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TOMOYO Linux Cross Reference
Linux/fs/hostfs/hostfs_kern.c

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  1 /*
  2  * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
  3  * Licensed under the GPL
  4  *
  5  * Ported the filesystem routines to 2.5.
  6  * 2003-02-10 Petr Baudis <pasky@ucw.cz>
  7  */
  8 
  9 #include <linux/fs.h>
 10 #include <linux/module.h>
 11 #include <linux/mm.h>
 12 #include <linux/pagemap.h>
 13 #include <linux/statfs.h>
 14 #include <linux/slab.h>
 15 #include <linux/seq_file.h>
 16 #include <linux/mount.h>
 17 #include <linux/namei.h>
 18 #include "hostfs.h"
 19 #include <init.h>
 20 #include <kern.h>
 21 
 22 struct hostfs_inode_info {
 23         int fd;
 24         fmode_t mode;
 25         struct inode vfs_inode;
 26 };
 27 
 28 static inline struct hostfs_inode_info *HOSTFS_I(struct inode *inode)
 29 {
 30         return list_entry(inode, struct hostfs_inode_info, vfs_inode);
 31 }
 32 
 33 #define FILE_HOSTFS_I(file) HOSTFS_I(file_inode(file))
 34 
 35 static int hostfs_d_delete(const struct dentry *dentry)
 36 {
 37         return 1;
 38 }
 39 
 40 static const struct dentry_operations hostfs_dentry_ops = {
 41         .d_delete               = hostfs_d_delete,
 42 };
 43 
 44 /* Changed in hostfs_args before the kernel starts running */
 45 static char *root_ino = "";
 46 static int append = 0;
 47 
 48 #define HOSTFS_SUPER_MAGIC 0x00c0ffee
 49 
 50 static const struct inode_operations hostfs_iops;
 51 static const struct inode_operations hostfs_dir_iops;
 52 static const struct inode_operations hostfs_link_iops;
 53 
 54 #ifndef MODULE
 55 static int __init hostfs_args(char *options, int *add)
 56 {
 57         char *ptr;
 58 
 59         ptr = strchr(options, ',');
 60         if (ptr != NULL)
 61                 *ptr++ = '\0';
 62         if (*options != '\0')
 63                 root_ino = options;
 64 
 65         options = ptr;
 66         while (options) {
 67                 ptr = strchr(options, ',');
 68                 if (ptr != NULL)
 69                         *ptr++ = '\0';
 70                 if (*options != '\0') {
 71                         if (!strcmp(options, "append"))
 72                                 append = 1;
 73                         else printf("hostfs_args - unsupported option - %s\n",
 74                                     options);
 75                 }
 76                 options = ptr;
 77         }
 78         return 0;
 79 }
 80 
 81 __uml_setup("hostfs=", hostfs_args,
 82 "hostfs=<root dir>,<flags>,...\n"
 83 "    This is used to set hostfs parameters.  The root directory argument\n"
 84 "    is used to confine all hostfs mounts to within the specified directory\n"
 85 "    tree on the host.  If this isn't specified, then a user inside UML can\n"
 86 "    mount anything on the host that's accessible to the user that's running\n"
 87 "    it.\n"
 88 "    The only flag currently supported is 'append', which specifies that all\n"
 89 "    files opened by hostfs will be opened in append mode.\n\n"
 90 );
 91 #endif
 92 
 93 static char *__dentry_name(struct dentry *dentry, char *name)
 94 {
 95         char *p = dentry_path_raw(dentry, name, PATH_MAX);
 96         char *root;
 97         size_t len;
 98 
 99         root = dentry->d_sb->s_fs_info;
100         len = strlen(root);
101         if (IS_ERR(p)) {
102                 __putname(name);
103                 return NULL;
104         }
105         strlcpy(name, root, PATH_MAX);
106         if (len > p - name) {
107                 __putname(name);
108                 return NULL;
109         }
110         if (p > name + len) {
111                 char *s = name + len;
112                 while ((*s++ = *p++) != '\0')
113                         ;
114         }
115         return name;
116 }
117 
118 static char *dentry_name(struct dentry *dentry)
