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Christoph Hellwige38f9812007-10-21 16:42:19 -07001/*
2 * Copyright (C) Neil Brown 2002
3 * Copyright (C) Christoph Hellwig 2007
4 *
5 * This file contains the code mapping from inodes to NFS file handles,
6 * and for mapping back from file handles to dentries.
7 *
8 * For details on why we do all the strange and hairy things in here
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04009 * take a look at Documentation/filesystems/nfs/Exporting.
Christoph Hellwige38f9812007-10-21 16:42:19 -070010 */
Christoph Hellwiga5694252007-07-17 04:04:28 -070011#include <linux/exportfs.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070012#include <linux/fs.h>
13#include <linux/file.h>
14#include <linux/module.h>
Christoph Hellwigd37065c2007-07-17 04:04:30 -070015#include <linux/mount.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070016#include <linux/namei.h>
David Howells745ca242008-11-14 10:39:22 +110017#include <linux/sched.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070018
Linus Torvalds1da177e2005-04-16 15:20:36 -070019#define dprintk(fmt, args...) do{}while(0)
20
Christoph Hellwig10f11c32007-07-17 04:04:31 -070021
Al Viro765927b2012-06-26 21:58:53 +040022static int get_name(const struct path *path, char *name, struct dentry *child);
Christoph Hellwig10f11c32007-07-17 04:04:31 -070023
24
Christoph Hellwige38f9812007-10-21 16:42:19 -070025static int exportfs_get_name(struct vfsmount *mnt, struct dentry *dir,
26 char *name, struct dentry *child)
Christoph Hellwig10f11c32007-07-17 04:04:31 -070027{
Christoph Hellwig39655162007-10-21 16:42:17 -070028 const struct export_operations *nop = dir->d_sb->s_export_op;
Al Viro765927b2012-06-26 21:58:53 +040029 struct path path = {.mnt = mnt, .dentry = dir};
Christoph Hellwig10f11c32007-07-17 04:04:31 -070030
31 if (nop->get_name)
32 return nop->get_name(dir, name, child);
33 else
Al Viro765927b2012-06-26 21:58:53 +040034 return get_name(&path, name, child);
Christoph Hellwig10f11c32007-07-17 04:04:31 -070035}
36
Christoph Hellwigfb66a192007-07-17 04:04:32 -070037/*
38 * Check if the dentry or any of it's aliases is acceptable.
39 */
Christoph Hellwige2f99012006-01-18 17:43:52 -080040static struct dentry *
41find_acceptable_alias(struct dentry *result,
42 int (*acceptable)(void *context, struct dentry *dentry),
43 void *context)
44{
45 struct dentry *dentry, *toput = NULL;
Nick Piggin873feea2011-01-07 17:50:06 +110046 struct inode *inode;
Christoph Hellwige2f99012006-01-18 17:43:52 -080047
Christoph Hellwigfb66a192007-07-17 04:04:32 -070048 if (acceptable(context, result))
49 return result;
50
Nick Piggin873feea2011-01-07 17:50:06 +110051 inode = result->d_inode;
52 spin_lock(&inode->i_lock);
Sasha Levinb67bfe02013-02-27 17:06:00 -080053 hlist_for_each_entry(dentry, &inode->i_dentry, d_alias) {
Nick Piggindc0474b2011-01-07 17:49:43 +110054 dget(dentry);
Nick Piggin873feea2011-01-07 17:50:06 +110055 spin_unlock(&inode->i_lock);
Christoph Hellwige2f99012006-01-18 17:43:52 -080056 if (toput)
57 dput(toput);
58 if (dentry != result && acceptable(context, dentry)) {
59 dput(result);
60 return dentry;
61 }
Nick Piggin873feea2011-01-07 17:50:06 +110062 spin_lock(&inode->i_lock);
Christoph Hellwige2f99012006-01-18 17:43:52 -080063 toput = dentry;
64 }
Nick Piggin873feea2011-01-07 17:50:06 +110065 spin_unlock(&inode->i_lock);
Christoph Hellwige2f99012006-01-18 17:43:52 -080066
67 if (toput)
68 dput(toput);
69 return NULL;
70}
71
J. Bruce Fieldsa056cc82013-10-16 21:09:30 -040072static bool dentry_connected(struct dentry *dentry)
73{
74 dget(dentry);
75 while (dentry->d_flags & DCACHE_DISCONNECTED) {
76 struct dentry *parent = dget_parent(dentry);
77
78 dput(dentry);
79 if (IS_ROOT(dentry)) {
80 dput(parent);
81 return false;
82 }
83 dentry = parent;
84 }
85 dput(dentry);
86 return true;
87}
88
J. Bruce Fields0dbc0182013-09-09 16:15:13 -040089static void clear_disconnected(struct dentry *dentry)
90{
91 dget(dentry);
92 while (dentry->d_flags & DCACHE_DISCONNECTED) {
93 struct dentry *parent = dget_parent(dentry);
94
95 WARN_ON_ONCE(IS_ROOT(dentry));
96
97 spin_lock(&dentry->d_lock);
98 dentry->d_flags &= ~DCACHE_DISCONNECTED;
99 spin_unlock(&dentry->d_lock);
100
101 dput(dentry);
102 dentry = parent;
103 }
104 dput(dentry);
