summaryrefslogtreecommitdiffstats
path: root/fs/nfs/namespace.c
blob: 607f6eb9cdb519f549ce19e590470d24e52ed90e (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
/*
 * linux/fs/nfs/namespace.c
 *
 * Copyright (C) 2005 Trond Myklebust <Trond.Myklebust@netapp.com>
 * - Modified by David Howells <dhowells@redhat.com>
 *
 * NFS namespace
 */

#include <linux/dcache.h>
#include <linux/mount.h>
#include <linux/namei.h>
#include <linux/nfs_fs.h>
#include <linux/string.h>
#include <linux/sunrpc/clnt.h>
#include <linux/vfs.h>
#include "internal.h"

#define NFSDBG_FACILITY		NFSDBG_VFS

static void nfs_expire_automounts(struct work_struct *work);

LIST_HEAD(nfs_automount_list);
static DECLARE_DELAYED_WORK(nfs_automount_task, nfs_expire_automounts);
int nfs_mountpoint_expiry_timeout = 500 * HZ;

static struct vfsmount *nfs_do_submount(const struct vfsmount *mnt_parent,
					const struct dentry *dentry,
					struct nfs_fh *fh,
					struct nfs_fattr *fattr);

/*
 * nfs_path - reconstruct the path given an arbitrary dentry
 * @base - arbitrary string to prepend to the path
 * @droot - pointer to root dentry for mountpoint
 * @dentry - pointer to dentry
 * @buffer - result buffer
 * @buflen - length of buffer
 *
 * Helper function for constructing the path from the
 * root dentry to an arbitrary hashed dentry.
 *
 * This is mainly for use in figuring out the path on the
 * server side when automounting on top of an existing partition.
 */
char *nfs_path(const char *base,
	       const struct dentry *droot,
	       const struct dentry *dentry,
	       char *buffer, ssize_t buflen)
{
	char *end = buffer+buflen;
	int namelen;

	*--end = '\0';
	buflen--;
	spin_lock(&dcache_lock);
	while (!IS_ROOT(dentry) && dentry != droot) {
		namelen = dentry->d_name.len;
		buflen -= namelen + 1;
		if (buflen < 0)
			goto Elong_unlock;
		end -= namelen;
		memcpy(end, dentry->d_name.name, namelen);
		*--end = '/';
		dentry = dentry->d_parent;
	}
	spin_unlock(&dcache_lock);
	namelen = strlen(base);
	/* Strip off excess slashes in base string */
	while (namelen > 0 && base[namelen - 1] == '/')
		namelen--;
	buflen -= namelen;
	if (buflen < 0)
		goto Elong;
	end -= namelen;
	memcpy(end, base, namelen);
	return end;
Elong_unlock:
	spin_unlock(&dcache_lock);
Elong:
	return ERR_PTR(-ENAMETOOLONG);
}

/*
 * nfs_follow_mountpoint - handle crossing a mountpoint on the server
 * @dentry - dentry of mountpoint
 * @nd - nameidata info
 *
 * When we encounter a mountpoint on the server, we want to set up
 * a mountpoint on the client too, to prevent inode numbers from
 * colliding, and to allow "df" to work properly.
 * On NFSv4, we also want to allow for the fact that different
 * filesystems may be migrated to different servers in a failover
 * situation, and that different filesystems may want to use
 * different security flavours.
 */
static void * nfs_follow_mountpoint(struct dentry *dentry, struct nameidata *nd)
{
	struct vfsmount *mnt;
	struct nfs_server *server = NFS_SERVER(dentry->d_inode);
	struct dentry *parent;
	struct nfs_fh fh;
	struct nfs_fattr fattr;
	int err;

	dprintk("--> nfs_follow_mountpoint()\n");

	BUG_ON(IS_ROOT(dentry));
	dprintk("%s: enter\n", __FUNCTION__);
	dput(nd->path.dentry);
	nd->path.dentry = dget(dentry);