119 {
120         char *name = __getname();
121         if (!name)
122                 return NULL;
123 
124         return __dentry_name(dentry, name); /* will unlock */
125 }
126 
127 static char *inode_name(struct inode *ino)
128 {
129         struct dentry *dentry;
130         char *name;
131 
132         dentry = d_find_alias(ino);
133         if (!dentry)
134                 return NULL;
135 
136         name = dentry_name(dentry);
137 
138         dput(dentry);
139 
140         return name;
141 }
142 
143 static char *follow_link(char *link)
144 {
145         int len, n;
146         char *name, *resolved, *end;
147 
148         len = 64;
149         while (1) {
150                 n = -ENOMEM;
151                 name = kmalloc(len, GFP_KERNEL);
152                 if (name == NULL)
153                         goto out;
154 
155                 n = hostfs_do_readlink(link, name, len);
156                 if (n < len)
157                         break;
158                 len *= 2;
159                 kfree(name);
160         }
161         if (n < 0)
162                 goto out_free;
163 
164         if (*name == '/')
165                 return name;
166 
167         end = strrchr(link, '/');
168         if (end == NULL)
169                 return name;
170 
171         *(end + 1) = '\0';
172         len = strlen(link) + strlen(name) + 1;
173 
174         resolved = kmalloc(len, GFP_KERNEL);
175         if (resolved == NULL) {
176                 n = -ENOMEM;
177                 goto out_free;
178         }
179 
180         sprintf(resolved, "%s%s", link, name);
181         kfree(name);
182         kfree(link);
183         return resolved;
184 
185  out_free:
186         kfree(name);
187  out:
188         return ERR_PTR(n);
189 }
190 
191 static struct inode *hostfs_iget(struct super_block *sb)
192 {
193         struct inode *inode = new_inode(sb);
194         if (!inode)
195                 return ERR_PTR(-ENOMEM);
196         return inode;
197 }
198 
199 int hostfs_statfs(struct dentry *dentry, struct kstatfs *sf)
200 {
201         /*
202          * do_statfs uses struct statfs64 internally, but the linux kernel
203          * struct statfs still has 32-bit versions for most of these fields,
204          * so we convert them here
205          */
206         int err;
207         long long f_blocks;
208         long long f_bfree;
209         long long f_bavail;
210         long long f_files;
211         long long f_ffree;
212 
213         err = do_statfs(dentry->d_sb->s_fs_info,
214                         &sf->f_bsize, &f_blocks, &f_bfree, &f_bavail, &f_files,
215                         &f_ffree, &sf->f_fsid, sizeof(sf->f_fsid),
216                         &sf->f_namelen);
217         if (err)
218                 return err;
219         sf->f_blocks = f_blocks;
220         sf->f_bfree = f_bfree;
221         sf->f_bavail = f_bavail;
222         sf->f_files = f_files;
223         sf->f_ffree = f_ffree;
224         sf->f_type = HOSTFS_SUPER_MAGIC;
225         return 0;
226 }
227 
228 static struct inode *hostfs_alloc_inode(struct super_block *sb)
229 {
230         struct hostfs_inode_info *hi;
231 
232         hi = kzalloc(sizeof(*hi), GFP_KERNEL);
233         if (hi == NULL)
234                 return NULL;
235         hi->fd = -1;
236         inode_init_once(&hi->vfs_inode);
237         return &hi->vfs_inode;
238 }
239 
240 static void hostfs_evict_inode(struct inode *inode)
241 {
242         truncate_inode_pages(&inode->i_data, 0);
243         clear_inode(inode);
244         if (HOSTFS_I(inode)->fd != -1) {
245                 close_file(&HOSTFS_I(inode)->fd);
246                 HOSTFS_I(inode)->fd = -1;
247         }
248 }
249 
250 static void hostfs_i_callback(struct rcu_head *head)
251 {
252         struct inode *inode = container_of(head, struct inode, i_rcu);
253         kfree(HOSTFS_I(inode));
254 }
255 
