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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;
Al Virob3d9b7a2012-06-09 13:51:19 -040047 struct hlist_node *p;
Christoph Hellwige2f99012006-01-18 17:43:52 -080048
Christoph Hellwigfb66a192007-07-17 04:04:32 -070049 if (acceptable(context, result))
50 return result;
51
Nick Piggin873feea2011-01-07 17:50:06 +110052 inode = result->d_inode;
53 spin_lock(&inode->i_lock);
Al Virob3d9b7a2012-06-09 13:51:19 -040054 hlist_for_each_entry(dentry, p, &inode->i_dentry, d_alias) {
Nick Piggindc0474b2011-01-07 17:49:43 +110055 dget(dentry);
Nick Piggin873feea2011-01-07 17:50:06 +110056 spin_unlock(&inode->i_lock);
Christoph Hellwige2f99012006-01-18 17:43:52 -080057 if (toput)
58 dput(toput);
59 if (dentry != result && acceptable(context, dentry)) {
60 dput(result);
61 return dentry;
62 }
Nick Piggin873feea2011-01-07 17:50:06 +110063 spin_lock(&inode->i_lock);
Christoph Hellwige2f99012006-01-18 17:43:52 -080064 toput = dentry;
65 }
Nick Piggin873feea2011-01-07 17:50:06 +110066 spin_unlock(&inode->i_lock);
Christoph Hellwige2f99012006-01-18 17:43:52 -080067
68 if (toput)
69 dput(toput);
70 return NULL;
71}
72
Christoph Hellwigdd90b502007-07-17 04:04:32 -070073/*
74 * Find root of a disconnected subtree and return a reference to it.
75 */
76static struct dentry *
77find_disconnected_root(struct dentry *dentry)
78{
79 dget(dentry);
Christoph Hellwig0461ee22010-10-13 11:56:37 -040080 while (!IS_ROOT(dentry)) {
81 struct dentry *parent = dget_parent(dentry);
82
83 if (!(parent->d_flags & DCACHE_DISCONNECTED)) {
84 dput(parent);
85 break;
86 }
87
Christoph Hellwigdd90b502007-07-17 04:04:32 -070088 dput(dentry);
89 dentry = parent;
Christoph Hellwigdd90b502007-07-17 04:04:32 -070090 }
Christoph Hellwigdd90b502007-07-17 04:04:32 -070091 return dentry;
92}
93
Christoph Hellwig019ab802007-07-17 04:04:33 -070094/*
95 * Make sure target_dir is fully connected to the dentry tree.
96 *
97 * It may already be, as the flag isn't always updated when connection happens.
98 */
99static int
Al Virof3f8e172008-08-11 12:39:47 -0400100reconnect_path(struct vfsmount *mnt, struct dentry *target_dir, char *nbuf)
Christoph Hellwig019ab802007-07-17 04:04:33 -0700101{
Christoph Hellwig019ab802007-07-17 04:04:33 -0700102 int noprogress = 0;
103 int err = -ESTALE;
104
105 /*
106 * It is possible that a confused file system might not let us complete
107 * the path to the root. For example, if get_parent returns a directory
108 * in which we cannot find a name for the child. While this implies a
109 * very sick filesystem we don't want it to cause knfsd to spin. Hence
110 * the noprogress counter. If we go through the loop 10 times (2 is
111 * probably enough) without getting anywhere, we just give up
112 */
113 while (target_dir->d_flags & DCACHE_DISCONNECTED && noprogress++ < 10) {
114 struct dentry *pd = find_disconnected_root(target_dir);
115
116 if (!IS_ROOT(pd)) {
117 /* must have found a connected parent - great */
118 spin_lock(&pd->d_lock);
119 pd->d_flags &= ~DCACHE_DISCONNECTED;
120 spin_unlock(&pd->d_lock);
121 noprogress = 0;
Christoph Hellwige38f9812007-10-21 16:42:19 -0700122 } else if (pd == mnt->mnt_sb->s_root) {
Christoph Hellwig019ab802007-07-17 04:04:33 -0700123 printk(KERN_ERR "export: Eeek filesystem root is not connected, impossible\n");
124 spin_lock(&pd->d_lock);
125 pd->d_flags &= ~DCACHE_DISCONNECTED;
126 spin_unlock(&pd->d_lock);
127 noprogress = 0;
128 } else {
129 /*
130 * We have hit the top of a disconnected path, try to
131 * find parent and connect.
