blob: c46f1a190b8d9ecedd8157530ecfc3ec9ccf16c4 [file] [log] [blame]
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);
Al Viro946e51f2014-10-26 19:19:16 -040053 hlist_for_each_entry(dentry, &inode->i_dentry, d_u.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);
Al Viro59551022016-01-22 15:40:57 -0500127 inode_lock(dentry->d_inode);
J. Bruce Fieldsbbf7a8a2013-10-17 11:13:00 -0400128 if (mnt->mnt_sb->s_export_op->get_parent)
129 parent = mnt->mnt_sb->s_export_op->get_parent(dentry);
Al Viro59551022016-01-22 15:40:57 -0500130 inode_unlock(dentry->d_inode);
J. Bruce Fieldsbbf7a8a2013-10-17 11:13:00 -0400131
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);
Al Viro59551022016-01-22 15:40:57 -0500146 inode_lock(parent->d_inode);
J. Bruce Fieldsbbf7a8a2013-10-17 11:13:00 -0400147 tmp = lookup_one_len(nbuf, parent, strlen(nbuf));
Al Viro59551022016-01-22 15:40:57 -0500148 inode_unlock(parent->d_inode);
J. Bruce Fieldsbbf7a8a2013-10-17 11:13:00 -0400149 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 */
Miklos Szerediac7576f2014-10-30 17:37:34 +0100244static int filldir_one(struct dir_context *ctx, 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{
Miklos Szerediac7576f2014-10-30 17:37:34 +0100247 struct getdents_callback *buf =
248 container_of(ctx, struct getdents_callback, ctx);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700249 int result = 0;
250
251 buf->sequence++;
Al Virodfc59e2c2013-09-06 16:55:36 -0400252 if (buf->ino == ino && len <= NAME_MAX) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700253 memcpy(buf->name, name, len);
254 buf->name[len] = '\0';
255 buf->found = 1;
256 result = -1;
257 }
258 return result;
259}
260
261/**
262 * get_name - default export_operations->get_name function
Fabian Frederick00f01792014-06-04 16:11:15 -0700263 * @path: the directory in which to find a name
Linus Torvalds1da177e2005-04-16 15:20:36 -0700264 * @name: a pointer to a %NAME_MAX+1 char buffer to store the name
265 * @child: the dentry for the child directory.
266 *
267 * calls readdir on the parent until it finds an entry with
268 * the same inode number as the child, and returns that.
269 */
Al Viro765927b2012-06-26 21:58:53 +0400270static int get_name(const struct path *path, char *name, struct dentry *child)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700271{
David Howells745ca242008-11-14 10:39:22 +1100272 const struct cred *cred = current_cred();
Al Viro765927b2012-06-26 21:58:53 +0400273 struct inode *dir = path->dentry->d_inode;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700274 int error;
275 struct file *file;
J. Bruce Fields950ee952013-09-10 11:41:12 -0400276 struct kstat stat;
277 struct path child_path = {
278 .mnt = path->mnt,
279 .dentry = child,
280 };
Al Viroac6614b2013-05-22 22:22:04 -0400281 struct getdents_callback buffer = {
282 .ctx.actor = filldir_one,
283 .name = name,
Al Viroac6614b2013-05-22 22:22:04 -0400284 };
Linus Torvalds1da177e2005-04-16 15:20:36 -0700285
286 error = -ENOTDIR;
287 if (!dir || !S_ISDIR(dir->i_mode))
288 goto out;
289 error = -EINVAL;
290 if (!dir->i_fop)
291 goto out;
292 /*
J. Bruce Fields950ee952013-09-10 11:41:12 -0400293 * inode->i_ino is unsigned long, kstat->ino is u64, so the
294 * former would be insufficient on 32-bit hosts when the
295 * filesystem supports 64-bit inode numbers. So we need to
296 * actually call ->getattr, not just read i_ino:
297 */
298 error = vfs_getattr_nosec(&child_path, &stat);
299 if (error)
300 return error;
301 buffer.ino = stat.ino;
302 /*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700303 * Open the directory ...