105}
106
Christoph Hellwig019ab802007-07-17 04:04:33 -0700107/*
J. Bruce Fieldsbbf7a8a2013-10-17 11:13:00 -0400108 * Reconnect a directory dentry with its parent.
109 *
110 * This can return a dentry, or NULL, or an error.
111 *
112 * In the first case the returned dentry is the parent of the given
113 * dentry, and may itself need to be reconnected to its parent.
114 *
115 * In the NULL case, a concurrent VFS operation has either renamed or
116 * removed this directory. The concurrent operation has reconnected our
117 * dentry, so we no longer need to.
118 */
119static struct dentry *reconnect_one(struct vfsmount *mnt,
120 struct dentry *dentry, char *nbuf)
121{
122 struct dentry *parent;
123 struct dentry *tmp;
124 int err;
125
126 parent = ERR_PTR(-EACCES);
127 mutex_lock(&dentry->d_inode->i_mutex);
128 if (mnt->mnt_sb->s_export_op->get_parent)
129 parent = mnt->mnt_sb->s_export_op->get_parent(dentry);
130 mutex_unlock(&dentry->d_inode->i_mutex);
131
132 if (IS_ERR(parent)) {
133 dprintk("%s: get_parent of %ld failed, err %d\n",
134 __func__, dentry->d_inode->i_ino, PTR_ERR(parent));
135 return parent;
136 }
137
138 dprintk("%s: find name of %lu in %lu\n", __func__,
139 dentry->d_inode->i_ino, parent->d_inode->i_ino);
140 err = exportfs_get_name(mnt, parent, nbuf, dentry);
141 if (err == -ENOENT)
142 goto out_reconnected;
143 if (err)
144 goto out_err;
145 dprintk("%s: found name: %s\n", __func__, nbuf);
146 mutex_lock(&parent->d_inode->i_mutex);
147 tmp = lookup_one_len(nbuf, parent, strlen(nbuf));
148 mutex_unlock(&parent->d_inode->i_mutex);
149 if (IS_ERR(tmp)) {
150 dprintk("%s: lookup failed: %d\n", __func__, PTR_ERR(tmp));
151 goto out_err;
152 }
153 if (tmp != dentry) {
154 dput(tmp);
155 goto out_reconnected;
156 }
157 dput(tmp);
158 if (IS_ROOT(dentry)) {
159 err = -ESTALE;
160 goto out_err;
161 }
162 return parent;
163
164out_err:
165 dput(parent);
166 return ERR_PTR(err);
167out_reconnected:
168 dput(parent);
169 /*
170 * Someone must have renamed our entry into another parent, in
171 * which case it has been reconnected by the rename.
172 *
173 * Or someone removed it entirely, in which case filehandle
174 * lookup will succeed but the directory is now IS_DEAD and
175 * subsequent operations on it will fail.
176 *
177 * Alternatively, maybe there was no race at all, and the
178 * filesystem is just corrupt and gave us a parent that doesn't
179 * actually contain any entry pointing to this inode. So,
180 * double check that this worked and return -ESTALE if not:
181 */
182 if (!dentry_connected(dentry))
183 return ERR_PTR(-ESTALE);
184 return NULL;
185}
186
187/*
Christoph Hellwig019ab802007-07-17 04:04:33 -0700188 * Make sure target_dir is fully connected to the dentry tree.
189 *
J. Bruce Fields78cee9a2013-10-22 20:59:19 -0400190 * On successful return, DCACHE_DISCONNECTED will be cleared on
191 * target_dir, and target_dir->d_parent->...->d_parent will reach the
192 * root of the filesystem.
