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 = cno + NILFS_MDT(cpfile)->mi_first_entry_offset - 1;
  44         do_div(tcno, nilfs_cpfile_checkpoints_per_block(cpfile));
  45         return (unsigned long)tcno;
  46 }
  47
  48 /* offset in block */
  49 static unsigned long
  50 nilfs_cpfile_get_offset(const struct inode *cpfile, __u64 cno)
  51 {
  52         __u64 tcno = cno + NILFS_MDT(cpfile)->mi_first_entry_offset - 1;
  53         return do_div(tcno, nilfs_cpfile_checkpoints_per_block(cpfile));
  54 }
  55
  56 static unsigned long
  57 nilfs_cpfile_checkpoints_in_block(const struct inode *cpfile,
  58                                   __u64 curr,
  59                                   __u64 max)
  60 {
  61         return min_t(__u64,
  62                      nilfs_cpfile_checkpoints_per_block(cpfile) -
  63                      nilfs_cpfile_get_offset(cpfile, curr),
  64                      max - curr);
  65 }
  66
  67 static inline int nilfs_cpfile_is_in_first(const struct inode *cpfile,
  68                                            __u64 cno)
  69 {
  70         return nilfs_cpfile_get_blkoff(cpfile, cno) == 0;
  71 }
  72
  73 static unsigned int
  74 nilfs_cpfile_block_add_valid_checkpoints(const struct inode *cpfile,
  75                                          struct buffer_head *bh,
  76                                          void *kaddr,
  77                                          unsigned int n)
  78 {
  79         struct nilfs_checkpoint *cp = kaddr + bh_offset(bh);
  80         unsigned int count;
  81
  82         count = le32_to_cpu(cp->cp_checkpoints_count) + n;
  83         cp->cp_checkpoints_count = cpu_to_le32(count);
  84         return count;
  85 }
  86
  87 static unsigned int
  88 nilfs_cpfile_block_sub_valid_checkpoints(const struct inode *cpfile,
  89                                          struct buffer_head *bh,
  90                                          void *kaddr,
  91                                          unsigned int n)
  92 {
  93         struct nilfs_checkpoint *cp = kaddr + bh_offset(bh);
  94         unsigned int count;
  95
  96         WARN_ON(le32_to_cpu(cp->cp_checkpoints_count) < n);
  97         count = le32_to_cpu(cp->cp_checkpoints_count) - n;
  98         cp->cp_checkpoints_count = cpu_to_le32(count);
  99         return count;
 100 }
 101
 102 static inline struct nilfs_cpfile_header *
 103 nilfs_cpfile_block_get_header(const struct inode *cpfile,
 104                               struct buffer_head *bh,
 105                               void *kaddr)
 106 {
 107         return kaddr + bh_offset(bh);
 108 }
 109
 110 static struct nilfs_checkpoint *
 111 nilfs_cpfile_block_get_checkpoint(const struct inode *cpfile, __u64 cno,
 112                                   struct buffer_head *bh,
 113                                   void *kaddr)
 114 {
 115         return kaddr + bh_offset(bh) + nilfs_cpfile_get_offset(cpfile, cno) *
 116                 NILFS_MDT(cpfile)->mi_entry_size;
 117 }
 118
 119 static void nilfs_cpfile_block_init(struct inode *cpfile,
 120                                     struct buffer_head *bh,
 121                                     void *kaddr)
 122 {
 123         struct nilfs_checkpoint *cp = kaddr + bh_offset(bh);
 124         size_t cpsz = NILFS_MDT(cpfile)->mi_entry_size;
 125         int n = nilfs_cpfile_checkpoints_per_block(cpfile);
 126
 127         while (n-- > 0) {
 128                 nilfs_checkpoint_set_invalid(cp);
 129                 cp = (void *)cp + cpsz;
 130         }
 131 }
 132
 133 static inline int nilfs_cpfile_get_header_block(struct inode *cpfile,
 134                                                 struct buffer_head **bhp)
 135 {
 136         return nilfs_mdt_get_block(cpfile, 0, 0, NULL, bhp);
 137 }
 138
 139 static inline int nilfs_cpfile_get_checkpoint_block(struct inode *cpfile,
 140                                                     __u64 cno,
 141                                                     int create,
 142                                                     struct buffer_head **bhp)
 143 {
 144         return nilfs_mdt_get_block(cpfile,
 145                                    nilfs_cpfile_get_blkoff(cpfile, cno),
 146                                    create, nilfs_cpfile_block_init, bhp);
 147 }
 148
 149 static inline int nilfs_cpfile_delete_checkpoint_block(struct inode *cpfile,
 150                                                        __u64 cno)
 151 {
 152         return nilfs_mdt_delete_block(cpfile,
 153                                       nilfs_cpfile_get_blkoff(cpfile, cno));
 154 }
 155
 156 /**
 157  * nilfs_cpfile_get_checkpoint - get a checkpoint
 158  * @cpfile: inode of checkpoint file
 159  * @cno: checkpoint number
 160  * @create: create flag
 161  * @cpp: pointer to a checkpoint
 162  * @bhp: pointer to a buffer head
 163  *
 164  * Description: nilfs_cpfile_get_checkpoint() acquires the checkpoint
 165  * specified by @cno. A new checkpoint will be created if @cno is the current
 166  * checkpoint number and @create is nonzero.