304 */
Al Viro765927b2012-06-26 21:58:53 +0400305 file = dentry_open(path, O_RDONLY, cred);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700306 error = PTR_ERR(file);
307 if (IS_ERR(file))
308 goto out;
309
310 error = -EINVAL;
Al Viro2233f312013-05-22 21:44:23 -0400311 if (!file->f_op->iterate)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700312 goto out_close;
313
Linus Torvalds1da177e2005-04-16 15:20:36 -0700314 buffer.sequence = 0;
315 while (1) {
316 int old_seq = buffer.sequence;
317
Al Viro5c0ba4e2013-05-15 13:52:59 -0400318 error = iterate_dir(file, &buffer.ctx);
Al Viro53c9c5c2008-08-24 07:29:52 -0400319 if (buffer.found) {
320 error = 0;
321 break;
322 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700323
324 if (error < 0)
325 break;
326
Linus Torvalds1da177e2005-04-16 15:20:36 -0700327 error = -ENOENT;
328 if (old_seq == buffer.sequence)
329 break;
330 }
331
332out_close:
333 fput(file);
334out:
335 return error;
336}
337
Linus Torvalds1da177e2005-04-16 15:20:36 -0700338/**
339 * export_encode_fh - default export_operations->encode_fh function
Al Virob0b03822012-04-02 14:34:06 -0400340 * @inode: the object to encode
Fabian Frederick00f01792014-06-04 16:11:15 -0700341 * @fid: where to store the file handle fragment
Linus Torvalds1da177e2005-04-16 15:20:36 -0700342 * @max_len: maximum length to store there
Al Virob0b03822012-04-02 14:34:06 -0400343 * @parent: parent directory inode, if wanted
Linus Torvalds1da177e2005-04-16 15:20:36 -0700344 *
345 * This default encode_fh function assumes that the 32 inode number
346 * is suitable for locating an inode, and that the generation number
347 * can be used to check that it is still valid. It places them in the
348 * filehandle fragment where export_decode_fh expects to find them.
349 */
Al Virob0b03822012-04-02 14:34:06 -0400350static int export_encode_fh(struct inode *inode, struct fid *fid,
351 int *max_len, struct inode *parent)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700352{
Linus Torvalds1da177e2005-04-16 15:20:36 -0700353 int len = *max_len;
Christoph Hellwig6e91ea22007-10-21 16:42:03 -0700354 int type = FILEID_INO32_GEN;
Aneesh Kumar K.V5fe0c232011-01-29 18:43:25 +0530355
Al Virob0b03822012-04-02 14:34:06 -0400356 if (parent && (len < 4)) {
Aneesh Kumar K.V5fe0c232011-01-29 18:43:25 +0530357 *max_len = 4;
Namjae Jeon216b6cb2012-08-29 10:10:10 -0400358 return FILEID_INVALID;
Aneesh Kumar K.V5fe0c232011-01-29 18:43:25 +0530359 } else if (len < 2) {
360 *max_len = 2;
Namjae Jeon216b6cb2012-08-29 10:10:10 -0400361 return FILEID_INVALID;
Aneesh Kumar K.V5fe0c232011-01-29 18:43:25 +0530362 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700363
364 len = 2;
Christoph Hellwig6e91ea22007-10-21 16:42:03 -0700365 fid->i32.ino = inode->i_ino;
366 fid->i32.gen = inode->i_generation;
Al Virob0b03822012-04-02 14:34:06 -0400367 if (parent) {
Christoph Hellwig6e91ea22007-10-21 16:42:03 -0700368 fid->i32.parent_ino = parent->i_ino;
369 fid->i32.parent_gen = parent->i_generation;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700370 len = 4;
Christoph Hellwig6e91ea22007-10-21 16:42:03 -0700371 type = FILEID_INO32_GEN_PARENT;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700372 }