256 static void hostfs_destroy_inode(struct inode *inode)
257 {
258         call_rcu(&inode->i_rcu, hostfs_i_callback);
259 }
260 
261 static int hostfs_show_options(struct seq_file *seq, struct dentry *root)
262 {
263         const char *root_path = root->d_sb->s_fs_info;
264         size_t offset = strlen(root_ino) + 1;
265 
266         if (strlen(root_path) > offset)
267                 seq_printf(seq, ",%s", root_path + offset);
268 
269         return 0;
270 }
271 
272 static const struct super_operations hostfs_sbops = {
273         .alloc_inode    = hostfs_alloc_inode,
274         .destroy_inode  = hostfs_destroy_inode,
275         .evict_inode    = hostfs_evict_inode,
276         .statfs         = hostfs_statfs,
277         .show_options   = hostfs_show_options,
278 };
279 
280 int hostfs_readdir(struct file *file, void *ent, filldir_t filldir)
281 {
282         void *dir;
283         char *name;
284         unsigned long long next, ino;
285         int error, len;
286         unsigned int type;
287 
288         name = dentry_name(file->f_path.dentry);
289         if (name == NULL)
290                 return -ENOMEM;
291         dir = open_dir(name, &error);
292         __putname(name);
293         if (dir == NULL)
294                 return -error;
295         next = file->f_pos;
296         while ((name = read_dir(dir, &next, &ino, &len, &type)) != NULL) {
297                 error = (*filldir)(ent, name, len, file->f_pos,
298                                    ino, type);
299                 if (error) break;
300                 file->f_pos = next;
301         }
302         close_dir(dir);
303         return 0;
304 }
305 
306 int hostfs_file_open(struct inode *ino, struct file *file)
307 {
308         static DEFINE_MUTEX(open_mutex);
309         char *name;
310         fmode_t mode = 0;
311         int err;
312         int r = 0, w = 0, fd;
313 
314         mode = file->f_mode & (FMODE_READ | FMODE_WRITE);
315         if ((mode & HOSTFS_I(ino)->mode) == mode)
316                 return 0;
317 
318         mode |= HOSTFS_I(ino)->mode;
319 
320 retry:
321         if (mode & FMODE_READ)
322                 r = 1;
323         if (mode & FMODE_WRITE)
324                 w = 1;
325         if (w)
326                 r = 1;
327 
328         name = dentry_name(file->f_path.dentry);
329         if (name == NULL)
330                 return -ENOMEM;
331 
332         fd = open_file(name, r, w, append);
333         __putname(name);
334         if (fd < 0)
335                 return fd;
336 
337         mutex_lock(&open_mutex);
338         /* somebody else had handled it first? */
339         if ((mode & HOSTFS_I(ino)->mode) == mode) {
340                 mutex_unlock(&open_mutex);
341                 return 0;
342         }
343         if ((mode | HOSTFS_I(ino)->mode) != mode) {
344                 mode |= HOSTFS_I(ino)->mode;
345                 mutex_unlock(&open_mutex);
346                 close_file(&fd);
347                 goto retry;
348         }
349         if (HOSTFS_I(ino)->fd == -1) {
350                 HOSTFS_I(ino)->fd = fd;
351         } else {
352                 err = replace_file(fd, HOSTFS_I(ino)->fd);
353                 close_file(&fd);
354                 if (err < 0) {
355                         mutex_unlock(&open_mutex);
356                         return err;
357                 }
358         }
359         HOSTFS_I(ino)->mode = mode;
360         mutex_unlock(&open_mutex);
361 
362         return 0;
363 }
364 
365 int hostfs_fsync(struct file *file, loff_t start, loff_t end, int datasync)
366 {
367         struct inode *inode = file->f_mapping->host;
368         int ret;
369 
370         ret = filemap_write_and_wait_range(inode->i_mapping, start, end);
371         if (ret)
372                 return ret;
373 
374         mutex_lock(&inode->i_mutex);
375         ret = fsync_file(HOSTFS_I(inode)->fd, datasync);