132 *
133 * Racing with some other process renaming a directory
134 * isn't much of a problem here. If someone renames
135 * the directory, it will end up properly connected,
136 * which is what we want
137 *
138 * Getting the parent can't be supported generically,
139 * the locking is too icky.
140 *
141 * Instead we just return EACCES. If server reboots
142 * or inodes get flushed, you lose
143 */
144 struct dentry *ppd = ERR_PTR(-EACCES);
145 struct dentry *npd;
146
147 mutex_lock(&pd->d_inode->i_mutex);
Christoph Hellwige38f9812007-10-21 16:42:19 -0700148 if (mnt->mnt_sb->s_export_op->get_parent)
149 ppd = mnt->mnt_sb->s_export_op->get_parent(pd);
Christoph Hellwig019ab802007-07-17 04:04:33 -0700150 mutex_unlock(&pd->d_inode->i_mutex);
151
152 if (IS_ERR(ppd)) {
153 err = PTR_ERR(ppd);
154 dprintk("%s: get_parent of %ld failed, err %d\n",
Harvey Harrison8e24eea2008-04-30 00:55:09 -0700155 __func__, pd->d_inode->i_ino, err);
Christoph Hellwig019ab802007-07-17 04:04:33 -0700156 dput(pd);
157 break;
158 }
159
Harvey Harrison8e24eea2008-04-30 00:55:09 -0700160 dprintk("%s: find name of %lu in %lu\n", __func__,
Christoph Hellwig019ab802007-07-17 04:04:33 -0700161 pd->d_inode->i_ino, ppd->d_inode->i_ino);
Christoph Hellwige38f9812007-10-21 16:42:19 -0700162 err = exportfs_get_name(mnt, ppd, nbuf, pd);
Christoph Hellwig019ab802007-07-17 04:04:33 -0700163 if (err) {
164 dput(ppd);
165 dput(pd);
166 if (err == -ENOENT)
167 /* some race between get_parent and
168 * get_name? just try again
169 */
170 continue;
171 break;
172 }
Harvey Harrison8e24eea2008-04-30 00:55:09 -0700173 dprintk("%s: found name: %s\n", __func__, nbuf);
Christoph Hellwig019ab802007-07-17 04:04:33 -0700174 mutex_lock(&ppd->d_inode->i_mutex);
175 npd = lookup_one_len(nbuf, ppd, strlen(nbuf));
176 mutex_unlock(&ppd->d_inode->i_mutex);
177 if (IS_ERR(npd)) {
178 err = PTR_ERR(npd);
179 dprintk("%s: lookup failed: %d\n",
Harvey Harrison8e24eea2008-04-30 00:55:09 -0700180 __func__, err);
Christoph Hellwig019ab802007-07-17 04:04:33 -0700181 dput(ppd);
182 dput(pd);
183 break;
184 }
185 /* we didn't really want npd, we really wanted
186 * a side-effect of the lookup.
187 * hopefully, npd == pd, though it isn't really
188 * a problem if it isn't
189 */
190 if (npd == pd)
191 noprogress = 0;
192 else
Harvey Harrison8e24eea2008-04-30 00:55:09 -0700193 printk("%s: npd != pd\n", __func__);
Christoph Hellwig019ab802007-07-17 04:04:33 -0700194 dput(npd);
195 dput(ppd);
196 if (IS_ROOT(pd)) {
197 /* something went wrong, we have to give up */
198 dput(pd);
199 break;
200 }
201 }
202 dput(pd);
203 }
204
205 if (target_dir->d_flags & DCACHE_DISCONNECTED) {
206 /* something went wrong - oh-well */
207 if (!err)
208 err = -ESTALE;
209 return err;
210 }
211
212 return 0;
213}
214
Linus Torvalds1da177e2005-04-16 15:20:36 -0700215struct getdents_callback {
216 char *name; /* name that was found. It already points to a
217 buffer NAME_MAX+1 is size */
218 unsigned long ino; /* the inum we are looking for */
219 int found; /* inode matched? */
220 int sequence; /* sequence counter */
221};
222
223/*
224 * A rather strange filldir function to capture
225 * the name matching the specified inode number.
