git.oblomov.eu Git - linux-2.6/blob - fs/btrfs/file.c

   1 /*
   2  * Copyright (C) 2007 Oracle.  All rights reserved.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public
   6  * License v2 as published by the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  11  * General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU General Public
  14  * License along with this program; if not, write to the
  15  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  16  * Boston, MA 021110-1307, USA.
  17  */
  18
  19 #include <linux/module.h>
  20 #include <linux/buffer_head.h>
  21 #include <linux/fs.h>
  22 #include <linux/pagemap.h>
  23 #include <linux/highmem.h>
  24 #include <linux/time.h>
  25 #include <linux/init.h>
  26 #include <linux/string.h>
  27 #include <linux/smp_lock.h>
  28 #include <linux/backing-dev.h>
  29 #include <linux/mpage.h>
  30 #include <linux/swap.h>
  31 #include <linux/writeback.h>
  32 #include <linux/statfs.h>
  33 #include <linux/compat.h>
  34 #include "ctree.h"
  35 #include "disk-io.h"
  36 #include "transaction.h"
  37 #include "btrfs_inode.h"
  38 #include "ioctl.h"
  39 #include "print-tree.h"
  40
  41
  42 static int btrfs_copy_from_user(loff_t pos, int num_pages, int write_bytes,
  43                                 struct page **prepared_pages,
  44                                 const char __user * buf)
  45 {
  46         long page_fault = 0;
  47         int i;
  48         int offset = pos & (PAGE_CACHE_SIZE - 1);
  49
  50         for (i = 0; i < num_pages && write_bytes > 0; i++, offset = 0) {
  51                 size_t count = min_t(size_t,
  52                                      PAGE_CACHE_SIZE - offset, write_bytes);
  53                 struct page *page = prepared_pages[i];
  54                 fault_in_pages_readable(buf, count);
  55
  56                 /* Copy data from userspace to the current page */
  57                 kmap(page);
  58                 page_fault = __copy_from_user(page_address(page) + offset,
  59                                               buf, count);
  60                 /* Flush processor's dcache for this page */
  61                 flush_dcache_page(page);
  62                 kunmap(page);
  63                 buf += count;
  64                 write_bytes -= count;
  65
  66                 if (page_fault)
  67                         break;
  68         }
  69         return page_fault ? -EFAULT : 0;
  70 }
  71
  72 static void btrfs_drop_pages(struct page **pages, size_t num_pages)
  73 {
  74         size_t i;
  75         for (i = 0; i < num_pages; i++) {
  76                 if (!pages[i])
  77                         break;
  78                 unlock_page(pages[i]);
  79                 mark_page_accessed(pages[i]);
  80                 page_cache_release(pages[i]);
  81         }
  82 }
  83
  84 static int dirty_and_release_pages(struct btrfs_trans_handle *trans,
  85                                    struct btrfs_root *root,
  86                                    struct file *file,
  87                                    struct page **pages,
  88                                    size_t num_pages,
  89                                    loff_t pos,
  90                                    size_t write_bytes)
  91 {
  92         int i;
  93         int offset;
  94         int err = 0;
  95         int ret;
  96         int this_write;
  97         struct inode *inode = file->f_path.dentry->d_inode;
  98         struct buffer_head *bh;
  99         struct btrfs_file_extent_item *ei;
 100
 101         for (i = 0; i < num_pages; i++) {
 102                 offset = pos & (PAGE_CACHE_SIZE -1);
 103                 this_write = min((size_t)PAGE_CACHE_SIZE - offset, write_bytes);
 104                 /* FIXME, one block at a time */
 105
 106                 bh = page_buffers(pages[i]);
 107
 108                 if (buffer_mapped(bh) && bh->b_blocknr == 0) {
 109                         struct btrfs_key key;
 110                         struct btrfs_path *path;
 111                         char *ptr, *kaddr;
 112                         u32 datasize;
 113
 114                         mutex_lock(&root->fs_info->fs_mutex);
 115                         trans = btrfs_start_transaction(root, 1);
 116                         btrfs_set_trans_block_group(trans, inode);
 117
 118                         /* create an inline extent, and copy the data in */
 119                         path = btrfs_alloc_path();
 120                         BUG_ON(!path);
