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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/magic.h>
 11 #include <linux/module.h>
 12 #include <linux/mm.h>
 13 #include <linux/pagemap.h>
 14 #include <linux/statfs.h>
 15 #include <linux/slab.h>
 16 #include <linux/seq_file.h>
 17 #include <linux/mount.h>
 18 #include <linux/namei.h>
 19 #include "hostfs.h"
 20 #include <init.h>
 21 #include <kern.h>
 22 
 23 struct hostfs_inode_info {
 24         int fd;
 25         fmode_t mode;
 26         struct inode vfs_inode;
 27         struct mutex open_mutex;
 28 };
 29 
 30 static inline struct hostfs_inode_info *HOSTFS_I(struct inode *inode)
 31 {
 32         return list_entry(inode, struct hostfs_inode_info, vfs_inode);
 33 }
 34 
 35 #define FILE_HOSTFS_I(file) HOSTFS_I(file_inode(file))
 36 
 37 /* Changed in hostfs_args before the kernel starts running */
 38 static char *root_ino = "";
 39 static int append = 0;
 40 
 41 static const struct inode_operations hostfs_iops;
 42 static const struct inode_operations hostfs_dir_iops;
 43 static const struct inode_operations hostfs_link_iops;
 44 
 45 #ifndef MODULE
 46 static int __init hostfs_args(char *options, int *add)
 47 {
 48         char *ptr;
 49 
 50         ptr = strchr(options, ',');
 51         if (ptr != NULL)
 52                 *ptr++ = '\0';
 53         if (*options != '\0')
 54                 root_ino = options;
 55 
 56         options = ptr;
 57         while (options) {
 58                 ptr = strchr(options, ',');
 59                 if (ptr != NULL)
 60                         *ptr++ = '\0';
 61                 if (*options != '\0') {
 62                         if (!strcmp(options, "append"))
 63                                 append = 1;
 64                         else printf("hostfs_args - unsupported option - %s\n",
 65                                     options);
 66                 }
 67                 options = ptr;
 68         }
 69         return 0;
 70 }
 71 
 72 __uml_setup("hostfs=", hostfs_args,
 73 "hostfs=<root dir>,<flags>,...\n"
 74 "    This is used to set hostfs parameters.  The root directory argument\n"
 75 "    is used to confine all hostfs mounts to within the specified directory\n"
 76 "    tree on the host.  If this isn't specified, then a user inside UML can\n"
 77 "    mount anything on the host that's accessible to the user that's running\n"
 78 "    it.\n"
 79 "    The only flag currently supported is 'append', which specifies that all\n"
 80 "    files opened by hostfs will be opened in append mode.\n\n"
 81 );
 82 #endif
 83 
 84 static char *__dentry_name(struct dentry *dentry, char *name)
 85 {
 86         char *p = dentry_path_raw(dentry, name, PATH_MAX);
 87         char *root;
 88         size_t len;
 89 
 90         root = dentry->d_sb->s_fs_info;
 91         len = strlen(root);
 92         if (IS_ERR(p)) {
 93                 __putname(name);
 94                 return NULL;
 95         }
 96 
 97         /*
 98          * This function relies on the fact that dentry_path_raw() will place
 99          * the path name at the end of the provided buffer.
