fs/relayfs/inode.c

   1 /*
   2  * VFS-related code for RelayFS, a high-speed data relay filesystem.
   3  *
   4  * Copyright (C) 2003-2005 - Tom Zanussi <zanussi@us.ibm.com>, IBM Corp
   5  * Copyright (C) 2003-2005 - Karim Yaghmour <karim@opersys.com>
   6  *
   7  * Based on ramfs, Copyright (C) 2002 - Linus Torvalds
   8  *
   9  * This file is released under the GPL.
  10  */
  11
  12 #include <linux/module.h>
  13 #include <linux/fs.h>
  14 #include <linux/mount.h>
  15 #include <linux/pagemap.h>
  16 #include <linux/init.h>
  17 #include <linux/string.h>
  18 #include <linux/backing-dev.h>
  19 #include <linux/namei.h>
  20 #include <linux/poll.h>
  21 #include <linux/relayfs_fs.h>
  22 #include "relay.h"
  23 #include "buffers.h"
  24
  25 #define RELAYFS_MAGIC                   0xF0B4A981
  26
  27 static struct vfsmount *                relayfs_mount;
  28 static int                              relayfs_mount_count;
  29 static kmem_cache_t *                   relayfs_inode_cachep;
  30
  31 static struct backing_dev_info          relayfs_backing_dev_info = {
  32         .ra_pages       = 0,    /* No readahead */
  33         .capabilities   = BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK,
  34 };
  35
  36 static struct inode *relayfs_get_inode(struct super_block *sb, int mode,
  37                                        struct rchan *chan)
  38 {
  39         struct rchan_buf *buf = NULL;
  40         struct inode *inode;
  41
  42         if (S_ISREG(mode)) {
  43                 BUG_ON(!chan);
  44                 buf = relay_create_buf(chan);
  45                 if (!buf)
  46                         return NULL;
  47         }
  48
  49         inode = new_inode(sb);
  50         if (!inode) {
  51                 relay_destroy_buf(buf);
  52                 return NULL;
  53         }
  54
  55         inode->i_mode = mode;
  56         inode->i_uid = 0;
  57         inode->i_gid = 0;
  58         inode->i_blksize = PAGE_CACHE_SIZE;
  59         inode->i_blocks = 0;
  60         inode->i_mapping->backing_dev_info = &relayfs_backing_dev_info;
  61         inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
  62         switch (mode & S_IFMT) {
  63         case S_IFREG:
  64                 inode->i_fop = &relayfs_file_operations;
  65                 RELAYFS_I(inode)->buf = buf;
  66                 break;
  67         case S_IFDIR:
  68                 inode->i_op = &simple_dir_inode_operations;
  69                 inode->i_fop = &simple_dir_operations;
  70
  71                 /* directory inodes start off with i_nlink == 2 (for "." entry) */
  72                 inode->i_nlink++;
  73                 break;
  74         default:
  75                 break;
  76         }
  77
  78         return inode;
  79 }
  80
  81 /**
  82  *      relayfs_create_entry - create a relayfs directory or file
  83  *      @name: the name of the file to create
  84  *      @parent: parent directory
  85  *      @mode: mode
  86  *      @chan: relay channel associated with the file
  87  *
  88  *      Returns the new dentry, NULL on failure
  89  *
  90  *      Creates a file or directory with the specifed permissions.
  91  */
  92 static struct dentry *relayfs_create_entry(const char *name,
  93                                            struct dentry *parent,
  94                                            int mode,
  95                                            struct rchan *chan)
  96 {
  97         struct dentry *d;
  98         struct inode *inode;
  99         int error = 0;
 100
 101         BUG_ON(!name || !(S_ISREG(mode) || S_ISDIR(mode)));
 102
 103         error = simple_pin_fs("relayfs", &relayfs_mount, &relayfs_mount_count);
 104         if (error) {
 105                 printk(KERN_ERR "Couldn't mount relayfs: errcode %d\n", error);
 106                 return NULL;
 107         }
 108
 109         if (!parent && relayfs_mount && relayfs_mount->mnt_sb)
 110                 parent = relayfs_mount->mnt_sb->s_root;
 111
 112         if (!parent) {
 113                 simple_release_fs(&relayfs_mount, &relayfs_mount_count);
 114                 return NULL;
 115         }
 116
 117         parent = dget(parent);
 118         down(&parent->d_inode->i_sem);
 119         d = lookup_one_len(name, parent, strlen(name));
 120         if (IS_ERR(d)) {
 121                 d = NULL;
 122                 goto release_mount;
 123         }
 124
 125         if (d->d_inode) {
 126                 d = NULL;
 127                 goto release_mount;
 128         }
 129
 130         inode = relayfs_get_inode(parent->d_inode->i_sb, mode, chan);
 131         if (!inode) {
 132                 d = NULL;
 133                 goto release_mount;
 134         }
 135
 136         d_instantiate(d, inode);
 137         dget(d);        /* Extra count - pin the dentry in core */
 138
 139         if (S_ISDIR(mode))
 140                 parent->d_inode->i_nlink++;
 141
 142         goto exit;
 143
 144 release_mount:
 145         simple_release_fs(&relayfs_mount, &relayfs_mount_count);
 146
 147 exit:
 148         up(&parent->d_inode->i_sem);
 149         dput(parent);
 150         return d;
 151 }
 152
 153 /**
 154  *      relayfs_create_file - create a file in the relay filesystem
 155  *      @name: the name of the file to create
 156  *      @parent: parent directory
 157  *      @mode: mode, if not specied the default perms are used
 158  *      @chan: channel associated with the file
 159  *
 160  *      Returns file dentry if successful, NULL otherwise.
