fs/nilfs2/cpfile.c

   1 /*
   2  * cpfile.c - NILFS checkpoint file.
   3  *
   4  * Copyright (C) 2006-2008 Nippon Telegraph and Telephone Corporation.
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 2 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program; if not, write to the Free Software
  18  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
  19  *
  20  * Written by Koji Sato <koji@osrg.net>.
  21  */
  22
  23 #include <linux/kernel.h>
  24 #include <linux/fs.h>
  25 #include <linux/string.h>
  26 #include <linux/buffer_head.h>
  27 #include <linux/errno.h>
  28 #include <linux/nilfs2_fs.h>
  29 #include "mdt.h"
  30 #include "cpfile.h"
  31
  32
  33 static inline unsigned long
  34 nilfs_cpfile_checkpoints_per_block(const struct inode *cpfile)
  35 {
  36         return NILFS_MDT(cpfile)->mi_entries_per_block;
  37 }
  38
  39 /* block number from the beginning of the file */
  40 static unsigned long
  41 nilfs_cpfile_get_blkoff(const struct inode *cpfile, __u64 cno)
  42 {
  43         __u64 tcno;
  44
  45         BUG_ON(cno == 0); /* checkpoint number 0 is invalid */
  46         tcno = cno + NILFS_MDT(cpfile)->mi_first_entry_offset - 1;
  47         do_div(tcno, nilfs_cpfile_checkpoints_per_block(cpfile));
  48         return (unsigned long)tcno;
  49 }
  50
  51 /* offset in block */
  52 static unsigned long
  53 nilfs_cpfile_get_offset(const struct inode *cpfile, __u64 cno)
  54 {
  55         __u64 tcno = cno + NILFS_MDT(cpfile)->mi_first_entry_offset - 1;
  56         return do_div(tcno, nilfs_cpfile_checkpoints_per_block(cpfile));
  57 }
  58
  59 static unsigned long
  60 nilfs_cpfile_checkpoints_in_block(const struct inode *cpfile,
  61                                   __u64 curr,
  62                                   __u64 max)
  63 {
  64         return min_t(__u64,
  65                      nilfs_cpfile_checkpoints_per_block(cpfile) -
  66                      nilfs_cpfile_get_offset(cpfile, curr),
  67                      max - curr);
  68 }
  69
  70 static inline int nilfs_cpfile_is_in_first(const struct inode *cpfile,
  71                                            __u64 cno)
  72 {
  73         return nilfs_cpfile_get_blkoff(cpfile, cno) == 0;
  74 }
  75
  76 static unsigned int
  77 nilfs_cpfile_block_add_valid_checkpoints(const struct inode *cpfile,
  78                                          struct buffer_head *bh,
  79                                          void *kaddr,
  80                                          unsigned int n)
  81 {
  82         struct nilfs_checkpoint *cp = kaddr + bh_offset(bh);
  83         unsigned int count;
  84
  85         count = le32_to_cpu(cp->cp_checkpoints_count) + n;
  86         cp->cp_checkpoints_count = cpu_to_le32(count);
  87         return count;
  88 }
  89
  90 static unsigned int
  91 nilfs_cpfile_block_sub_valid_checkpoints(const struct inode *cpfile,
  92                                          struct buffer_head *bh,
  93                                          void *kaddr,
  94                                          unsigned int n)
  95 {
  96         struct nilfs_checkpoint *cp = kaddr + bh_offset(bh);
  97         unsigned int count;
  98
  99         BUG_ON(le32_to_cpu(cp->cp_checkpoints_count) < n);
 100         count = le32_to_cpu(cp->cp_checkpoints_count) - n;
 101         cp->cp_checkpoints_count = cpu_to_le32(count);
 102         return count;
 103 }
 104
 105 static inline struct nilfs_cpfile_header *
 106 nilfs_cpfile_block_get_header(const struct inode *cpfile,
 107                               struct buffer_head *bh,
 108                               void *kaddr)
 109 {
 110         return kaddr + bh_offset(bh);
 111 }
 112
 113 static struct nilfs_checkpoint *
 114 nilfs_cpfile_block_get_checkpoint(const struct inode *cpfile, __u64 cno,
 115                                   struct buffer_head *bh,
 116                                   void *kaddr)
 117 {
 118         return kaddr + bh_offset(bh) + nilfs_cpfile_get_offset(cpfile, cno) *
 119                 NILFS_MDT(cpfile)->mi_entry_size;
 120 }
 121
 122 static void nilfs_cpfile_block_init(struct inode *cpfile,
 123                                     struct buffer_head *bh,
 124                                     void *kaddr)
 125 {
 126         struct nilfs_checkpoint *cp = kaddr + bh_offset(bh);
 127         size_t cpsz = NILFS_MDT(cpfile)->mi_entry_size;
 128         int n = nilfs_cpfile_checkpoints_per_block(cpfile);
 129
 130         while (n-- > 0) {
 131                 nilfs_checkpoint_set_invalid(cp);
 132                 cp = (void *)cp + cpsz;
 133         }
 134 }
 135
 136 static inline int nilfs_cpfile_get_header_block(struct inode *cpfile,