100          */
101         BUG_ON(p + strlen(p) + 1 != name + PATH_MAX);
102 
103         strlcpy(name, root, PATH_MAX);
104         if (len > p - name) {
105                 __putname(name);
106                 return NULL;
107         }
108 
109         if (p > name + len)
110                 strcpy(name + len, p);
111 
112         return name;
113 }
114 
115 static char *dentry_name(struct dentry *dentry)
116 {
117         char *name = __getname();
118         if (!name)
119                 return NULL;
120 
121         return __dentry_name(dentry, name);
122 }
123 
124 static char *inode_name(struct inode *ino)
125 {
126         struct dentry *dentry;
127         char *name;
128 
129         dentry = d_find_alias(ino);
130         if (!dentry)
131                 return NULL;
132 
133         name = dentry_name(dentry);
134 
135         dput(dentry);
136 
137         return name;
138 }
139 
140 static char *follow_link(char *link)
141 {
142         char *name, *resolved, *end;
143         int n;
144 
145         name = kmalloc(PATH_MAX, GFP_KERNEL);
146         if (!name) {
147                 n = -ENOMEM;
148                 goto out_free;
149         }
150 
151         n = hostfs_do_readlink(link, name, PATH_MAX);
152         if (n < 0)
153                 goto out_free;
154         else if (n == PATH_MAX) {
155                 n = -E2BIG;
156                 goto out_free;
157         }
158 
159         if (*name == '/')
160                 return name;
161 
162         end = strrchr(link, '/');
163         if (end == NULL)
164                 return name;
165 
166         *(end + 1) = '\0';
167 
168         resolved = kasprintf(GFP_KERNEL, "%s%s", link, name);
169         if (resolved == NULL) {
170                 n = -ENOMEM;
171                 goto out_free;
172         }
173 
174         kfree(name);
175         return resolved;
176 
177  out_free:
178         kfree(name);
179         return ERR_PTR(n);
180 }
181 
182 static struct inode *hostfs_iget(struct super_block *sb)
183 {
184         struct inode *inode = new_inode(sb);
185         if (!inode)
186                 return ERR_PTR(-ENOMEM);
187         return inode;
188 }
189 
190 static int hostfs_statfs(struct dentry *dentry, struct kstatfs *sf)
191 {
192         /*
193          * do_statfs uses struct statfs64 internally, but the linux kernel
194          * struct statfs still has 32-bit versions for most of these fields,
195          * so we convert them here
196          */
197         int err;
198         long long f_blocks;
199         long long f_bfree;
200         long long f_bavail;
201         long long f_files;
202         long long f_ffree;
203 
204         err = do_statfs(dentry->d_sb->s_fs_info,
205                         &sf->f_bsize, &f_blocks, &f_bfree, &f_bavail, &f_files,
206                         &f_ffree, &sf->f_fsid, sizeof(sf->f_fsid),
207                         &sf->f_namelen);
208         if (err)
209                 return err;
210         sf->f_blocks = f_blocks;
211         sf->f_bfree = f_bfree;
212         sf->f_bavail = f_bavail;
213         sf->f_files = f_files;
214         sf->f_ffree = f_ffree;
215         sf->f_type = HOSTFS_SUPER_MAGIC;
216         return 0;
217 }
218 
219 static struct inode *hostfs_alloc_inode(struct super_block *sb)
220 {
221         struct hostfs_inode_info *hi;
222 
223         hi = kmalloc(sizeof(*hi), GFP_KERNEL_ACCOUNT);
224         if (hi == NULL)
225                 return NULL;
226         hi->fd = -1;
227         hi->mode = 0;
228         inode_init_once(&hi->vfs_inode);
229         mutex_init(&hi->open_mutex);
230         return &hi->vfs_inode;
231 }
232 
233 static void hostfs_evict_inode(struct inode *inode)
234 {
235         truncate_inode_pages_final(&inode->i_data);
236         clear_inode(inode);
237         if (HOSTFS_I(inode)->fd != -1) {
238                 close_file(&HOSTFS_I(inode)->fd);
239                 HOSTFS_I(inode)->fd = -1;
240         }
241 }
242 
243 static void hostfs_free_inode(struct inode *inode)
244 {
245         kfree(HOSTFS_I(inode));
246 }
247 
248 static int hostfs_show_options(struct seq_file *seq, struct dentry *root)
