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1/*
2 * linux/fs/nfs/namespace.c
3 *
4 * Copyright (C) 2005 Trond Myklebust <Trond.Myklebust@netapp.com>
5 * - Modified by David Howells <dhowells@redhat.com>
6 *
7 * NFS namespace
8 */
9
10#include <linux/module.h>
11#include <linux/dcache.h>
12#include <linux/gfp.h>
13#include <linux/mount.h>
14#include <linux/namei.h>
15#include <linux/nfs_fs.h>
16#include <linux/string.h>
17#include <linux/sunrpc/clnt.h>
18#include <linux/vfs.h>
19#include <linux/sunrpc/gss_api.h>
20#include "internal.h"
21
22#define NFSDBG_FACILITY NFSDBG_VFS
23
24static void nfs_expire_automounts(struct work_struct *work);
25
26static LIST_HEAD(nfs_automount_list);
27static DECLARE_DELAYED_WORK(nfs_automount_task, nfs_expire_automounts);
28int nfs_mountpoint_expiry_timeout = 500 * HZ;
29
30/*
31 * nfs_path - reconstruct the path given an arbitrary dentry
32 * @base - used to return pointer to the end of devname part of path
33 * @dentry - pointer to dentry
34 * @buffer - result buffer
35 * @buflen - length of buffer
36 * @flags - options (see below)
37 *
38 * Helper function for constructing the server pathname
39 * by arbitrary hashed dentry.
40 *
41 * This is mainly for use in figuring out the path on the
42 * server side when automounting on top of an existing partition
43 * and in generating /proc/mounts and friends.
44 *
45 * Supported flags:
46 * NFS_PATH_CANONICAL: ensure there is exactly one slash after
47 * the original device (export) name
48 * (if unset, the original name is returned verbatim)
49 */
50char *nfs_path(char **p, struct dentry *dentry, char *buffer, ssize_t buflen,
51 unsigned flags)
52{
53 char *end;
54 int namelen;
55 unsigned seq;
56 const char *base;
57
58rename_retry:
59 end = buffer+buflen;
60 *--end = '\0';
61 buflen--;
62
63 seq = read_seqbegin(&rename_lock);
64 rcu_read_lock();
65 while (1) {
66 spin_lock(&dentry->d_lock);
67 if (IS_ROOT(dentry))
68 break;
69 namelen = dentry->d_name.len;
70 buflen -= namelen + 1;
71 if (buflen < 0)
72 goto Elong_unlock;
73 end -= namelen;
74 memcpy(end, dentry->d_name.name, namelen);
75 *--end = '/';
76 spin_unlock(&dentry->d_lock);
77 dentry = dentry->d_parent;
78 }
79 if (read_seqretry(&rename_lock, seq)) {
80 spin_unlock(&dentry->d_lock);
81 rcu_read_unlock();
82 goto rename_retry;
83 }
84 if ((flags & NFS_PATH_CANONICAL) && *end != '/') {
85 if (--buflen < 0) {
86 spin_unlock(&dentry->d_lock);
87 rcu_read_unlock();
88 goto Elong;
89 }
90 *--end = '/';
91 }
92 *p = end;
93 base = dentry->d_fsdata;
94 if (!base) {
95 spin_unlock(&dentry->d_lock);
96 rcu_read_unlock();
97 WARN_ON(1);
98 return end;
99 }
100 namelen = strlen(base);
101 if (*end == '/') {
102 /* Strip off excess slashes in base string */
103 while (namelen > 0 && base[namelen - 1] == '/')
104 namelen--;
105 }
106 buflen -= namelen;
107 if (buflen < 0) {
108 spin_unlock(&dentry->d_lock);
109 rcu_read_unlock();
110 goto Elong;
111 }
112 end -= namelen;
113 memcpy(end, base, namelen);
114 spin_unlock(&dentry->d_lock);
115 rcu_read_unlock();
116 return end;
117Elong_unlock:
118 spin_unlock(&dentry->d_lock);
119 rcu_read_unlock();
120 if (read_seqretry(&rename_lock, seq))
121 goto rename_retry;
122Elong:
123 return ERR_PTR(-ENAMETOOLONG);
124}
125EXPORT_SYMBOL_GPL(nfs_path);
126
127/*
128 * nfs_d_automount - Handle crossing a mountpoint on the server
129 * @path - The mountpoint
130 *
131 * When we encounter a mountpoint on the server, we want to set up
132 * a mountpoint on the client too, to prevent inode numbers from
133 * colliding, and to allow "df" to work properly.
134 * On NFSv4, we also want to allow for the fact that different
135 * filesystems may be migrated to different servers in a failover
136 * situation, and that different filesystems may want to use
137 * different security flavours.