 137                                                 struct buffer_head **bhp)
 138 {
 139         return nilfs_mdt_get_block(cpfile, 0, 0, NULL, bhp);
 140 }
 141
 142 static inline int nilfs_cpfile_get_checkpoint_block(struct inode *cpfile,
 143                                                     __u64 cno,
 144                                                     int create,
 145                                                     struct buffer_head **bhp)
 146 {
 147         return nilfs_mdt_get_block(cpfile,
 148                                    nilfs_cpfile_get_blkoff(cpfile, cno),
 149                                    create, nilfs_cpfile_block_init, bhp);
 150 }
 151
 152 static inline int nilfs_cpfile_delete_checkpoint_block(struct inode *cpfile,
 153                                                        __u64 cno)
 154 {
 155         return nilfs_mdt_delete_block(cpfile,
 156                                       nilfs_cpfile_get_blkoff(cpfile, cno));
 157 }
 158
 159 /**
 160  * nilfs_cpfile_get_checkpoint - get a checkpoint
 161  * @cpfile: inode of checkpoint file
 162  * @cno: checkpoint number
 163  * @create: create flag
 164  * @cpp: pointer to a checkpoint
 165  * @bhp: pointer to a buffer head
 166  *
 167  * Description: nilfs_cpfile_get_checkpoint() acquires the checkpoint
 168  * specified by @cno. A new checkpoint will be created if @cno is the current
 169  * checkpoint number and @create is nonzero.
 170  *
 171  * Return Value: On success, 0 is returned, and the checkpoint and the
 172  * buffer head of the buffer on which the checkpoint is located are stored in
 173  * the place pointed by @cpp and @bhp, respectively. On error, one of the
 174  * following negative error codes is returned.
 175  *
 176  * %-EIO - I/O error.
 177  *
 178  * %-ENOMEM - Insufficient amount of memory available.
 179  *
 180  * %-ENOENT - No such checkpoint.
 181  */
 182 int nilfs_cpfile_get_checkpoint(struct inode *cpfile,
 183                                 __u64 cno,
 184                                 int create,
 185                                 struct nilfs_checkpoint **cpp,
 186                                 struct buffer_head **bhp)
 187 {
 188         struct buffer_head *header_bh, *cp_bh;
 189         struct nilfs_cpfile_header *header;
 190         struct nilfs_checkpoint *cp;
 191         void *kaddr;
 192         int ret;
 193
 194         BUG_ON(cno < 1 || cno > nilfs_mdt_cno(cpfile) ||
 195                (cno < nilfs_mdt_cno(cpfile) && create));
 196
 197         down_write(&NILFS_MDT(cpfile)->mi_sem);
 198
 199         ret = nilfs_cpfile_get_header_block(cpfile, &header_bh);
 200         if (ret < 0)
 201                 goto out_sem;
 202         ret = nilfs_cpfile_get_checkpoint_block(cpfile, cno, create, &cp_bh);
 203         if (ret < 0)
 204                 goto out_header;
 205         kaddr = kmap(cp_bh->b_page);
 206         cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, cp_bh, kaddr);
 207         if (nilfs_checkpoint_invalid(cp)) {
 208                 if (!create) {
 209                         kunmap(cp_bh->b_page);
 210                         brelse(cp_bh);
 211                         ret = -ENOENT;
 212                         goto out_header;
 213                 }
 214                 /* a newly-created checkpoint */
 215                 nilfs_checkpoint_clear_invalid(cp);
 216                 if (!nilfs_cpfile_is_in_first(cpfile, cno))
 217                         nilfs_cpfile_block_add_valid_checkpoints(cpfile, cp_bh,
 218                                                                  kaddr, 1);
 219                 nilfs_mdt_mark_buffer_dirty(cp_bh);
 220
 221                 kaddr = kmap_atomic(header_bh->b_page, KM_USER0);
 222                 header = nilfs_cpfile_block_get_header(cpfile, header_bh,
 223                                                        kaddr);
 224                 le64_add_cpu(&header->ch_ncheckpoints, 1);
 225                 kunmap_atomic(kaddr, KM_USER0);
 226                 nilfs_mdt_mark_buffer_dirty(header_bh);
 227                 nilfs_mdt_mark_dirty(cpfile);
 228         }
 229
 230         if (cpp != NULL)
 231                 *cpp = cp;
 232         *bhp = cp_bh;
 233
 234  out_header:
 235         brelse(header_bh);
 236
 237  out_sem:
 238         up_write(&NILFS_MDT(cpfile)->mi_sem);
 239         return ret;
 240 }
 241
 242 /**
 243  * nilfs_cpfile_put_checkpoint - put a checkpoint
 244  * @cpfile: inode of checkpoint file
 245  * @cno: checkpoint number
 246  * @bh: buffer head
 247  *
 248  * Description: nilfs_cpfile_put_checkpoint() releases the checkpoint
 249  * specified by @cno. @bh must be the buffer head which has been returned by
 250  * a previous call to nilfs_cpfile_get_checkpoint() with @cno.