376         mutex_unlock(&inode->i_mutex);
377 
378         return ret;
379 }
380 
381 static const struct file_operations hostfs_file_fops = {
382         .llseek         = generic_file_llseek,
383         .read           = do_sync_read,
384         .splice_read    = generic_file_splice_read,
385         .aio_read       = generic_file_aio_read,
386         .aio_write      = generic_file_aio_write,
387         .write          = do_sync_write,
388         .mmap           = generic_file_mmap,
389         .open           = hostfs_file_open,
390         .release        = NULL,
391         .fsync          = hostfs_fsync,
392 };
393 
394 static const struct file_operations hostfs_dir_fops = {
395         .llseek         = generic_file_llseek,
396         .readdir        = hostfs_readdir,
397         .read           = generic_read_dir,
398 };
399 
400 int hostfs_writepage(struct page *page, struct writeback_control *wbc)
401 {
402         struct address_space *mapping = page->mapping;
403         struct inode *inode = mapping->host;
404         char *buffer;
405         unsigned long long base;
406         int count = PAGE_CACHE_SIZE;
407         int end_index = inode->i_size >> PAGE_CACHE_SHIFT;
408         int err;
409 
410         if (page->index >= end_index)
411                 count = inode->i_size & (PAGE_CACHE_SIZE-1);
412 
413         buffer = kmap(page);
414         base = ((unsigned long long) page->index) << PAGE_CACHE_SHIFT;
415 
416         err = write_file(HOSTFS_I(inode)->fd, &base, buffer, count);
417         if (err != count) {
418                 ClearPageUptodate(page);
419                 goto out;
420         }
421 
422         if (base > inode->i_size)
423                 inode->i_size = base;
424 
425         if (PageError(page))
426                 ClearPageError(page);
427         err = 0;
428 
429  out:
430         kunmap(page);
431 
432         unlock_page(page);
433         return err;
434 }
435 
436 int hostfs_readpage(struct file *file, struct page *page)
437 {
438         char *buffer;
439         long long start;
440         int err = 0;
441 
442         start = (long long) page->index << PAGE_CACHE_SHIFT;
443         buffer = kmap(page);
444         err = read_file(FILE_HOSTFS_I(file)->fd, &start, buffer,
445                         PAGE_CACHE_SIZE);
446         if (err < 0)
447                 goto out;
448 
449         memset(&buffer[err], 0, PAGE_CACHE_SIZE - err);
450 
451         flush_dcache_page(page);
452         SetPageUptodate(page);
453         if (PageError(page)) ClearPageError(page);
454         err = 0;
455  out:
456         kunmap(page);
457         unlock_page(page);
458         return err;
459 }
460 
461 int hostfs_write_begin(struct file *file, struct address_space *mapping,
462                         loff_t pos, unsigned len, unsigned flags,
463                         struct page **pagep, void **fsdata)
464 {
465         pgoff_t index = pos >> PAGE_CACHE_SHIFT;
466 
467         *pagep = grab_cache_page_write_begin(mapping, index, flags);
468         if (!*pagep)
469                 return -ENOMEM;
470         return 0;
471 }
472 
473 int hostfs_write_end(struct file *file, struct address_space *mapping,
474                         loff_t pos, unsigned len, unsigned copied,
475                         struct page *page, void *fsdata)
476 {
477         struct inode *inode = mapping->host;
478         void *buffer;
479         unsigned from = pos & (PAGE_CACHE_SIZE - 1);
480         int err;
481 
482         buffer = kmap(page);
483         err = write_file(FILE_HOSTFS_I(file)->fd, &pos, buffer + from, copied);
484         kunmap(page);
485 
486         if (!PageUptodate(page) && err == PAGE_CACHE_SIZE)
487                 SetPageUptodate(page);
488 
489         /*
490          * If err > 0, write_file has added err to pos, so we are comparing
491          * i_size against the last byte written.
