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Linux/fs/afs/mntpt.c

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  1 /* mountpoint management
  2  *
  3  * Copyright (C) 2002 Red Hat, Inc. All Rights Reserved.
  4  * Written by David Howells (dhowells@redhat.com)
  5  *
  6  * This program is free software; you can redistribute it and/or
  7  * modify it under the terms of the GNU General Public License
  8  * as published by the Free Software Foundation; either version
  9  * 2 of the License, or (at your option) any later version.
 10  */
 11 
 12 #include <linux/kernel.h>
 13 #include <linux/module.h>
 14 #include <linux/init.h>
 15 #include <linux/fs.h>
 16 #include <linux/pagemap.h>
 17 #include <linux/mount.h>
 18 #include <linux/namei.h>
 19 #include <linux/gfp.h>
 20 #include "internal.h"
 21 
 22 
 23 static struct dentry *afs_mntpt_lookup(struct inode *dir,
 24                                        struct dentry *dentry,
 25                                        unsigned int flags);
 26 static int afs_mntpt_open(struct inode *inode, struct file *file);
 27 static void afs_mntpt_expiry_timed_out(struct work_struct *work);
 28 
 29 const struct file_operations afs_mntpt_file_operations = {
 30         .open           = afs_mntpt_open,
 31         .llseek         = noop_llseek,
 32 };
 33 
 34 const struct inode_operations afs_mntpt_inode_operations = {
 35         .lookup         = afs_mntpt_lookup,
 36         .readlink       = page_readlink,
 37         .getattr        = afs_getattr,
 38 };
 39 
 40 const struct inode_operations afs_autocell_inode_operations = {
 41         .getattr        = afs_getattr,
 42 };
 43 
 44 static LIST_HEAD(afs_vfsmounts);
 45 static DECLARE_DELAYED_WORK(afs_mntpt_expiry_timer, afs_mntpt_expiry_timed_out);
 46 
 47 static unsigned long afs_mntpt_expiry_timeout = 10 * 60;
 48 
 49 /*
 50  * check a symbolic link to see whether it actually encodes a mountpoint
 51  * - sets the AFS_VNODE_MOUNTPOINT flag on the vnode appropriately
 52  */
 53 int afs_mntpt_check_symlink(struct afs_vnode *vnode, struct key *key)
 54 {
 55         struct page *page;
 56         size_t size;
 57         char *buf;
 58         int ret;
 59 
 60         _enter("{%x:%u,%u}",
 61                vnode->fid.vid, vnode->fid.vnode, vnode->fid.unique);
 62 
 63         /* read the contents of the symlink into the pagecache */
 64         page = read_cache_page(AFS_VNODE_TO_I(vnode)->i_mapping, 0,
 65                                afs_page_filler, key);
 66         if (IS_ERR(page)) {
 67                 ret = PTR_ERR(page);
 68                 goto out;
 69         }
 70 
 71         ret = -EIO;
 72         if (PageError(page))
 73                 goto out_free;
 74 
 75         buf = kmap(page);
 76 
 77         /* examine the symlink's contents */
 78         size = vnode->status.size;
 79         _debug("symlink to %*.*s", (int) size, (int) size, buf);
 80 
 81         if (size > 2 &&
 82             (buf[0] == '%' || buf[0] == '#') &&
 83             buf[size - 1] == '.'
 84             ) {
 85                 _debug("symlink is a mountpoint");
 86                 spin_lock(&vnode->lock);
 87                 set_bit(AFS_VNODE_MOUNTPOINT, &vnode->flags);
 88                 vnode->vfs_inode.i_flags |= S_AUTOMOUNT;
 89                 spin_unlock(&vnode->lock);
 90         }
 91 
 92         ret = 0;
 93 
 94         kunmap(page);
 95 out_free:
 96         page_cache_release(page);
 97 out:
 98         _leave(" = %d", ret);
 99         return ret;
100 }
101 
102 /*
103  * no valid lookup procedure on this sort of dir
104  */
105 static struct dentry *afs_mntpt_lookup(struct inode *dir,
106                                        struct dentry *dentry,
107                                        unsigned int flags)
108 {
109         _enter("%p,%p{%pd2}", dir, dentry, dentry);
110         return ERR_PTR(-EREMOTE);
111 }
112 
113 /*
114  * no valid open procedure on this sort of dir
115  */
116 static int afs_mntpt_open(struct inode *inode, struct file *file)
117 {
118         _enter("%p,%p{%pD2}", inode, file, file);
119         return -EREMOTE;
120 }
121 
122 /*
123  * create a vfsmount to be automounted
124  */
125 static struct vfsmount *afs_mntpt_do_automount(struct dentry *mntpt)
126 {
127         struct afs_super_info *super;
128         struct vfsmount *mnt;
129         struct afs_vnode *vnode;
130         struct page *page;
131         char *devname, *options;
132         bool rwpath = false;
133         int ret;
134 
135         _enter("{%pd}", mntpt);
136 
137         BUG_ON(!mntpt->d_inode);
138 
139         ret = -ENOMEM;
140         devname = (char *) get_zeroed_page(GFP_KERNEL);