 121                         key.objectid = inode->i_ino;
 122                         key.offset = pages[i]->index << PAGE_CACHE_SHIFT;
 123                         key.flags = 0;
 124                         btrfs_set_key_type(&key, BTRFS_EXTENT_DATA_KEY);
 125                         BUG_ON(write_bytes >= PAGE_CACHE_SIZE);
 126                         datasize = offset +
 127                                 btrfs_file_extent_calc_inline_size(write_bytes);
 128
 129                         ret = btrfs_insert_empty_item(trans, root, path, &key,
 130                                                       datasize);
 131                         BUG_ON(ret);
 132                         ei = btrfs_item_ptr(btrfs_buffer_leaf(path->nodes[0]),
 133                                path->slots[0], struct btrfs_file_extent_item);
 134                         btrfs_set_file_extent_generation(ei, trans->transid);
 135                         btrfs_set_file_extent_type(ei,
 136                                                    BTRFS_FILE_EXTENT_INLINE);
 137                         ptr = btrfs_file_extent_inline_start(ei);
 138
 139                         kaddr = kmap_atomic(bh->b_page, KM_USER0);
 140                         btrfs_memcpy(root, path->nodes[0]->b_data,
 141                                      ptr, kaddr + bh_offset(bh),
 142                                      offset + write_bytes);
 143                         kunmap_atomic(kaddr, KM_USER0);
 144
 145                         mark_buffer_dirty(path->nodes[0]);
 146                         btrfs_free_path(path);
 147                         ret = btrfs_end_transaction(trans, root);
 148                         BUG_ON(ret);
 149                         mutex_unlock(&root->fs_info->fs_mutex);
 150                 }
 151
 152                 ret = btrfs_commit_write(file, pages[i], offset,
 153                                          offset + this_write);
 154                 pos += this_write;
 155                 if (ret) {
 156                         err = ret;
 157                         goto failed;
 158                 }
 159                 WARN_ON(this_write > write_bytes);
 160                 write_bytes -= this_write;
 161         }
 162 failed:
 163         return err;
 164 }
 165
 166 /*
 167  * this is very complex, but the basic idea is to drop all extents
 168  * in the range start - end.  hint_block is filled in with a block number
 169  * that would be a good hint to the block allocator for this file.
 170  *
 171  * If an extent intersects the range but is not entirely inside the range
 172  * it is either truncated or split.  Anything entirely inside the range
 173  * is deleted from the tree.
 174  */
 175 int btrfs_drop_extents(struct btrfs_trans_handle *trans,
 176                        struct btrfs_root *root, struct inode *inode,
 177                        u64 start, u64 end, u64 *hint_block)
 178 {
 179         int ret;
 180         struct btrfs_key key;
 181         struct btrfs_leaf *leaf;
 182         int slot;
 183         struct btrfs_file_extent_item *extent;
 184         u64 extent_end = 0;
 185         int keep;
 186         struct btrfs_file_extent_item old;
 187         struct btrfs_path *path;
 188         u64 search_start = start;
 189         int bookend;
 190         int found_type;
 191         int found_extent;
 192         int found_inline;
 193
 194         path = btrfs_alloc_path();
 195         if (!path)
 196                 return -ENOMEM;
 197         while(1) {
 198                 btrfs_release_path(root, path);
 199                 ret = btrfs_lookup_file_extent(trans, root, path, inode->i_ino,
 200                                                search_start, -1);
 201                 if (ret < 0)
 202                         goto out;
 203                 if (ret > 0) {
 204                         if (path->slots[0] == 0) {
 205                                 ret = 0;
 206                                 goto out;
 207                         }
 208                         path->slots[0]--;
 209                 }
 210 next_slot:
 211                 keep = 0;
 212                 bookend = 0;
 213                 found_extent = 0;
 214                 found_inline = 0;
 215                 extent = NULL;
 216                 leaf = btrfs_buffer_leaf(path->nodes[0]);
 217                 slot = path->slots[0];
 218                 ret = 0;
 219                 btrfs_disk_key_to_cpu(&key, &leaf->items[slot].key);