138 */
139struct vfsmount *nfs_d_automount(struct path *path)
140{
141 struct vfsmount *mnt;
142 struct nfs_server *server = NFS_SERVER(d_inode(path->dentry));
143 struct nfs_fh *fh = NULL;
144 struct nfs_fattr *fattr = NULL;
145
146 if (IS_ROOT(path->dentry))
147 return ERR_PTR(-ESTALE);
148
149 mnt = ERR_PTR(-ENOMEM);
150 fh = nfs_alloc_fhandle();
151 fattr = nfs_alloc_fattr();
152 if (fh == NULL || fattr == NULL)
153 goto out;
154
155 mnt = server->nfs_client->rpc_ops->submount(server, path->dentry, fh, fattr);
156 if (IS_ERR(mnt))
157 goto out;
158
159 mntget(mnt); /* prevent immediate expiration */
160 mnt_set_expiry(mnt, &nfs_automount_list);
161 schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);
162
163out:
164 nfs_free_fattr(fattr);
165 nfs_free_fhandle(fh);
166 return mnt;
167}
168
169static int
170nfs_namespace_getattr(const struct path *path, struct kstat *stat,
171 u32 request_mask, unsigned int query_flags)
172{
173 if (NFS_FH(d_inode(path->dentry))->size != 0)
174 return nfs_getattr(path, stat, request_mask, query_flags);
175 generic_fillattr(d_inode(path->dentry), stat);
176 return 0;
177}
178
179static int
180nfs_namespace_setattr(struct dentry *dentry, struct iattr *attr)
181{
182 if (NFS_FH(d_inode(dentry))->size != 0)
183 return nfs_setattr(dentry, attr);
184 return -EACCES;
185}
186
187const struct inode_operations nfs_mountpoint_inode_operations = {
188 .getattr = nfs_getattr,
189 .setattr = nfs_setattr,
190};
191
192const struct inode_operations nfs_referral_inode_operations = {
193 .getattr = nfs_namespace_getattr,
194 .setattr = nfs_namespace_setattr,
195};
196
197static void nfs_expire_automounts(struct work_struct *work)
198{
199 struct list_head *list = &nfs_automount_list;
200
201 mark_mounts_for_expiry(list);
202 if (!list_empty(list))
203 schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);
204}
205
206void nfs_release_automount_timer(void)
207{
208 if (list_empty(&nfs_automount_list))
209 cancel_delayed_work(&nfs_automount_task);
210}
211
212/*
213 * Clone a mountpoint of the appropriate type
214 */
215static struct vfsmount *nfs_do_clone_mount(struct nfs_server *server,
216 const char *devname,
217 struct nfs_clone_mount *mountdata)
218{
219 return vfs_submount(mountdata->dentry, &nfs_xdev_fs_type, devname, mountdata);
220}
221
222/**
223 * nfs_do_submount - set up mountpoint when crossing a filesystem boundary
224 * @dentry - parent directory
225 * @fh - filehandle for new root dentry
226 * @fattr - attributes for new root inode
227 * @authflavor - security flavor to use when performing the mount
228 *
229 */
230struct vfsmount *nfs_do_submount(struct dentry *dentry, struct nfs_fh *fh,
231 struct nfs_fattr *fattr, rpc_authflavor_t authflavor)
232{
233 struct nfs_clone_mount mountdata = {
234 .sb = dentry->d_sb,
235 .dentry = dentry,
236 .fh = fh,
237 .fattr = fattr,
238 .authflavor = authflavor,
239 };
240 struct vfsmount *mnt;
241 char *page = (char *) __get_free_page(GFP_USER);
242 char *devname;
243
244 if (page == NULL)
245 return ERR_PTR(-ENOMEM);
246
247 devname = nfs_devname(dentry, page, PAGE_SIZE);
248 if (IS_ERR(devname))
249 mnt = ERR_CAST(devname);
250 else
251 mnt = nfs_do_clone_mount(NFS_SB(dentry->d_sb), devname, &mountdata);
252
253 free_page((unsigned long)page);
254 return mnt;
255}
256EXPORT_SYMBOL_GPL(nfs_do_submount);
257
258struct vfsmount *nfs_submount(struct nfs_server *server, struct dentry *dentry,
259 struct nfs_fh *fh, struct nfs_fattr *fattr)
260{
261 int err;
262 struct dentry *parent = dget_parent(dentry);
263
264 /* Look it up again to get its attributes */
265 err = server->nfs_client->rpc_ops->lookup(d_inode(parent), &dentry->d_name, fh, fattr, NULL);
266 dput(parent);
267 if (err != 0)
268 return ERR_PTR(err);
269
270 return nfs_do_submount(dentry, fh, fattr, server->client->cl_auth->au_flavor);
271}
272EXPORT_SYMBOL_GPL(nfs_submount);
1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * linux/fs/nfs/namespace.c
4 *
5 * Copyright (C) 2005 Trond Myklebust <Trond.Myklebust@netapp.com>
6 * - Modified by David Howells <dhowells@redhat.com>
7 *
8 * NFS namespace
9 */
10
11#include <linux/module.h>
12#include <linux/dcache.h>
13#include <linux/gfp.h>
14#include <linux/mount.h>
15#include <linux/namei.h>
16#include <linux/nfs_fs.h>
17#include <linux/string.h>
18#include <linux/sunrpc/clnt.h>
19#include <linux/vfs.h>
20#include <linux/sunrpc/gss_api.h>
21#include "internal.h"
22
23#define NFSDBG_FACILITY NFSDBG_VFS
24
25static void nfs_expire_automounts(struct work_struct *work);
26
27static LIST_HEAD(nfs_automount_list);
28static DECLARE_DELAYED_WORK(nfs_automount_task, nfs_expire_automounts);
29int nfs_mountpoint_expiry_timeout = 500 * HZ;
30
31/*
32 * nfs_path - reconstruct the path given an arbitrary dentry
33 * @base - used to return pointer to the end of devname part of path
34 * @dentry - pointer to dentry
35 * @buffer - result buffer
36 * @buflen - length of buffer
37 * @flags - options (see below)
38 *
39 * Helper function for constructing the server pathname
40 * by arbitrary hashed dentry.
