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/dcache.h>
 11#include <linux/gfp.h>
 12#include <linux/mount.h>
 13#include <linux/namei.h>
 14#include <linux/nfs_fs.h>
 15#include <linux/string.h>
 16#include <linux/sunrpc/clnt.h>
 17#include <linux/vfs.h>
 18#include <linux/sunrpc/gss_api.h>
 19#include "internal.h"
 20
 21#define NFSDBG_FACILITY		NFSDBG_VFS
 22
 23static void nfs_expire_automounts(struct work_struct *work);
 24
 25static LIST_HEAD(nfs_automount_list);
 26static DECLARE_DELAYED_WORK(nfs_automount_task, nfs_expire_automounts);
 27int nfs_mountpoint_expiry_timeout = 500 * HZ;
 28
 29/*
 30 * nfs_path - reconstruct the path given an arbitrary dentry
 31 * @base - used to return pointer to the end of devname part of path
 32 * @dentry - pointer to dentry
 33 * @buffer - result buffer
 34 * @buflen - length of buffer
 35 *
 36 * Helper function for constructing the server pathname
 37 * by arbitrary hashed dentry.
 38 *
 39 * This is mainly for use in figuring out the path on the
 40 * server side when automounting on top of an existing partition
 41 * and in generating /proc/mounts and friends.
 42 */
 43char *nfs_path(char **p, struct dentry *dentry, char *buffer, ssize_t buflen)
 44{
 45	char *end;
 46	int namelen;
 47	unsigned seq;
 48	const char *base;
 49
 50rename_retry:
 51	end = buffer+buflen;
 52	*--end = '\0';
 53	buflen--;
 54
 55	seq = read_seqbegin(&rename_lock);
 56	rcu_read_lock();
 57	while (1) {
 58		spin_lock(&dentry->d_lock);
 59		if (IS_ROOT(dentry))
 60			break;
 61		namelen = dentry->d_name.len;
 62		buflen -= namelen + 1;
 63		if (buflen < 0)
 64			goto Elong_unlock;
 65		end -= namelen;
 66		memcpy(end, dentry->d_name.name, namelen);
 67		*--end = '/';
 68		spin_unlock(&dentry->d_lock);
 69		dentry = dentry->d_parent;
 70	}
 71	if (read_seqretry(&rename_lock, seq)) {
 72		spin_unlock(&dentry->d_lock);
 73		rcu_read_unlock();
 74		goto rename_retry;
 75	}
 76	if (*end != '/') {
 77		if (--buflen < 0) {
 78			spin_unlock(&dentry->d_lock);
 79			rcu_read_unlock();
 80			goto Elong;
 81		}
 82		*--end = '/';
 83	}
 84	*p = end;
 85	base = dentry->d_fsdata;
 86	if (!base) {
 87		spin_unlock(&dentry->d_lock);
 88		rcu_read_unlock();
 89		WARN_ON(1);
 90		return end;
 91	}
 92	namelen = strlen(base);
 93	/* Strip off excess slashes in base string */
 94	while (namelen > 0 && base[namelen - 1] == '/')
 95		namelen--;
 96	buflen -= namelen;
 97	if (buflen < 0) {
 98		spin_unlock(&dentry->d_lock);
 99		rcu_read_unlock();
100		goto Elong;
101	}
102	end -= namelen;
103	memcpy(end, base, namelen);
104	spin_unlock(&dentry->d_lock);
105	rcu_read_unlock();
106	return end;
107Elong_unlock:
108	spin_unlock(&dentry->d_lock);
109	rcu_read_unlock();
110	if (read_seqretry(&rename_lock, seq))
111		goto rename_retry;
112Elong:
113	return ERR_PTR(-ENAMETOOLONG);
114}
115
116/*
117 * nfs_d_automount - Handle crossing a mountpoint on the server
118 * @path - The mountpoint
119 *
120 * When we encounter a mountpoint on the server, we want to set up
121 * a mountpoint on the client too, to prevent inode numbers from
122 * colliding, and to allow "df" to work properly.
123 * On NFSv4, we also want to allow for the fact that different
124 * filesystems may be migrated to different servers in a failover
125 * situation, and that different filesystems may want to use
126 * different security flavours.