249 {
250         const char *root_path = root->d_sb->s_fs_info;
251         size_t offset = strlen(root_ino) + 1;
252 
253         if (strlen(root_path) > offset)
254                 seq_show_option(seq, root_path + offset, NULL);
255 
256         if (append)
257                 seq_puts(seq, ",append");
258 
259         return 0;
260 }
261 
262 static const struct super_operations hostfs_sbops = {
263         .alloc_inode    = hostfs_alloc_inode,
264         .free_inode     = hostfs_free_inode,
265         .evict_inode    = hostfs_evict_inode,
266         .statfs         = hostfs_statfs,
267         .show_options   = hostfs_show_options,
268 };
269 
270 static int hostfs_readdir(struct file *file, struct dir_context *ctx)
271 {
272         void *dir;
273         char *name;
274         unsigned long long next, ino;
275         int error, len;
276         unsigned int type;
277 
278         name = dentry_name(file->f_path.dentry);
279         if (name == NULL)
280                 return -ENOMEM;
281         dir = open_dir(name, &error);
282         __putname(name);
283         if (dir == NULL)
284                 return -error;
285         next = ctx->pos;
286         seek_dir(dir, next);
287         while ((name = read_dir(dir, &next, &ino, &len, &type)) != NULL) {
288                 if (!dir_emit(ctx, name, len, ino, type))
289                         break;
290                 ctx->pos = next;
291         }
292         close_dir(dir);
293         return 0;
294 }
295 
296 static int hostfs_open(struct inode *ino, struct file *file)
297 {
298         char *name;
299         fmode_t mode;
300         int err;
301         int r, w, fd;
302 
303         mode = file->f_mode & (FMODE_READ | FMODE_WRITE);
304         if ((mode & HOSTFS_I(ino)->mode) == mode)
305                 return 0;
306 
307         mode |= HOSTFS_I(ino)->mode;
308 
309 retry:
310         r = w = 0;
311 
312         if (mode & FMODE_READ)
313                 r = 1;
314         if (mode & FMODE_WRITE)
315                 r = w = 1;
316 
317         name = dentry_name(d_real(file->f_path.dentry, file->f_inode));
318         if (name == NULL)
319                 return -ENOMEM;
320 
321         fd = open_file(name, r, w, append);
322         __putname(name);
323         if (fd < 0)
324                 return fd;
325 
326         mutex_lock(&HOSTFS_I(ino)->open_mutex);
327         /* somebody else had handled it first? */
328         if ((mode & HOSTFS_I(ino)->mode) == mode) {
329                 mutex_unlock(&HOSTFS_I(ino)->open_mutex);
330                 close_file(&fd);
331                 return 0;
332         }
333         if ((mode | HOSTFS_I(ino)->mode) != mode) {
334                 mode |= HOSTFS_I(ino)->mode;
335                 mutex_unlock(&HOSTFS_I(ino)->open_mutex);
336                 close_file(&fd);
337                 goto retry;
338         }
339         if (HOSTFS_I(ino)->fd == -1) {
340                 HOSTFS_I(ino)->fd = fd;
341         } else {
342                 err = replace_file(fd, HOSTFS_I(ino)->fd);
343                 close_file(&fd);
344                 if (err < 0) {
345                         mutex_unlock(&HOSTFS_I(ino)->open_mutex);
346                         return err;
347                 }
348         }
349         HOSTFS_I(ino)->mode = mode;
350         mutex_unlock(&HOSTFS_I(ino)->open_mutex);
351 
352         return 0;
353 }
354 
355 static int hostfs_file_release(struct inode *inode, struct file *file)
356 {
357         filemap_write_and_wait(inode->i_mapping);
358 
359         return 0;
360 }
361 
362 static int hostfs_fsync(struct file *file, loff_t start, loff_t end,
363                         int datasync)
364 {
365         struct inode *inode = file->f_mapping->host;
366         int ret;
367 
368         ret = file_write_and_wait_range(file, start, end);
369         if (ret)
370                 return ret;
371 
372         inode_lock(inode);
373         ret = fsync_file(HOSTFS_I(inode)->fd, datasync);
374         inode_unlock(inode);
375 
376         return ret;
377 }
378 
379 static const struct file_operations hostfs_file_fops = {