 251  */
 252 void nilfs_cpfile_put_checkpoint(struct inode *cpfile, __u64 cno,
 253                                  struct buffer_head *bh)
 254 {
 255         kunmap(bh->b_page);
 256         brelse(bh);
 257 }
 258
 259 /**
 260  * nilfs_cpfile_delete_checkpoints - delete checkpoints
 261  * @cpfile: inode of checkpoint file
 262  * @start: start checkpoint number
 263  * @end: end checkpoint numer
 264  *
 265  * Description: nilfs_cpfile_delete_checkpoints() deletes the checkpoints in
 266  * the period from @start to @end, excluding @end itself. The checkpoints
 267  * which have been already deleted are ignored.
 268  *
 269  * Return Value: On success, 0 is returned. On error, one of the following
 270  * negative error codes is returned.
 271  *
 272  * %-EIO - I/O error.
 273  *
 274  * %-ENOMEM - Insufficient amount of memory available.
 275  *
 276  * %-EINVAL - invalid checkpoints.
 277  */
 278 int nilfs_cpfile_delete_checkpoints(struct inode *cpfile,
 279                                     __u64 start,
 280                                     __u64 end)
 281 {
 282         struct buffer_head *header_bh, *cp_bh;
 283         struct nilfs_cpfile_header *header;
 284         struct nilfs_checkpoint *cp;
 285         size_t cpsz = NILFS_MDT(cpfile)->mi_entry_size;
 286         __u64 cno;
 287         void *kaddr;
 288         unsigned long tnicps;
 289         int ret, ncps, nicps, count, i;
 290
 291         if ((start == 0) || (start > end)) {
 292                 printk(KERN_CRIT "%s: start = %llu, end = %llu\n",
 293                        __func__,
 294                        (unsigned long long)start,
 295                        (unsigned long long)end);
 296                 BUG();
 297         }
 298
 299         /* cannot delete the latest checkpoint */
 300         if (start == nilfs_mdt_cno(cpfile) - 1)
 301                 return -EPERM;
 302
 303         down_write(&NILFS_MDT(cpfile)->mi_sem);
 304
 305         ret = nilfs_cpfile_get_header_block(cpfile, &header_bh);
 306         if (ret < 0)
 307                 goto out_sem;
 308         tnicps = 0;
 309
 310         for (cno = start; cno < end; cno += ncps) {
 311                 ncps = nilfs_cpfile_checkpoints_in_block(cpfile, cno, end);
 312                 ret = nilfs_cpfile_get_checkpoint_block(cpfile, cno, 0, &cp_bh);
 313                 if (ret < 0) {
 314                         if (ret != -ENOENT)
 315                                 goto out_sem;
 316                         /* skip hole */
 317                         ret = 0;
 318                         continue;
 319                 }
 320
 321                 kaddr = kmap_atomic(cp_bh->b_page, KM_USER0);
 322                 cp = nilfs_cpfile_block_get_checkpoint(
 323                         cpfile, cno, cp_bh, kaddr);
 324                 nicps = 0;
 325                 for (i = 0; i < ncps; i++, cp = (void *)cp + cpsz) {
 326                         BUG_ON(nilfs_checkpoint_snapshot(cp));
 327                         if (!nilfs_checkpoint_invalid(cp)) {
 328                                 nilfs_checkpoint_set_invalid(cp);
 329                                 nicps++;
 330                         }
 331                 }
 332                 if (nicps > 0) {
 333                         tnicps += nicps;
 334                         nilfs_mdt_mark_buffer_dirty(cp_bh);
 335                         nilfs_mdt_mark_dirty(cpfile);
 336                         if (!nilfs_cpfile_is_in_first(cpfile, cno) &&
 337                             (count = nilfs_cpfile_block_sub_valid_checkpoints(
 338                                     cpfile, cp_bh, kaddr, nicps)) == 0) {
 339                                 /* make hole */
 340                                 kunmap_atomic(kaddr, KM_USER0);
 341                                 brelse(cp_bh);
 342                                 ret = nilfs_cpfile_delete_checkpoint_block(
 343                                         cpfile, cno);
 344                                 if (ret == 0)
 345                                         continue;
 346                                 printk(KERN_ERR "%s: cannot delete block\n",
 347                                        __func__);
 348                                 goto out_sem;
 349                         }
 350                 }
 351