 167  *
 168  * Return Value: On success, 0 is returned, and the checkpoint and the
 169  * buffer head of the buffer on which the checkpoint is located are stored in
 170  * the place pointed by @cpp and @bhp, respectively. On error, one of the
 171  * following negative error codes is returned.
 172  *
 173  * %-EIO - I/O error.
 174  *
 175  * %-ENOMEM - Insufficient amount of memory available.
 176  *
 177  * %-ENOENT - No such checkpoint.
 178  *
 179  * %-EINVAL - invalid checkpoint.
 180  */
 181 int nilfs_cpfile_get_checkpoint(struct inode *cpfile,
 182                                 __u64 cno,
 183                                 int create,
 184                                 struct nilfs_checkpoint **cpp,
 185                                 struct buffer_head **bhp)
 186 {
 187         struct buffer_head *header_bh, *cp_bh;
 188         struct nilfs_cpfile_header *header;
 189         struct nilfs_checkpoint *cp;
 190         void *kaddr;
 191         int ret;
 192
 193         if (unlikely(cno < 1 || cno > nilfs_mdt_cno(cpfile) ||
 194                      (cno < nilfs_mdt_cno(cpfile) && create)))
 195                 return -EINVAL;
 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 (unlikely(start == 0 || start > end)) {
 292                 printk(KERN_ERR "%s: invalid range of checkpoint numbers: "
 293                        "[%llu, %llu)\n", __func__,
 294                        (unsigned long long)start, (unsigned long long)end);
 295                 return -EINVAL;
 296         }
 297
 298         /* cannot delete the latest checkpoint */
 299         if (start == nilfs_mdt_cno(cpfile) - 1)
 300                 return -EPERM;
 301
 302         down_write(&NILFS_MDT(cpfile)->mi_sem);
 303
 304         ret = nilfs_cpfile_get_header_block(cpfile, &header_bh);
 305         if (ret < 0)
 306                 goto out_sem;
 307         tnicps = 0;
 308
 309         for (cno = start; cno < end; cno += ncps) {
 310                 ncps = nilfs_cpfile_checkpoints_in_block(cpfile, cno, end);
 311                 ret = nilfs_cpfile_get_checkpoint_block(cpfile, cno, 0, &cp_bh);
 312                 if (ret < 0) {
 313                         if (ret != -ENOENT)
 314                                 goto out_sem;
 315                         /* skip hole */
 316                         ret = 0;
 317                         continue;
 318                 }
 319
 320                 kaddr = kmap_atomic(cp_bh->b_page, KM_USER0);
 321                 cp = nilfs_cpfile_block_get_checkpoint(
 322                         cpfile, cno, cp_bh, kaddr);
 323                 nicps = 0;
 324                 for (i = 0; i < ncps; i++, cp = (void *)cp + cpsz) {
 325                         WARN_ON(nilfs_checkpoint_snapshot(cp));
 326                         if (!nilfs_checkpoint_invalid(cp)) {
 327                                 nilfs_checkpoint_set_invalid(cp);
 328                                 nicps++;
 329                         }
 330                 }
 331                 if (nicps > 0) {
 332                         tnicps += nicps;
 333                         nilfs_mdt_mark_buffer_dirty(cp_bh);
 334                         nilfs_mdt_mark_dirty(cpfile);
 335                         if (!nilfs_cpfile_is_in_first(cpfile, cno) &&
 336                             (count = nilfs_cpfile_block_sub_valid_checkpoints(
 337                                     cpfile, cp_bh, kaddr, nicps)) == 0) {
 338                                 /* make hole */
 339                                 kunmap_atomic(kaddr, KM_USER0);
 340                                 brelse(cp_bh);
 341                                 ret = nilfs_cpfile_delete_checkpoint_block(