380         .llseek         = generic_file_llseek,
381         .splice_read    = generic_file_splice_read,
382         .read_iter      = generic_file_read_iter,
383         .write_iter     = generic_file_write_iter,
384         .mmap           = generic_file_mmap,
385         .open           = hostfs_open,
386         .release        = hostfs_file_release,
387         .fsync          = hostfs_fsync,
388 };
389 
390 static const struct file_operations hostfs_dir_fops = {
391         .llseek         = generic_file_llseek,
392         .iterate_shared = hostfs_readdir,
393         .read           = generic_read_dir,
394         .open           = hostfs_open,
395         .fsync          = hostfs_fsync,
396 };
397 
398 static int hostfs_writepage(struct page *page, struct writeback_control *wbc)
399 {
400         struct address_space *mapping = page->mapping;
401         struct inode *inode = mapping->host;
402         char *buffer;
403         loff_t base = page_offset(page);
404         int count = PAGE_SIZE;
405         int end_index = inode->i_size >> PAGE_SHIFT;
406         int err;
407 
408         if (page->index >= end_index)
409                 count = inode->i_size & (PAGE_SIZE-1);
410 
411         buffer = kmap(page);
412 
413         err = write_file(HOSTFS_I(inode)->fd, &base, buffer, count);
414         if (err != count) {
415                 ClearPageUptodate(page);
416                 goto out;
417         }
418 
419         if (base > inode->i_size)
420                 inode->i_size = base;
421 
422         if (PageError(page))
423                 ClearPageError(page);
424         err = 0;
425 
426  out:
427         kunmap(page);
428 
429         unlock_page(page);
430         return err;
431 }
432 
433 static int hostfs_readpage(struct file *file, struct page *page)
434 {
435         char *buffer;
436         loff_t start = page_offset(page);
437         int bytes_read, ret = 0;
438 
439         buffer = kmap(page);
440         bytes_read = read_file(FILE_HOSTFS_I(file)->fd, &start, buffer,
441                         PAGE_SIZE);
442         if (bytes_read < 0) {
443                 ClearPageUptodate(page);
444                 SetPageError(page);
445                 ret = bytes_read;
446                 goto out;
447         }
448 
449         memset(buffer + bytes_read, 0, PAGE_SIZE - bytes_read);
450 
451         ClearPageError(page);
452         SetPageUptodate(page);
453 
454  out:
455         flush_dcache_page(page);
456         kunmap(page);
457         unlock_page(page);
458         return ret;
459 }
460 
461 static 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_SHIFT;
466 
467         *pagep = grab_cache_page_write_begin(mapping, index, flags);
468         if (!*pagep)
469                 return -ENOMEM;
470         return 0;
471 }
472 
473 static 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_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_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         put_page(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         case S_IFREG:
536                 ino->i_op = &hostfs_iops;
537                 ino->i_fop = &hostfs_file_fops;
538                 ino->i_mapping->a_ops = &hostfs_aops;
539                 break;
540         default:
541                 return -EIO;
542         }
543 
544         ino->i_ino = st.ino;
545         ino->i_mode = st.mode;
546         set_nlink(ino, st.nlink);
547         i_uid_write(ino, st.uid);
548         i_gid_write(ino, st.gid);
549         ino->i_atime = (struct timespec64){ st.atime.tv_sec, st.atime.tv_nsec };
550         ino->i_mtime = (struct timespec64){ st.mtime.tv_sec, st.mtime.tv_nsec };
551         ino->i_ctime = (struct timespec64){ st.ctime.tv_sec, st.ctime.tv_nsec };
552         ino->i_size = st.size;
553         ino->i_blocks = st.blocks;
554         return 0;
555 }
556 
557 static int hostfs_create(struct inode *dir, struct dentry *dentry, umode_t mode,
558                          bool excl)
559 {
560         struct inode *inode;
561         char *name;
562         int error, fd;
563 
564         inode = hostfs_iget(dir->i_sb);