373 *max_len = len;
374 return type;
375}
376
Cyrill Gorcunov711c7bf2012-12-17 16:05:08 -0800377int exportfs_encode_inode_fh(struct inode *inode, struct fid *fid,
378 int *max_len, struct inode *parent)
379{
380 const struct export_operations *nop = inode->i_sb->s_export_op;
381
382 if (nop && nop->encode_fh)
383 return nop->encode_fh(inode, fid->raw, max_len, parent);
384
385 return export_encode_fh(inode, fid, max_len, parent);
386}
387EXPORT_SYMBOL_GPL(exportfs_encode_inode_fh);
388
Christoph Hellwig6e91ea22007-10-21 16:42:03 -0700389int exportfs_encode_fh(struct dentry *dentry, struct fid *fid, int *max_len,
Christoph Hellwigd37065c2007-07-17 04:04:30 -0700390 int connectable)
391{
Christoph Hellwig10f11c32007-07-17 04:04:31 -0700392 int error;
Al Virob0b03822012-04-02 14:34:06 -0400393 struct dentry *p = NULL;
394 struct inode *inode = dentry->d_inode, *parent = NULL;
Christoph Hellwigd37065c2007-07-17 04:04:30 -0700395
Al Virob0b03822012-04-02 14:34:06 -0400396 if (connectable && !S_ISDIR(inode->i_mode)) {
397 p = dget_parent(dentry);
398 /*
399 * note that while p might've ceased to be our parent already,
400 * it's still pinned by and still positive.
401 */
402 parent = p->d_inode;
403 }
Cyrill Gorcunov711c7bf2012-12-17 16:05:08 -0800404
405 error = exportfs_encode_inode_fh(inode, fid, max_len, parent);
Al Virob0b03822012-04-02 14:34:06 -0400406 dput(p);
Christoph Hellwig10f11c32007-07-17 04:04:31 -0700407
408 return error;
Christoph Hellwigd37065c2007-07-17 04:04:30 -0700409}
410EXPORT_SYMBOL_GPL(exportfs_encode_fh);
411
Christoph Hellwig6e91ea22007-10-21 16:42:03 -0700412struct dentry *exportfs_decode_fh(struct vfsmount *mnt, struct fid *fid,
413 int fh_len, int fileid_type,
414 int (*acceptable)(void *, struct dentry *), void *context)
Christoph Hellwigd37065c2007-07-17 04:04:30 -0700415{
Christoph Hellwig39655162007-10-21 16:42:17 -0700416 const struct export_operations *nop = mnt->mnt_sb->s_export_op;
Christoph Hellwig25961102007-10-21 16:42:05 -0700417 struct dentry *result, *alias;
Al Virof3f8e172008-08-11 12:39:47 -0400418 char nbuf[NAME_MAX+1];
Christoph Hellwig25961102007-10-21 16:42:05 -0700419 int err;
Christoph Hellwigd37065c2007-07-17 04:04:30 -0700420
Christoph Hellwig25961102007-10-21 16:42:05 -0700421 /*
Christoph Hellwig25961102007-10-21 16:42:05 -0700422 * Try to get any dentry for the given file handle from the filesystem.
423 */
Aneesh Kumar K.Vbecfd1f2011-01-29 18:43:26 +0530424 if (!nop || !nop->fh_to_dentry)
425 return ERR_PTR(-ESTALE);
Christoph Hellwig25961102007-10-21 16:42:05 -0700426 result = nop->fh_to_dentry(mnt->mnt_sb, fid, fh_len, fileid_type);
J. Bruce Fieldsa4f4d6d2008-12-08 18:24:18 -0500427 if (!result)
428 result = ERR_PTR(-ESTALE);
Christoph Hellwig25961102007-10-21 16:42:05 -0700429 if (IS_ERR(result))
430 return result;
431
David Howellse36cb0b2015-01-29 12:02:35 +0000432 if (d_is_dir(result)) {
Christoph Hellwig25961102007-10-21 16:42:05 -0700433 /*
434 * This request is for a directory.
435 *
436 * On the positive side there is only one dentry for each
437 * directory inode. On the negative side this implies that we
438 * to ensure our dentry is connected all the way up to the
439 * filesystem root.