193 *
194 * Whenever DCACHE_DISCONNECTED is unset, target_dir is fully connected.
195 * But the converse is not true: target_dir may have DCACHE_DISCONNECTED
196 * set but already be connected. In that case we'll verify the
197 * connection to root and then clear the flag.
198 *
199 * Note that target_dir could be removed by a concurrent operation. In
200 * that case reconnect_path may still succeed with target_dir fully
201 * connected, but further operations using the filehandle will fail when
202 * necessary (due to S_DEAD being set on the directory).
Christoph Hellwig019ab802007-07-17 04:04:33 -0700203 */
204static int
Al Virof3f8e172008-08-11 12:39:47 -0400205reconnect_path(struct vfsmount *mnt, struct dentry *target_dir, char *nbuf)
Christoph Hellwig019ab802007-07-17 04:04:33 -0700206{
J. Bruce Fieldsf27c9292013-10-17 21:34:21 -0400207 struct dentry *dentry, *parent;
Christoph Hellwig019ab802007-07-17 04:04:33 -0700208
J. Bruce Fieldsf27c9292013-10-17 21:34:21 -0400209 dentry = dget(target_dir);
Christoph Hellwig019ab802007-07-17 04:04:33 -0700210
J. Bruce Fieldsf27c9292013-10-17 21:34:21 -0400211 while (dentry->d_flags & DCACHE_DISCONNECTED) {
J. Bruce Fieldsefbf2012013-10-17 21:42:35 -0400212 BUG_ON(dentry == mnt->mnt_sb->s_root);
Christoph Hellwig854ff5c2013-10-16 15:48:53 -0400213
J. Bruce Fieldsf27c9292013-10-17 21:34:21 -0400214 if (IS_ROOT(dentry))
215 parent = reconnect_one(mnt, dentry, nbuf);
216 else
217 parent = dget_parent(dentry);
218
219 if (!parent)
J. Bruce Fields0dbc0182013-09-09 16:15:13 -0400220 break;
J. Bruce Fieldsefbf2012013-10-17 21:42:35 -0400221 dput(dentry);
J. Bruce Fieldsf27c9292013-10-17 21:34:21 -0400222 if (IS_ERR(parent))
223 return PTR_ERR(parent);
224 dentry = parent;
Christoph Hellwig019ab802007-07-17 04:04:33 -0700225 }
J. Bruce Fieldsf27c9292013-10-17 21:34:21 -0400226 dput(dentry);
J. Bruce Fieldsa056cc82013-10-16 21:09:30 -0400227 clear_disconnected(target_dir);
228 return 0;
Christoph Hellwig019ab802007-07-17 04:04:33 -0700229}
230
Linus Torvalds1da177e2005-04-16 15:20:36 -0700231struct getdents_callback {
Al Viro5c0ba4e2013-05-15 13:52:59 -0400232 struct dir_context ctx;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700233 char *name; /* name that was found. It already points to a
234 buffer NAME_MAX+1 is size */
J. Bruce Fields950ee952013-09-10 11:41:12 -0400235 u64 ino; /* the inum we are looking for */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700236 int found; /* inode matched? */
237 int sequence; /* sequence counter */
238};
239
240/*
241 * A rather strange filldir function to capture
242 * the name matching the specified inode number.
243 */
244static int filldir_one(void * __buf, const char * name, int len,
David Howellsafefdbb2006-10-03 01:13:46 -0700245 loff_t pos, u64 ino, unsigned int d_type)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700246{
247 struct getdents_callback *buf = __buf;
248 int result = 0;
249
250 buf->sequence++;
Al Virodfc59e2c2013-09-06 16:55:36 -0400251 if (buf->ino == ino && len <= NAME_MAX) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700252 memcpy(buf->name, name, len);
253 buf->name[len] = '\0';
254 buf->found = 1;
255 result = -1;
256 }
257 return result;
258}
259
260/**
261 * get_name - default export_operations->get_name function
Fabian Frederick00f01792014-06-04 16:11:15 -0700262 * @path: the directory in which to find a name
Linus Torvalds1da177e2005-04-16 15:20:36 -0700263 * @name: a pointer to a %NAME_MAX+1 char buffer to store the name
264 * @child: the dentry for the child directory.
265 *
266 * calls readdir on the parent until it finds an entry with
267 * the same inode number as the child, and returns that.