565         if (IS_ERR(inode)) {
566                 error = PTR_ERR(inode);
567                 goto out;
568         }
569 
570         error = -ENOMEM;
571         name = dentry_name(dentry);
572         if (name == NULL)
573                 goto out_put;
574 
575         fd = file_create(name, mode & 0777);
576         if (fd < 0)
577                 error = fd;
578         else
579                 error = read_name(inode, name);
580 
581         __putname(name);
582         if (error)
583                 goto out_put;
584 
585         HOSTFS_I(inode)->fd = fd;
586         HOSTFS_I(inode)->mode = FMODE_READ | FMODE_WRITE;
587         d_instantiate(dentry, inode);
588         return 0;
589 
590  out_put:
591         iput(inode);
592  out:
593         return error;
594 }
595 
596 static struct dentry *hostfs_lookup(struct inode *ino, struct dentry *dentry,
597                                     unsigned int flags)
598 {
599         struct inode *inode;
600         char *name;
601         int err;
602 
603         inode = hostfs_iget(ino->i_sb);
604         if (IS_ERR(inode))
605                 goto out;
606 
607         err = -ENOMEM;
608         name = dentry_name(dentry);
609         if (name) {
610                 err = read_name(inode, name);
611                 __putname(name);
612         }
613         if (err) {
614                 iput(inode);
615                 inode = (err == -ENOENT) ? NULL : ERR_PTR(err);
616         }
617  out:
618         return d_splice_alias(inode, dentry);
619 }
620 
621 static int hostfs_link(struct dentry *to, struct inode *ino,
622                        struct dentry *from)
623 {
624         char *from_name, *to_name;
625         int err;
626 
627         if ((from_name = dentry_name(from)) == NULL)
628                 return -ENOMEM;
629         to_name = dentry_name(to);
630         if (to_name == NULL) {
631                 __putname(from_name);
632                 return -ENOMEM;
633         }
634         err = link_file(to_name, from_name);
635         __putname(from_name);
636         __putname(to_name);
637         return err;
638 }
639 
640 static int hostfs_unlink(struct inode *ino, struct dentry *dentry)
641 {
642         char *file;
643         int err;
644 
645         if (append)
646                 return -EPERM;
647 
648         if ((file = dentry_name(dentry)) == NULL)
649                 return -ENOMEM;
650 
651         err = unlink_file(file);
652         __putname(file);
653         return err;
654 }
655 
656 static int hostfs_symlink(struct inode *ino, struct dentry *dentry,
657                           const char *to)
658 {
659         char *file;
660         int err;
661 
662         if ((file = dentry_name(dentry)) == NULL)
663                 return -ENOMEM;
664         err = make_symlink(file, to);
665         __putname(file);
666         return err;
667 }
668 
669 static int hostfs_mkdir(struct inode *ino, struct dentry *dentry, umode_t mode)
670 {
671         char *file;
672         int err;
673 
674         if ((file = dentry_name(dentry)) == NULL)
675                 return -ENOMEM;
676         err = do_mkdir(file, mode);
677         __putname(file);
678         return err;
679 }
680 
681 static int hostfs_rmdir(struct inode *ino, struct dentry *dentry)
682 {
683         char *file;
684         int err;
685 
686         if ((file = dentry_name(dentry)) == NULL)
687                 return -ENOMEM;
688         err = hostfs_do_rmdir(file);
689         __putname(file);
690         return err;
691 }
692 
693 static int hostfs_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
694 {
695         struct inode *inode;
696         char *name;
697         int err;
698 
699         inode = hostfs_iget(dir->i_sb);
700         if (IS_ERR(inode)) {
701                 err = PTR_ERR(inode);
702                 goto out;
703         }
704 
705         err = -ENOMEM;
706         name = dentry_name(dentry);
707         if (name == NULL)
708                 goto out_put;
709 
710         init_special_inode(inode, mode, dev);
711         err = do_mknod(name, mode, MAJOR(dev), MINOR(dev));
712         if (err)