 342                                         cpfile, cno);
 343                                 if (ret == 0)
 344                                         continue;
 345                                 printk(KERN_ERR "%s: cannot delete block\n",
 346                                        __func__);
 347                                 goto out_sem;
 348                         }
 349                 }
 350
 351                 kunmap_atomic(kaddr, KM_USER0);
 352                 brelse(cp_bh);
 353         }
 354
 355         if (tnicps > 0) {
 356                 kaddr = kmap_atomic(header_bh->b_page, KM_USER0);
 357                 header = nilfs_cpfile_block_get_header(cpfile, header_bh,
 358                                                        kaddr);
 359                 le64_add_cpu(&header->ch_ncheckpoints, -(u64)tnicps);
 360                 nilfs_mdt_mark_buffer_dirty(header_bh);
 361                 nilfs_mdt_mark_dirty(cpfile);
 362                 kunmap_atomic(kaddr, KM_USER0);
 363         }
 364         brelse(header_bh);
 365
 366  out_sem:
 367         up_write(&NILFS_MDT(cpfile)->mi_sem);
 368         return ret;
 369 }
 370
 371 static void nilfs_cpfile_checkpoint_to_cpinfo(struct inode *cpfile,
 372                                               struct nilfs_checkpoint *cp,
 373                                               struct nilfs_cpinfo *ci)
 374 {
 375         ci->ci_flags = le32_to_cpu(cp->cp_flags);
 376         ci->ci_cno = le64_to_cpu(cp->cp_cno);
 377         ci->ci_create = le64_to_cpu(cp->cp_create);
 378         ci->ci_nblk_inc = le64_to_cpu(cp->cp_nblk_inc);
 379         ci->ci_inodes_count = le64_to_cpu(cp->cp_inodes_count);
 380         ci->ci_blocks_count = le64_to_cpu(cp->cp_blocks_count);
 381         ci->ci_next = le64_to_cpu(cp->cp_snapshot_list.ssl_next);
 382 }
 383
 384 static ssize_t nilfs_cpfile_do_get_cpinfo(struct inode *cpfile, __u64 *cnop,
 385                                           struct nilfs_cpinfo *ci, size_t nci)
 386 {
 387         struct nilfs_checkpoint *cp;
 388         struct buffer_head *bh;
 389         size_t cpsz = NILFS_MDT(cpfile)->mi_entry_size;
 390         __u64 cur_cno = nilfs_mdt_cno(cpfile), cno = *cnop;
 391         void *kaddr;
 392         int n, ret;
 393         int ncps, i;
 394
 395         if (cno == 0)
 396                 return -ENOENT; /* checkpoint number 0 is invalid */
 397         down_read(&NILFS_MDT(cpfile)->mi_sem);
 398
 399         for (n = 0; cno < cur_cno && n < nci; cno += ncps) {
 400                 ncps = nilfs_cpfile_checkpoints_in_block(cpfile, cno, cur_cno);
 401                 ret = nilfs_cpfile_get_checkpoint_block(cpfile, cno, 0, &bh);
 402                 if (ret < 0) {
 403                         if (ret != -ENOENT)
 404                                 goto out;
 405                         continue; /* skip hole */
 406                 }
 407
 408                 kaddr = kmap_atomic(bh->b_page, KM_USER0);
 409                 cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, bh, kaddr);
 410                 for (i = 0; i < ncps && n < nci; i++, cp = (void *)cp + cpsz) {
 411                         if (!nilfs_checkpoint_invalid(cp))
 412                                 nilfs_cpfile_checkpoint_to_cpinfo(
 413                                         cpfile, cp, &ci[n++]);
 414                 }
 415                 kunmap_atomic(kaddr, KM_USER0);
 416                 brelse(bh);
 417         }
 418
 419         ret = n;
 420         if (n > 0)
 421                 *cnop = ci[n - 1].ci_cno + 1;
 422
 423  out:
 424         up_read(&NILFS_MDT(cpfile)->mi_sem);
 425         return ret;
 426 }
 427
 428 static ssize_t nilfs_cpfile_do_get_ssinfo(struct inode *cpfile, __u64 *cnop,