268 */
Al Viro765927b2012-06-26 21:58:53 +0400269static int get_name(const struct path *path, char *name, struct dentry *child)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700270{
David Howells745ca242008-11-14 10:39:22 +1100271 const struct cred *cred = current_cred();
Al Viro765927b2012-06-26 21:58:53 +0400272 struct inode *dir = path->dentry->d_inode;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700273 int error;
274 struct file *file;
J. Bruce Fields950ee952013-09-10 11:41:12 -0400275 struct kstat stat;
276 struct path child_path = {
277 .mnt = path->mnt,
278 .dentry = child,
279 };
Al Viroac6614b2013-05-22 22:22:04 -0400280 struct getdents_callback buffer = {
281 .ctx.actor = filldir_one,
282 .name = name,
Al Viroac6614b2013-05-22 22:22:04 -0400283 };
Linus Torvalds1da177e2005-04-16 15:20:36 -0700284
285 error = -ENOTDIR;
286 if (!dir || !S_ISDIR(dir->i_mode))
287 goto out;
288 error = -EINVAL;
289 if (!dir->i_fop)
290 goto out;
291 /*
J. Bruce Fields950ee952013-09-10 11:41:12 -0400292 * inode->i_ino is unsigned long, kstat->ino is u64, so the
293 * former would be insufficient on 32-bit hosts when the
294 * filesystem supports 64-bit inode numbers. So we need to
295 * actually call ->getattr, not just read i_ino:
296 */
297 error = vfs_getattr_nosec(&child_path, &stat);
298 if (error)
299 return error;
300 buffer.ino = stat.ino;
301 /*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700302 * Open the directory ...
303 */
Al Viro765927b2012-06-26 21:58:53 +0400304 file = dentry_open(path, O_RDONLY, cred);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700305 error = PTR_ERR(file);
306 if (IS_ERR(file))
307 goto out;
308
309 error = -EINVAL;
Al Viro2233f312013-05-22 21:44:23 -0400310 if (!file->f_op->iterate)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700311 goto out_close;
312
Linus Torvalds1da177e2005-04-16 15:20:36 -0700313 buffer.sequence = 0;
314 while (1) {
315 int old_seq = buffer.sequence;
316
Al Viro5c0ba4e2013-05-15 13:52:59 -0400317 error = iterate_dir(file, &buffer.ctx);
Al Viro53c9c5c2008-08-24 07:29:52 -0400318 if (buffer.found) {
319 error = 0;
320 break;
321 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700322
323 if (error < 0)
324 break;
325
Linus Torvalds1da177e2005-04-16 15:20:36 -0700326 error = -ENOENT;
327 if (old_seq == buffer.sequence)
328 break;
329 }
330
331out_close:
332 fput(file);
333out:
334 return error;
335}
336
Linus Torvalds1da177e2005-04-16 15:20:36 -0700337/**
338 * export_encode_fh - default export_operations->encode_fh function
Al Virob0b03822012-04-02 14:34:06 -0400339 * @inode: the object to encode
Fabian Frederick00f01792014-06-04 16:11:15 -0700340 * @fid: where to store the file handle fragment
Linus Torvalds1da177e2005-04-16 15:20:36 -0700341 * @max_len: maximum length to store there
Al Virob0b03822012-04-02 14:34:06 -0400342 * @parent: parent directory inode, if wanted
Linus Torvalds1da177e2005-04-16 15:20:36 -0700343 *
344 * This default encode_fh function assumes that the 32 inode number
345 * is suitable for locating an inode, and that the generation number
346 * can be used to check that it is still valid. It places them in the
347 * filehandle fragment where export_decode_fh expects to find them.