492          */
493         if (err > 0 && (pos > inode->i_size))
494                 inode->i_size = pos;
495         unlock_page(page);
496         page_cache_release(page);
497 
498         return err;
499 }
500 
501 static const struct address_space_operations hostfs_aops = {
502         .writepage      = hostfs_writepage,
503         .readpage       = hostfs_readpage,
504         .set_page_dirty = __set_page_dirty_nobuffers,
505         .write_begin    = hostfs_write_begin,
506         .write_end      = hostfs_write_end,
507 };
508 
509 static int read_name(struct inode *ino, char *name)
510 {
511         dev_t rdev;
512         struct hostfs_stat st;
513         int err = stat_file(name, &st, -1);
514         if (err)
515                 return err;
516 
517         /* Reencode maj and min with the kernel encoding.*/
518         rdev = MKDEV(st.maj, st.min);
519 
520         switch (st.mode & S_IFMT) {
521         case S_IFLNK:
522                 ino->i_op = &hostfs_link_iops;
523                 break;
524         case S_IFDIR:
525                 ino->i_op = &hostfs_dir_iops;
526                 ino->i_fop = &hostfs_dir_fops;
527                 break;
528         case S_IFCHR:
529         case S_IFBLK:
530         case S_IFIFO:
531         case S_IFSOCK:
532                 init_special_inode(ino, st.mode & S_IFMT, rdev);
533                 ino->i_op = &hostfs_iops;
534                 break;
535 
536         default:
537                 ino->i_op = &hostfs_iops;
538                 ino->i_fop = &hostfs_file_fops;
539                 ino->i_mapping->a_ops = &hostfs_aops;
540         }
541 
542         ino->i_ino = st.ino;
543         ino->i_mode = st.mode;
544         set_nlink(ino, st.nlink);
545         i_uid_write(ino, st.uid);
546         i_gid_write(ino, st.gid);
547         ino->i_atime = st.atime;
548         ino->i_mtime = st.mtime;
549         ino->i_ctime = st.ctime;
550         ino->i_size = st.size;
551         ino->i_blocks = st.blocks;
552         return 0;
553 }
554 
555 int hostfs_create(struct inode *dir, struct dentry *dentry, umode_t mode,
556                   bool excl)
557 {
558         struct inode *inode;
559         char *name;
560         int error, fd;
561 
562         inode = hostfs_iget(dir->i_sb);
563         if (IS_ERR(inode)) {
564                 error = PTR_ERR(inode);
565                 goto out;
566         }
567 
568         error = -ENOMEM;
569         name = dentry_name(dentry);
570         if (name == NULL)
571                 goto out_put;
572 
573         fd = file_create(name,
574                          mode & S_IRUSR, mode & S_IWUSR, mode & S_IXUSR,
575                          mode & S_IRGRP, mode & S_IWGRP, mode & S_IXGRP,
576                          mode & S_IROTH, mode & S_IWOTH, mode & S_IXOTH);
577         if (fd < 0)
578                 error = fd;
579         else
580                 error = read_name(inode, name);
581 
582         __putname(name);
583         if (error)
584                 goto out_put;
585 
586         HOSTFS_I(inode)->fd = fd;
587         HOSTFS_I(inode)->mode = FMODE_READ | FMODE_WRITE;
588         d_instantiate(dentry, inode);
589         return 0;
590 
591  out_put:
592         iput(inode);
593  out:
594         return error;
595 }
596 
597 struct dentry *hostfs_lookup(struct inode *ino, struct dentry *dentry,
598                              unsigned int flags)
599 {
600         struct inode *inode;
601         char *name;
602         int err;
603 
604         inode = hostfs_iget(ino->i_sb);
605         if (IS_ERR(inode)) {
606                 err = PTR_ERR(inode);
607                 goto out;
608         }
609 
610         err = -ENOMEM;
611         name = dentry_name(dentry);
612         if (name == NULL)
613                 goto out_put;
614 
615         err = read_name(inode, name);
616 
617         __putname(name);
618         if (err == -ENOENT) {
619                 iput(inode);
620                 inode = NULL;