 429                                           struct nilfs_cpinfo *ci, size_t nci)
 430 {
 431         struct buffer_head *bh;
 432         struct nilfs_cpfile_header *header;
 433         struct nilfs_checkpoint *cp;
 434         __u64 curr = *cnop, next;
 435         unsigned long curr_blkoff, next_blkoff;
 436         void *kaddr;
 437         int n = 0, ret;
 438
 439         down_read(&NILFS_MDT(cpfile)->mi_sem);
 440
 441         if (curr == 0) {
 442                 ret = nilfs_cpfile_get_header_block(cpfile, &bh);
 443                 if (ret < 0)
 444                         goto out;
 445                 kaddr = kmap_atomic(bh->b_page, KM_USER0);
 446                 header = nilfs_cpfile_block_get_header(cpfile, bh, kaddr);
 447                 curr = le64_to_cpu(header->ch_snapshot_list.ssl_next);
 448                 kunmap_atomic(kaddr, KM_USER0);
 449                 brelse(bh);
 450                 if (curr == 0) {
 451                         ret = 0;
 452                         goto out;
 453                 }
 454         } else if (unlikely(curr == ~(__u64)0)) {
 455                 ret = 0;
 456                 goto out;
 457         }
 458
 459         curr_blkoff = nilfs_cpfile_get_blkoff(cpfile, curr);
 460         ret = nilfs_cpfile_get_checkpoint_block(cpfile, curr, 0, &bh);
 461         if (unlikely(ret < 0)) {
 462                 if (ret == -ENOENT)
 463                         ret = 0; /* No snapshots (started from a hole block) */
 464                 goto out;
 465         }
 466         kaddr = kmap_atomic(bh->b_page, KM_USER0);
 467         while (n < nci) {
 468                 cp = nilfs_cpfile_block_get_checkpoint(cpfile, curr, bh, kaddr);
 469                 curr = ~(__u64)0; /* Terminator */
 470                 if (unlikely(nilfs_checkpoint_invalid(cp) ||
 471                              !nilfs_checkpoint_snapshot(cp)))
 472                         break;
 473                 nilfs_cpfile_checkpoint_to_cpinfo(cpfile, cp, &ci[n++]);
 474                 next = le64_to_cpu(cp->cp_snapshot_list.ssl_next);
 475                 if (next == 0)
 476                         break; /* reach end of the snapshot list */
 477
 478                 next_blkoff = nilfs_cpfile_get_blkoff(cpfile, next);
 479                 if (curr_blkoff != next_blkoff) {
 480                         kunmap_atomic(kaddr, KM_USER0);
 481                         brelse(bh);
 482                         ret = nilfs_cpfile_get_checkpoint_block(cpfile, next,
 483                                                                 0, &bh);
 484                         if (unlikely(ret < 0)) {
 485                                 WARN_ON(ret == -ENOENT);
 486                                 goto out;
 487                         }
 488                         kaddr = kmap_atomic(bh->b_page, KM_USER0);
 489                 }
 490                 curr = next;
 491                 curr_blkoff = next_blkoff;
 492         }
 493         kunmap_atomic(kaddr, KM_USER0);
 494         brelse(bh);
 495         *cnop = curr;
 496         ret = n;
 497
 498  out:
 499         up_read(&NILFS_MDT(cpfile)->mi_sem);
 500         return ret;
 501 }
 502
 503 /**
 504  * nilfs_cpfile_get_cpinfo -
 505  * @cpfile:
 506  * @cno:
 507  * @ci:
 508  * @nci:
 509  */
 510
 511 ssize_t nilfs_cpfile_get_cpinfo(struct inode *cpfile, __u64 *cnop, int mode,
 512                                 struct nilfs_cpinfo *ci, size_t nci)
 513 {
 514         switch (mode) {
 515         case NILFS_CHECKPOINT:
 516                 return nilfs_cpfile_do_get_cpinfo(cpfile, cnop, ci, nci);
 517         case NILFS_SNAPSHOT:
