fs/libfs.c

   1 /*
   2  *      fs/libfs.c
   3  *      Library for filesystems writers.
   4  */
   5
   6 #include <linux/pagemap.h>
   7 #include <linux/mount.h>
   8 #include <linux/vfs.h>
   9
  10 int simple_getattr(struct vfsmount *mnt, struct dentry *dentry,
  11                    struct kstat *stat)
  12 {
  13         struct inode *inode = dentry->d_inode;
  14         generic_fillattr(inode, stat);
  15         stat->blocks = inode->i_mapping->nrpages << (PAGE_CACHE_SHIFT - 9);
  16         return 0;
  17 }
  18
  19 int simple_statfs(struct super_block *sb, struct kstatfs *buf)
  20 {
  21         buf->f_type = sb->s_magic;
  22         buf->f_bsize = PAGE_CACHE_SIZE;
  23         buf->f_namelen = NAME_MAX;
  24         return 0;
  25 }
  26
  27 /*
  28  * Lookup the data. This is trivial - if the dentry didn't already
  29  * exist, we know it is negative.
  30  */
  31
  32 struct dentry *simple_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
  33 {
  34         d_add(dentry, NULL);
  35         return NULL;
  36 }
  37
  38 int simple_sync_file(struct file * file, struct dentry *dentry, int datasync)
  39 {
  40         return 0;
  41 }
  42
  43 int dcache_dir_open(struct inode *inode, struct file *file)
  44 {
  45         static struct qstr cursor_name = {.len = 1, .name = "."};
  46
  47         file->private_data = d_alloc(file->f_dentry, &cursor_name);
  48
  49         return file->private_data ? 0 : -ENOMEM;
  50 }
  51
  52 int dcache_dir_close(struct inode *inode, struct file *file)
  53 {
  54         dput(file->private_data);
  55         return 0;
  56 }
  57
  58 loff_t dcache_dir_lseek(struct file *file, loff_t offset, int origin)
  59 {
  60         down(&file->f_dentry->d_inode->i_sem);
  61         switch (origin) {
  62                 case 1:
  63                         offset += file->f_pos;
  64                 case 0:
  65                         if (offset >= 0)
  66                                 break;
  67                 default:
  68                         up(&file->f_dentry->d_inode->i_sem);
  69                         return -EINVAL;
  70         }
  71         if (offset != file->f_pos) {
  72                 file->f_pos = offset;
  73                 if (file->f_pos >= 2) {
  74                         struct list_head *p;
  75                         struct dentry *cursor = file->private_data;
  76                         loff_t n = file->f_pos - 2;
  77
  78                         spin_lock(&dcache_lock);
  79                         p = file->f_dentry->d_subdirs.next;
  80                         while (n && p != &file->f_dentry->d_subdirs) {
  81                                 struct dentry *next;
  82                                 next = list_entry(p, struct dentry, d_child);
  83                                 if (!d_unhashed(next) && next->d_inode)
  84                                         n--;
  85                                 p = p->next;
  86                         }
  87                         list_del(&cursor->d_child);
  88                         list_add_tail(&cursor->d_child, p);
  89                         spin_unlock(&dcache_lock);
  90                 }
  91         }
  92         up(&file->f_dentry->d_inode->i_sem);
  93         return offset;
  94 }
  95
  96 /* Relationship between i_mode and the DT_xxx types */
  97 static inline unsigned char dt_type(struct inode *inode)
  98 {
  99         return (inode->i_mode >> 12) & 15;
 100 }
 101
 102 /*
 103  * Directory is locked and all positive dentries in it are safe, since
 104  * for ramfs-type trees they can't go away without unlink() or rmdir(),
 105  * both impossible due to the lock on directory.
