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