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TOMOYO Linux Cross Reference
Linux/fs/nfs/namespace.c

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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 
 24 static void nfs_expire_automounts(struct work_struct *work);
 25 
 26 static LIST_HEAD(nfs_automount_list);
 27 static DECLARE_DELAYED_WORK(nfs_automount_task, nfs_expire_automounts);
 28 int 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  */
 50 char *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 
 58 rename_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;
117 Elong_unlock:
118         spin_unlock(&dentry->d_lock);
119         rcu_read_unlock();
120         if (read_seqretry(&rename_lock, seq))
121                 goto rename_retry;
122 Elong:
123         return ERR_PTR(-ENAMETOOLONG);
124 }
125 EXPORT_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  */
139 struct 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 
163 out:
164         nfs_free_fattr(fattr);
165         nfs_free_fhandle(fh);
166         return mnt;
167 }
168 
169 static int
170 nfs_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 
179 static int
180 nfs_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 
187 const struct inode_operations nfs_mountpoint_inode_operations = {
188         .getattr        = nfs_getattr,
189         .setattr        = nfs_setattr,
190 };
191 
192 const struct inode_operations nfs_referral_inode_operations = {
193         .getattr        = nfs_namespace_getattr,
194         .setattr        = nfs_namespace_setattr,
195 };
196 
197 static 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 
206 void 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  */
215 static 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  */
230 struct 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 }
256 EXPORT_SYMBOL_GPL(nfs_do_submount);
257 
258 struct 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 }
272 EXPORT_SYMBOL_GPL(nfs_submount);
273 

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