Re: [PATCH V4 1/2] NFSD: Offer write delegation for OPEN with OPEN4_SHARE_ACCESS_WRITE

[Jeff Layton <jlayton@kernel.org>]

On Tue, 2025-03-04 at 12:38 -0800, Dai Ngo wrote:
> RFC8881, section 9.1.2 says:
> 
>   "In the case of READ, the server may perform the corresponding
>    check on the access mode, or it may choose to allow READ for
>    OPEN4_SHARE_ACCESS_WRITE, to accommodate clients whose WRITE
>    implementation may unavoidably do (e.g., due to buffer cache
>    constraints)."
> 
> and in section 10.4.1:
>    "Similarly, when closing a file opened for OPEN4_SHARE_ACCESS_WRITE/
>    OPEN4_SHARE_ACCESS_BOTH and if an OPEN_DELEGATE_WRITE delegation
>    is in effect"
> 
> This patch offers write delegation for OPEN with OPEN4_SHARE_ACCESS_WRITE
> only. Also deleted no longer use find_rw_file().
> 
> Signed-off-by: Dai Ngo <dai.ngo@oracle.com>
> ---
>  fs/nfsd/nfs4state.c | 34 +++++++++++++---------------------
>  1 file changed, 13 insertions(+), 21 deletions(-)
> 
> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> index 0f97f2c62b3a..b533225e57cf 100644
> --- a/fs/nfsd/nfs4state.c
> +++ b/fs/nfsd/nfs4state.c
> @@ -633,18 +633,6 @@ find_readable_file(struct nfs4_file *f)
>  	return ret;
>  }
>  
> -static struct nfsd_file *
> -find_rw_file(struct nfs4_file *f)
> -{
> -	struct nfsd_file *ret;
> -
> -	spin_lock(&f->fi_lock);
> -	ret = nfsd_file_get(f->fi_fds[O_RDWR]);
> -	spin_unlock(&f->fi_lock);
> -
> -	return ret;
> -}
> -
>  struct nfsd_file *
>  find_any_file(struct nfs4_file *f)
>  {
> @@ -5382,7 +5370,6 @@ static int nfsd4_cb_recall_done(struct nfsd4_callback *cb,
>  	if (dp->dl_stid.sc_status)
>  		/* CLOSED or REVOKED */
>  		return 1;
> -
>  	switch (task->tk_status) {
>  	case 0:
>  		return 1;
> @@ -5987,14 +5974,19 @@ nfs4_set_delegation(struct nfsd4_open *open, struct nfs4_ol_stateid *stp,
>  	 *  "An OPEN_DELEGATE_WRITE delegation allows the client to handle,
>  	 *   on its own, all opens."
>  	 *
> -	 * Furthermore the client can use a write delegation for most READ
> -	 * operations as well, so we require a O_RDWR file here.
> +	 * Furthermore, section 9.1.2 says:
> +	 *
> +	 *  "In the case of READ, the server may perform the corresponding
> +	 *  check on the access mode, or it may choose to allow READ for
> +	 *  OPEN4_SHARE_ACCESS_WRITE, to accommodate clients whose WRITE
> +	 *  implementation may unavoidably do (e.g., due to buffer cache
> +	 *  constraints)."
>  	 *
> -	 * Offer a write delegation in the case of a BOTH open, and ensure
> -	 * we get the O_RDWR descriptor.
> +	 *  We choose to offer a write delegation for OPEN with the
> +	 *  OPEN4_SHARE_ACCESS_WRITE access mode to accommodate such clients.
>  	 */
> -	if ((open->op_share_access & NFS4_SHARE_ACCESS_BOTH) == NFS4_SHARE_ACCESS_BOTH) {
> -		nf = find_rw_file(fp);
> +	if (open->op_share_access & NFS4_SHARE_ACCESS_WRITE) {
> +		nf = find_writeable_file(fp);
>  		dl_type = deleg_ts ? OPEN_DELEGATE_WRITE_ATTRS_DELEG : OPEN_DELEGATE_WRITE;
>  	}
>  
> @@ -6116,7 +6108,7 @@ static bool
>  nfs4_delegation_stat(struct nfs4_delegation *dp, struct svc_fh *currentfh,
>  		     struct kstat *stat)
>  {
> -	struct nfsd_file *nf = find_rw_file(dp->dl_stid.sc_file);
> +	struct nfsd_file *nf = find_writeable_file(dp->dl_stid.sc_file);
>  	struct path path;
>  	int rc;
>  
> @@ -7063,7 +7055,7 @@ nfsd4_lookup_stateid(struct nfsd4_compound_state *cstate,
>  		return_revoked = true;
>  	if (typemask & SC_TYPE_DELEG)
>  		/* Always allow REVOKED for DELEG so we can
> -		 * retturn the appropriate error.
> +		 * return the appropriate error.
>  		 */
>  		statusmask |= SC_STATUS_REVOKED;
>  

This patch also looks good.

The only other issue I have with this is the patch ordering. If a
bisect lands between these two patches then delegations won't work
quite right. Is there a reason to order the patches this way?

Reviewed-by: Jeff Layton <jlayton@kernel.org>