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

[Dai Ngo <dai.ngo@xxxxxxxxxx>]

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@xxxxxxxxxx>
---
 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);
 
-- 
2.9.5