 352                 kunmap_atomic(kaddr, KM_USER0);
 353                 brelse(cp_bh);
 354         }
 355
 356         if (tnicps > 0) {
 357                 kaddr = kmap_atomic(header_bh->b_page, KM_USER0);
 358                 header = nilfs_cpfile_block_get_header(cpfile, header_bh,
 359                                                        kaddr);
 360                 le64_add_cpu(&header->ch_ncheckpoints, -(u64)tnicps);
 361                 nilfs_mdt_mark_buffer_dirty(header_bh);
 362                 nilfs_mdt_mark_dirty(cpfile);
 363                 kunmap_atomic(kaddr, KM_USER0);
 364         }
 365         brelse(header_bh);
 366
 367  out_sem:
 368         up_write(&NILFS_MDT(cpfile)->mi_sem);
 369         return ret;
 370 }
 371
 372 static void nilfs_cpfile_checkpoint_to_cpinfo(struct inode *cpfile,
 373                                               struct nilfs_checkpoint *cp,
 374                                               struct nilfs_cpinfo *ci)
 375 {
 376         ci->ci_flags = le32_to_cpu(cp->cp_flags);
 377         ci->ci_cno = le64_to_cpu(cp->cp_cno);
 378         ci->ci_create = le64_to_cpu(cp->cp_create);
 379         ci->ci_nblk_inc = le64_to_cpu(cp->cp_nblk_inc);
 380         ci->ci_inodes_count = le64_to_cpu(cp->cp_inodes_count);
 381         ci->ci_blocks_count = le64_to_cpu(cp->cp_blocks_count);
 382         ci->ci_next = le64_to_cpu(cp->cp_snapshot_list.ssl_next);
 383 }
 384
 385 static ssize_t nilfs_cpfile_do_get_cpinfo(struct inode *cpfile, __u64 cno,
 386                                           struct nilfs_cpinfo *ci, size_t nci)
 387 {
 388         struct nilfs_checkpoint *cp;
 389         struct buffer_head *bh;
 390         size_t cpsz = NILFS_MDT(cpfile)->mi_entry_size;
 391         __u64 cur_cno = nilfs_mdt_cno(cpfile);
 392         void *kaddr;
 393         int n, ret;
 394         int ncps, i;
 395
 396         down_read(&NILFS_MDT(cpfile)->mi_sem);
 397
 398         for (n = 0; cno < cur_cno && n < nci; cno += ncps) {
 399                 ncps = nilfs_cpfile_checkpoints_in_block(cpfile, cno, cur_cno);
 400                 ret = nilfs_cpfile_get_checkpoint_block(cpfile, cno, 0, &bh);
 401                 if (ret < 0) {
 402                         if (ret != -ENOENT)
 403                                 goto out;
 404                         continue; /* skip hole */
 405                 }
 406
 407                 kaddr = kmap_atomic(bh->b_page, KM_USER0);
 408                 cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, bh, kaddr);
 409                 for (i = 0; i < ncps && n < nci; i++, cp = (void *)cp + cpsz) {
 410                         if (!nilfs_checkpoint_invalid(cp))
 411                                 nilfs_cpfile_checkpoint_to_cpinfo(
 412                                         cpfile, cp, &ci[n++]);
 413                 }
 414                 kunmap_atomic(kaddr, KM_USER0);
 415                 brelse(bh);
 416         }
 417
 418         ret = n;
 419
 420  out:
 421         up_read(&NILFS_MDT(cpfile)->mi_sem);
 422         return ret;
 423 }
 424
 425 static ssize_t nilfs_cpfile_do_get_ssinfo(struct inode *cpfile, __u64 cno,
 426                                           struct nilfs_cpinfo *ci, size_t nci)
 427 {
 428         struct buffer_head *bh;
 429         struct nilfs_cpfile_header *header;
 430         struct nilfs_checkpoint *cp;
 431         __u64 curr, next;
 432         unsigned long curr_blkoff, next_blkoff;
 433         void *kaddr;
 434         int n, ret;
 435
 436         down_read(&NILFS_MDT(cpfile)->mi_sem);
 437
 438         if (cno == 0) {
 439                 ret = nilfs_cpfile_get_header_block(cpfile, &bh);
 440                 if (ret < 0)
 441                         goto out;
 442                 kaddr = kmap_atomic(bh->b_page, KM_USER0);
 443                 header = nilfs_cpfile_block_get_header(cpfile, bh, kaddr);
 444                 curr = le64_to_cpu(header->ch_snapshot_list.ssl_next);
 445                 kunmap_atomic(kaddr, KM_USER0);
 446                 brelse(bh);
 447                 if (curr == 0) {
 448                         ret = 0;
 449                         goto out;
 450                 }
 451         } else
 452                 curr = cno;
 453         curr_blkoff = nilfs_cpfile_get_blkoff(cpfile, curr);
 454         ret = nilfs_cpfile_get_checkpoint_block(cpfile, curr, 0, &bh);