127 */
128struct vfsmount *nfs_d_automount(struct path *path)
129{
130	struct vfsmount *mnt;
131	struct nfs_server *server = NFS_SERVER(path->dentry->d_inode);
132	struct nfs_fh *fh = NULL;
133	struct nfs_fattr *fattr = NULL;
134
135	dprintk("--> nfs_d_automount()\n");
136
137	mnt = ERR_PTR(-ESTALE);
138	if (IS_ROOT(path->dentry))
139		goto out_nofree;
140
141	mnt = ERR_PTR(-ENOMEM);
142	fh = nfs_alloc_fhandle();
143	fattr = nfs_alloc_fattr();
144	if (fh == NULL || fattr == NULL)
145		goto out;
146
147	dprintk("%s: enter\n", __func__);
148
149	mnt = server->nfs_client->rpc_ops->submount(server, path->dentry, fh, fattr);
150	if (IS_ERR(mnt))
151		goto out;
152
153	dprintk("%s: done, success\n", __func__);
154	mntget(mnt); /* prevent immediate expiration */
155	mnt_set_expiry(mnt, &nfs_automount_list);
156	schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);
157
158out:
159	nfs_free_fattr(fattr);
160	nfs_free_fhandle(fh);
161out_nofree:
162	if (IS_ERR(mnt))
163		dprintk("<-- %s(): error %ld\n", __func__, PTR_ERR(mnt));
164	else
165		dprintk("<-- %s() = %p\n", __func__, mnt);
166	return mnt;
167}
168
169const struct inode_operations nfs_mountpoint_inode_operations = {
170	.getattr	= nfs_getattr,
171};
172
173const struct inode_operations nfs_referral_inode_operations = {
174};
175
176static void nfs_expire_automounts(struct work_struct *work)
177{
178	struct list_head *list = &nfs_automount_list;
179
180	mark_mounts_for_expiry(list);
181	if (!list_empty(list))
182		schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);
183}
184
185void nfs_release_automount_timer(void)
186{
187	if (list_empty(&nfs_automount_list))
188		cancel_delayed_work(&nfs_automount_task);
189}
190
191/*
192 * Clone a mountpoint of the appropriate type
193 */
194static struct vfsmount *nfs_do_clone_mount(struct nfs_server *server,
195					   const char *devname,
196					   struct nfs_clone_mount *mountdata)
197{
198#ifdef CONFIG_NFS_V4
199	struct vfsmount *mnt = ERR_PTR(-EINVAL);
200	switch (server->nfs_client->rpc_ops->version) {
201		case 2:
202		case 3:
203			mnt = vfs_kern_mount(&nfs_xdev_fs_type, 0, devname, mountdata);
204			break;
205		case 4:
206			mnt = vfs_kern_mount(&nfs4_xdev_fs_type, 0, devname, mountdata);
207	}
208	return mnt;
209#else
210	return vfs_kern_mount(&nfs_xdev_fs_type, 0, devname, mountdata);
211#endif
212}
213
214/**
215 * nfs_do_submount - set up mountpoint when crossing a filesystem boundary
216 * @dentry - parent directory
217 * @fh - filehandle for new root dentry
218 * @fattr - attributes for new root inode
219 * @authflavor - security flavor to use when performing the mount
220 *
221 */
222struct vfsmount *nfs_do_submount(struct dentry *dentry, struct nfs_fh *fh,
223				 struct nfs_fattr *fattr, rpc_authflavor_t authflavor)
224{
225	struct nfs_clone_mount mountdata = {
226		.sb = dentry->d_sb,
227		.dentry = dentry,
228		.fh = fh,
229		.fattr = fattr,
230		.authflavor = authflavor,
231	};
232	struct vfsmount *mnt = ERR_PTR(-ENOMEM);
233	char *page = (char *) __get_free_page(GFP_USER);
234	char *devname;
235
236	dprintk("--> nfs_do_submount()\n");
237
238	dprintk("%s: submounting on %s/%s\n", __func__,
239			dentry->d_parent->d_name.name,
240			dentry->d_name.name);
241	if (page == NULL)
242		goto out;
243	devname = nfs_devname(dentry, page, PAGE_SIZE);
244	mnt = (struct vfsmount *)devname;
245	if (IS_ERR(devname))
246		goto free_page;
247	mnt = nfs_do_clone_mount(NFS_SB(dentry->d_sb), devname, &mountdata);
248free_page:
249	free_page((unsigned long)page);
250out:
251	dprintk("%s: done\n", __func__);
252
253	dprintk("<-- nfs_do_submount() = %p\n", mnt);
254	return mnt;
255}
256
257struct vfsmount *nfs_submount(struct nfs_server *server, struct dentry *dentry,
258			      struct nfs_fh *fh, struct nfs_fattr *fattr)
259{
260	int err;
261	struct dentry *parent = dget_parent(dentry);
262
263	/* Look it up again to get its attributes */
264	err = server->nfs_client->rpc_ops->lookup(parent->d_inode, &dentry->d_name, fh, fattr);
265	dput(parent);
266	if (err != 0)
267		return ERR_PTR(err);
268
269	return nfs_do_submount(dentry, fh, fattr, server->client->cl_auth->au_flavor);
270}