1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Copyright (C) 2024 Mike Snitzer <snitzer@hammerspace.com>
4 * Copyright (C) 2024 NeilBrown <neilb@suse.de>
5 */
6
7 #include <linux/module.h>
8 #include <linux/list.h>
9 #include <linux/nfslocalio.h>
10 #include <net/netns/generic.h>
11
12 MODULE_LICENSE("GPL");
13 MODULE_DESCRIPTION("NFS localio protocol bypass support");
14
15 static DEFINE_SPINLOCK(nfs_uuid_lock);
16
17 /*
18 * Global list of nfs_uuid_t instances
19 * that is protected by nfs_uuid_lock.
20 */
21 static LIST_HEAD(nfs_uuids);
22
23 void nfs_uuid_init(nfs_uuid_t *nfs_uuid)
24 {
25 nfs_uuid->net = NULL;
26 nfs_uuid->dom = NULL;
27 INIT_LIST_HEAD(&nfs_uuid->list);
28 }
29 EXPORT_SYMBOL_GPL(nfs_uuid_init);
30
31 bool nfs_uuid_begin(nfs_uuid_t *nfs_uuid)
32 {
33 spin_lock(&nfs_uuid_lock);
34 /* Is this nfs_uuid already in use? */
35 if (!list_empty(&nfs_uuid->list)) {
36 spin_unlock(&nfs_uuid_lock);
37 return false;
38 }
39 uuid_gen(&nfs_uuid->uuid);
40 list_add_tail(&nfs_uuid->list, &nfs_uuids);
41 spin_unlock(&nfs_uuid_lock);
42
43 return true;
44 }
45 EXPORT_SYMBOL_GPL(nfs_uuid_begin);
46
47 void nfs_uuid_end(nfs_uuid_t *nfs_uuid)
48 {
49 if (nfs_uuid->net == NULL) {
50 spin_lock(&nfs_uuid_lock);
51 if (nfs_uuid->net == NULL)
52 list_del_init(&nfs_uuid->list);
53 spin_unlock(&nfs_uuid_lock);
54 }
55 }
56 EXPORT_SYMBOL_GPL(nfs_uuid_end);
57
58 static nfs_uuid_t * nfs_uuid_lookup_locked(const uuid_t *uuid)
59 {
60 nfs_uuid_t *nfs_uuid;
61
62 list_for_each_entry(nfs_uuid, &nfs_uuids, list)
63 if (uuid_equal(&nfs_uuid->uuid, uuid))
64 return nfs_uuid;
65
66 return NULL;
67 }
68
69 static struct module *nfsd_mod;
70
71 void nfs_uuid_is_local(const uuid_t *uuid, struct list_head *list,
72 struct net *net, struct auth_domain *dom,
73 struct module *mod)
74 {
75 nfs_uuid_t *nfs_uuid;
76
77 spin_lock(&nfs_uuid_lock);
78 nfs_uuid = nfs_uuid_lookup_locked(uuid);
79 if (nfs_uuid) {
80 kref_get(&dom->ref);
81 nfs_uuid->dom = dom;
82 /*
83 * We don't hold a ref on the net, but instead put
84 * ourselves on a list so the net pointer can be
85 * invalidated.