348 */
Al Virob0b03822012-04-02 14:34:06 -0400349static int export_encode_fh(struct inode *inode, struct fid *fid,
350 int *max_len, struct inode *parent)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700351{
Linus Torvalds1da177e2005-04-16 15:20:36 -0700352 int len = *max_len;
Christoph Hellwig6e91ea22007-10-21 16:42:03 -0700353 int type = FILEID_INO32_GEN;
Aneesh Kumar K.V5fe0c232011-01-29 18:43:25 +0530354
Al Virob0b03822012-04-02 14:34:06 -0400355 if (parent && (len < 4)) {
Aneesh Kumar K.V5fe0c232011-01-29 18:43:25 +0530356 *max_len = 4;
Namjae Jeon216b6cb2012-08-29 10:10:10 -0400357 return FILEID_INVALID;
Aneesh Kumar K.V5fe0c232011-01-29 18:43:25 +0530358 } else if (len < 2) {
359 *max_len = 2;
Namjae Jeon216b6cb2012-08-29 10:10:10 -0400360 return FILEID_INVALID;
Aneesh Kumar K.V5fe0c232011-01-29 18:43:25 +0530361 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700362
363 len = 2;
Christoph Hellwig6e91ea22007-10-21 16:42:03 -0700364 fid->i32.ino = inode->i_ino;
365 fid->i32.gen = inode->i_generation;
Al Virob0b03822012-04-02 14:34:06 -0400366 if (parent) {
Christoph Hellwig6e91ea22007-10-21 16:42:03 -0700367 fid->i32.parent_ino = parent->i_ino;
368 fid->i32.parent_gen = parent->i_generation;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700369 len = 4;
Christoph Hellwig6e91ea22007-10-21 16:42:03 -0700370 type = FILEID_INO32_GEN_PARENT;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700371 }
372 *max_len = len;
373 return type;
374}
375
Cyrill Gorcunov711c7bf2012-12-17 16:05:08 -0800376int exportfs_encode_inode_fh(struct inode *inode, struct fid *fid,
377 int *max_len, struct inode *parent)
378{
379 const struct export_operations *nop = inode->i_sb->s_export_op;
380
381 if (nop && nop->encode_fh)
382 return nop->encode_fh(inode, fid->raw, max_len, parent);
383
384 return export_encode_fh(inode, fid, max_len, parent);
385}
386EXPORT_SYMBOL_GPL(exportfs_encode_inode_fh);
387
Christoph Hellwig6e91ea22007-10-21 16:42:03 -0700388int exportfs_encode_fh(struct dentry *dentry, struct fid *fid, int *max_len,
Christoph Hellwigd37065c2007-07-17 04:04:30 -0700389 int connectable)
390{
Christoph Hellwig10f11c32007-07-17 04:04:31 -0700391 int error;
Al Virob0b03822012-04-02 14:34:06 -0400392 struct dentry *p = NULL;
393 struct inode *inode = dentry->d_inode, *parent = NULL;
Christoph Hellwigd37065c2007-07-17 04:04:30 -0700394
Al Virob0b03822012-04-02 14:34:06 -0400395 if (connectable && !S_ISDIR(inode->i_mode)) {
396 p = dget_parent(dentry);
397 /*
398 * note that while p might've ceased to be our parent already,
399 * it's still pinned by and still positive.
400 */
401 parent = p->d_inode;
402 }
Cyrill Gorcunov711c7bf2012-12-17 16:05:08 -0800403
404 error = exportfs_encode_inode_fh(inode, fid, max_len, parent);
Al Virob0b03822012-04-02 14:34:06 -0400405 dput(p);
Christoph Hellwig10f11c32007-07-17 04:04:31 -0700406
407 return error;
Christoph Hellwigd37065c2007-07-17 04:04:30 -0700408}
409EXPORT_SYMBOL_GPL(exportfs_encode_fh);
410
Christoph Hellwig6e91ea22007-10-21 16:42:03 -0700411struct dentry *exportfs_decode_fh(struct vfsmount *mnt, struct fid *fid,
412 int fh_len, int fileid_type,
413 int (*acceptable)(void *, struct dentry *), void *context)
Christoph Hellwigd37065c2007-07-17 04:04:30 -0700414{
Christoph Hellwig39655162007-10-21 16:42:17 -0700415 const struct export_operations *nop = mnt->mnt_sb->s_export_op;
Christoph Hellwig25961102007-10-21 16:42:05 -0700416 struct dentry *result, *alias;
Al Virof3f8e172008-08-11 12:39:47 -0400417 char nbuf[NAME_MAX+1];
Christoph Hellwig25961102007-10-21 16:42:05 -0700418 int err;
Christoph Hellwigd37065c2007-07-17 04:04:30 -0700419
Christoph Hellwig25961102007-10-21 16:42:05 -0700420 /*
Christoph Hellwig25961102007-10-21 16:42:05 -0700421 * Try to get any dentry for the given file handle from the filesystem.