 220                 if (key.offset >= end || key.objectid != inode->i_ino) {
 221                         goto out;
 222                 }
 223                 if (btrfs_key_type(&key) > BTRFS_EXTENT_DATA_KEY) {
 224                         goto out;
 225                 }
 226                 if (btrfs_key_type(&key) == BTRFS_EXTENT_DATA_KEY) {
 227                         extent = btrfs_item_ptr(leaf, slot,
 228                                                 struct btrfs_file_extent_item);
 229                         found_type = btrfs_file_extent_type(extent);
 230                         if (found_type == BTRFS_FILE_EXTENT_REG) {
 231                                 extent_end = key.offset +
 232                                         (btrfs_file_extent_num_blocks(extent) <<
 233                                          inode->i_blkbits);
 234                                 found_extent = 1;
 235                         } else if (found_type == BTRFS_FILE_EXTENT_INLINE) {
 236                                 found_inline = 1;
 237                                 extent_end = key.offset +
 238                                      btrfs_file_extent_inline_len(leaf->items +
 239                                                                   slot);
 240                         }
 241                 } else {
 242                         extent_end = search_start;
 243                 }
 244
 245                 /* we found nothing we can drop */
 246                 if ((!found_extent && !found_inline) ||
 247                     search_start >= extent_end) {
 248                         int nextret;
 249                         u32 nritems;
 250                         nritems = btrfs_header_nritems(
 251                                         btrfs_buffer_header(path->nodes[0]));
 252                         if (slot >= nritems - 1) {
 253                                 nextret = btrfs_next_leaf(root, path);
 254                                 if (nextret)
 255                                         goto out;
 256                         } else {
 257                                 path->slots[0]++;
 258                         }
 259                         goto next_slot;
 260                 }
 261
 262                 /* FIXME, there's only one inline extent allowed right now */
 263                 if (found_inline) {
 264                         u64 mask = root->blocksize - 1;
 265                         search_start = (extent_end + mask) & ~mask;
 266                 } else
 267                         search_start = extent_end;
 268
 269                 if (end < extent_end && end >= key.offset) {
 270                         if (found_extent) {
 271                                 u64 disk_blocknr =
 272                                         btrfs_file_extent_disk_blocknr(extent);
 273                                 u64 disk_num_blocks =
 274                                       btrfs_file_extent_disk_num_blocks(extent);
 275                                 memcpy(&old, extent, sizeof(old));
 276                                 if (disk_blocknr != 0) {
 277                                         ret = btrfs_inc_extent_ref(trans, root,
 278                                                  disk_blocknr, disk_num_blocks);
 279                                         BUG_ON(ret);
 280                                 }
 281                         }
 282                         WARN_ON(found_inline);
 283                         bookend = 1;
 284                 }
 285                 /* truncate existing extent */
 286                 if (start > key.offset) {
 287                         u64 new_num;
 288                         u64 old_num;
 289                         keep = 1;
 290                         WARN_ON(start & (root->blocksize - 1));
 291                         if (found_extent) {
 292                                 new_num = (start - key.offset) >>
 293                                         inode->i_blkbits;
 294                                 old_num = btrfs_file_extent_num_blocks(extent);
 295                                 *hint_block =
 296                                         btrfs_file_extent_disk_blocknr(extent);
 297                                 if (btrfs_file_extent_disk_blocknr(extent)) {
 298                                         inode->i_blocks -=
 299                                                 (old_num - new_num) << 3;
 300                                 }