 518                 return nilfs_cpfile_do_get_ssinfo(cpfile, cnop, ci, nci);
 519         default:
 520                 return -EINVAL;
 521         }
 522 }
 523
 524 /**
 525  * nilfs_cpfile_delete_checkpoint -
 526  * @cpfile:
 527  * @cno:
 528  */
 529 int nilfs_cpfile_delete_checkpoint(struct inode *cpfile, __u64 cno)
 530 {
 531         struct nilfs_cpinfo ci;
 532         __u64 tcno = cno;
 533         ssize_t nci;
 534         int ret;
 535
 536         nci = nilfs_cpfile_do_get_cpinfo(cpfile, &tcno, &ci, 1);
 537         if (nci < 0)
 538                 return nci;
 539         else if (nci == 0 || ci.ci_cno != cno)
 540                 return -ENOENT;
 541
 542         /* cannot delete the latest checkpoint nor snapshots */
 543         ret = nilfs_cpinfo_snapshot(&ci);
 544         if (ret < 0)
 545                 return ret;
 546         else if (ret > 0 || cno == nilfs_mdt_cno(cpfile) - 1)
 547                 return -EPERM;
 548
 549         return nilfs_cpfile_delete_checkpoints(cpfile, cno, cno + 1);
 550 }
 551
 552 static struct nilfs_snapshot_list *
 553 nilfs_cpfile_block_get_snapshot_list(const struct inode *cpfile,
 554                                      __u64 cno,
 555                                      struct buffer_head *bh,
 556                                      void *kaddr)
 557 {
 558         struct nilfs_cpfile_header *header;
 559         struct nilfs_checkpoint *cp;
 560         struct nilfs_snapshot_list *list;
 561
 562         if (cno != 0) {
 563                 cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, bh, kaddr);
 564                 list = &cp->cp_snapshot_list;
 565         } else {
 566                 header = nilfs_cpfile_block_get_header(cpfile, bh, kaddr);
 567                 list = &header->ch_snapshot_list;
 568         }
 569         return list;
 570 }
 571
 572 static int nilfs_cpfile_set_snapshot(struct inode *cpfile, __u64 cno)
 573 {
 574         struct buffer_head *header_bh, *curr_bh, *prev_bh, *cp_bh;
 575         struct nilfs_cpfile_header *header;
 576         struct nilfs_checkpoint *cp;
 577         struct nilfs_snapshot_list *list;
 578         __u64 curr, prev;
 579         unsigned long curr_blkoff, prev_blkoff;
 580         void *kaddr;
 581         int ret;
 582
 583         if (cno == 0)
 584                 return -ENOENT; /* checkpoint number 0 is invalid */
 585         down_write(&NILFS_MDT(cpfile)->mi_sem);
 586
 587         ret = nilfs_cpfile_get_checkpoint_block(cpfile, cno, 0, &cp_bh);
 588         if (ret < 0)
 589                 goto out_sem;
 590         kaddr = kmap_atomic(cp_bh->b_page, KM_USER0);
 591         cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, cp_bh, kaddr);
 592         if (nilfs_checkpoint_invalid(cp)) {
 593                 ret = -ENOENT;
 594                 kunmap_atomic(kaddr, KM_USER0);
 595                 goto out_cp;
 596         }
 597         if (nilfs_checkpoint_snapshot(cp)) {
 598                 ret = 0;
 599                 kunmap_atomic(kaddr, KM_USER0);
 600                 goto out_cp;
 601         }
 602         kunmap_atomic(kaddr, KM_USER0);
 603
 604         ret = nilfs_cpfile_get_header_block(cpfile, &header_bh);
 605         if (ret < 0)
 606                 goto out_cp;
 607         kaddr = kmap_atomic(header_bh->b_page, KM_USER0);
 608         header = nilfs_cpfile_block_get_header(cpfile, header_bh, kaddr);
 609         list = &header->ch_snapshot_list;
 610         curr_bh = header_bh;
 611         get_bh(curr_bh);
 612         curr = 0;
 613         curr_blkoff = 0;
 614         prev = le64_to_cpu(list->ssl_prev);
 615         while (prev > cno) {
 616                 prev_blkoff = nilfs_cpfile_get_blkoff(cpfile, prev);