422 */
Aneesh Kumar K.Vbecfd1f2011-01-29 18:43:26 +0530423 if (!nop || !nop->fh_to_dentry)
424 return ERR_PTR(-ESTALE);
Christoph Hellwig25961102007-10-21 16:42:05 -0700425 result = nop->fh_to_dentry(mnt->mnt_sb, fid, fh_len, fileid_type);
J. Bruce Fieldsa4f4d6d2008-12-08 18:24:18 -0500426 if (!result)
427 result = ERR_PTR(-ESTALE);
Christoph Hellwig25961102007-10-21 16:42:05 -0700428 if (IS_ERR(result))
429 return result;
430
431 if (S_ISDIR(result->d_inode->i_mode)) {
432 /*
433 * This request is for a directory.
434 *
435 * On the positive side there is only one dentry for each
436 * directory inode. On the negative side this implies that we
437 * to ensure our dentry is connected all the way up to the
438 * filesystem root.
439 */
440 if (result->d_flags & DCACHE_DISCONNECTED) {
Al Virof3f8e172008-08-11 12:39:47 -0400441 err = reconnect_path(mnt, result, nbuf);
Christoph Hellwig25961102007-10-21 16:42:05 -0700442 if (err)
443 goto err_result;
444 }
445
446 if (!acceptable(context, result)) {
447 err = -EACCES;
448 goto err_result;
449 }
450
451 return result;
452 } else {
453 /*
454 * It's not a directory. Life is a little more complicated.
455 */
456 struct dentry *target_dir, *nresult;
Christoph Hellwig25961102007-10-21 16:42:05 -0700457
458 /*
459 * See if either the dentry we just got from the filesystem
460 * or any alias for it is acceptable. This is always true
461 * if this filesystem is exported without the subtreecheck
462 * option. If the filesystem is exported with the subtree
463 * check option there's a fair chance we need to look at
464 * the parent directory in the file handle and make sure
465 * it's connected to the filesystem root.
466 */
467 alias = find_acceptable_alias(result, acceptable, context);
468 if (alias)
469 return alias;
470
471 /*
472 * Try to extract a dentry for the parent directory from the
473 * file handle. If this fails we'll have to give up.
474 */
475 err = -ESTALE;
476 if (!nop->fh_to_parent)
477 goto err_result;
478
479 target_dir = nop->fh_to_parent(mnt->mnt_sb, fid,
480 fh_len, fileid_type);
J. Bruce Fieldsa4f4d6d2008-12-08 18:24:18 -0500481 if (!target_dir)
482 goto err_result;
Christoph Hellwig25961102007-10-21 16:42:05 -0700483 err = PTR_ERR(target_dir);
484 if (IS_ERR(target_dir))
485 goto err_result;
486
487 /*
488 * And as usual we need to make sure the parent directory is
489 * connected to the filesystem root. The VFS really doesn't
490 * like disconnected directories..
491 */
Al Virof3f8e172008-08-11 12:39:47 -0400492 err = reconnect_path(mnt, target_dir, nbuf);
Christoph Hellwig25961102007-10-21 16:42:05 -0700493 if (err) {
494 dput(target_dir);
495 goto err_result;
496 }
497
498 /*
499 * Now that we've got both a well-connected parent and a
500 * dentry for the inode we're after, make sure that our
501 * inode is actually connected to the parent.
502 */
Christoph Hellwige38f9812007-10-21 16:42:19 -0700503 err = exportfs_get_name(mnt, target_dir, nbuf, result);
Christoph Hellwig25961102007-10-21 16:42:05 -0700504 if (!err) {
505 mutex_lock(&target_dir->d_inode->i_mutex);
506 nresult = lookup_one_len(nbuf, target_dir,
507 strlen(nbuf));
508 mutex_unlock(&target_dir->d_inode->i_mutex);
509 if (!IS_ERR(nresult)) {
510 if (nresult->d_inode) {
511 dput(result);
512 result = nresult;
513 } else
514 dput(nresult);
515 }
516 }
517
518 /*
519 * At this point we are done with the parent, but it's pinned
520 * by the child dentry anyway.
521 */
522 dput(target_dir);
523
524 /*
525 * And finally make sure the dentry is actually acceptable
526 * to NFSD.
527 */
528 alias = find_acceptable_alias(result, acceptable, context);
529 if (!alias) {
530 err = -EACCES;
531 goto err_result;
532 }
533
534 return alias;
535 }
536
537 err_result:
538 dput(result);
539 return ERR_PTR(err);
Christoph Hellwigd37065c2007-07-17 04:04:30 -0700540}
541EXPORT_SYMBOL_GPL(exportfs_decode_fh);
542
Linus Torvalds1da177e2005-04-16 15:20:36 -0700543MODULE_LICENSE("GPL");