621         }
622         else if (err)
623                 goto out_put;
624 
625         d_add(dentry, inode);
626         return NULL;
627 
628  out_put:
629         iput(inode);
630  out:
631         return ERR_PTR(err);
632 }
633 
634 int hostfs_link(struct dentry *to, struct inode *ino, struct dentry *from)
635 {
636         char *from_name, *to_name;
637         int err;
638 
639         if ((from_name = dentry_name(from)) == NULL)
640                 return -ENOMEM;
641         to_name = dentry_name(to);
642         if (to_name == NULL) {
643                 __putname(from_name);
644                 return -ENOMEM;
645         }
646         err = link_file(to_name, from_name);
647         __putname(from_name);
648         __putname(to_name);
649         return err;
650 }
651 
652 int hostfs_unlink(struct inode *ino, struct dentry *dentry)
653 {
654         char *file;
655         int err;
656 
657         if (append)
658                 return -EPERM;
659 
660         if ((file = dentry_name(dentry)) == NULL)
661                 return -ENOMEM;
662 
663         err = unlink_file(file);
664         __putname(file);
665         return err;
666 }
667 
668 int hostfs_symlink(struct inode *ino, struct dentry *dentry, const char *to)
669 {
670         char *file;
671         int err;
672 
673         if ((file = dentry_name(dentry)) == NULL)
674                 return -ENOMEM;
675         err = make_symlink(file, to);
676         __putname(file);
677         return err;
678 }
679 
680 int hostfs_mkdir(struct inode *ino, struct dentry *dentry, umode_t mode)
681 {
682         char *file;
683         int err;
684 
685         if ((file = dentry_name(dentry)) == NULL)
686                 return -ENOMEM;
687         err = do_mkdir(file, mode);
688         __putname(file);
689         return err;
690 }
691 
692 int hostfs_rmdir(struct inode *ino, struct dentry *dentry)
693 {
694         char *file;
695         int err;
696 
697         if ((file = dentry_name(dentry)) == NULL)
698                 return -ENOMEM;
699         err = do_rmdir(file);
700         __putname(file);
701         return err;
702 }
703 
704 static int hostfs_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
705 {
706         struct inode *inode;
707         char *name;
708         int err;
709 
710         inode = hostfs_iget(dir->i_sb);
711         if (IS_ERR(inode)) {
712                 err = PTR_ERR(inode);
713                 goto out;
714         }
715 
716         err = -ENOMEM;
717         name = dentry_name(dentry);
718         if (name == NULL)
719                 goto out_put;
720 
721         init_special_inode(inode, mode, dev);
722         err = do_mknod(name, mode, MAJOR(dev), MINOR(dev));
723         if (!err)
724                 goto out_free;
725 
726         err = read_name(inode, name);
727         __putname(name);
728         if (err)
729                 goto out_put;
730         if (err)
731                 goto out_put;
732 
733         d_instantiate(dentry, inode);
734         return 0;
735 
736  out_free:
737         __putname(name);
738  out_put:
739         iput(inode);
740  out:
741         return err;
742 }
743 
744 int hostfs_rename(struct inode *from_ino, struct dentry *from,
745                   struct inode *to_ino, struct dentry *to)
746 {
747         char *from_name, *to_name;
748         int err;
749 
750         if ((from_name = dentry_name(from)) == NULL)
751                 return -ENOMEM;
752         if ((to_name = dentry_name(to)) == NULL) {
753                 __putname(from_name);
754                 return -ENOMEM;
755         }
756         err = rename_file(from_name, to_name);
757         __putname(from_name);
758         __putname(to_name);
759         return err;
760 }
761 
762 int hostfs_permission(struct inode *ino, int desired)
763 {
764         char *name;
765         int r = 0, w = 0, x = 0, err;
766 
767         if (desired & MAY_NOT_BLOCK)