440 */
441 if (result->d_flags & DCACHE_DISCONNECTED) {
Al Virof3f8e172008-08-11 12:39:47 -0400442 err = reconnect_path(mnt, result, nbuf);
Christoph Hellwig25961102007-10-21 16:42:05 -0700443 if (err)
444 goto err_result;
445 }
446
447 if (!acceptable(context, result)) {
448 err = -EACCES;
449 goto err_result;
450 }
451
452 return result;
453 } else {
454 /*
455 * It's not a directory. Life is a little more complicated.
456 */
457 struct dentry *target_dir, *nresult;
Christoph Hellwig25961102007-10-21 16:42:05 -0700458
459 /*
460 * See if either the dentry we just got from the filesystem
461 * or any alias for it is acceptable. This is always true
462 * if this filesystem is exported without the subtreecheck
463 * option. If the filesystem is exported with the subtree
464 * check option there's a fair chance we need to look at
465 * the parent directory in the file handle and make sure
466 * it's connected to the filesystem root.
467 */
468 alias = find_acceptable_alias(result, acceptable, context);
469 if (alias)
470 return alias;
471
472 /*
473 * Try to extract a dentry for the parent directory from the
474 * file handle. If this fails we'll have to give up.
475 */
476 err = -ESTALE;
477 if (!nop->fh_to_parent)
478 goto err_result;
479
480 target_dir = nop->fh_to_parent(mnt->mnt_sb, fid,
481 fh_len, fileid_type);
J. Bruce Fieldsa4f4d6d2008-12-08 18:24:18 -0500482 if (!target_dir)
483 goto err_result;
Christoph Hellwig25961102007-10-21 16:42:05 -0700484 err = PTR_ERR(target_dir);
485 if (IS_ERR(target_dir))
486 goto err_result;
487
488 /*
489 * And as usual we need to make sure the parent directory is
490 * connected to the filesystem root. The VFS really doesn't
491 * like disconnected directories..
492 */
Al Virof3f8e172008-08-11 12:39:47 -0400493 err = reconnect_path(mnt, target_dir, nbuf);
Christoph Hellwig25961102007-10-21 16:42:05 -0700494 if (err) {
495 dput(target_dir);
496 goto err_result;
497 }
498
499 /*
500 * Now that we've got both a well-connected parent and a
501 * dentry for the inode we're after, make sure that our
502 * inode is actually connected to the parent.
503 */
Christoph Hellwige38f9812007-10-21 16:42:19 -0700504 err = exportfs_get_name(mnt, target_dir, nbuf, result);
Christoph Hellwig25961102007-10-21 16:42:05 -0700505 if (!err) {
Al Viro59551022016-01-22 15:40:57 -0500506 inode_lock(target_dir->d_inode);
Christoph Hellwig25961102007-10-21 16:42:05 -0700507 nresult = lookup_one_len(nbuf, target_dir,
508 strlen(nbuf));
Al Viro59551022016-01-22 15:40:57 -0500509 inode_unlock(target_dir->d_inode);
Christoph Hellwig25961102007-10-21 16:42:05 -0700510 if (!IS_ERR(nresult)) {
511 if (nresult->d_inode) {
512 dput(result);
513 result = nresult;
514 } else
515 dput(nresult);
516 }
517 }
518
519 /*
520 * At this point we are done with the parent, but it's pinned
521 * by the child dentry anyway.
522 */
523 dput(target_dir);
524
525 /*
526 * And finally make sure the dentry is actually acceptable
527 * to NFSD.
528 */
529 alias = find_acceptable_alias(result, acceptable, context);
530 if (!alias) {
531 err = -EACCES;
532 goto err_result;
533 }
534
535 return alias;
536 }
537
538 err_result:
539 dput(result);
540 return ERR_PTR(err);
Christoph Hellwigd37065c2007-07-17 04:04:30 -0700541}
542EXPORT_SYMBOL_GPL(exportfs_decode_fh);
543
Linus Torvalds1da177e2005-04-16 15:20:36 -0700544MODULE_LICENSE("GPL");