 455         if (ret < 0)
 456                 goto out;
 457         kaddr = kmap_atomic(bh->b_page, KM_USER0);
 458         for (n = 0; n < nci; n++) {
 459                 cp = nilfs_cpfile_block_get_checkpoint(
 460                         cpfile, curr, bh, kaddr);
 461                 nilfs_cpfile_checkpoint_to_cpinfo(cpfile, cp, &ci[n]);
 462                 next = le64_to_cpu(cp->cp_snapshot_list.ssl_next);
 463                 if (next == 0) {
 464                         curr = next;
 465                         n++;
 466                         break;
 467                 }
 468                 next_blkoff = nilfs_cpfile_get_blkoff(cpfile, next);
 469                 if (curr_blkoff != next_blkoff) {
 470                         kunmap_atomic(kaddr, KM_USER0);
 471                         brelse(bh);
 472                         ret = nilfs_cpfile_get_checkpoint_block(cpfile, next,
 473                                                                 0, &bh);
 474                         if (ret < 0)
 475                                 goto out;
 476                         kaddr = kmap_atomic(bh->b_page, KM_USER0);
 477                 }
 478                 curr = next;
 479                 curr_blkoff = next_blkoff;
 480         }
 481         kunmap_atomic(kaddr, KM_USER0);
 482         brelse(bh);
 483         ret = n;
 484
 485  out:
 486         up_read(&NILFS_MDT(cpfile)->mi_sem);
 487         return ret;
 488 }
 489
 490 /**
 491  * nilfs_cpfile_get_cpinfo -
 492  * @cpfile:
 493  * @cno:
 494  * @ci:
 495  * @nci:
 496  */
 497 ssize_t nilfs_cpfile_get_cpinfo(struct inode *cpfile,
 498                                 __u64 cno, int mode,
 499                                 struct nilfs_cpinfo *ci, size_t nci)
 500 {
 501         switch (mode) {
 502         case NILFS_CHECKPOINT:
 503                 return nilfs_cpfile_do_get_cpinfo(cpfile, cno, ci, nci);
 504         case NILFS_SNAPSHOT:
 505                 return nilfs_cpfile_do_get_ssinfo(cpfile, cno, ci, nci);
 506         default:
 507                 return -EINVAL;
 508         }
 509 }
 510
 511 /**
 512  * nilfs_cpfile_delete_checkpoint -
 513  * @cpfile:
 514  * @cno:
 515  */
 516 int nilfs_cpfile_delete_checkpoint(struct inode *cpfile, __u64 cno)
 517 {
 518         struct nilfs_cpinfo ci;
 519         ssize_t nci;
 520         int ret;
 521
 522         /* checkpoint number 0 is invalid */
 523         if (cno == 0)
 524                 return -ENOENT;
 525         nci = nilfs_cpfile_do_get_cpinfo(cpfile, cno, &ci, 1);
 526         if (nci < 0)
 527                 return nci;
 528         else if (nci == 0 || ci.ci_cno != cno)
 529                 return -ENOENT;
 530
 531         /* cannot delete the latest checkpoint nor snapshots */
 532         ret = nilfs_cpinfo_snapshot(&ci);
 533         if (ret < 0)
 534                 return ret;
 535         else if (ret > 0 || cno == nilfs_mdt_cno(cpfile) - 1)
 536                 return -EPERM;
 537
 538         return nilfs_cpfile_delete_checkpoints(cpfile, cno, cno + 1);
 539 }
 540
 541 static struct nilfs_snapshot_list *
 542 nilfs_cpfile_block_get_snapshot_list(const struct inode *cpfile,
 543                                      __u64 cno,
 544                                      struct buffer_head *bh,
 545                                      void *kaddr)
 546 {
 547         struct nilfs_cpfile_header *header;
 548         struct nilfs_checkpoint *cp;
 549         struct nilfs_snapshot_list *list;
 550
 551         if (cno != 0) {
 552                 cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, bh, kaddr);
 553                 list = &cp->cp_snapshot_list;
 554         } else {
 555                 header = nilfs_cpfile_block_get_header(cpfile, bh, kaddr);
 556                 list = &header->ch_snapshot_list;
 557         }
 558         return list;
 559 }
 560
 561 static int nilfs_cpfile_set_snapshot(struct inode *cpfile, __u64 cno)
 562 {
 563         struct buffer_head *header_bh, *curr_bh, *prev_bh, *cp_bh;
 564         struct nilfs_cpfile_header *header;
 565         struct nilfs_checkpoint *cp;
 566         struct nilfs_snapshot_list *list;
 567         __u64 curr, prev;
 568         unsigned long curr_blkoff, prev_blkoff;
 569         void *kaddr;
 570         int ret;
 571