 106  */
 107
 108 int dcache_readdir(struct file * filp, void * dirent, filldir_t filldir)
 109 {
 110         struct dentry *dentry = filp->f_dentry;
 111         struct dentry *cursor = filp->private_data;
 112         struct list_head *p, *q = &cursor->d_child;
 113         ino_t ino;
 114         int i = filp->f_pos;
 115
 116         switch (i) {
 117                 case 0:
 118                         ino = dentry->d_inode->i_ino;
 119                         if (filldir(dirent, ".", 1, i, ino, DT_DIR) < 0)
 120                                 break;
 121                         filp->f_pos++;
 122                         i++;
 123                         /* fallthrough */
 124                 case 1:
 125                         ino = parent_ino(dentry);
 126                         if (filldir(dirent, "..", 2, i, ino, DT_DIR) < 0)
 127                                 break;
 128                         filp->f_pos++;
 129                         i++;
 130                         /* fallthrough */
 131                 default:
 132                         spin_lock(&dcache_lock);
 133                         if (filp->f_pos == 2) {
 134                                 list_del(q);
 135                                 list_add(q, &dentry->d_subdirs);
 136                         }
 137                         for (p=q->next; p != &dentry->d_subdirs; p=p->next) {
 138                                 struct dentry *next;
 139                                 next = list_entry(p, struct dentry, d_child);
 140                                 if (d_unhashed(next) || !next->d_inode)
 141                                         continue;
 142
 143                                 spin_unlock(&dcache_lock);
 144                                 if (filldir(dirent, next->d_name.name, next->d_name.len, filp->f_pos, next->d_inode->i_ino, dt_type(next->d_inode)) < 0)
 145                                         return 0;
 146                                 spin_lock(&dcache_lock);
 147                                 /* next is still alive */
 148                                 list_del(q);
 149                                 list_add(q, p);
 150                                 p = q;
 151                                 filp->f_pos++;
 152                         }
 153                         spin_unlock(&dcache_lock);
 154         }
 155         return 0;
 156 }
 157
 158 ssize_t generic_read_dir(struct file *filp, char __user *buf, size_t siz, loff_t *ppos)
 159 {
 160         return -EISDIR;
 161 }
 162
 163 struct file_operations simple_dir_operations = {
 164         .open           = dcache_dir_open,
 165         .release        = dcache_dir_close,
 166         .llseek         = dcache_dir_lseek,
 167         .read           = generic_read_dir,
 168         .readdir        = dcache_readdir,
 169 };
 170
 171 struct inode_operations simple_dir_inode_operations = {
 172         .lookup         = simple_lookup,
 173 };
 174
 175 /*
 176  * Common helper for pseudo-filesystems (sockfs, pipefs, bdev - stuff that
 177  * will never be mountable)
 178  */
 179 struct super_block *
 180 get_sb_pseudo(struct file_system_type *fs_type, char *name,
 181         struct super_operations *ops, unsigned long magic)
 182 {
 183         struct super_block *s = sget(fs_type, NULL, set_anon_super, NULL);
 184         static struct super_operations default_ops = {.statfs = simple_statfs};
 185         struct dentry *dentry;
 186         struct inode *root;
 187         struct qstr d_name = {.name = name, .len = strlen(name)};
 188
 189         if (IS_ERR(s))
 190                 return s;
 191
 192         s->s_flags = MS_NOUSER;
 193         s->s_maxbytes = ~0ULL;
 194         s->s_blocksize = 1024;
 195         s->s_blocksize_bits = 10;
 196         s->s_magic = magic;
 197         s->s_op = ops ? ops : &default_ops;
 198         root = new_inode(s);
 199         if (!root)
 200                 goto Enomem;
 201         root->i_mode = S_IFDIR | S_IRUSR | S_IWUSR;
 202         root->i_uid = root->i_gid = 0;
 203         root->i_atime = root->i_mtime = root->i_ctime = CURRENT_TIME;