 301                                 btrfs_set_file_extent_num_blocks(extent,
 302                                                                  new_num);
 303                                 mark_buffer_dirty(path->nodes[0]);
 304                         } else {
 305                                 WARN_ON(1);
 306                         }
 307                 }
 308                 /* delete the entire extent */
 309                 if (!keep) {
 310                         u64 disk_blocknr = 0;
 311                         u64 disk_num_blocks = 0;
 312                         u64 extent_num_blocks = 0;
 313                         if (found_extent) {
 314                                 disk_blocknr =
 315                                       btrfs_file_extent_disk_blocknr(extent);
 316                                 disk_num_blocks =
 317                                       btrfs_file_extent_disk_num_blocks(extent);
 318                                 extent_num_blocks =
 319                                       btrfs_file_extent_num_blocks(extent);
 320                                 *hint_block =
 321                                         btrfs_file_extent_disk_blocknr(extent);
 322                         }
 323                         ret = btrfs_del_item(trans, root, path);
 324                         BUG_ON(ret);
 325                         btrfs_release_path(root, path);
 326                         extent = NULL;
 327                         if (found_extent && disk_blocknr != 0) {
 328                                 inode->i_blocks -= extent_num_blocks << 3;
 329                                 ret = btrfs_free_extent(trans, root,
 330                                                         disk_blocknr,
 331                                                         disk_num_blocks, 0);
 332                         }
 333
 334                         BUG_ON(ret);
 335                         if (!bookend && search_start >= end) {
 336                                 ret = 0;
 337                                 goto out;
 338                         }
 339                         if (!bookend)
 340                                 continue;
 341                 }
 342                 /* create bookend, splitting the extent in two */
 343                 if (bookend && found_extent) {
 344                         struct btrfs_key ins;
 345                         ins.objectid = inode->i_ino;
 346                         ins.offset = end;
 347                         ins.flags = 0;
 348                         btrfs_set_key_type(&ins, BTRFS_EXTENT_DATA_KEY);
 349                         btrfs_release_path(root, path);
 350                         ret = btrfs_insert_empty_item(trans, root, path, &ins,
 351                                                       sizeof(*extent));
 352
 353                         if (ret) {
 354                                 btrfs_print_leaf(root, btrfs_buffer_leaf(path->nodes[0]));
 355                                 printk("got %d on inserting %Lu %u %Lu start %Lu end %Lu found %Lu %Lu\n", ret , ins.objectid, ins.flags, ins.offset, start, end, key.offset, extent_end);
 356                         }
 357                         BUG_ON(ret);
 358                         extent = btrfs_item_ptr(
 359                                     btrfs_buffer_leaf(path->nodes[0]),
 360                                     path->slots[0],
 361                                     struct btrfs_file_extent_item);
 362                         btrfs_set_file_extent_disk_blocknr(extent,
 363                                     btrfs_file_extent_disk_blocknr(&old));
 364                         btrfs_set_file_extent_disk_num_blocks(extent,
 365                                     btrfs_file_extent_disk_num_blocks(&old));
 366
 367                         btrfs_set_file_extent_offset(extent,
 368                                     btrfs_file_extent_offset(&old) +
 369                                     ((end - key.offset) >> inode->i_blkbits));
 370                         WARN_ON(btrfs_file_extent_num_blocks(&old) <
 371                                 (extent_end - end) >> inode->i_blkbits);
 372                         btrfs_set_file_extent_num_blocks(extent,
 373                                     (extent_end - end) >> inode->i_blkbits);
 374
 375                         btrfs_set_file_extent_type(extent,
 376                                                    BTRFS_FILE_EXTENT_REG);
 377                         btrfs_set_file_extent_generation(extent,
