NOTIFY is not
>> >> >> implemented, either. I find that in preprocss_nfs41_op() in
>> >> >> callback_xdr.c, whenever a CB_NOTIFY is encountered, an
>> >> >> NFS4ERR_NOTSUPP is returned directly.
>> >> >
>> >> > CB_NOTIFY is not currently supported on the Linux NFS client.
>> >> >
>> >> >>
>> >> >> Am I missing something? Or they are just not supported in the current version?
>> >> >>
>> >> >> Thanks a lot!
>> >> >>
>> >> >> best,
>> >> >>
>> >> >> Yudong
>> >> >>
>> >> >> On Mon, Aug 2, 2010 at 5:17 PM, Yudong Gao <[email protected]> wrote:
>> >> >>> Hi,
>> >> >>>
>> >> >>> I am looking at the delegation implementation in the source code of
>> >> >>> NFS 4.1 in kernel 2.6.32.15. I can find the code for read delegation,
>> >> >>> which is working and can serve the read requests locally. But I can
>> >> >>> never find the code about write delegation, which is supposed to cache
>> >> >>> the write update locally. I try to look at the functions including
>> >> >>> nfs_writepage(s), nfs_file_flush() but none of them checks or uses the
>> >> >>> write delegation.
>> >> >>>
>> >> >>> Is write delegation currently implemented in NFS 4.1?
>> >> >
>> >> > Write delegation is supported but I don't think write behavior changes - writes are still cached and flushed as without a write delegation. The write delegation does prevent open/close and lock/locku from being put on the wire.
>> >> >
>> >> > -->Andy
>> >> >
>> >> >>>
>> >> >>> Thanks!
>> >> >>>
>> >> >>> best,
>> >> >>>
>> >> >>> Yudong
>> >> >>>
>> >> >> --
>> >> >> To unsubscribe from this list: send the line "unsubscribe linux-nfs" in
>> >> >> the body of a message to [email protected]
>> >> >> 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 [email protected]
>> >> More majordomo info at ?http://vger.kernel.org/majordomo-info.html
>> >
>> >
>> >
>> >
>
>
>
>
I see. But according to the spec, the write delegation is supposed to
break the close-to-open consistency so that the client can avoid
flushing dirty page to server when closing the file. Is this part
implemented? I can not find it in the source code...
Another question is how the nfs file write interacts with fscache? I
was not able to find the code that update the page copy in fscache
when the page in memory is modified.
Thanks a lot!
best,
Yudong
On Wed, Aug 4, 2010 at 2:22 PM, Trond Myklebust
<[email protected]> wrote:
> On Wed, 2010-08-04 at 14:11 -0700, Yudong Gao wrote:
>> Thanks for the reply, Andy!
>>
>> So the write delegation can only reduce the unnecessary open/close and
>> lock/locku. But if a client modify the same page for multiple times,
>> e.g. editing the file in a editor, is there any optimization to
>> prevent the client from sending the half-updated pages? Ideally only
>> the final update need to be put on the wire.
>>
>
> Yes. However that optimisation is not linked to whether or not we hold a
> write delegation. The NFS client assumes close-to-open cache
> consistency, and so will cache writes until either the VM tries to
> reclaim memory by writing out dirty page, or the application calls one
> of fcntl(F_UNLCK), fsync() or close().
>
> Trond
>
>> Thanks!
>>
>> best,
>>
>> Yudong
>>
>> On Wed, Aug 4, 2010 at 1:59 PM, Andy Adamson <[email protected]> wrote:
>> >
>> > On Aug 4, 2010, at 3:21 PM, Yudong Gao wrote:
>> >
>> >> Hi,
>> >>
>> >> I am not able to find the implementation of directory delegation,
>> >> either. Similarly, the callback functions CB_NOTIFY is not
>> >> implemented, either. I find that in preprocss_nfs41_op() in
>> >> callback_xdr.c, whenever a CB_NOTIFY is encountered, an
>> >> NFS4ERR_NOTSUPP is returned directly.