 572         down_write(&NILFS_MDT(cpfile)->mi_sem);
 573
 574         ret = nilfs_cpfile_get_checkpoint_block(cpfile, cno, 0, &cp_bh);
 575         if (ret < 0)
 576                 goto out_sem;
 577         kaddr = kmap_atomic(cp_bh->b_page, KM_USER0);
 578         cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, cp_bh, kaddr);
 579         if (nilfs_checkpoint_invalid(cp)) {
 580                 ret = -ENOENT;
 581                 kunmap_atomic(kaddr, KM_USER0);
 582                 goto out_cp;
 583         }
 584         if (nilfs_checkpoint_snapshot(cp)) {
 585                 ret = 0;
 586                 kunmap_atomic(kaddr, KM_USER0);
 587                 goto out_cp;
 588         }
 589         kunmap_atomic(kaddr, KM_USER0);
 590
 591         ret = nilfs_cpfile_get_header_block(cpfile, &header_bh);
 592         if (ret < 0)
 593                 goto out_cp;
 594         kaddr = kmap_atomic(header_bh->b_page, KM_USER0);
 595         header = nilfs_cpfile_block_get_header(cpfile, header_bh, kaddr);
 596         list = &header->ch_snapshot_list;
 597         curr_bh = header_bh;
 598         get_bh(curr_bh);
 599         curr = 0;
 600         curr_blkoff = 0;
 601         prev = le64_to_cpu(list->ssl_prev);
 602         while (prev > cno) {
 603                 prev_blkoff = nilfs_cpfile_get_blkoff(cpfile, prev);
 604                 curr = prev;
 605                 if (curr_blkoff != prev_blkoff) {
 606                         kunmap_atomic(kaddr, KM_USER0);
 607                         brelse(curr_bh);
 608                         ret = nilfs_cpfile_get_checkpoint_block(cpfile, curr,
 609                                                                 0, &curr_bh);
 610                         if (ret < 0)
 611                                 goto out_header;
 612                         kaddr = kmap_atomic(curr_bh->b_page, KM_USER0);
 613                 }
 614                 curr_blkoff = prev_blkoff;
 615                 cp = nilfs_cpfile_block_get_checkpoint(
 616                         cpfile, curr, curr_bh, kaddr);
 617                 list = &cp->cp_snapshot_list;
 618                 prev = le64_to_cpu(list->ssl_prev);
 619         }
 620         kunmap_atomic(kaddr, KM_USER0);
 621
 622         if (prev != 0) {
 623                 ret = nilfs_cpfile_get_checkpoint_block(cpfile, prev, 0,
 624                                                         &prev_bh);
 625                 if (ret < 0)
 626                         goto out_curr;
 627         } else {
 628                 prev_bh = header_bh;
 629                 get_bh(prev_bh);
 630         }
 631
 632         kaddr = kmap_atomic(curr_bh->b_page, KM_USER0);
 633         list = nilfs_cpfile_block_get_snapshot_list(
 634                 cpfile, curr, curr_bh, kaddr);
 635         list->ssl_prev = cpu_to_le64(cno);
 636         kunmap_atomic(kaddr, KM_USER0);
 637
 638         kaddr = kmap_atomic(cp_bh->b_page, KM_USER0);
 639         cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, cp_bh, kaddr);
 640         cp->cp_snapshot_list.ssl_next = cpu_to_le64(curr);
 641         cp->cp_snapshot_list.ssl_prev = cpu_to_le64(prev);
 642         nilfs_checkpoint_set_snapshot(cp);
 643         kunmap_atomic(kaddr, KM_USER0);
 644
 645         kaddr = kmap_atomic(prev_bh->b_page, KM_USER0);
 646         list = nilfs_cpfile_block_get_snapshot_list(
 647                 cpfile, prev, prev_bh, kaddr);
 648         list->ssl_next = cpu_to_le64(cno);
 649         kunmap_atomic(kaddr, KM_USER0);
 650
 651         kaddr = kmap_atomic(header_bh->b_page, KM_USER0);
 652         header = nilfs_cpfile_block_get_header(cpfile, header_bh, kaddr);
 653         le64_add_cpu(&header->ch_nsnapshots, 1);
 654         kunmap_atomic(kaddr, KM_USER0);
 655
 656         nilfs_mdt_mark_buffer_dirty(prev_bh);
 657         nilfs_mdt_mark_buffer_dirty(curr_bh);
 658         nilfs_mdt_mark_buffer_dirty(cp_bh);
 659         nilfs_mdt_mark_buffer_dirty(header_bh);
 660         nilfs_mdt_mark_dirty(cpfile);
 661
 662         brelse(prev_bh);
 663
 664  out_curr:
 665         brelse(curr_bh);
 666
 667  out_header:
 668         brelse(header_bh);
 669
 670  out_cp:
 671         brelse(cp_bh);
 672
 673  out_sem:
 674         up_write(&NILFS_MDT(cpfile)->mi_sem);
 675         return ret;
 676 }
 677