86 */
87 list_move(&nfs_uuid->list, list);
88 rcu_assign_pointer(nfs_uuid->net, net);
89
90 __module_get(mod);
91 nfsd_mod = mod;
92 }
93 spin_unlock(&nfs_uuid_lock);
94 }
95 EXPORT_SYMBOL_GPL(nfs_uuid_is_local);
96
97 static void nfs_uuid_put_locked(nfs_uuid_t *nfs_uuid)
98 {
99 if (nfs_uuid->net) {
100 module_put(nfsd_mod);
101 nfs_uuid->net = NULL;
102 }
103 if (nfs_uuid->dom) {
104 auth_domain_put(nfs_uuid->dom);
105 nfs_uuid->dom = NULL;
106 }
107 list_del_init(&nfs_uuid->list);
108 }
109
110 void nfs_uuid_invalidate_clients(struct list_head *list)
111 {
112 nfs_uuid_t *nfs_uuid, *tmp;
113
114 spin_lock(&nfs_uuid_lock);
115 list_for_each_entry_safe(nfs_uuid, tmp, list, list)
116 nfs_uuid_put_locked(nfs_uuid);
117 spin_unlock(&nfs_uuid_lock);
118 }
119 EXPORT_SYMBOL_GPL(nfs_uuid_invalidate_clients);
120
121 void nfs_uuid_invalidate_one_client(nfs_uuid_t *nfs_uuid)
122 {
123 if (nfs_uuid->net) {
124 spin_lock(&nfs_uuid_lock);
125 nfs_uuid_put_locked(nfs_uuid);
126 spin_unlock(&nfs_uuid_lock);
127 }
128 }
129 EXPORT_SYMBOL_GPL(nfs_uuid_invalidate_one_client);
130
131 struct nfsd_file *nfs_open_local_fh(nfs_uuid_t *uuid,
132 struct rpc_clnt *rpc_clnt, const struct cred *cred,
133 const struct nfs_fh *nfs_fh, const fmode_t fmode)
134 {
135 struct net *net;
136 struct nfsd_file *localio;
137
138 /*
139 * Not running in nfsd context, so must safely get reference on nfsd_serv.
140 * But the server may already be shutting down, if so disallow new localio.
141 * uuid->net is NOT a counted reference, but rcu_read_lock() ensures that
142 * if uuid->net is not NULL, then calling nfsd_serv_try_get() is safe
143 * and if it succeeds we will have an implied reference to the net.
144 *
145 * Otherwise NFS may not have ref on NFSD and therefore cannot safely
146 * make 'nfs_to' calls.
147 */
148 rcu_read_lock();
149 net = rcu_dereference(uuid->net);
150 if (!net || !nfs_to->nfsd_serv_try_get(net)) {
151 rcu_read_unlock();
152 return ERR_PTR(-ENXIO);
153 }
154 rcu_read_unlock();
155 /* We have an implied reference to net thanks to nfsd_serv_try_get */
156 localio = nfs_to->nfsd_open_local_fh(net, uuid->dom, rpc_clnt,
157 cred, nfs_fh, fmode);
158 if (IS_ERR(localio)) {
159 rcu_read_lock();
160 nfs_to->nfsd_serv_put(net);
161 rcu_read_unlock();
162 }
163 return localio;
164 }
165 EXPORT_SYMBOL_GPL(nfs_open_local_fh);
166
167 /*
168 * The NFS LOCALIO code needs to call into NFSD using various symbols,
169 * but cannot be statically linked, because that will make the NFS
170 * module always depend on the NFSD module.
171 *
172 * 'nfs_to' provides NFS access to NFSD functions needed for LOCALIO,
173 * its lifetime is tightly coupled to the NFSD module and will always
174 * be available to NFS LOCALIO because any successful client<->server
175 * LOCALIO handshake results in a reference on the NFSD module (above),
176 * so NFS implicitly holds a reference to the NFSD module and its
177 * functions in the 'nfs_to' nfsd_localio_operations cannot disappear.
178 *
179 * If the last NFS client using LOCALIO disconnects (and its reference
180 * on NFSD dropped) then NFSD could be unloaded, resulting in 'nfs_to'
181 * functions being invalid pointers. But if NFSD isn't loaded then NFS
182 * will not be able to handshake with NFSD and will have no cause to
183 * try to call 'nfs_to' function pointers. If/when NFSD is reloaded it
184 * will reinitialize the 'nfs_to' function pointers and make LOCALIO
185 * possible.
186 */
187 const struct nfsd_localio_operations *nfs_to;
188 EXPORT_SYMBOL_GPL(nfs_to);
189
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