>> >
>> > CB_NOTIFY is not currently supported on the Linux NFS client.
>> >
>> >>
>> >> Am I missing something? Or they are just not supported in the current version?
>> >>
>> >> Thanks a lot!
>> >>
>> >> best,
>> >>
>> >> Yudong
>> >>
>> >> On Mon, Aug 2, 2010 at 5:17 PM, Yudong Gao <[email protected]> wrote:
>> >>> Hi,
>> >>>
>> >>> I am looking at the delegation implementation in the source code of
>> >>> NFS 4.1 in kernel 2.6.32.15. I can find the code for read delegation,
>> >>> which is working and can serve the read requests locally. But I can
>> >>> never find the code about write delegation, which is supposed to cache
>> >>> the write update locally. I try to look at the functions including
>> >>> nfs_writepage(s), nfs_file_flush() but none of them checks or uses the
>> >>> write delegation.
>> >>>
>> >>> Is write delegation currently implemented in NFS 4.1?
>> >
>> > Write delegation is supported but I don't think write behavior changes - writes are still cached and flushed as without a write delegation. The write delegation does prevent open/close and lock/locku from being put on the wire.
>> >
>> > -->Andy
>> >
>> >>>
>> >>> Thanks!
>> >>>
>> >>> best,
>> >>>
>> >>> Yudong
>> >>>
>> >> --
>> >> To unsubscribe from this list: send the line "unsubscribe linux-nfs" in
>> >> the body of a message to [email protected]
>> >> 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 [email protected]
>> More majordomo info at ?http://vger.kernel.org/majordomo-info.html
>
>
>
>
Thanks for the reply, Andy!
So the write delegation can only reduce the unnecessary open/close and
lock/locku. But if a client modify the same page for multiple times,
e.g. editing the file in a editor, is there any optimization to
prevent the client from sending the half-updated pages? Ideally only
the final update need to be put on the wire.
Thanks!
best,
Yudong
On Wed, Aug 4, 2010 at 1:59 PM, Andy Adamson <[email protected]> wrote:
>
> On Aug 4, 2010, at 3:21 PM, Yudong Gao wrote:
>
>> Hi,
>>
>> I am not able to find the implementation of directory delegation,
>> either. Similarly, the callback functions CB_NOTIFY is not
>> implemented, either. I find that in preprocss_nfs41_op() in
>> callback_xdr.c, whenever a CB_NOTIFY is encountered, an
>> NFS4ERR_NOTSUPP is returned directly.
>
> CB_NOTIFY is not currently supported on the Linux NFS client.
>
>>
>> Am I missing something? Or they are just not supported in the current version?
>>
>> Thanks a lot!
>>
>> best,
>>
>> Yudong
>>
>> On Mon, Aug 2, 2010 at 5:17 PM, Yudong Gao <[email protected]> wrote:
>>> Hi,
>>>
>>> I am looking at the delegation implementation in the source code of
>>> NFS 4.1 in kernel 2.6.32.15. I can find the code for read delegation,
>>> which is working and can serve the read requests locally. But I can
>>> never find the code about write delegation, which is supposed to cache
>>> the write update locally. I try to look at the functions including
>>> nfs_writepage(s), nfs_file_flush() but none of them checks or uses the
>>> write delegation.
>>>
>>> Is write delegation currently implemented in NFS 4.1?
>
> Write delegation is supported but I don't think write behavior changes - writes are still cached and flushed as without a write delegation. The write delegation does prevent open/close and lock/locku from being put on the wire.
>
> -->Andy
>
>>>
>>> Thanks!
>>>
>>> best,
>>>
>>> Yudong
>>>
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-nfs" in
>> the body of a message to [email protected]
>> More majordomo info at ?http://vger.kernel.org/majordomo-info.html
>
>