 204         dentry = d_alloc(NULL, &d_name);
 205         if (!dentry) {
 206                 iput(root);
 207                 goto Enomem;
 208         }
 209         dentry->d_sb = s;
 210         dentry->d_parent = dentry;
 211         d_instantiate(dentry, root);
 212         s->s_root = dentry;
 213         s->s_flags |= MS_ACTIVE;
 214         return s;
 215
 216 Enomem:
 217         up_write(&s->s_umount);
 218         deactivate_super(s);
 219         return ERR_PTR(-ENOMEM);
 220 }
 221
 222 int simple_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
 223 {
 224         struct inode *inode = old_dentry->d_inode;
 225
 226         inode->i_nlink++;
 227         atomic_inc(&inode->i_count);
 228         dget(dentry);
 229         d_instantiate(dentry, inode);
 230         return 0;
 231 }
 232
 233 static inline int simple_positive(struct dentry *dentry)
 234 {
 235         return dentry->d_inode && !d_unhashed(dentry);
 236 }
 237
 238 int simple_empty(struct dentry *dentry)
 239 {
 240         struct dentry *child;
 241         int ret = 0;
 242
 243         spin_lock(&dcache_lock);
 244         list_for_each_entry(child, &dentry->d_subdirs, d_child)
 245                 if (simple_positive(child))
 246                         goto out;
 247         ret = 1;
 248 out:
 249         spin_unlock(&dcache_lock);
 250         return ret;
 251 }
 252
 253 int simple_unlink(struct inode *dir, struct dentry *dentry)
 254 {
 255         struct inode *inode = dentry->d_inode;
 256
 257         inode->i_nlink--;
 258         dput(dentry);
 259         return 0;
 260 }
 261
 262 int simple_rmdir(struct inode *dir, struct dentry *dentry)
 263 {
 264         if (!simple_empty(dentry))
 265                 return -ENOTEMPTY;
 266
 267         dentry->d_inode->i_nlink--;
 268         simple_unlink(dir, dentry);
 269         dir->i_nlink--;
 270         return 0;
 271 }
 272
 273 int simple_rename(struct inode *old_dir, struct dentry *old_dentry,
 274                 struct inode *new_dir, struct dentry *new_dentry)
 275 {
 276         int they_are_dirs = S_ISDIR(old_dentry->d_inode->i_mode);
 277
 278         if (!simple_empty(new_dentry))
 279                 return -ENOTEMPTY;
 280
 281         if (new_dentry->d_inode) {
 282                 simple_unlink(new_dir, new_dentry);
 283                 if (they_are_dirs)
 284                         old_dir->i_nlink--;
 285         } else if (they_are_dirs) {
 286                 old_dir->i_nlink--;
 287                 new_dir->i_nlink++;
 288         }
 289         return 0;
 290 }
 291
 292 int simple_readpage(struct file *file, struct page *page)
 293 {
 294         void *kaddr;
 295
 296         if (PageUptodate(page))
 297                 goto out;
 298
 299         kaddr = kmap_atomic(page, KM_USER0);
 300         memset(kaddr, 0, PAGE_CACHE_SIZE);
 301         kunmap_atomic(kaddr, KM_USER0);
 302         flush_dcache_page(page);
 303         SetPageUptodate(page);
 304 out:
 305         unlock_page(page);
 306         return 0;
 307 }
 308
 309 int simple_prepare_write(struct file *file, struct page *page,
 310                         unsigned from, unsigned to)
 311 {
 312         if (!PageUptodate(page)) {
 313                 if (to - from != PAGE_CACHE_SIZE) {
 314                         void *kaddr = kmap_atomic(page, KM_USER0);
 315                         memset(kaddr, 0, from);
 316                         memset(kaddr + to, 0, PAGE_CACHE_SIZE - to);
 317                         flush_dcache_page(page);
 318                         kunmap_atomic(kaddr, KM_USER0);
 319                 }
 320                 SetPageUptodate(page);
 321         }
 322         return 0;
 323 }
 324
 325 int simple_commit_write(struct file *file, struct page *page,
 326                         unsigned offset, unsigned to)
 327 {
 328         struct inode *inode = page->mapping->host;
 329         loff_t pos = ((loff_t)page->index << PAGE_CACHE_SHIFT) + to;
 330
 331         /*
 332          * No need to use i_size_read() here, the i_size
 333          * cannot change under us because we hold the i_sem.