 617                 curr = prev;
 618                 if (curr_blkoff != prev_blkoff) {
 619                         kunmap_atomic(kaddr, KM_USER0);
 620                         brelse(curr_bh);
 621                         ret = nilfs_cpfile_get_checkpoint_block(cpfile, curr,
 622                                                                 0, &curr_bh);
 623                         if (ret < 0)
 624                                 goto out_header;
 625                         kaddr = kmap_atomic(curr_bh->b_page, KM_USER0);
 626                 }
 627                 curr_blkoff = prev_blkoff;
 628                 cp = nilfs_cpfile_block_get_checkpoint(
 629                         cpfile, curr, curr_bh, kaddr);
 630                 list = &cp->cp_snapshot_list;
 631                 prev = le64_to_cpu(list->ssl_prev);
 632         }
 633         kunmap_atomic(kaddr, KM_USER0);
 634
 635         if (prev != 0) {
 636                 ret = nilfs_cpfile_get_checkpoint_block(cpfile, prev, 0,
 637                                                         &prev_bh);
 638                 if (ret < 0)
 639                         goto out_curr;
 640         } else {
 641                 prev_bh = header_bh;
 642                 get_bh(prev_bh);
 643         }
 644
 645         kaddr = kmap_atomic(curr_bh->b_page, KM_USER0);
 646         list = nilfs_cpfile_block_get_snapshot_list(
 647                 cpfile, curr, curr_bh, kaddr);
 648         list->ssl_prev = cpu_to_le64(cno);
 649         kunmap_atomic(kaddr, KM_USER0);
 650
 651         kaddr = kmap_atomic(cp_bh->b_page, KM_USER0);
 652         cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, cp_bh, kaddr);
 653         cp->cp_snapshot_list.ssl_next = cpu_to_le64(curr);
 654         cp->cp_snapshot_list.ssl_prev = cpu_to_le64(prev);
 655         nilfs_checkpoint_set_snapshot(cp);
 656         kunmap_atomic(kaddr, KM_USER0);
 657
 658         kaddr = kmap_atomic(prev_bh->b_page, KM_USER0);
 659         list = nilfs_cpfile_block_get_snapshot_list(
 660                 cpfile, prev, prev_bh, kaddr);
 661         list->ssl_next = cpu_to_le64(cno);
 662         kunmap_atomic(kaddr, KM_USER0);
 663
 664         kaddr = kmap_atomic(header_bh->b_page, KM_USER0);
 665         header = nilfs_cpfile_block_get_header(cpfile, header_bh, kaddr);
 666         le64_add_cpu(&header->ch_nsnapshots, 1);
 667         kunmap_atomic(kaddr, KM_USER0);
 668
 669         nilfs_mdt_mark_buffer_dirty(prev_bh);
 670         nilfs_mdt_mark_buffer_dirty(curr_bh);
 671         nilfs_mdt_mark_buffer_dirty(cp_bh);
 672         nilfs_mdt_mark_buffer_dirty(header_bh);
 673         nilfs_mdt_mark_dirty(cpfile);
 674
 675         brelse(prev_bh);
 676
 677  out_curr:
 678         brelse(curr_bh);
 679
 680  out_header:
 681         brelse(header_bh);
 682
 683  out_cp:
 684         brelse(cp_bh);
 685
 686  out_sem:
 687         up_write(&NILFS_MDT(cpfile)->mi_sem);
 688         return ret;
 689 }
 690
 691 static int nilfs_cpfile_clear_snapshot(struct inode *cpfile, __u64 cno)
 692 {
 693         struct buffer_head *header_bh, *next_bh, *prev_bh, *cp_bh;
 694         struct nilfs_cpfile_header *header;
 695         struct nilfs_checkpoint *cp;
 696         struct nilfs_snapshot_list *list;
 697         __u64 next, prev;
 698         void *kaddr;
 699         int ret;
 700
 701         if (cno == 0)
 702                 return -ENOENT; /* checkpoint number 0 is invalid */
 703         down_write(&NILFS_MDT(cpfile)->mi_sem);
 704
 705         ret = nilfs_cpfile_get_checkpoint_block(cpfile, cno, 0, &cp_bh);
 706         if (ret < 0)
 707                 goto out_sem;
 708         kaddr = kmap_atomic(cp_bh->b_page, KM_USER0);
