Re: [PATCH v5 1/3] NFSD: enable support for write delegation

[Jeff Layton <jlayton@kernel.org>]

On Mon, 2023-05-22 at 16:52 -0700, Dai Ngo wrote:
> This patch grants 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.
> 
> Add trace point to track whether read or write delegation is granted.
> 
> Signed-off-by: Dai Ngo <dai.ngo@oracle.com>
> ---
>  fs/nfsd/nfs4state.c | 28 +++++++++++++++++++---------
>  fs/nfsd/trace.h     |  1 +
>  2 files changed, 20 insertions(+), 9 deletions(-)
> 
> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> index 6e61fa3acaf1..b90b74a5e66e 100644
> --- a/fs/nfsd/nfs4state.c
> +++ b/fs/nfsd/nfs4state.c
> @@ -1144,7 +1144,7 @@ static void block_delegations(struct knfsd_fh *fh)
>  
>  static struct nfs4_delegation *
>  alloc_init_deleg(struct nfs4_client *clp, struct nfs4_file *fp,
> -		 struct nfs4_clnt_odstate *odstate)
> +		struct nfs4_clnt_odstate *odstate, u32 dl_type)
>  {
>  	struct nfs4_delegation *dp;
>  	long n;
> @@ -1170,7 +1170,7 @@ alloc_init_deleg(struct nfs4_client *clp, struct nfs4_file *fp,
>  	INIT_LIST_HEAD(&dp->dl_recall_lru);
>  	dp->dl_clnt_odstate = odstate;
>  	get_clnt_odstate(odstate);
> -	dp->dl_type = NFS4_OPEN_DELEGATE_READ;
> +	dp->dl_type = dl_type;
>  	dp->dl_retries = 1;
>  	dp->dl_recalled = false;
>  	nfsd4_init_cb(&dp->dl_recall, dp->dl_stid.sc_client,
> @@ -5451,6 +5451,7 @@ nfs4_set_delegation(struct nfsd4_open *open, struct nfs4_ol_stateid *stp,
>  	struct nfs4_delegation *dp;
>  	struct nfsd_file *nf;
>  	struct file_lock *fl;
> +	u32 dl_type;
>  
>  	/*
>  	 * The fi_had_conflict and nfs_get_existing_delegation checks
> @@ -5460,7 +5461,13 @@ nfs4_set_delegation(struct nfsd4_open *open, struct nfs4_ol_stateid *stp,
>  	if (fp->fi_had_conflict)
>  		return ERR_PTR(-EAGAIN);
>  
> -	nf = find_readable_file(fp);
> +	if (open->op_share_access & NFS4_SHARE_ACCESS_WRITE) {
> +		nf = find_writeable_file(fp);
> +		dl_type = NFS4_OPEN_DELEGATE_WRITE;
> +	} else {
> +		nf = find_readable_file(fp);
> +		dl_type = NFS4_OPEN_DELEGATE_READ;
> +	}
>  	if (!nf) {
>  		/*
>  		 * We probably could attempt another open and get a read
> @@ -5491,11 +5498,11 @@ nfs4_set_delegation(struct nfsd4_open *open, struct nfs4_ol_stateid *stp,
>  		return ERR_PTR(status);
>  
>  	status = -ENOMEM;
> -	dp = alloc_init_deleg(clp, fp, odstate);
> +	dp = alloc_init_deleg(clp, fp, odstate, dl_type);
>  	if (!dp)
>  		goto out_delegees;
>  
> -	fl = nfs4_alloc_init_lease(dp, NFS4_OPEN_DELEGATE_READ);
> +	fl = nfs4_alloc_init_lease(dp, dl_type);
>  	if (!fl)
>  		goto out_clnt_odstate;
>  
> @@ -5590,8 +5597,6 @@ nfs4_open_delegation(struct nfsd4_open *open, struct nfs4_ol_stateid *stp,
>  		case NFS4_OPEN_CLAIM_PREVIOUS:
>  			if (!cb_up)
>  				open->op_recall = 1;
> -			if (open->op_delegate_type != NFS4_OPEN_DELEGATE_READ)
> -				goto out_no_deleg;
>  			break;
>  		case NFS4_OPEN_CLAIM_NULL:
>  			parent = currentfh;
> @@ -5616,8 +5621,13 @@ nfs4_open_delegation(struct nfsd4_open *open, struct nfs4_ol_stateid *stp,
>  
>  	memcpy(&open->op_delegate_stateid, &dp->dl_stid.sc_stateid, sizeof(dp->dl_stid.sc_stateid));
>  
> -	trace_nfsd_deleg_read(&dp->dl_stid.sc_stateid);
> -	open->op_delegate_type = NFS4_OPEN_DELEGATE_READ;
> +	if (open->op_share_access & NFS4_SHARE_ACCESS_WRITE) {
> +		open->op_delegate_type = NFS4_OPEN_DELEGATE_WRITE;
> +		trace_nfsd_deleg_write(&dp->dl_stid.sc_stateid);
> +	} else {
> +		open->op_delegate_type = NFS4_OPEN_DELEGATE_READ;
> +		trace_nfsd_deleg_read(&dp->dl_stid.sc_stateid);
> +	}
>  	nfs4_put_stid(&dp->dl_stid);
>  	return;
>  out_no_deleg:
> diff --git a/fs/nfsd/trace.h b/fs/nfsd/trace.h
> index 4183819ea082..a14cf8684255 100644
> --- a/fs/nfsd/trace.h
> +++ b/fs/nfsd/trace.h
> @@ -607,6 +607,7 @@ DEFINE_STATEID_EVENT(layout_recall_release);
>  
>  DEFINE_STATEID_EVENT(open);
>  DEFINE_STATEID_EVENT(deleg_read);
> +DEFINE_STATEID_EVENT(deleg_write);
>  DEFINE_STATEID_EVENT(deleg_return);
>  DEFINE_STATEID_EVENT(deleg_recall);
>  

This one looks fine and is fairly straightforward.

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