226 */
227static int filldir_one(void * __buf, const char * name, int len,
David Howellsafefdbb2006-10-03 01:13:46 -0700228 loff_t pos, u64 ino, unsigned int d_type)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700229{
230 struct getdents_callback *buf = __buf;
231 int result = 0;
232
233 buf->sequence++;
234 if (buf->ino == ino) {
235 memcpy(buf->name, name, len);
236 buf->name[len] = '\0';
237 buf->found = 1;
238 result = -1;
239 }
240 return result;
241}
242
243/**
244 * get_name - default export_operations->get_name function
245 * @dentry: the directory in which to find a name
246 * @name: a pointer to a %NAME_MAX+1 char buffer to store the name
247 * @child: the dentry for the child directory.
248 *
249 * calls readdir on the parent until it finds an entry with
250 * the same inode number as the child, and returns that.
251 */
Al Viro765927b2012-06-26 21:58:53 +0400252static int get_name(const struct path *path, char *name, struct dentry *child)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700253{
David Howells745ca242008-11-14 10:39:22 +1100254 const struct cred *cred = current_cred();
Al Viro765927b2012-06-26 21:58:53 +0400255 struct inode *dir = path->dentry->d_inode;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700256 int error;
257 struct file *file;
258 struct getdents_callback buffer;
259
260 error = -ENOTDIR;
261 if (!dir || !S_ISDIR(dir->i_mode))
262 goto out;
263 error = -EINVAL;
264 if (!dir->i_fop)
265 goto out;
266 /*
267 * Open the directory ...
268 */
Al Viro765927b2012-06-26 21:58:53 +0400269 file = dentry_open(path, O_RDONLY, cred);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700270 error = PTR_ERR(file);
271 if (IS_ERR(file))
272 goto out;
273
274 error = -EINVAL;
275 if (!file->f_op->readdir)
276 goto out_close;
277
278 buffer.name = name;
279 buffer.ino = child->d_inode->i_ino;
280 buffer.found = 0;
281 buffer.sequence = 0;
282 while (1) {
283 int old_seq = buffer.sequence;
284
285 error = vfs_readdir(file, filldir_one, &buffer);
Al Viro53c9c5c2008-08-24 07:29:52 -0400286 if (buffer.found) {
287 error = 0;
288 break;
289 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700290
291 if (error < 0)
292 break;
293
Linus Torvalds1da177e2005-04-16 15:20:36 -0700294 error = -ENOENT;
295 if (old_seq == buffer.sequence)
296 break;
297 }
298
299out_close:
300 fput(file);
301out:
302 return error;
303}
304
Linus Torvalds1da177e2005-04-16 15:20:36 -0700305/**
306 * export_encode_fh - default export_operations->encode_fh function
Al Virob0b03822012-04-02 14:34:06 -0400307 * @inode: the object to encode
Linus Torvalds1da177e2005-04-16 15:20:36 -0700308 * @fh: where to store the file handle fragment
309 * @max_len: maximum length to store there
Al Virob0b03822012-04-02 14:34:06 -0400310 * @parent: parent directory inode, if wanted
Linus Torvalds1da177e2005-04-16 15:20:36 -0700311 *
312 * This default encode_fh function assumes that the 32 inode number
313 * is suitable for locating an inode, and that the generation number
314 * can be used to check that it is still valid. It places them in the
315 * filehandle fragment where export_decode_fh expects to find them.