 709         cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, cp_bh, kaddr);
 710         if (nilfs_checkpoint_invalid(cp)) {
 711                 ret = -ENOENT;
 712                 kunmap_atomic(kaddr, KM_USER0);
 713                 goto out_cp;
 714         }
 715         if (!nilfs_checkpoint_snapshot(cp)) {
 716                 ret = 0;
 717                 kunmap_atomic(kaddr, KM_USER0);
 718                 goto out_cp;
 719         }
 720
 721         list = &cp->cp_snapshot_list;
 722         next = le64_to_cpu(list->ssl_next);
 723         prev = le64_to_cpu(list->ssl_prev);
 724         kunmap_atomic(kaddr, KM_USER0);
 725
 726         ret = nilfs_cpfile_get_header_block(cpfile, &header_bh);
 727         if (ret < 0)
 728                 goto out_cp;
 729         if (next != 0) {
 730                 ret = nilfs_cpfile_get_checkpoint_block(cpfile, next, 0,
 731                                                         &next_bh);
 732                 if (ret < 0)
 733                         goto out_header;
 734         } else {
 735                 next_bh = header_bh;
 736                 get_bh(next_bh);
 737         }
 738         if (prev != 0) {
 739                 ret = nilfs_cpfile_get_checkpoint_block(cpfile, prev, 0,
 740                                                         &prev_bh);
 741                 if (ret < 0)
 742                         goto out_next;
 743         } else {
 744                 prev_bh = header_bh;
 745                 get_bh(prev_bh);
 746         }
 747
 748         kaddr = kmap_atomic(next_bh->b_page, KM_USER0);
 749         list = nilfs_cpfile_block_get_snapshot_list(
 750                 cpfile, next, next_bh, kaddr);
 751         list->ssl_prev = cpu_to_le64(prev);
 752         kunmap_atomic(kaddr, KM_USER0);
 753
 754         kaddr = kmap_atomic(prev_bh->b_page, KM_USER0);
 755         list = nilfs_cpfile_block_get_snapshot_list(
 756                 cpfile, prev, prev_bh, kaddr);
 757         list->ssl_next = cpu_to_le64(next);
 758         kunmap_atomic(kaddr, KM_USER0);
 759
 760         kaddr = kmap_atomic(cp_bh->b_page, KM_USER0);
 761         cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, cp_bh, kaddr);
 762         cp->cp_snapshot_list.ssl_next = cpu_to_le64(0);
 763         cp->cp_snapshot_list.ssl_prev = cpu_to_le64(0);
 764         nilfs_checkpoint_clear_snapshot(cp);
 765         kunmap_atomic(kaddr, KM_USER0);
 766
 767         kaddr = kmap_atomic(header_bh->b_page, KM_USER0);
 768         header = nilfs_cpfile_block_get_header(cpfile, header_bh, kaddr);
 769         le64_add_cpu(&header->ch_nsnapshots, -1);
 770         kunmap_atomic(kaddr, KM_USER0);
 771
 772         nilfs_mdt_mark_buffer_dirty(next_bh);
 773         nilfs_mdt_mark_buffer_dirty(prev_bh);
 774         nilfs_mdt_mark_buffer_dirty(cp_bh);
 775         nilfs_mdt_mark_buffer_dirty(header_bh);
 776         nilfs_mdt_mark_dirty(cpfile);
 777
 778         brelse(prev_bh);
 779
 780  out_next:
 781         brelse(next_bh);
 782
 783  out_header:
 784         brelse(header_bh);
 785
 786  out_cp:
 787         brelse(cp_bh);
 788
 789  out_sem:
 790         up_write(&NILFS_MDT(cpfile)->mi_sem);
 791         return ret;
 792 }
 793
 794 /**
 795  * nilfs_cpfile_is_snapshot -
 796  * @cpfile: inode of checkpoint file
 797  * @cno: checkpoint number
 798  *
 799  * Description:
 800  *
 801  * Return Value: On success, 1 is returned if the checkpoint specified by
 802  * @cno is a snapshot, or 0 if not. On error, one of the following negative
 803  * error codes is returned.
 804  *
 805  * %-EIO - I/O error.
 806  *
 807  * %-ENOMEM - Insufficient amount of memory available.
 808  *
 809  * %-ENOENT - No such checkpoint.