 378                                     btrfs_file_extent_generation(&old));
 379                         btrfs_mark_buffer_dirty(path->nodes[0]);
 380                         if (btrfs_file_extent_disk_blocknr(&old) != 0) {
 381                                 inode->i_blocks +=
 382                                       btrfs_file_extent_num_blocks(extent) << 3;
 383                         }
 384                         ret = 0;
 385                         goto out;
 386                 }
 387         }
 388 out:
 389         btrfs_free_path(path);
 390         return ret;
 391 }
 392
 393 /*
 394  * this gets pages into the page cache and locks them down
 395  */
 396 static int prepare_pages(struct btrfs_root *root,
 397                          struct file *file,
 398                          struct page **pages,
 399                          size_t num_pages,
 400                          loff_t pos,
 401                          unsigned long first_index,
 402                          unsigned long last_index,
 403                          size_t write_bytes)
 404 {
 405         int i;
 406         unsigned long index = pos >> PAGE_CACHE_SHIFT;
 407         struct inode *inode = file->f_path.dentry->d_inode;
 408         int offset;
 409         int err = 0;
 410         int this_write;
 411         struct buffer_head *bh;
 412         struct buffer_head *head;
 413         loff_t isize = i_size_read(inode);
 414         struct btrfs_trans_handle *trans;
 415         u64 hint_block;
 416         u64 num_blocks;
 417         u64 alloc_extent_start;
 418         u64 start_pos;
 419         struct btrfs_key ins;
 420
 421         start_pos = pos & ~((u64)PAGE_CACHE_SIZE - 1);
 422         num_blocks = (write_bytes + pos - start_pos + root->blocksize - 1) >>
 423                         inode->i_blkbits;
 424
 425         memset(pages, 0, num_pages * sizeof(struct page *));
 426
 427         for (i = 0; i < num_pages; i++) {
 428                 pages[i] = grab_cache_page(inode->i_mapping, index + i);
 429                 if (!pages[i]) {
 430                         err = -ENOMEM;
 431                         goto failed_release;
 432                 }
 433         }
 434
 435         mutex_lock(&root->fs_info->fs_mutex);
 436         trans = btrfs_start_transaction(root, 1);
 437         if (!trans) {
 438                 err = -ENOMEM;
 439                 mutex_unlock(&root->fs_info->fs_mutex);
 440                 goto out_unlock;
 441         }
 442         btrfs_set_trans_block_group(trans, inode);
 443         /* FIXME blocksize != 4096 */
 444         inode->i_blocks += num_blocks << 3;
 445         hint_block = 0;
 446
 447         /* FIXME...EIEIO, ENOSPC and more */
 448
 449         /* step one, delete the existing extents in this range */
 450         /* FIXME blocksize != pagesize */
 451         if (start_pos < inode->i_size) {
 452                 err = btrfs_drop_extents(trans, root, inode,
 453                          start_pos, (pos + write_bytes + root->blocksize -1) &
 454                          ~((u64)root->blocksize - 1), &hint_block);
 455                 BUG_ON(err);
 456         }
 457
 458         /* insert any holes we need to create */
 459         if (inode->i_size < start_pos) {
 460                 u64 last_pos_in_file;
 461                 u64 hole_size;
 462                 u64 mask = root->blocksize - 1;
 463                 last_pos_in_file = (isize + mask) & ~mask;
 464                 hole_size = (start_pos - last_pos_in_file + mask) & ~mask;
 465                 hole_size >>= inode->i_blkbits;
 466                 if (last_pos_in_file < start_pos) {
 467                         err = btrfs_insert_file_extent(trans, root,
 468                                                        inode->i_ino,
 469                                                        last_pos_in_file,
 470                                                        0, 0, hole_size);
 471                 }
 472                 BUG_ON(err);
 473         }
 474
 475         /*
 476          * either allocate an extent for the new bytes or setup the key
 477          * to show we are doing inline data in the extent
 478          */
 479         if (isize >= PAGE_CACHE_SIZE || pos + write_bytes < inode->i_size ||
 480             pos + write_bytes - start_pos > BTRFS_MAX_INLINE_DATA_SIZE(root)) {
 481                 err = btrfs_alloc_extent(trans, root, inode->i_ino,
 482                                          num_blocks, hint_block, (u64)-1,