 678 static int nilfs_cpfile_clear_snapshot(struct inode *cpfile, __u64 cno)
 679 {
 680         struct buffer_head *header_bh, *next_bh, *prev_bh, *cp_bh;
 681         struct nilfs_cpfile_header *header;
 682         struct nilfs_checkpoint *cp;
 683         struct nilfs_snapshot_list *list;
 684         __u64 next, prev;
 685         void *kaddr;
 686         int ret;
 687
 688         down_write(&NILFS_MDT(cpfile)->mi_sem);
 689
 690         ret = nilfs_cpfile_get_checkpoint_block(cpfile, cno, 0, &cp_bh);
 691         if (ret < 0)
 692                 goto out_sem;
 693         kaddr = kmap_atomic(cp_bh->b_page, KM_USER0);
 694         cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, cp_bh, kaddr);
 695         if (nilfs_checkpoint_invalid(cp)) {
 696                 ret = -ENOENT;
 697                 kunmap_atomic(kaddr, KM_USER0);
 698                 goto out_cp;
 699         }
 700         if (!nilfs_checkpoint_snapshot(cp)) {
 701                 ret = 0;
 702                 kunmap_atomic(kaddr, KM_USER0);
 703                 goto out_cp;
 704         }
 705
 706         list = &cp->cp_snapshot_list;
 707         next = le64_to_cpu(list->ssl_next);
 708         prev = le64_to_cpu(list->ssl_prev);
 709         kunmap_atomic(kaddr, KM_USER0);
 710
 711         ret = nilfs_cpfile_get_header_block(cpfile, &header_bh);
 712         if (ret < 0)
 713                 goto out_cp;
 714         if (next != 0) {
 715                 ret = nilfs_cpfile_get_checkpoint_block(cpfile, next, 0,
 716                                                         &next_bh);
 717                 if (ret < 0)
 718                         goto out_header;
 719         } else {
 720                 next_bh = header_bh;
 721                 get_bh(next_bh);
 722         }
 723         if (prev != 0) {
 724                 ret = nilfs_cpfile_get_checkpoint_block(cpfile, prev, 0,
 725                                                         &prev_bh);
 726                 if (ret < 0)
 727                         goto out_next;
 728         } else {
 729                 prev_bh = header_bh;
 730                 get_bh(prev_bh);
 731         }
 732
 733         kaddr = kmap_atomic(next_bh->b_page, KM_USER0);
 734         list = nilfs_cpfile_block_get_snapshot_list(
 735                 cpfile, next, next_bh, kaddr);
 736         list->ssl_prev = cpu_to_le64(prev);
 737         kunmap_atomic(kaddr, KM_USER0);
 738
 739         kaddr = kmap_atomic(prev_bh->b_page, KM_USER0);
 740         list = nilfs_cpfile_block_get_snapshot_list(
 741                 cpfile, prev, prev_bh, kaddr);
 742         list->ssl_next = cpu_to_le64(next);
 743         kunmap_atomic(kaddr, KM_USER0);
 744
 745         kaddr = kmap_atomic(cp_bh->b_page, KM_USER0);
 746         cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, cp_bh, kaddr);
 747         cp->cp_snapshot_list.ssl_next = cpu_to_le64(0);
 748         cp->cp_snapshot_list.ssl_prev = cpu_to_le64(0);
 749         nilfs_checkpoint_clear_snapshot(cp);
 750         kunmap_atomic(kaddr, KM_USER0);
 751
 752         kaddr = kmap_atomic(header_bh->b_page, KM_USER0);
 753         header = nilfs_cpfile_block_get_header(cpfile, header_bh, kaddr);
 754         le64_add_cpu(&header->ch_nsnapshots, -1);
 755         kunmap_atomic(kaddr, KM_USER0);
 756
 757         nilfs_mdt_mark_buffer_dirty(next_bh);
 758         nilfs_mdt_mark_buffer_dirty(prev_bh);
 759         nilfs_mdt_mark_buffer_dirty(cp_bh);
 760         nilfs_mdt_mark_buffer_dirty(header_bh);
 761         nilfs_mdt_mark_dirty(cpfile);
 762
 763         brelse(prev_bh);
 764
 765  out_next:
 766         brelse(next_bh);
 767
 768  out_header:
 769         brelse(header_bh);
 770
 771  out_cp:
 772         brelse(cp_bh);
 773
 774  out_sem:
 775         up_write(&NILFS_MDT(cpfile)->mi_sem);
 776         return ret;
 777 }
 778
 779 /**
 780  * nilfs_cpfile_is_snapshot -
 781  * @cpfile: inode of checkpoint file
 782  * @cno: checkpoint number
 783  *
 784  * Description:
 785  *
 786  * Return Value: On success, 1 is returned if the checkpoint specified by
 787  * @cno is a snapshot, or 0 if not. On error, one of the following negative
 788  * error codes is returned.
 789  *
 790  * %-EIO - I/O error.
 791  *
 792  * %-ENOMEM - Insufficient amount of memory available.
 793  *
 794  * %-ENOENT - No such checkpoint.