141         if (!devname)
142                 goto error_no_devname;
143 
144         options = (char *) get_zeroed_page(GFP_KERNEL);
145         if (!options)
146                 goto error_no_options;
147 
148         vnode = AFS_FS_I(mntpt->d_inode);
149         if (test_bit(AFS_VNODE_PSEUDODIR, &vnode->flags)) {
150                 /* if the directory is a pseudo directory, use the d_name */
151                 static const char afs_root_cell[] = ":root.cell.";
152                 unsigned size = mntpt->d_name.len;
153 
154                 ret = -ENOENT;
155                 if (size < 2 || size > AFS_MAXCELLNAME)
156                         goto error_no_page;
157 
158                 if (mntpt->d_name.name[0] == '.') {
159                         devname[0] = '#';
160                         memcpy(devname + 1, mntpt->d_name.name, size - 1);
161                         memcpy(devname + size, afs_root_cell,
162                                sizeof(afs_root_cell));
163                         rwpath = true;
164                 } else {
165                         devname[0] = '%';
166                         memcpy(devname + 1, mntpt->d_name.name, size);
167                         memcpy(devname + size + 1, afs_root_cell,
168                                sizeof(afs_root_cell));
169                 }
170         } else {
171                 /* read the contents of the AFS special symlink */
172                 loff_t size = i_size_read(mntpt->d_inode);
173                 char *buf;
174 
175                 ret = -EINVAL;
176                 if (size > PAGE_SIZE - 1)
177                         goto error_no_page;
178 
179                 page = read_mapping_page(mntpt->d_inode->i_mapping, 0, NULL);
180                 if (IS_ERR(page)) {
181                         ret = PTR_ERR(page);
182                         goto error_no_page;
183                 }
184 
185                 ret = -EIO;
186                 if (PageError(page))
187                         goto error;
188 
189                 buf = kmap_atomic(page);
190                 memcpy(devname, buf, size);
191                 kunmap_atomic(buf);
192                 page_cache_release(page);
193                 page = NULL;
194         }
195 
196         /* work out what options we want */
197         super = AFS_FS_S(mntpt->d_sb);
198         memcpy(options, "cell=", 5);
199         strcpy(options + 5, super->volume->cell->name);
200         if (super->volume->type == AFSVL_RWVOL || rwpath)
201                 strcat(options, ",rwpath");
202 
203         /* try and do the mount */
204         _debug("--- attempting mount %s -o %s ---", devname, options);
205         mnt = vfs_kern_mount(&afs_fs_type, 0, devname, options);
206         _debug("--- mount result %p ---", mnt);
207 
208         free_page((unsigned long) devname);
209         free_page((unsigned long) options);
210         _leave(" = %p", mnt);
211         return mnt;
212 
213 error:
214         page_cache_release(page);
215 error_no_page:
216         free_page((unsigned long) options);
217 error_no_options:
218         free_page((unsigned long) devname);
219 error_no_devname:
220         _leave(" = %d", ret);
221         return ERR_PTR(ret);
222 }
223 
224 /*
225  * handle an automount point
226  */
227 struct vfsmount *afs_d_automount(struct path *path)
228 {
229         struct vfsmount *newmnt;
230 
231         _enter("{%pd}", path->dentry);
232 
233         newmnt = afs_mntpt_do_automount(path->dentry);
234         if (IS_ERR(newmnt))
235                 return newmnt;
236 
237         mntget(newmnt); /* prevent immediate expiration */
238         mnt_set_expiry(newmnt, &afs_vfsmounts);
239         queue_delayed_work(afs_wq, &afs_mntpt_expiry_timer,
240                            afs_mntpt_expiry_timeout * HZ);
241         _leave(" = %p", newmnt);
242         return newmnt;
243 }
244 
245 /*
246  * handle mountpoint expiry timer going off
247  */
248 static void afs_mntpt_expiry_timed_out(struct work_struct *work)
249 {
250         _enter("");
251 
252         if (!list_empty(&afs_vfsmounts)) {
253                 mark_mounts_for_expiry(&afs_vfsmounts);
254                 queue_delayed_work(afs_wq, &afs_mntpt_expiry_timer,
255                                    afs_mntpt_expiry_timeout * HZ);
256         }
257 
258         _leave("");
259 }
260 
261 /*
262  * kill the AFS mountpoint timer if it's still running
263  */
264 void afs_mntpt_kill_timer(void)
265 {
266         _enter("");
267 
268         ASSERT(list_empty(&afs_vfsmounts));
269         cancel_delayed_work_sync(&afs_mntpt_expiry_timer);
270 }
271 

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