713                 goto out_free;
714 
715         err = read_name(inode, name);
716         __putname(name);
717         if (err)
718                 goto out_put;
719 
720         d_instantiate(dentry, inode);
721         return 0;
722 
723  out_free:
724         __putname(name);
725  out_put:
726         iput(inode);
727  out:
728         return err;
729 }
730 
731 static int hostfs_rename2(struct inode *old_dir, struct dentry *old_dentry,
732                           struct inode *new_dir, struct dentry *new_dentry,
733                           unsigned int flags)
734 {
735         char *old_name, *new_name;
736         int err;
737 
738         if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE))
739                 return -EINVAL;
740 
741         old_name = dentry_name(old_dentry);
742         if (old_name == NULL)
743                 return -ENOMEM;
744         new_name = dentry_name(new_dentry);
745         if (new_name == NULL) {
746                 __putname(old_name);
747                 return -ENOMEM;
748         }
749         if (!flags)
750                 err = rename_file(old_name, new_name);
751         else
752                 err = rename2_file(old_name, new_name, flags);
753 
754         __putname(old_name);
755         __putname(new_name);
756         return err;
757 }
758 
759 static int hostfs_permission(struct inode *ino, int desired)
760 {
761         char *name;
762         int r = 0, w = 0, x = 0, err;
763 
764         if (desired & MAY_NOT_BLOCK)
765                 return -ECHILD;
766 
767         if (desired & MAY_READ) r = 1;
768         if (desired & MAY_WRITE) w = 1;
769         if (desired & MAY_EXEC) x = 1;
770         name = inode_name(ino);
771         if (name == NULL)
772                 return -ENOMEM;
773 
774         if (S_ISCHR(ino->i_mode) || S_ISBLK(ino->i_mode) ||
775             S_ISFIFO(ino->i_mode) || S_ISSOCK(ino->i_mode))
776                 err = 0;
777         else
778                 err = access_file(name, r, w, x);
779         __putname(name);
780         if (!err)
781                 err = generic_permission(ino, desired);
782         return err;
783 }
784 
785 static int hostfs_setattr(struct dentry *dentry, struct iattr *attr)
786 {
787         struct inode *inode = d_inode(dentry);
788         struct hostfs_iattr attrs;
789         char *name;
790         int err;
791 
792         int fd = HOSTFS_I(inode)->fd;
793 
794         err = setattr_prepare(dentry, attr);
795         if (err)
796                 return err;
797 
798         if (append)
799                 attr->ia_valid &= ~ATTR_SIZE;
800 
801         attrs.ia_valid = 0;
802         if (attr->ia_valid & ATTR_MODE) {
803                 attrs.ia_valid |= HOSTFS_ATTR_MODE;
804                 attrs.ia_mode = attr->ia_mode;
805         }
806         if (attr->ia_valid & ATTR_UID) {
807                 attrs.ia_valid |= HOSTFS_ATTR_UID;
808                 attrs.ia_uid = from_kuid(&init_user_ns, attr->ia_uid);
809         }
810         if (attr->ia_valid & ATTR_GID) {
811                 attrs.ia_valid |= HOSTFS_ATTR_GID;
812                 attrs.ia_gid = from_kgid(&init_user_ns, attr->ia_gid);
813         }
814         if (attr->ia_valid & ATTR_SIZE) {
815                 attrs.ia_valid |= HOSTFS_ATTR_SIZE;
816                 attrs.ia_size = attr->ia_size;
817         }
818         if (attr->ia_valid & ATTR_ATIME) {
819                 attrs.ia_valid |= HOSTFS_ATTR_ATIME;
820                 attrs.ia_atime = (struct hostfs_timespec)
821                         { attr->ia_atime.tv_sec, attr->ia_atime.tv_nsec };
822         }
823         if (attr->ia_valid & ATTR_MTIME) {
824                 attrs.ia_valid |= HOSTFS_ATTR_MTIME;
825                 attrs.ia_mtime = (struct hostfs_timespec)
826                         { attr->ia_mtime.tv_sec, attr->ia_mtime.tv_nsec };
827         }
828         if (attr->ia_valid & ATTR_CTIME) {
829                 attrs.ia_valid |= HOSTFS_ATTR_CTIME;
830                 attrs.ia_ctime = (struct hostfs_timespec)
831                         { attr->ia_ctime.tv_sec, attr->ia_ctime.tv_nsec };