 161  *
 162  *      The file will be created user r on behalf of current user.
 163  */
 164 struct dentry *relayfs_create_file(const char *name, struct dentry *parent,
 165                                    int mode, struct rchan *chan)
 166 {
 167         if (!mode)
 168                 mode = S_IRUSR;
 169         mode = (mode & S_IALLUGO) | S_IFREG;
 170
 171         return relayfs_create_entry(name, parent, mode, chan);
 172 }
 173
 174 /**
 175  *      relayfs_create_dir - create a directory in the relay filesystem
 176  *      @name: the name of the directory to create
 177  *      @parent: parent directory, NULL if parent should be fs root
 178  *
 179  *      Returns directory dentry if successful, NULL otherwise.
 180  *
 181  *      The directory will be created world rwx on behalf of current user.
 182  */
 183 struct dentry *relayfs_create_dir(const char *name, struct dentry *parent)
 184 {
 185         int mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
 186         return relayfs_create_entry(name, parent, mode, NULL);
 187 }
 188
 189 /**
 190  *      relayfs_remove - remove a file or directory in the relay filesystem
 191  *      @dentry: file or directory dentry
 192  *
 193  *      Returns 0 if successful, negative otherwise.
 194  */
 195 int relayfs_remove(struct dentry *dentry)
 196 {
 197         struct dentry *parent;
 198         int error = 0;
 199
 200         if (!dentry)
 201                 return -EINVAL;
 202         parent = dentry->d_parent;
 203         if (!parent)
 204                 return -EINVAL;
 205
 206         parent = dget(parent);
 207         down(&parent->d_inode->i_sem);
 208         if (dentry->d_inode) {
 209                 if (S_ISDIR(dentry->d_inode->i_mode))
 210                         error = simple_rmdir(parent->d_inode, dentry);
 211                 else
 212                         error = simple_unlink(parent->d_inode, dentry);
 213                 if (!error)
 214                         d_delete(dentry);
 215         }
 216         if (!error)
 217                 dput(dentry);
 218         up(&parent->d_inode->i_sem);
 219         dput(parent);
 220
 221         if (!error)
 222                 simple_release_fs(&relayfs_mount, &relayfs_mount_count);
 223
 224         return error;
 225 }
 226
 227 /**
 228  *      relayfs_remove_dir - remove a directory in the relay filesystem
 229  *      @dentry: directory dentry
 230  *
 231  *      Returns 0 if successful, negative otherwise.
 232  */
 233 int relayfs_remove_dir(struct dentry *dentry)
 234 {
 235         return relayfs_remove(dentry);
 236 }
 237
 238 /**
 239  *      relayfs_open - open file op for relayfs files
 240  *      @inode: the inode
 241  *      @filp: the file
 242  *
 243  *      Increments the channel buffer refcount.
 244  */
 245 static int relayfs_open(struct inode *inode, struct file *filp)
 246 {
 247         struct rchan_buf *buf = RELAYFS_I(inode)->buf;
 248         kref_get(&buf->kref);
 249
 250         return 0;
 251 }
 252
 253 /**
 254  *      relayfs_mmap - mmap file op for relayfs files
 255  *      @filp: the file
 256  *      @vma: the vma describing what to map
 257  *
 258  *      Calls upon relay_mmap_buf to map the file into user space.