768                 return -ECHILD;
769 
770         if (desired & MAY_READ) r = 1;
771         if (desired & MAY_WRITE) w = 1;
772         if (desired & MAY_EXEC) x = 1;
773         name = inode_name(ino);
774         if (name == NULL)
775                 return -ENOMEM;
776 
777         if (S_ISCHR(ino->i_mode) || S_ISBLK(ino->i_mode) ||
778             S_ISFIFO(ino->i_mode) || S_ISSOCK(ino->i_mode))
779                 err = 0;
780         else
781                 err = access_file(name, r, w, x);
782         __putname(name);
783         if (!err)
784                 err = generic_permission(ino, desired);
785         return err;
786 }
787 
788 int hostfs_setattr(struct dentry *dentry, struct iattr *attr)
789 {
790         struct inode *inode = dentry->d_inode;
791         struct hostfs_iattr attrs;
792         char *name;
793         int err;
794 
795         int fd = HOSTFS_I(inode)->fd;
796 
797         err = inode_change_ok(inode, attr);
798         if (err)
799                 return err;
800 
801         if (append)
802                 attr->ia_valid &= ~ATTR_SIZE;
803 
804         attrs.ia_valid = 0;
805         if (attr->ia_valid & ATTR_MODE) {
806                 attrs.ia_valid |= HOSTFS_ATTR_MODE;
807                 attrs.ia_mode = attr->ia_mode;
808         }
809         if (attr->ia_valid & ATTR_UID) {
810                 attrs.ia_valid |= HOSTFS_ATTR_UID;
811                 attrs.ia_uid = from_kuid(&init_user_ns, attr->ia_uid);
812         }
813         if (attr->ia_valid & ATTR_GID) {
814                 attrs.ia_valid |= HOSTFS_ATTR_GID;
815                 attrs.ia_gid = from_kgid(&init_user_ns, attr->ia_gid);
816         }
817         if (attr->ia_valid & ATTR_SIZE) {
818                 attrs.ia_valid |= HOSTFS_ATTR_SIZE;
819                 attrs.ia_size = attr->ia_size;
820         }
821         if (attr->ia_valid & ATTR_ATIME) {
822                 attrs.ia_valid |= HOSTFS_ATTR_ATIME;
823                 attrs.ia_atime = attr->ia_atime;
824         }
825         if (attr->ia_valid & ATTR_MTIME) {
826                 attrs.ia_valid |= HOSTFS_ATTR_MTIME;
827                 attrs.ia_mtime = attr->ia_mtime;
828         }
829         if (attr->ia_valid & ATTR_CTIME) {
830                 attrs.ia_valid |= HOSTFS_ATTR_CTIME;
831                 attrs.ia_ctime = attr->ia_ctime;
832         }
833         if (attr->ia_valid & ATTR_ATIME_SET) {
834                 attrs.ia_valid |= HOSTFS_ATTR_ATIME_SET;
835         }
836         if (attr->ia_valid & ATTR_MTIME_SET) {
837                 attrs.ia_valid |= HOSTFS_ATTR_MTIME_SET;
838         }
839         name = dentry_name(dentry);
840         if (name == NULL)
841                 return -ENOMEM;
842         err = set_attr(name, &attrs, fd);
843         __putname(name);
844         if (err)
845                 return err;
846 
847         if ((attr->ia_valid & ATTR_SIZE) &&
848             attr->ia_size != i_size_read(inode))
849                 truncate_setsize(inode, attr->ia_size);
850 
851         setattr_copy(inode, attr);
852         mark_inode_dirty(inode);
853         return 0;
854 }
855 
856 static const struct inode_operations hostfs_iops = {
857         .permission     = hostfs_permission,
858         .setattr        = hostfs_setattr,
859 };
860 
861 static const struct inode_operations hostfs_dir_iops = {
862         .create         = hostfs_create,
863         .lookup         = hostfs_lookup,
864         .link           = hostfs_link,
865         .unlink         = hostfs_unlink,
866         .symlink        = hostfs_symlink,
867         .mkdir          = hostfs_mkdir,
868         .rmdir          = hostfs_rmdir,
869         .mknod          = hostfs_mknod,
870         .rename         = hostfs_rename,
871         .permission     = hostfs_permission,
872         .setattr        = hostfs_setattr,
873 };
874 
875 static void *hostfs_follow_link(struct dentry *dentry, struct nameidata *nd)
876 {
877         char *link = __getname();