	/* Look it up again */
	parent = dget_parent(nd->path.dentry);
	err = server->nfs_client->rpc_ops->lookup(parent->d_inode,
						  &nd->path.dentry->d_name,
						  &fh, &fattr);
	dput(parent);
	if (err != 0)
		goto out_err;

	if (fattr.valid & NFS_ATTR_FATTR_V4_REFERRAL)
		mnt = nfs_do_refmount(nd->path.mnt, nd->path.dentry);
	else
		mnt = nfs_do_submount(nd->path.mnt, nd->path.dentry, &fh,
				      &fattr);
	err = PTR_ERR(mnt);
	if (IS_ERR(mnt))
		goto out_err;

	mntget(mnt);
	err = do_add_mount(mnt, nd, nd->path.mnt->mnt_flags|MNT_SHRINKABLE,
			   &nfs_automount_list);
	if (err < 0) {
		mntput(mnt);
		if (err == -EBUSY)
			goto out_follow;
		goto out_err;
	}
	mntput(nd->path.mnt);
	dput(nd->path.dentry);
	nd->path.mnt = mnt;
	nd->path.dentry = dget(mnt->mnt_root);
	schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);
out:
	dprintk("%s: done, returned %d\n", __FUNCTION__, err);

	dprintk("<-- nfs_follow_mountpoint() = %d\n", err);
	return ERR_PTR(err);
out_err:
	path_put(&nd->path);
	goto out;
out_follow:
	while (d_mountpoint(nd->path.dentry) &&
	       follow_down(&nd->path.mnt, &nd->path.dentry))
		;
	err = 0;
	goto out;
}

const struct inode_operations nfs_mountpoint_inode_operations = {
	.follow_link	= nfs_follow_mountpoint,
	.getattr	= nfs_getattr,
};

const struct inode_operations nfs_referral_inode_operations = {
	.follow_link	= nfs_follow_mountpoint,
};

static void nfs_expire_automounts(struct work_struct *work)
{
	struct list_head *list = &nfs_automount_list;

	mark_mounts_for_expiry(list);
	if (!list_empty(list))
		schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);
}

void nfs_release_automount_timer(void)
{
	if (list_empty(&nfs_automount_list))
		cancel_delayed_work(&nfs_automount_task);
}

/*
 * Clone a mountpoint of the appropriate type
 */
static struct vfsmount *nfs_do_clone_mount(struct nfs_server *server,
					   const char *devname,
					   struct nfs_clone_mount *mountdata)
{
#ifdef CONFIG_NFS_V4
	struct vfsmount *mnt = NULL;
	switch (server->nfs_client->rpc_ops->version) {
		case 2:
		case 3:
			mnt = vfs_kern_mount(&nfs_xdev_fs_type, 0, devname, mountdata);
			break;
		case 4:
			mnt = vfs_kern_mount(&nfs4_xdev_fs_type, 0, devname, mountdata);
	}
	return mnt;
#else
	return vfs_kern_mount(&nfs_xdev_fs_type, 0, devname, mountdata);
#endif
}

/**
 * nfs_do_submount - set up mountpoint when crossing a filesystem boundary
 * @mnt_parent - mountpoint of parent directory
 * @dentry - parent directory
 * @fh - filehandle for new root dentry
 * @fattr - attributes for new root inode
 *
 */
static struct vfsmount *nfs_do_submount(const struct vfsmount *mnt_parent,
					const struct dentry *dentry,
					struct nfs_fh *fh,
					struct nfs_fattr *fattr)
{
	struct nfs_clone_mount mountdata = {
		.sb = mnt_parent->mnt_sb,
		.dentry = dentry,
		.fh = fh,
		.fattr = fattr,
	};
	struct vfsmount *mnt = ERR_PTR(-ENOMEM);
	char *page = (char *) __get_free_page(GFP_USER);
	char *devname;

	dprintk("--> nfs_do_submount()\n");

	dprintk("%s: submounting on %s/%s\n", __FUNCTION__,
			dentry->d_parent->d_name.name,
			dentry->d_name.name);
	if (page == NULL)
		goto out;
	devname = nfs_devname(mnt_parent, dentry, page, PAGE_SIZE);
	mnt = (struct vfsmount *)devname;
	if (IS_ERR(devname))
		goto free_page;
	mnt = nfs_do_clone_mount(NFS_SB(mnt_parent->mnt_sb), devname, &mountdata);
free_page:
	free_page((unsigned long)page);
out:
	dprintk("%s: done\n", __FUNCTION__);

	dprintk("<-- nfs_do_submount() = %p\n", mnt);
	return mnt;
}