 483                                          &ins, 1);
 484                 BUG_ON(err);
 485                 err = btrfs_insert_file_extent(trans, root, inode->i_ino,
 486                                        start_pos, ins.objectid, ins.offset,
 487                                        ins.offset);
 488                 BUG_ON(err);
 489         } else {
 490                 ins.offset = 0;
 491                 ins.objectid = 0;
 492         }
 493         BUG_ON(err);
 494         alloc_extent_start = ins.objectid;
 495         err = btrfs_end_transaction(trans, root);
 496         mutex_unlock(&root->fs_info->fs_mutex);
 497
 498         for (i = 0; i < num_pages; i++) {
 499                 cancel_dirty_page(pages[i], PAGE_CACHE_SIZE);
 500                 wait_on_page_writeback(pages[i]);
 501                 offset = pos & (PAGE_CACHE_SIZE -1);
 502                 this_write = min((size_t)PAGE_CACHE_SIZE - offset, write_bytes);
 503                 if (!page_has_buffers(pages[i])) {
 504                         create_empty_buffers(pages[i],
 505                                              root->fs_info->sb->s_blocksize,
 506                                              (1 << BH_Uptodate));
 507                 }
 508                 head = page_buffers(pages[i]);
 509                 bh = head;
 510                 do {
 511                         err = btrfs_map_bh_to_logical(root, bh,
 512                                                       alloc_extent_start);
 513                         BUG_ON(err);
 514                         if (err)
 515                                 goto failed_truncate;
 516                         bh = bh->b_this_page;
 517                         if (alloc_extent_start)
 518                                 alloc_extent_start++;
 519                 } while (bh != head);
 520                 pos += this_write;
 521                 WARN_ON(this_write > write_bytes);
 522                 write_bytes -= this_write;
 523         }
 524         return 0;
 525
 526 failed_release:
 527         btrfs_drop_pages(pages, num_pages);
 528         return err;
 529
 530 failed_truncate:
 531         btrfs_drop_pages(pages, num_pages);
 532         if (pos > isize)
 533                 vmtruncate(inode, isize);
 534         return err;
 535
 536 out_unlock:
 537         mutex_unlock(&root->fs_info->fs_mutex);
 538         goto failed_release;
 539
 540 }
 541
 542 static ssize_t btrfs_file_write(struct file *file, const char __user *buf,
 543                                 size_t count, loff_t *ppos)
 544 {
 545         loff_t pos;
 546         size_t num_written = 0;
 547         int err = 0;
 548         int ret = 0;
 549         struct inode *inode = file->f_path.dentry->d_inode;
 550         struct btrfs_root *root = BTRFS_I(inode)->root;
 551         struct page **pages = NULL;
 552         int nrptrs;
 553         struct page *pinned[2];
 554         unsigned long first_index;
 555         unsigned long last_index;
 556
 557         nrptrs = min((count + PAGE_CACHE_SIZE - 1) / PAGE_CACHE_SIZE,
 558                      PAGE_CACHE_SIZE / (sizeof(struct page *)));
 559         pinned[0] = NULL;
 560         pinned[1] = NULL;
 561         if (file->f_flags & O_DIRECT)
 562                 return -EINVAL;
 563         pos = *ppos;
 564         vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE);
 565         current->backing_dev_info = inode->i_mapping->backing_dev_info;
 566         err = generic_write_checks(file, &pos, &count, S_ISBLK(inode->i_mode));
 567         if (err)
 568                 goto out;
 569         if (count == 0)
 570                 goto out;
 571         err = remove_suid(file->f_path.dentry);
 572         if (err)
 573                 goto out;
 574         file_update_time(file);
 575
 576         pages = kmalloc(nrptrs * sizeof(struct page *), GFP_KERNEL);
 577
 578         mutex_lock(&inode->i_mutex);
 579         first_index = pos >> PAGE_CACHE_SHIFT;
 580         last_index = (pos + count) >> PAGE_CACHE_SHIFT;
 581
 582         /*
 583          * there are lots of better ways to do this, but this code
 584          * makes sure the first and last page in the file range are
 585          * up to date and ready for cow
 586          */
 587         if ((pos & (PAGE_CACHE_SIZE - 1))) {
 588                 pinned[0] = grab_cache_page(inode->i_mapping, first_index);
 589                 if (!PageUptodate(pinned[0])) {
 590                         ret = btrfs_readpage(NULL, pinned[0]);