41 *
42 * This is mainly for use in figuring out the path on the
43 * server side when automounting on top of an existing partition
44 * and in generating /proc/mounts and friends.
45 *
46 * Supported flags:
47 * NFS_PATH_CANONICAL: ensure there is exactly one slash after
48 * the original device (export) name
49 * (if unset, the original name is returned verbatim)
50 */
51char *nfs_path(char **p, struct dentry *dentry, char *buffer, ssize_t buflen,
52 unsigned flags)
53{
54 char *end;
55 int namelen;
56 unsigned seq;
57 const char *base;
58
59rename_retry:
60 end = buffer+buflen;
61 *--end = '\0';
62 buflen--;
63
64 seq = read_seqbegin(&rename_lock);
65 rcu_read_lock();
66 while (1) {
67 spin_lock(&dentry->d_lock);
68 if (IS_ROOT(dentry))
69 break;
70 namelen = dentry->d_name.len;
71 buflen -= namelen + 1;
72 if (buflen < 0)
73 goto Elong_unlock;
74 end -= namelen;
75 memcpy(end, dentry->d_name.name, namelen);
76 *--end = '/';
77 spin_unlock(&dentry->d_lock);
78 dentry = dentry->d_parent;
79 }
80 if (read_seqretry(&rename_lock, seq)) {
81 spin_unlock(&dentry->d_lock);
82 rcu_read_unlock();
83 goto rename_retry;
84 }
85 if ((flags & NFS_PATH_CANONICAL) && *end != '/') {
86 if (--buflen < 0) {
87 spin_unlock(&dentry->d_lock);
88 rcu_read_unlock();
89 goto Elong;
90 }
91 *--end = '/';
92 }
93 *p = end;
94 base = dentry->d_fsdata;
95 if (!base) {
96 spin_unlock(&dentry->d_lock);
97 rcu_read_unlock();
98 WARN_ON(1);
99 return end;
100 }
101 namelen = strlen(base);
102 if (*end == '/') {
103 /* Strip off excess slashes in base string */
104 while (namelen > 0 && base[namelen - 1] == '/')
105 namelen--;
106 }
107 buflen -= namelen;
108 if (buflen < 0) {
109 spin_unlock(&dentry->d_lock);
110 rcu_read_unlock();
111 goto Elong;
112 }
113 end -= namelen;
114 memcpy(end, base, namelen);
115 spin_unlock(&dentry->d_lock);
116 rcu_read_unlock();
117 return end;
118Elong_unlock:
119 spin_unlock(&dentry->d_lock);
120 rcu_read_unlock();
121 if (read_seqretry(&rename_lock, seq))
122 goto rename_retry;
123Elong:
124 return ERR_PTR(-ENAMETOOLONG);
125}
126EXPORT_SYMBOL_GPL(nfs_path);
127
128/*
129 * nfs_d_automount - Handle crossing a mountpoint on the server
130 * @path - The mountpoint
131 *
132 * When we encounter a mountpoint on the server, we want to set up
133 * a mountpoint on the client too, to prevent inode numbers from
134 * colliding, and to allow "df" to work properly.
135 * On NFSv4, we also want to allow for the fact that different
136 * filesystems may be migrated to different servers in a failover
137 * situation, and that different filesystems may want to use
138 * different security flavours.
