[PATCH 3/5] NFSD: Report WND4_CONTENTION for a recently recalled file

[Chuck Lever <cel@kernel.org>]

NFSD grants no delegation on a file for 30 to 60 seconds after
recalling one. __alloc_init_deleg() enforces that by returning NULL
when delegation_blocked() finds the filehandle, the same result it
gives when NFSD is at max_delegations or out of memory.
nfs4_set_delegation() reports all three as -ENOMEM, and the reply
carries WND4_RESOURCE.

Return ERR_PTR(-EAGAIN) from __alloc_init_deleg() for a blocked
filehandle and ERR_PTR(-ENOMEM) for the other failures. Pass that
errno up through nfs4_set_delegation() so that
nfsd4_open_deleg_none_ext() reports WND4_CONTENTION.
alloc_init_dir_deleg() continues to return NULL for every failure,
so directory delegations are unaffected.

Signed-off-by: Chuck Lever <cel@kernel.org>
---
 fs/nfsd/nfs4state.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 46e7343e050a..6ed53864c9be 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -1263,7 +1263,7 @@ __alloc_init_deleg(struct nfs4_client *clp, struct nfs4_file *fp,
 	long n;
 
 	if (delegation_blocked(&fp->fi_fhandle))
-		return NULL;
+		return ERR_PTR(-EAGAIN);
 
 	n = atomic_long_inc_return(&num_delegations);
 	atomic_long_inc(&nn->nfsd_delegations);
@@ -1300,7 +1300,7 @@ __alloc_init_deleg(struct nfs4_client *clp, struct nfs4_file *fp,
 out_dec:
 	atomic_long_dec(&num_delegations);
 	atomic_long_dec(&nn->nfsd_delegations);
-	return NULL;
+	return ERR_PTR(-ENOMEM);
 }
 
 static struct nfs4_delegation *
@@ -1310,8 +1310,8 @@ alloc_init_deleg(struct nfs4_client *clp, struct nfs4_file *fp,
 	struct nfs4_delegation *dp;
 
 	dp = __alloc_init_deleg(clp, fp, odstate, dl_type, nfs4_free_deleg);
-	if (!dp)
-		return NULL;
+	if (IS_ERR(dp))
+		return dp;
 
 	nfsd4_init_cb(&dp->dl_cb_fattr.ncf_getattr, dp->dl_stid.sc_client,
 			&nfsd4_cb_getattr_ops, NFSPROC4_CLNT_CB_GETATTR);
@@ -1345,7 +1345,7 @@ alloc_init_dir_deleg(struct nfs4_client *clp, struct nfs4_file *fp)
 	int npages;
 
 	dp = __alloc_init_deleg(clp, fp, NULL, NFS4_OPEN_DELEGATE_READ, nfs4_free_dir_deleg);
-	if (!dp)
+	if (IS_ERR(dp))
 		return NULL;
 
 	ncn = &dp->dl_cb_notify;
@@ -7088,8 +7088,10 @@ nfs4_set_delegation(struct nfsd4_open *open,
 
 	status = -ENOMEM;
 	dp = alloc_init_deleg(clp, fp, odstate, dl_type);
-	if (!dp)
+	if (IS_ERR(dp)) {
+		status = PTR_ERR(dp);
 		goto out_delegees;
+	}
 
 	/*
 	 * Record the granting slot before kernel_setlease() makes @dp

-- 
2.55.0