 810  */
 811 int nilfs_cpfile_is_snapshot(struct inode *cpfile, __u64 cno)
 812 {
 813         struct buffer_head *bh;
 814         struct nilfs_checkpoint *cp;
 815         void *kaddr;
 816         int ret;
 817
 818         if (cno == 0)
 819                 return -ENOENT; /* checkpoint number 0 is invalid */
 820         down_read(&NILFS_MDT(cpfile)->mi_sem);
 821
 822         ret = nilfs_cpfile_get_checkpoint_block(cpfile, cno, 0, &bh);
 823         if (ret < 0)
 824                 goto out;
 825         kaddr = kmap_atomic(bh->b_page, KM_USER0);
 826         cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, bh, kaddr);
 827         ret = nilfs_checkpoint_snapshot(cp);
 828         kunmap_atomic(kaddr, KM_USER0);
 829         brelse(bh);
 830
 831  out:
 832         up_read(&NILFS_MDT(cpfile)->mi_sem);
 833         return ret;
 834 }
 835
 836 /**
 837  * nilfs_cpfile_change_cpmode - change checkpoint mode
 838  * @cpfile: inode of checkpoint file
 839  * @cno: checkpoint number
 840  * @status: mode of checkpoint
 841  *
 842  * Description: nilfs_change_cpmode() changes the mode of the checkpoint
 843  * specified by @cno. The mode @mode is NILFS_CHECKPOINT or NILFS_SNAPSHOT.
 844  *
 845  * Return Value: On success, 0 is returned. On error, one of the following
 846  * negative error codes is returned.
 847  *
 848  * %-EIO - I/O error.
 849  *
 850  * %-ENOMEM - Insufficient amount of memory available.
 851  *
 852  * %-ENOENT - No such checkpoint.
 853  */
 854 int nilfs_cpfile_change_cpmode(struct inode *cpfile, __u64 cno, int mode)
 855 {
 856         struct the_nilfs *nilfs;
 857         int ret;
 858
 859         nilfs = NILFS_MDT(cpfile)->mi_nilfs;
 860
 861         switch (mode) {
 862         case NILFS_CHECKPOINT:
 863                 /*
 864                  * Check for protecting existing snapshot mounts:
 865                  * bd_mount_sem is used to make this operation atomic and
 866                  * exclusive with a new mount job.  Though it doesn't cover
 867                  * umount, it's enough for the purpose.
 868                  */
 869                 down(&nilfs->ns_bdev->bd_mount_sem);
 870                 if (nilfs_checkpoint_is_mounted(nilfs, cno, 1)) {
 871                         /* Current implementation does not have to protect
 872                            plain read-only mounts since they are exclusive
 873                            with a read/write mount and are protected from the
 874                            cleaner. */
 875                         ret = -EBUSY;
 876                 } else
 877                         ret = nilfs_cpfile_clear_snapshot(cpfile, cno);
 878                 up(&nilfs->ns_bdev->bd_mount_sem);
 879                 return ret;
 880         case NILFS_SNAPSHOT:
 881                 return nilfs_cpfile_set_snapshot(cpfile, cno);
 882         default:
 883                 return -EINVAL;
 884         }
 885 }
 886
 887 /**
 888  * nilfs_cpfile_get_stat - get checkpoint statistics
 889  * @cpfile: inode of checkpoint file
 890  * @stat: pointer to a structure of checkpoint statistics
 891  *
 892  * Description: nilfs_cpfile_get_stat() returns information about checkpoints.
 893  *
 894  * Return Value: On success, 0 is returned, and checkpoints information is
 895  * stored in the place pointed by @stat. On error, one of the following
 896  * negative error codes is returned.
 897  *
 898  * %-EIO - I/O error.
 899  *
 900  * %-ENOMEM - Insufficient amount of memory available.
 901  */
 902 int nilfs_cpfile_get_stat(struct inode *cpfile, struct nilfs_cpstat *cpstat)
 903 {
 904         struct buffer_head *bh;
 905         struct nilfs_cpfile_header *header;
 906         void *kaddr;
 907         int ret;
 908
 909         down_read(&NILFS_MDT(cpfile)->mi_sem);
 910
 911         ret = nilfs_cpfile_get_header_block(cpfile, &bh);
 912         if (ret < 0)
 913                 goto out_sem;
 914         kaddr = kmap_atomic(bh->b_page, KM_USER0);
 915         header = nilfs_cpfile_block_get_header(cpfile, bh, kaddr);
 916         cpstat->cs_cno = nilfs_mdt_cno(cpfile);
 917         cpstat->cs_ncps = le64_to_cpu(header->ch_ncheckpoints);
 918         cpstat->cs_nsss = le64_to_cpu(header->ch_nsnapshots);
 919         kunmap_atomic(kaddr, KM_USER0);
 920         brelse(bh);
 921
 922  out_sem:
 923         up_read(&NILFS_MDT(cpfile)->mi_sem);
 924         return ret;
 925 }