 259  */
 260 static int relayfs_mmap(struct file *filp, struct vm_area_struct *vma)
 261 {
 262         struct inode *inode = filp->f_dentry->d_inode;
 263         return relay_mmap_buf(RELAYFS_I(inode)->buf, vma);
 264 }
 265
 266 /**
 267  *      relayfs_poll - poll file op for relayfs files
 268  *      @filp: the file
 269  *      @wait: poll table
 270  *
 271  *      Poll implemention.
 272  */
 273 static unsigned int relayfs_poll(struct file *filp, poll_table *wait)
 274 {
 275         unsigned int mask = 0;
 276         struct inode *inode = filp->f_dentry->d_inode;
 277         struct rchan_buf *buf = RELAYFS_I(inode)->buf;
 278
 279         if (buf->finalized)
 280                 return POLLERR;
 281
 282         if (filp->f_mode & FMODE_READ) {
 283                 poll_wait(filp, &buf->read_wait, wait);
 284                 if (!relay_buf_empty(buf))
 285                         mask |= POLLIN | POLLRDNORM;
 286         }
 287
 288         return mask;
 289 }
 290
 291 /**
 292  *      relayfs_release - release file op for relayfs files
 293  *      @inode: the inode
 294  *      @filp: the file
 295  *
 296  *      Decrements the channel refcount, as the filesystem is
 297  *      no longer using it.
 298  */
 299 static int relayfs_release(struct inode *inode, struct file *filp)
 300 {
 301         struct rchan_buf *buf = RELAYFS_I(inode)->buf;
 302         kref_put(&buf->kref, relay_remove_buf);
 303
 304         return 0;
 305 }
 306
 307 /**
 308  *      relayfs_read_consume - update the consumed count for the buffer
 309  */
 310 static void relayfs_read_consume(struct rchan_buf *buf,
 311                                  size_t read_pos,
 312                                  size_t bytes_consumed)
 313 {
 314         size_t subbuf_size = buf->chan->subbuf_size;
 315         size_t n_subbufs = buf->chan->n_subbufs;
 316         size_t read_subbuf;
 317
 318         if (buf->bytes_consumed + bytes_consumed > subbuf_size) {
 319                 relay_subbufs_consumed(buf->chan, buf->cpu, 1);
 320                 buf->bytes_consumed = 0;
 321         }
 322
 323         buf->bytes_consumed += bytes_consumed;
 324         read_subbuf = read_pos / buf->chan->subbuf_size;
 325         if (buf->bytes_consumed + buf->padding[read_subbuf] == subbuf_size) {
 326                 if ((read_subbuf == buf->subbufs_produced % n_subbufs) &&
 327                     (buf->offset == subbuf_size))
 328                         return;
 329                 relay_subbufs_consumed(buf->chan, buf->cpu, 1);
 330                 buf->bytes_consumed = 0;
 331         }
 332 }
 333
 334 /**
 335  *      relayfs_read_avail - boolean, are there unconsumed bytes available?
 336  */
 337 static int relayfs_read_avail(struct rchan_buf *buf, size_t read_pos)
 338 {
 339         size_t bytes_produced, bytes_consumed, write_offset;
 340         size_t subbuf_size = buf->chan->subbuf_size;
 341         size_t n_subbufs = buf->chan->n_subbufs;
 342         size_t produced = buf->subbufs_produced % n_subbufs;
 343         size_t consumed = buf->subbufs_consumed % n_subbufs;
 344
 345         write_offset = buf->offset > subbuf_size ? subbuf_size : buf->offset;
 346
 347         if (consumed > produced) {
 348                 if ((produced > n_subbufs) &&
 349                     (produced + n_subbufs - consumed <= n_subbufs))
 350                         produced += n_subbufs;
 351         } else if (consumed == produced) {
 352                 if (buf->offset > subbuf_size) {
 353                         produced += n_subbufs;
 354                         if (buf->subbufs_produced == buf->subbufs_consumed)
 355                                 consumed += n_subbufs;
 356                 }
 357         }
 358
 359         if (buf->offset > subbuf_size)
 360                 bytes_produced = (produced - 1) * subbuf_size + write_offset;
 361         else
 362                 bytes_produced = produced * subbuf_size + write_offset;
 363         bytes_consumed = consumed * subbuf_size + buf->bytes_consumed;
 364
 365         if (bytes_produced == bytes_consumed)
 366                 return 0;
 367
 368         relayfs_read_consume(buf, read_pos, 0);
 369
 370         return 1;
 371 }
 372
 373 /**
 374  *      relayfs_read_subbuf_avail - return bytes available in sub-buffer
 375  */
 376 static size_t relayfs_read_subbuf_avail(size_t read_pos,
 377                                         struct rchan_buf *buf)
 378 {
 379         size_t padding, avail = 0;
 380         size_t read_subbuf, read_offset, write_subbuf, write_offset;
 381         size_t subbuf_size = buf->chan->subbuf_size;
 382
 383         write_subbuf = (buf->data - buf->start) / subbuf_size;
 384         write_offset = buf->offset > subbuf_size ? subbuf_size : buf->offset;
 385         read_subbuf = read_pos / subbuf_size;
 386         read_offset = read_pos % subbuf_size;
 387         padding = buf->padding[read_subbuf];
 388
 389         if (read_subbuf == write_subbuf) {
 390                 if (read_offset + padding < write_offset)
 391                         avail = write_offset - (read_offset + padding);
 392         } else
 393                 avail = (subbuf_size - padding) - read_offset;
 394
 395         return avail;
 396 }
 397
 398 /**
 399  *      relayfs_read_start_pos - find the first available byte to read
 400  *
 401  *      If the read_pos is in the middle of padding, return the
 402  *      position of the first actually available byte, otherwise
 403  *      return the original value.