316 */
Al Virob0b03822012-04-02 14:34:06 -0400317static int export_encode_fh(struct inode *inode, struct fid *fid,
318 int *max_len, struct inode *parent)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700319{
Linus Torvalds1da177e2005-04-16 15:20:36 -0700320 int len = *max_len;
Christoph Hellwig6e91ea22007-10-21 16:42:03 -0700321 int type = FILEID_INO32_GEN;
Aneesh Kumar K.V5fe0c232011-01-29 18:43:25 +0530322
Al Virob0b03822012-04-02 14:34:06 -0400323 if (parent && (len < 4)) {
Aneesh Kumar K.V5fe0c232011-01-29 18:43:25 +0530324 *max_len = 4;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700325 return 255;
Aneesh Kumar K.V5fe0c232011-01-29 18:43:25 +0530326 } else if (len < 2) {
327 *max_len = 2;
328 return 255;
329 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700330
331 len = 2;
Christoph Hellwig6e91ea22007-10-21 16:42:03 -0700332 fid->i32.ino = inode->i_ino;
333 fid->i32.gen = inode->i_generation;
Al Virob0b03822012-04-02 14:34:06 -0400334 if (parent) {
Christoph Hellwig6e91ea22007-10-21 16:42:03 -0700335 fid->i32.parent_ino = parent->i_ino;
336 fid->i32.parent_gen = parent->i_generation;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700337 len = 4;
Christoph Hellwig6e91ea22007-10-21 16:42:03 -0700338 type = FILEID_INO32_GEN_PARENT;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700339 }
340 *max_len = len;
341 return type;
342}
343
Christoph Hellwig6e91ea22007-10-21 16:42:03 -0700344int exportfs_encode_fh(struct dentry *dentry, struct fid *fid, int *max_len,
Christoph Hellwigd37065c2007-07-17 04:04:30 -0700345 int connectable)
346{
Christoph Hellwig39655162007-10-21 16:42:17 -0700347 const struct export_operations *nop = dentry->d_sb->s_export_op;
Christoph Hellwig10f11c32007-07-17 04:04:31 -0700348 int error;
Al Virob0b03822012-04-02 14:34:06 -0400349 struct dentry *p = NULL;
350 struct inode *inode = dentry->d_inode, *parent = NULL;
Christoph Hellwigd37065c2007-07-17 04:04:30 -0700351
Al Virob0b03822012-04-02 14:34:06 -0400352 if (connectable && !S_ISDIR(inode->i_mode)) {
353 p = dget_parent(dentry);
354 /*
355 * note that while p might've ceased to be our parent already,
356 * it's still pinned by and still positive.
357 */
358 parent = p->d_inode;
359 }
Christoph Hellwig10f11c32007-07-17 04:04:31 -0700360 if (nop->encode_fh)
Al Virob0b03822012-04-02 14:34:06 -0400361 error = nop->encode_fh(inode, fid->raw, max_len, parent);
Christoph Hellwig10f11c32007-07-17 04:04:31 -0700362 else
Al Virob0b03822012-04-02 14:34:06 -0400363 error = export_encode_fh(inode, fid, max_len, parent);
364 dput(p);
Christoph Hellwig10f11c32007-07-17 04:04:31 -0700365
366 return error;
Christoph Hellwigd37065c2007-07-17 04:04:30 -0700367}
368EXPORT_SYMBOL_GPL(exportfs_encode_fh);
369
Christoph Hellwig6e91ea22007-10-21 16:42:03 -0700370struct dentry *exportfs_decode_fh(struct vfsmount *mnt, struct fid *fid,
371 int fh_len, int fileid_type,
372 int (*acceptable)(void *, struct dentry *), void *context)
Christoph Hellwigd37065c2007-07-17 04:04:30 -0700373{
Christoph Hellwig39655162007-10-21 16:42:17 -0700374 const struct export_operations *nop = mnt->mnt_sb->s_export_op;
Christoph Hellwig25961102007-10-21 16:42:05 -0700375 struct dentry *result, *alias;
Al Virof3f8e172008-08-11 12:39:47 -0400376 char nbuf[NAME_MAX+1];
Christoph Hellwig25961102007-10-21 16:42:05 -0700377 int err;
Christoph Hellwigd37065c2007-07-17 04:04:30 -0700378
Christoph Hellwig25961102007-10-21 16:42:05 -0700379 /*
Christoph Hellwig25961102007-10-21 16:42:05 -0700380 * Try to get any dentry for the given file handle from the filesystem.
381 */
Aneesh Kumar K.Vbecfd1f2011-01-29 18:43:26 +0530382 if (!nop || !nop->fh_to_dentry)
383 return ERR_PTR(-ESTALE);
Christoph Hellwig25961102007-10-21 16:42:05 -0700384 result = nop->fh_to_dentry(mnt->mnt_sb, fid, fh_len, fileid_type);
J. Bruce Fieldsa4f4d6d2008-12-08 18:24:18 -0500385 if (!result)
386 result = ERR_PTR(-ESTALE);
Christoph Hellwig25961102007-10-21 16:42:05 -0700387 if (IS_ERR(result))
388 return result;
389
390 if (S_ISDIR(result->d_inode->i_mode)) {
391 /*
392 * This request is for a directory.