139 */
140struct vfsmount *nfs_d_automount(struct path *path)
141{
142 struct vfsmount *mnt;
143 struct nfs_server *server = NFS_SERVER(d_inode(path->dentry));
144 struct nfs_fh *fh = NULL;
145 struct nfs_fattr *fattr = NULL;
146
147 if (IS_ROOT(path->dentry))
148 return ERR_PTR(-ESTALE);
149
150 mnt = ERR_PTR(-ENOMEM);
151 fh = nfs_alloc_fhandle();
152 fattr = nfs_alloc_fattr();
153 if (fh == NULL || fattr == NULL)
154 goto out;
155
156 mnt = server->nfs_client->rpc_ops->submount(server, path->dentry, fh, fattr);
157 if (IS_ERR(mnt))
158 goto out;
159
160 mntget(mnt); /* prevent immediate expiration */
161 mnt_set_expiry(mnt, &nfs_automount_list);
162 schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);
163
164out:
165 nfs_free_fattr(fattr);
166 nfs_free_fhandle(fh);
167 return mnt;
168}
169
170static int
171nfs_namespace_getattr(const struct path *path, struct kstat *stat,
172 u32 request_mask, unsigned int query_flags)
173{
174 if (NFS_FH(d_inode(path->dentry))->size != 0)
175 return nfs_getattr(path, stat, request_mask, query_flags);
176 generic_fillattr(d_inode(path->dentry), stat);
177 return 0;
178}
179
180static int
181nfs_namespace_setattr(struct dentry *dentry, struct iattr *attr)
182{
183 if (NFS_FH(d_inode(dentry))->size != 0)
184 return nfs_setattr(dentry, attr);
185 return -EACCES;
186}
187
188const struct inode_operations nfs_mountpoint_inode_operations = {
189 .getattr = nfs_getattr,
190 .setattr = nfs_setattr,
191};
192
193const struct inode_operations nfs_referral_inode_operations = {
194 .getattr = nfs_namespace_getattr,
195 .setattr = nfs_namespace_setattr,
196};
197
198static void nfs_expire_automounts(struct work_struct *work)
199{
200 struct list_head *list = &nfs_automount_list;
201
202 mark_mounts_for_expiry(list);
203 if (!list_empty(list))
204 schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);
205}
206
207void nfs_release_automount_timer(void)
208{
209 if (list_empty(&nfs_automount_list))
210 cancel_delayed_work(&nfs_automount_task);
211}
212
213/*
214 * Clone a mountpoint of the appropriate type
215 */
216static struct vfsmount *nfs_do_clone_mount(struct nfs_server *server,
217 const char *devname,
218 struct nfs_clone_mount *mountdata)
219{
220 return vfs_submount(mountdata->dentry, &nfs_xdev_fs_type, devname, mountdata);
221}
222
223/**
224 * nfs_do_submount - set up mountpoint when crossing a filesystem boundary
225 * @dentry: parent directory
226 * @fh: filehandle for new root dentry
227 * @fattr: attributes for new root inode
228 * @authflavor: security flavor to use when performing the mount
229 *
230 */
231struct vfsmount *nfs_do_submount(struct dentry *dentry, struct nfs_fh *fh,
232 struct nfs_fattr *fattr, rpc_authflavor_t authflavor)
233{
234 struct nfs_clone_mount mountdata = {
235 .sb = dentry->d_sb,
236 .dentry = dentry,
237 .fh = fh,
238 .fattr = fattr,
239 .authflavor = authflavor,
240 };
241 struct vfsmount *mnt;
242 char *page = (char *) __get_free_page(GFP_USER);
243 char *devname;
244
245 if (page == NULL)
246 return ERR_PTR(-ENOMEM);
247
248 devname = nfs_devname(dentry, page, PAGE_SIZE);
249 if (IS_ERR(devname))
250 mnt = ERR_CAST(devname);
251 else
252 mnt = nfs_do_clone_mount(NFS_SB(dentry->d_sb), devname, &mountdata);
253
254 free_page((unsigned long)page);
255 return mnt;
256}
257EXPORT_SYMBOL_GPL(nfs_do_submount);
258
259struct vfsmount *nfs_submount(struct nfs_server *server, struct dentry *dentry,
260 struct nfs_fh *fh, struct nfs_fattr *fattr)
261{
262 int err;
263 struct dentry *parent = dget_parent(dentry);
264
265 /* Look it up again to get its attributes */
266 err = server->nfs_client->rpc_ops->lookup(d_inode(parent), &dentry->d_name, fh, fattr, NULL);
267 dput(parent);
268 if (err != 0)
269 return ERR_PTR(err);
270
271 return nfs_do_submount(dentry, fh, fattr, server->client->cl_auth->au_flavor);
272}
273EXPORT_SYMBOL_GPL(nfs_submount);