 404  */
 405 static size_t relayfs_read_start_pos(size_t read_pos,
 406                                      struct rchan_buf *buf)
 407 {
 408         size_t read_subbuf, padding, padding_start, padding_end;
 409         size_t subbuf_size = buf->chan->subbuf_size;
 410         size_t n_subbufs = buf->chan->n_subbufs;
 411
 412         read_subbuf = read_pos / subbuf_size;
 413         padding = buf->padding[read_subbuf];
 414         padding_start = (read_subbuf + 1) * subbuf_size - padding;
 415         padding_end = (read_subbuf + 1) * subbuf_size;
 416         if (read_pos >= padding_start && read_pos < padding_end) {
 417                 read_subbuf = (read_subbuf + 1) % n_subbufs;
 418                 read_pos = read_subbuf * subbuf_size;
 419         }
 420
 421         return read_pos;
 422 }
 423
 424 /**
 425  *      relayfs_read_end_pos - return the new read position
 426  */
 427 static size_t relayfs_read_end_pos(struct rchan_buf *buf,
 428                                    size_t read_pos,
 429                                    size_t count)
 430 {
 431         size_t read_subbuf, padding, end_pos;
 432         size_t subbuf_size = buf->chan->subbuf_size;
 433         size_t n_subbufs = buf->chan->n_subbufs;
 434
 435         read_subbuf = read_pos / subbuf_size;
 436         padding = buf->padding[read_subbuf];
 437         if (read_pos % subbuf_size + count + padding == subbuf_size)
 438                 end_pos = (read_subbuf + 1) * subbuf_size;
 439         else
 440                 end_pos = read_pos + count;
 441         if (end_pos >= subbuf_size * n_subbufs)
 442                 end_pos = 0;
 443
 444         return end_pos;
 445 }
 446
 447 /**
 448  *      relayfs_read - read file op for relayfs files
 449  *      @filp: the file
 450  *      @buffer: the userspace buffer
 451  *      @count: number of bytes to read
 452  *      @ppos: position to read from
 453  *
 454  *      Reads count bytes or the number of bytes available in the
 455  *      current sub-buffer being read, whichever is smaller.
