Re: [PATCH v5 00/10] NFSD support for asynchronous COPY

[Olga Kornievskaia <aglo@umich.edu>]

On Fri, Oct 13, 2017 at 5:26 PM, J. Bruce Fields <bfields@redhat.com> wrote:
> On Fri, Oct 13, 2017 at 04:54:02PM -0400, Olga Kornievskaia wrote:
>> To do asynchronous copies, NFSD creates a new kthread to handle the request.
>> Upon receiving the COPY, it generates a unique copy stateid (stored in a
>> global list for keeping track of state for OFFLOAD_STATUS to be queried by),
>> starts the thread, and replies back to the client. nfsd4_copy arguments that
>> are allocated on the stack are copies for the kthread.
>>
>> In the async copy handler, it calls into VFS copy_file_range() (for synch
>> we keep the 4MB chunk and requested size for the async copy). If error is
>> encountered it's saved but also we save the amount of data copied so far.
>> Once done, the results are queued for the callback workqueue and sent via
>> CB_OFFLOAD.
>>
>> When the server received an OFFLOAD_CANCEL, it will find the kthread running
>> the copy and will send a SIGPENDING and kthread_stop() and it will interrupt
>> the ongoing do_splice() and once vfs returns we are choosing not to send
>> the CB_OFFLOAD back to the client.
>>
>> When the server receives an OFFLOAD_STATUS, it will find the kthread running
>> the copy and will query the i_size_read() of the associated filehandle of
>> the destination file and return the result.
>
> That assumes we're copying into a previously empty file?

Sigh. Alright, then it's back to my original solution where I broke
everything into 4MB calls and kept track of bytes copies so far.

>
> --b.
>
>>
>> v5:
>> 1. reimplementing asynchronous copy to use kthreads instead of the workqueue
>> 2. store asynchronous copies in the list of the nfs4_client structure
>> 3. when copying nfsd4_copy datastructure for the async copy refcount the
>> nfs4_client structure as well as struct file src/dst structure
>> 4. add refcount to the nfsd4_copy structure to coordinate with offload_status
>> and offload_cancel
>> 5. offload_cancel/copy_shutdown sets the SIGPENDING in the copy's thread to
>> interrupt do_splice and calls kthread_stop to wait for the copy to stop
>> 6. offload_cancel adds MODIFIES_SOMETHING to flags
>> 7. offload_status reports the size of the destination file form i_size_read()
>> instead of before 4MB loop updated chunk size.
>> 8. for async copy call vfs_copy_file_range() with the whole copy size. still
>> keep the loop to do more the MAX_RW_COUNT that do_splice can do.
>>
>> Olga Kornievskaia (10):
>>   NFSD CB_OFFLOAD xdr
>>   NFSD OFFLOAD_STATUS xdr
>>   NFSD OFFLOAD_CANCEL xdr
>>   NFSD xdr callback stateid in async COPY reply
>>   NFSD first draft of async copy
>>   NFSD return nfs4_stid in nfs4_preprocess_stateid_op
>>   NFSD create new stateid for async copy
>>   NFSD handle OFFLOAD_CANCEL op
>>   NFSD support OFFLOAD_STATUS
>>   NFSD stop queued async copies on client shutdown
>>
>>  fs/nfsd/netns.h        |   8 ++
>>  fs/nfsd/nfs4callback.c |  97 +++++++++++++++
>>  fs/nfsd/nfs4proc.c     | 321 ++++++++++++++++++++++++++++++++++++++++++++-----
>>  fs/nfsd/nfs4state.c    |  77 +++++++++++-
>>  fs/nfsd/nfs4xdr.c      |  50 ++++++--
>>  fs/nfsd/nfsctl.c       |   1 +
>>  fs/nfsd/state.h        |  21 +++-
>>  fs/nfsd/xdr4.h         |  28 +++++
>>  fs/nfsd/xdr4cb.h       |  10 ++
>>  9 files changed, 576 insertions(+), 37 deletions(-)
>>
>> --
>> 1.8.3.1
>>
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