 795  */
 796 int nilfs_cpfile_is_snapshot(struct inode *cpfile, __u64 cno)
 797 {
 798         struct buffer_head *bh;
 799         struct nilfs_checkpoint *cp;
 800         void *kaddr;
 801         int ret;
 802
 803         down_read(&NILFS_MDT(cpfile)->mi_sem);
 804
 805         ret = nilfs_cpfile_get_checkpoint_block(cpfile, cno, 0, &bh);
 806         if (ret < 0)
 807                 goto out;
 808         kaddr = kmap_atomic(bh->b_page, KM_USER0);
 809         cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, bh, kaddr);
 810         ret = nilfs_checkpoint_snapshot(cp);
 811         kunmap_atomic(kaddr, KM_USER0);
 812         brelse(bh);
 813
 814  out:
 815         up_read(&NILFS_MDT(cpfile)->mi_sem);
 816         return ret;
 817 }
 818
 819 /**
 820  * nilfs_cpfile_change_cpmode - change checkpoint mode
 821  * @cpfile: inode of checkpoint file
 822  * @cno: checkpoint number
 823  * @status: mode of checkpoint
 824  *
 825  * Description: nilfs_change_cpmode() changes the mode of the checkpoint
 826  * specified by @cno. The mode @mode is NILFS_CHECKPOINT or NILFS_SNAPSHOT.
 827  *
 828  * Return Value: On success, 0 is returned. On error, one of the following
 829  * negative error codes is returned.
 830  *
 831  * %-EIO - I/O error.
 832  *
 833  * %-ENOMEM - Insufficient amount of memory available.
 834  *
 835  * %-ENOENT - No such checkpoint.
 836  */
 837 int nilfs_cpfile_change_cpmode(struct inode *cpfile, __u64 cno, int mode)
 838 {
 839         struct the_nilfs *nilfs;
 840         int ret;
 841
 842         nilfs = NILFS_MDT(cpfile)->mi_nilfs;
 843
 844         switch (mode) {
 845         case NILFS_CHECKPOINT:
 846                 /*
 847                  * Check for protecting existing snapshot mounts:
 848                  * bd_mount_sem is used to make this operation atomic and
 849                  * exclusive with a new mount job.  Though it doesn't cover
 850                  * umount, it's enough for the purpose.
 851                  */
 852                 down(&nilfs->ns_bdev->bd_mount_sem);
 853                 if (nilfs_checkpoint_is_mounted(nilfs, cno, 1)) {
 854                         /* Current implementation does not have to protect
 855                            plain read-only mounts since they are exclusive
 856                            with a read/write mount and are protected from the
 857                            cleaner. */
 858                         ret = -EBUSY;
 859                 } else
 860                         ret = nilfs_cpfile_clear_snapshot(cpfile, cno);
 861                 up(&nilfs->ns_bdev->bd_mount_sem);
 862                 return ret;
 863         case NILFS_SNAPSHOT:
 864                 return nilfs_cpfile_set_snapshot(cpfile, cno);
 865         default:
 866                 return -EINVAL;
 867         }
 868 }
 869
 870 /**
 871  * nilfs_cpfile_get_stat - get checkpoint statistics
 872  * @cpfile: inode of checkpoint file
 873  * @stat: pointer to a structure of checkpoint statistics
 874  *
 875  * Description: nilfs_cpfile_get_stat() returns information about checkpoints.
 876  *
 877  * Return Value: On success, 0 is returned, and checkpoints information is
 878  * stored in the place pointed by @stat. On error, one of the following
 879  * negative error codes is returned.
 880  *
 881  * %-EIO - I/O error.
 882  *
 883  * %-ENOMEM - Insufficient amount of memory available.
 884  */
 885 int nilfs_cpfile_get_stat(struct inode *cpfile, struct nilfs_cpstat *cpstat)
 886 {
 887         struct buffer_head *bh;
 888         struct nilfs_cpfile_header *header;
 889         void *kaddr;
 890         int ret;
 891
 892         down_read(&NILFS_MDT(cpfile)->mi_sem);
 893
 894         ret = nilfs_cpfile_get_header_block(cpfile, &bh);
 895         if (ret < 0)
 896                 goto out_sem;
 897         kaddr = kmap_atomic(bh->b_page, KM_USER0);
 898         header = nilfs_cpfile_block_get_header(cpfile, bh, kaddr);
 899         cpstat->cs_cno = nilfs_mdt_cno(cpfile);
 900         cpstat->cs_ncps = le64_to_cpu(header->ch_ncheckpoints);
 901         cpstat->cs_nsss = le64_to_cpu(header->ch_nsnapshots);
 902         kunmap_atomic(kaddr, KM_USER0);
 903         brelse(bh);
 904
 905  out_sem:
 906         up_read(&NILFS_MDT(cpfile)->mi_sem);
 907         return ret;
 908 }