 456  */
 457 static ssize_t relayfs_read(struct file *filp,
 458                             char __user *buffer,
 459                             size_t count,
 460                             loff_t *ppos)
 461 {
 462         struct inode *inode = filp->f_dentry->d_inode;
 463         struct rchan_buf *buf = RELAYFS_I(inode)->buf;
 464         size_t read_start, avail;
 465         ssize_t ret = 0;
 466         void *from;
 467
 468         down(&inode->i_sem);
 469         if(!relayfs_read_avail(buf, *ppos))
 470                 goto out;
 471
 472         read_start = relayfs_read_start_pos(*ppos, buf);
 473         avail = relayfs_read_subbuf_avail(read_start, buf);
 474         if (!avail)
 475                 goto out;
 476
 477         from = buf->start + read_start;
 478         ret = count = min(count, avail);
 479         if (copy_to_user(buffer, from, count)) {
 480                 ret = -EFAULT;
 481                 goto out;
 482         }
 483         relayfs_read_consume(buf, read_start, count);
 484         *ppos = relayfs_read_end_pos(buf, read_start, count);
 485 out:
 486         up(&inode->i_sem);
 487         return ret;
 488 }
 489
 490 /**
 491  *      relayfs alloc_inode() implementation
 492  */
 493 static struct inode *relayfs_alloc_inode(struct super_block *sb)
 494 {
 495         struct relayfs_inode_info *p = kmem_cache_alloc(relayfs_inode_cachep, SLAB_KERNEL);
 496         if (!p)
 497                 return NULL;
 498         p->buf = NULL;
 499
 500         return &p->vfs_inode;
 501 }
 502
 503 /**
 504  *      relayfs destroy_inode() implementation
 505  */
 506 static void relayfs_destroy_inode(struct inode *inode)
 507 {
 508         if (RELAYFS_I(inode)->buf)
 509                 relay_destroy_buf(RELAYFS_I(inode)->buf);
 510
 511         kmem_cache_free(relayfs_inode_cachep, RELAYFS_I(inode));
 512 }
 513
 514 static void init_once(void *p, kmem_cache_t *cachep, unsigned long flags)
 515 {
 516         struct relayfs_inode_info *i = p;
 517         if ((flags & (SLAB_CTOR_VERIFY | SLAB_CTOR_CONSTRUCTOR)) == SLAB_CTOR_CONSTRUCTOR)
 518                 inode_init_once(&i->vfs_inode);
 519 }
 520
 521 struct file_operations relayfs_file_operations = {
 522         .open           = relayfs_open,
 523         .poll           = relayfs_poll,
 524         .mmap           = relayfs_mmap,
 525         .read           = relayfs_read,
 526         .llseek         = no_llseek,
 527         .release        = relayfs_release,
 528 };
 529
 530 static struct super_operations relayfs_ops = {
 531         .statfs         = simple_statfs,
 532         .drop_inode     = generic_delete_inode,
 533         .alloc_inode    = relayfs_alloc_inode,
 534         .destroy_inode  = relayfs_destroy_inode,
 535 };
 536
 537 static int relayfs_fill_super(struct super_block * sb, void * data, int silent)
 538 {
 539         struct inode *inode;
 540         struct dentry *root;
 541         int mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
 542
 543         sb->s_blocksize = PAGE_CACHE_SIZE;
 544         sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
 545         sb->s_magic = RELAYFS_MAGIC;
 546         sb->s_op = &relayfs_ops;
 547         inode = relayfs_get_inode(sb, mode, NULL);
 548
 549         if (!inode)
 550                 return -ENOMEM;
 551
 552         root = d_alloc_root(inode);
 553         if (!root) {
 554                 iput(inode);
 555                 return -ENOMEM;
 556         }
 557         sb->s_root = root;
 558
 559         return 0;
 560 }
 561
 562 static struct super_block * relayfs_get_sb(struct file_system_type *fs_type,
 563                                            int flags, const char *dev_name,
 564                                            void *data)
 565 {
 566         return get_sb_single(fs_type, flags, data, relayfs_fill_super);
 567 }
 568
 569 static struct file_system_type relayfs_fs_type = {
 570         .owner          = THIS_MODULE,
 571         .name           = "relayfs",
 572         .get_sb         = relayfs_get_sb,
 573         .kill_sb        = kill_litter_super,
 574 };
 575
 576 static int __init init_relayfs_fs(void)
 577 {
 578         int err;
 579
 580         relayfs_inode_cachep = kmem_cache_create("relayfs_inode_cache",
 581                                 sizeof(struct relayfs_inode_info), 0,
 582                                 0, init_once, NULL);
 583         if (!relayfs_inode_cachep)
 584                 return -ENOMEM;
 585
 586         err = register_filesystem(&relayfs_fs_type);
 587         if (err)
 588                 kmem_cache_destroy(relayfs_inode_cachep);
 589
 590         return err;
 591 }
 592
 593 static void __exit exit_relayfs_fs(void)
 594 {
 595         unregister_filesystem(&relayfs_fs_type);
 596         kmem_cache_destroy(relayfs_inode_cachep);
 597 }
 598
 599 module_init(init_relayfs_fs)
 600 module_exit(exit_relayfs_fs)
 601
 602 EXPORT_SYMBOL_GPL(relayfs_file_operations);
 603 EXPORT_SYMBOL_GPL(relayfs_create_dir);
 604 EXPORT_SYMBOL_GPL(relayfs_remove_dir);
 605
 606 MODULE_AUTHOR("Tom Zanussi <zanussi@us.ibm.com> and Karim Yaghmour <karim@opersys.com>");
 607 MODULE_DESCRIPTION("Relay Filesystem");
 608 MODULE_LICENSE("GPL");
 609