878         if (link) {
879                 char *path = dentry_name(dentry);
880                 int err = -ENOMEM;
881                 if (path) {
882                         err = hostfs_do_readlink(path, link, PATH_MAX);
883                         if (err == PATH_MAX)
884                                 err = -E2BIG;
885                         __putname(path);
886                 }
887                 if (err < 0) {
888                         __putname(link);
889                         link = ERR_PTR(err);
890                 }
891         } else {
892                 link = ERR_PTR(-ENOMEM);
893         }
894 
895         nd_set_link(nd, link);
896         return NULL;
897 }
898 
899 static void hostfs_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
900 {
901         char *s = nd_get_link(nd);
902         if (!IS_ERR(s))
903                 __putname(s);
904 }
905 
906 static const struct inode_operations hostfs_link_iops = {
907         .readlink       = generic_readlink,
908         .follow_link    = hostfs_follow_link,
909         .put_link       = hostfs_put_link,
910 };
911 
912 static int hostfs_fill_sb_common(struct super_block *sb, void *d, int silent)
913 {
914         struct inode *root_inode;
915         char *host_root_path, *req_root = d;
916         int err;
917 
918         sb->s_blocksize = 1024;
919         sb->s_blocksize_bits = 10;
920         sb->s_magic = HOSTFS_SUPER_MAGIC;
921         sb->s_op = &hostfs_sbops;
922         sb->s_d_op = &hostfs_dentry_ops;
923         sb->s_maxbytes = MAX_LFS_FILESIZE;
924 
925         /* NULL is printed as <NULL> by sprintf: avoid that. */
926         if (req_root == NULL)
927                 req_root = "";
928 
929         err = -ENOMEM;
930         sb->s_fs_info = host_root_path =
931                 kmalloc(strlen(root_ino) + strlen(req_root) + 2, GFP_KERNEL);
932         if (host_root_path == NULL)
933                 goto out;
934 
935         sprintf(host_root_path, "%s/%s", root_ino, req_root);
936 
937         root_inode = new_inode(sb);
938         if (!root_inode)
939                 goto out;
940 
941         err = read_name(root_inode, host_root_path);
942         if (err)
943                 goto out_put;
944 
945         if (S_ISLNK(root_inode->i_mode)) {
946                 char *name = follow_link(host_root_path);
947                 if (IS_ERR(name))
948                         err = PTR_ERR(name);
949                 else
950                         err = read_name(root_inode, name);
951                 kfree(name);
952                 if (err)
953                         goto out_put;
954         }
955 
956         err = -ENOMEM;
957         sb->s_root = d_make_root(root_inode);
958         if (sb->s_root == NULL)
959                 goto out;
960 
961         return 0;
962 
963 out_put:
964         iput(root_inode);
965 out:
966         return err;
967 }
968 
969 static struct dentry *hostfs_read_sb(struct file_system_type *type,
970                           int flags, const char *dev_name,
971                           void *data)
972 {
973         return mount_nodev(type, flags, data, hostfs_fill_sb_common);
974 }
975 
976 static void hostfs_kill_sb(struct super_block *s)
977 {
978         kill_anon_super(s);
979         kfree(s->s_fs_info);
980 }
981 
982 static struct file_system_type hostfs_type = {
983         .owner          = THIS_MODULE,
984         .name           = "hostfs",
985         .mount          = hostfs_read_sb,
986         .kill_sb        = hostfs_kill_sb,
987         .fs_flags       = 0,
988 };
989 MODULE_ALIAS_FS("hostfs");
990 
991 static int __init init_hostfs(void)
992 {
993         return register_filesystem(&hostfs_type);
994 }
995 
996 static void __exit exit_hostfs(void)
997 {
998         unregister_filesystem(&hostfs_type);
999 }
1000 
1001 module_init(init_hostfs)
1002 module_exit(exit_hostfs)
1003 MODULE_LICENSE("GPL");
1004 

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