nfsd/sunrpc: add svc_rqst->rq_private pointer and remove rq_lease_breaker

rq_lease_breaker has always been a NFSv4 specific layering violation in
svc_rqst. The reason it's there though is that we need a place that is
thread-local, and accessible from the svc_rqst pointer.

Add a new rq_private pointer to struct svc_rqst. This is intended for
use by the threads that are handling the service. sunrpc code doesn't
touch it.

In nfsd, define a new struct nfsd_thread_local_info. nfsd declares one
of these on the stack and puts a pointer to it in rq_private.

Add a new ntli_lease_breaker field to the new struct and convert all of
the places that access rq_lease_breaker to use the new field instead.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Benjamin Coddington <bcodding@hammerspace.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

5 files changed, 21 insertions, 5 deletions

diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
index 6880c5c520e7..85e94c30285a 100644
--- a/fs/nfsd/nfs4proc.c
+++ b/fs/nfsd/nfs4proc.c
@@ -3043,6 +3043,7 @@ nfsd4_proc_compound(struct svc_rqst *rqstp)
 	struct svc_fh *current_fh = &cstate->current_fh;
 	struct svc_fh *save_fh = &cstate->save_fh;
 	struct nfsd_net *nn = net_generic(SVC_NET(rqstp), nfsd_net_id);
+	struct nfsd_thread_local_info *ntli = rqstp->rq_private;
 	__be32		status;
 
 	resp->xdr = &rqstp->rq_res_stream;
@@ -3081,7 +3082,7 @@ nfsd4_proc_compound(struct svc_rqst *rqstp)
 	}
 	check_if_stalefh_allowed(args);
 
-	rqstp->rq_lease_breaker = (void **)&cstate->clp;
+	ntli->ntli_lease_breaker = &cstate->clp;
 
 	trace_nfsd_compound(rqstp, args->tag, args->taglen, args->client_opcnt);
 	while (!status && resp->opcnt < args->opcnt) {
diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 6b9c399b89df..d8b0bd8ac842 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -5535,13 +5535,15 @@ nfsd_break_deleg_cb(struct file_lease *fl)
 static bool nfsd_breaker_owns_lease(struct file_lease *fl)
 {
 	struct nfs4_delegation *dl = fl->c.flc_owner;
+	struct nfsd_thread_local_info *ntli;
 	struct svc_rqst *rqst;
 	struct nfs4_client *clp;
 
 	rqst = nfsd_current_rqst();
 	if (!nfsd_v4client(rqst))
 		return false;
-	clp = *(rqst->rq_lease_breaker);
+	ntli = rqst->rq_private;
+	clp = *ntli->ntli_lease_breaker;
 	return dl->dl_stid.sc_client == clp;
 }
 
@@ -9348,13 +9350,14 @@ __be32
 nfsd4_deleg_getattr_conflict(struct svc_rqst *rqstp, struct dentry *dentry,
 			     struct nfs4_delegation **pdp)
 {
-	__be32 status;
 	struct nfsd_net *nn = net_generic(SVC_NET(rqstp), nfsd_net_id);
+	struct nfsd_thread_local_info *ntli = rqstp->rq_private;
 	struct file_lock_context *ctx;
 	struct nfs4_delegation *dp = NULL;
 	struct file_lease *fl;
 	struct nfs4_cb_fattr *ncf;
 	struct inode *inode = d_inode(dentry);
+	__be32 status;
 
 	ctx = locks_inode_context(inode);
 	if (!ctx)
@@ -9375,7 +9378,7 @@ nfsd4_deleg_getattr_conflict(struct svc_rqst *rqstp, struct dentry *dentry,
 		break;
 	}
 	if (dp == NULL || dp == NON_NFSD_LEASE ||
-	    dp->dl_recall.cb_clp == *(rqstp->rq_lease_breaker)) {
+	    dp->dl_recall.cb_clp == *(ntli->ntli_lease_breaker)) {
 		spin_unlock(&ctx->flc_lock);
 		if (dp == NON_NFSD_LEASE) {
 			status = nfserrno(nfsd_open_break_lease(inode,
diff --git a/fs/nfsd/nfsd.h b/fs/nfsd/nfsd.h
index a01d70953358..938906c6d10c 100644
--- a/fs/nfsd/nfsd.h
+++ b/fs/nfsd/nfsd.h
@@ -82,6 +82,10 @@ extern atomic_t			nfsd_th_cnt;		/* number of available threads */
 
 extern const struct seq_operations nfs_exports_op;
 
+struct nfsd_thread_local_info {
+	struct nfs4_client	**ntli_lease_breaker;
+};
+
 /*
  * Common void argument and result helpers
  */
diff --git a/fs/nfsd/nfssvc.c b/fs/nfsd/nfssvc.c
index 4a04208393b8..fd979e5392a1 100644
--- a/fs/nfsd/nfssvc.c
+++ b/fs/nfsd/nfssvc.c
@@ -887,6 +887,7 @@ nfsd(void *vrqstp)
 	struct svc_xprt *perm_sock = list_entry(rqstp->rq_server->sv_permsocks.next, typeof(struct svc_xprt), xpt_list);
 	struct net *net = perm_sock->xpt_net;
 	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
+	struct nfsd_thread_local_info ntli = { };
 	bool have_mutex = false;
 
 	/* At this point, the thread shares current->fs
@@ -901,6 +902,10 @@ nfsd(void *vrqstp)
 
 	set_freezable();
 
+	/* use dynamic allocation if ntli should ever become large */
+	static_assert(sizeof(struct nfsd_thread_local_info) < 256);
+	rqstp->rq_private = &ntli;
+
 	/*
 	 * The main request loop
 	 */
diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h
index 4dc14c7a711b..ab8237ba9596 100644
--- a/include/linux/sunrpc/svc.h
+++ b/include/linux/sunrpc/svc.h
@@ -175,6 +175,9 @@ static inline unsigned long svc_serv_maxpages(const struct svc_serv *serv)
 /*
  * The context of a single thread, including the request currently being
  * processed.
+ *
+ * RPC programs are free to use rq_private to stash thread-local information.
+ * The sunrpc layer will not access it.
  */
 struct svc_rqst {
 	struct list_head	rq_all;		/* all threads list */
@@ -251,7 +254,7 @@ struct svc_rqst {
 	unsigned long		bc_to_initval;
 	unsigned int		bc_to_retries;
 	unsigned int		rq_status_counter; /* RPC processing counter */
-	void			**rq_lease_breaker; /* The v4 client breaking a lease */
+	void			*rq_private;	/* For use by the service thread */
 };
 
 /* bits for rq_flags */