[v4,0/4] NFSD: add support for NFSv4 write delegation

Message

Dai Ngo May 20, 2023, 9:36 p.m. UTC

NFSD: add support for NFSv4 write delegation

The NFSv4 server currently supports read delegation using VFS lease
which is implemented using file_lock. 

This patch series add write delegation support for NFSv4 server by:

    . remove the check for F_WRLCK in generic_add_lease to allow
      file_lock to be used for write delegation.  

    . grant write delegation for OPEN with NFS4_SHARE_ACCESS_WRITE
      if there is no conflict with other OPENs.

Write delegation conflict with another OPEN, REMOVE, RENAME and SETATTR
are handled the same as read delegation using notify_change, try_break_deleg.

Changes since v1:

[PATCH 3/4] NFSD: add supports for CB_GETATTR callback
- remove WARN_ON_ONCE from encode_bitmap4
- replace decode_bitmap4 with xdr_stream_decode_uint32_array
- replace xdr_inline_decode and xdr_decode_hyper in decode_cb_getattr
   with xdr_stream_decode_u64. Also remove the un-needed likely().
- modify signature of encode_cb_getattr4args to take pointer to
   nfs4_cb_fattr
- replace decode_attr_length with xdr_stream_decode_u32
- rename decode_cb_getattr to decode_cb_fattr4
- fold the initialization of cb_cinfo and cb_fsize into decode_cb_fattr4
- rename ncf_cb_cinfo to ncf_cb_change to avoid confusion of cindo usage
  in fs/nfsd/nfs4xdr.c
- correct NFS4_dec_cb_getattr_sz and update size description

[PATCH 4/4] NFSD: handle GETATTR conflict with write delegation
- change nfs4_handle_wrdeleg_conflict returns __be32 to fix test robot
- change ncf_cb_cinfo to ncf_cb_change to avoid confusion of cindo usage
  in fs/nfsd/nfs4xdr.c

Changes since v2:

[PATCH 2/4] NFSD: enable support for write delegation
- rename 'deleg' to 'dl_type' in nfs4_set_delegation
- remove 'wdeleg' in nfs4_open_delegation

- drop [PATCH 3/4] NFSD: add supports for CB_GETATTR callback
  and [PATCH 4/4] NFSD: handle GETATTR conflict with write delegation
  for futher clarification of the benefits of these patches

Changes since v3:

- recall write delegation when there is GETATTR from 2nd client
- add trace point to track when write delegation is granted

Comments

Chuck Lever III May 21, 2023, 4:08 p.m. UTC | #1

> On May 20, 2023, at 5:36 PM, Dai Ngo <[e-mail]> wrote:
> 
> NFSD: add support for NFSv4 write delegation
> 
> The NFSv4 server currently supports read delegation using VFS lease
> which is implemented using file_lock. 
> 
> This patch series add write delegation support for NFSv4 server by:
> 
>    . remove the check for F_WRLCK in generic_add_lease to allow
>      file_lock to be used for write delegation.  
> 
>    . grant write delegation for OPEN with NFS4_SHARE_ACCESS_WRITE
>      if there is no conflict with other OPENs.
> 
> Write delegation conflict with another OPEN, REMOVE, RENAME and SETATTR
> are handled the same as read delegation using notify_change, try_break_deleg.
> 
> Changes since v1:
> 
> [PATCH 3/4] NFSD: add supports for CB_GETATTR callback
> - remove WARN_ON_ONCE from encode_bitmap4
> - replace decode_bitmap4 with xdr_stream_decode_uint32_array
> - replace xdr_inline_decode and xdr_decode_hyper in decode_cb_getattr
>   with xdr_stream_decode_u64. Also remove the un-needed likely().
> - modify signature of encode_cb_getattr4args to take pointer to
>   nfs4_cb_fattr
> - replace decode_attr_length with xdr_stream_decode_u32
> - rename decode_cb_getattr to decode_cb_fattr4
> - fold the initialization of cb_cinfo and cb_fsize into decode_cb_fattr4
> - rename ncf_cb_cinfo to ncf_cb_change to avoid confusion of cindo usage
>  in fs/nfsd/nfs4xdr.c
> - correct NFS4_dec_cb_getattr_sz and update size description
> 
> [PATCH 4/4] NFSD: handle GETATTR conflict with write delegation
> - change nfs4_handle_wrdeleg_conflict returns __be32 to fix test robot
> - change ncf_cb_cinfo to ncf_cb_change to avoid confusion of cindo usage
>  in fs/nfsd/nfs4xdr.c
> 
> Changes since v2:
> 
> [PATCH 2/4] NFSD: enable support for write delegation
> - rename 'deleg' to 'dl_type' in nfs4_set_delegation
> - remove 'wdeleg' in nfs4_open_delegation
> 
> - drop [PATCH 3/4] NFSD: add supports for CB_GETATTR callback
>  and [PATCH 4/4] NFSD: handle GETATTR conflict with write delegation
>  for futher clarification of the benefits of these patches
> 
> Changes since v3:
> 
> - recall write delegation when there is GETATTR from 2nd client
> - add trace point to track when write delegation is granted 
> 

I'll apply this series to nfsd-next. There are a handful of
changes I'd like to make (with permission):

- Squash 4/4 into 2/4
- Apply 1/4 last instead of first
- Add Jeff's Reviewed-by at least to 1/4 and 2/4

3/4 gives us a platform for measuring recalls triggered by
GETATTR. It might not make any difference if we add a new
counter for that -- but a tracepoint could also do it without
altering the kernel/userspace API. I'm still pondering it.


--
Chuck Lever