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_rename2,
871         .permission     = hostfs_permission,
872         .setattr        = hostfs_setattr,
873 };
874 
875 static const char *hostfs_get_link(struct dentry *dentry,
876                                    struct inode *inode,
877                                    struct delayed_call *done)
878 {
879         char *link;
880         if (!dentry)
881                 return ERR_PTR(-ECHILD);
882         link = kmalloc(PATH_MAX, GFP_KERNEL);
883         if (link) {
884                 char *path = dentry_name(dentry);
885                 int err = -ENOMEM;
886                 if (path) {
887                         err = hostfs_do_readlink(path, link, PATH_MAX);
888                         if (err == PATH_MAX)
889                                 err = -E2BIG;
890                         __putname(path);
891                 }
892                 if (err < 0) {
893                         kfree(link);
894                         return ERR_PTR(err);
895                 }
896         } else {
897                 return ERR_PTR(-ENOMEM);
898         }
899 
900         set_delayed_call(done, kfree_link, link);
901         return link;
902 }
903 
904 static const struct inode_operations hostfs_link_iops = {
905         .get_link       = hostfs_get_link,
906 };
907 
908 static int hostfs_fill_sb_common(struct super_block *sb, void *d, int silent)
909 {
910         struct inode *root_inode;
911         char *host_root_path, *req_root = d;
912         int err;
913 
914         sb->s_blocksize = 1024;
915         sb->s_blocksize_bits = 10;
916         sb->s_magic = HOSTFS_SUPER_MAGIC;
917         sb->s_op = &hostfs_sbops;
918         sb->s_d_op = &simple_dentry_operations;
919         sb->s_maxbytes = MAX_LFS_FILESIZE;
920 
921         /* NULL is printed as '(null)' by printf(): avoid that. */
922         if (req_root == NULL)
923                 req_root = "";
924 
925         err = -ENOMEM;
926         sb->s_fs_info = host_root_path =
927                 kasprintf(GFP_KERNEL, "%s/%s", root_ino, req_root);
928         if (host_root_path == NULL)
929                 goto out;
930 
931         root_inode = new_inode(sb);
932         if (!root_inode)
933                 goto out;
934 
935         err = read_name(root_inode, host_root_path);
936         if (err)
937                 goto out_put;
938 
939         if (S_ISLNK(root_inode->i_mode)) {
940                 char *name = follow_link(host_root_path);
941                 if (IS_ERR(name)) {
942                         err = PTR_ERR(name);
943                         goto out_put;
944                 }
945                 err = read_name(root_inode, name);
946                 kfree(name);
947                 if (err)
948                         goto out_put;
949         }
950 
951         err = -ENOMEM;
952         sb->s_root = d_make_root(root_inode);
953         if (sb->s_root == NULL)
954                 goto out;
955 
956         return 0;
957 
958 out_put:
959         iput(root_inode);
960 out:
961         return err;
962 }
963 
964 static struct dentry *hostfs_read_sb(struct file_system_type *type,
965                           int flags, const char *dev_name,
966                           void *data)
967 {
968         return mount_nodev(type, flags, data, hostfs_fill_sb_common);
969 }
970 
971 static void hostfs_kill_sb(struct super_block *s)
972 {
973         kill_anon_super(s);
974         kfree(s->s_fs_info);
975 }
976 
977 static struct file_system_type hostfs_type = {
978         .owner          = THIS_MODULE,
979         .name           = "hostfs",
980         .mount          = hostfs_read_sb,
981         .kill_sb        = hostfs_kill_sb,
982         .fs_flags       = 0,
983 };
984 MODULE_ALIAS_FS("hostfs");
985 
986 static int __init init_hostfs(void)
987 {
988         return register_filesystem(&hostfs_type);
989 }
990 
991 static void __exit exit_hostfs(void)
992 {
993         unregister_filesystem(&hostfs_type);
994 }
995 
996 module_init(init_hostfs)
997 module_exit(exit_hostfs)
998 MODULE_LICENSE("GPL");
999 

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