 591                         BUG_ON(ret);
 592                         wait_on_page_locked(pinned[0]);
 593                 } else {
 594                         unlock_page(pinned[0]);
 595                 }
 596         }
 597         if ((pos + count) & (PAGE_CACHE_SIZE - 1)) {
 598                 pinned[1] = grab_cache_page(inode->i_mapping, last_index);
 599                 if (!PageUptodate(pinned[1])) {
 600                         ret = btrfs_readpage(NULL, pinned[1]);
 601                         BUG_ON(ret);
 602                         wait_on_page_locked(pinned[1]);
 603                 } else {
 604                         unlock_page(pinned[1]);
 605                 }
 606         }
 607
 608         while(count > 0) {
 609                 size_t offset = pos & (PAGE_CACHE_SIZE - 1);
 610                 size_t write_bytes = min(count, nrptrs *
 611                                         (size_t)PAGE_CACHE_SIZE -
 612                                          offset);
 613                 size_t num_pages = (write_bytes + PAGE_CACHE_SIZE - 1) >>
 614                                         PAGE_CACHE_SHIFT;
 615
 616                 WARN_ON(num_pages > nrptrs);
 617                 memset(pages, 0, sizeof(pages));
 618                 ret = prepare_pages(root, file, pages, num_pages,
 619                                     pos, first_index, last_index,
 620                                     write_bytes);
 621                 BUG_ON(ret);
 622
 623                 ret = btrfs_copy_from_user(pos, num_pages,
 624                                            write_bytes, pages, buf);
 625                 BUG_ON(ret);
 626
 627                 ret = dirty_and_release_pages(NULL, root, file, pages,
 628                                               num_pages, pos, write_bytes);
 629                 BUG_ON(ret);
 630                 btrfs_drop_pages(pages, num_pages);
 631
 632                 buf += write_bytes;
 633                 count -= write_bytes;
 634                 pos += write_bytes;
 635                 num_written += write_bytes;
 636
 637                 balance_dirty_pages_ratelimited_nr(inode->i_mapping, num_pages);
 638                 btrfs_btree_balance_dirty(root);
 639                 cond_resched();
 640         }
 641         mutex_unlock(&inode->i_mutex);
 642 out:
 643         kfree(pages);
 644         if (pinned[0])
 645                 page_cache_release(pinned[0]);
 646         if (pinned[1])
 647                 page_cache_release(pinned[1]);
 648         *ppos = pos;
 649         current->backing_dev_info = NULL;
 650         mark_inode_dirty(inode);
 651         return num_written ? num_written : err;
 652 }
 653
 654 static int btrfs_sync_file(struct file *file,
 655                            struct dentry *dentry, int datasync)
 656 {
 657         struct inode *inode = dentry->d_inode;
 658         struct btrfs_root *root = BTRFS_I(inode)->root;
 659         int ret;
 660         struct btrfs_trans_handle *trans;
 661
 662         /*
 663          * FIXME, use inode generation number to check if we can skip the
 664          * commit
 665          */
 666         mutex_lock(&root->fs_info->fs_mutex);
 667         trans = btrfs_start_transaction(root, 1);
 668         if (!trans) {
 669                 ret = -ENOMEM;
 670                 goto out;
 671         }
 672         ret = btrfs_commit_transaction(trans, root);
 673         mutex_unlock(&root->fs_info->fs_mutex);
 674 out:
 675         return ret > 0 ? EIO : ret;
 676 }
 677
 678 static struct vm_operations_struct btrfs_file_vm_ops = {
 679         .nopage         = filemap_nopage,
 680         .populate       = filemap_populate,
 681         .page_mkwrite   = btrfs_page_mkwrite,
 682 };
 683
 684 static int btrfs_file_mmap(struct file  *filp, struct vm_area_struct *vma)
 685 {
 686         vma->vm_ops = &btrfs_file_vm_ops;
 687         file_accessed(filp);
 688         return 0;
 689 }
 690
 691 struct file_operations btrfs_file_operations = {
 692         .llseek         = generic_file_llseek,
 693         .read           = do_sync_read,
 694         .aio_read       = generic_file_aio_read,
 695         .write          = btrfs_file_write,
 696         .mmap           = btrfs_file_mmap,
 697         .open           = generic_file_open,
 698         .ioctl          = btrfs_ioctl,
 699         .fsync          = btrfs_sync_file,
 700 #ifdef CONFIG_COMPAT
 701         .compat_ioctl   = btrfs_compat_ioctl,
 702 #endif
 703 };
 704