 334          */
 335         if (pos > inode->i_size)
 336                 i_size_write(inode, pos);
 337         set_page_dirty(page);
 338         return 0;
 339 }
 340
 341 int simple_fill_super(struct super_block *s, int magic, struct tree_descr *files)
 342 {
 343         static struct super_operations s_ops = {.statfs = simple_statfs};
 344         struct inode *inode;
 345         struct dentry *root;
 346         struct dentry *dentry;
 347         int i;
 348
 349         s->s_blocksize = PAGE_CACHE_SIZE;
 350         s->s_blocksize_bits = PAGE_CACHE_SHIFT;
 351         s->s_magic = magic;
 352         s->s_op = &s_ops;
 353
 354         inode = new_inode(s);
 355         if (!inode)
 356                 return -ENOMEM;
 357         inode->i_mode = S_IFDIR | 0755;
 358         inode->i_uid = inode->i_gid = 0;
 359         inode->i_blksize = PAGE_CACHE_SIZE;
 360         inode->i_blocks = 0;
 361         inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
 362         inode->i_op = &simple_dir_inode_operations;
 363         inode->i_fop = &simple_dir_operations;
 364         root = d_alloc_root(inode);
 365         if (!root) {
 366                 iput(inode);
 367                 return -ENOMEM;
 368         }
 369         for (i = 0; !files->name || files->name[0]; i++, files++) {
 370                 struct qstr name;
 371                 if (!files->name)
 372                         continue;
 373                 name.name = files->name;
 374                 name.len = strlen(name.name);
 375                 name.hash = full_name_hash(name.name, name.len);
 376                 dentry = d_alloc(root, &name);
 377                 if (!dentry)
 378                         goto out;
 379                 inode = new_inode(s);
 380                 if (!inode)
 381                         goto out;
 382                 inode->i_mode = S_IFREG | files->mode;
 383                 inode->i_uid = inode->i_gid = 0;
 384                 inode->i_blksize = PAGE_CACHE_SIZE;
 385                 inode->i_blocks = 0;
 386                 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
 387                 inode->i_fop = files->ops;
 388                 inode->i_ino = i;
 389                 d_add(dentry, inode);
 390         }
 391         s->s_root = root;
 392         return 0;
 393 out:
 394         d_genocide(root);
 395         dput(root);
 396         return -ENOMEM;
 397 }
 398
 399 static spinlock_t pin_fs_lock = SPIN_LOCK_UNLOCKED;
 400
 401 int simple_pin_fs(char *name, struct vfsmount **mount, int *count)
 402 {
 403         struct vfsmount *mnt = NULL;
 404         spin_lock(&pin_fs_lock);
 405         if (unlikely(!*mount)) {
 406                 spin_unlock(&pin_fs_lock);
 407                 mnt = do_kern_mount(name, 0, name, NULL);
 408                 if (IS_ERR(mnt))
 409                         return PTR_ERR(mnt);
 410                 spin_lock(&pin_fs_lock);
 411                 if (!*mount)
 412                         *mount = mnt;
 413         }
 414         mntget(*mount);
 415         ++*count;
 416         spin_unlock(&pin_fs_lock);
 417         mntput(mnt);
 418         return 0;
 419 }
 420
 421 void simple_release_fs(struct vfsmount **mount, int *count)
 422 {
 423         struct vfsmount *mnt;
 424         spin_lock(&pin_fs_lock);
 425         mnt = *mount;
 426         if (!--*count)
 427                 *mount = NULL;
 428         spin_unlock(&pin_fs_lock);
 429         mntput(mnt);
 430 }