393 *
394 * On the positive side there is only one dentry for each
395 * directory inode. On the negative side this implies that we
396 * to ensure our dentry is connected all the way up to the
397 * filesystem root.
398 */
399 if (result->d_flags & DCACHE_DISCONNECTED) {
Al Virof3f8e172008-08-11 12:39:47 -0400400 err = reconnect_path(mnt, result, nbuf);
Christoph Hellwig25961102007-10-21 16:42:05 -0700401 if (err)
402 goto err_result;
403 }
404
405 if (!acceptable(context, result)) {
406 err = -EACCES;
407 goto err_result;
408 }
409
410 return result;
411 } else {
412 /*
413 * It's not a directory. Life is a little more complicated.
414 */
415 struct dentry *target_dir, *nresult;
Christoph Hellwig25961102007-10-21 16:42:05 -0700416
417 /*
418 * See if either the dentry we just got from the filesystem
419 * or any alias for it is acceptable. This is always true
420 * if this filesystem is exported without the subtreecheck
421 * option. If the filesystem is exported with the subtree
422 * check option there's a fair chance we need to look at
423 * the parent directory in the file handle and make sure
424 * it's connected to the filesystem root.
425 */
426 alias = find_acceptable_alias(result, acceptable, context);
427 if (alias)
428 return alias;
429
430 /*
431 * Try to extract a dentry for the parent directory from the
432 * file handle. If this fails we'll have to give up.
433 */
434 err = -ESTALE;
435 if (!nop->fh_to_parent)
436 goto err_result;
437
438 target_dir = nop->fh_to_parent(mnt->mnt_sb, fid,
439 fh_len, fileid_type);
J. Bruce Fieldsa4f4d6d2008-12-08 18:24:18 -0500440 if (!target_dir)
441 goto err_result;
Christoph Hellwig25961102007-10-21 16:42:05 -0700442 err = PTR_ERR(target_dir);
443 if (IS_ERR(target_dir))
444 goto err_result;
445
446 /*
447 * And as usual we need to make sure the parent directory is
448 * connected to the filesystem root. The VFS really doesn't
449 * like disconnected directories..
450 */
Al Virof3f8e172008-08-11 12:39:47 -0400451 err = reconnect_path(mnt, target_dir, nbuf);
Christoph Hellwig25961102007-10-21 16:42:05 -0700452 if (err) {
453 dput(target_dir);
454 goto err_result;
455 }
456
457 /*
458 * Now that we've got both a well-connected parent and a
459 * dentry for the inode we're after, make sure that our
460 * inode is actually connected to the parent.
461 */
Christoph Hellwige38f9812007-10-21 16:42:19 -0700462 err = exportfs_get_name(mnt, target_dir, nbuf, result);
Christoph Hellwig25961102007-10-21 16:42:05 -0700463 if (!err) {
464 mutex_lock(&target_dir->d_inode->i_mutex);
465 nresult = lookup_one_len(nbuf, target_dir,
466 strlen(nbuf));
467 mutex_unlock(&target_dir->d_inode->i_mutex);
468 if (!IS_ERR(nresult)) {
469 if (nresult->d_inode) {
470 dput(result);
471 result = nresult;
472 } else
473 dput(nresult);
474 }
475 }
476
477 /*
478 * At this point we are done with the parent, but it's pinned
479 * by the child dentry anyway.
480 */
481 dput(target_dir);
482
483 /*
484 * And finally make sure the dentry is actually acceptable
485 * to NFSD.
486 */
487 alias = find_acceptable_alias(result, acceptable, context);
488 if (!alias) {
489 err = -EACCES;
490 goto err_result;
491 }
492
493 return alias;
494 }
495
496 err_result:
497 dput(result);
498 return ERR_PTR(err);
Christoph Hellwigd37065c2007-07-17 04:04:30 -0700499}
500EXPORT_SYMBOL_GPL(exportfs_decode_fh);
501
Linus Torvalds1da177e2005-04-16 15:20:36 -0700502MODULE_LICENSE("GPL");