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         down_write(&NILFS_MDT(cpfile)->mi_sem);
 299
 300         ret = nilfs_cpfile_get_header_block(cpfile, &header_bh);
 301         if (ret < 0)
 302                 goto out_sem;
 303         tnicps = 0;
 304
 305         for (cno = start; cno < end; cno += ncps) {
 306                 ncps = nilfs_cpfile_checkpoints_in_block(cpfile, cno, end);
 307                 ret = nilfs_cpfile_get_checkpoint_block(cpfile, cno, 0, &cp_bh);
 308                 if (ret < 0) {
 309                         if (ret != -ENOENT)
 310                                 break;
 311                         /* skip hole */
 312                         ret = 0;
 313                         continue;
 314                 }
 315
 316                 kaddr = kmap_atomic(cp_bh->b_page, KM_USER0);
 317                 cp = nilfs_cpfile_block_get_checkpoint(
 318                         cpfile, cno, cp_bh, kaddr);
 319                 nicps = 0;
 320                 for (i = 0; i < ncps; i++, cp = (void *)cp + cpsz) {
 321                         WARN_ON(nilfs_checkpoint_snapshot(cp));
 322                         if (!nilfs_checkpoint_invalid(cp)) {
 323                                 nilfs_checkpoint_set_invalid(cp);
 324                                 nicps++;
 325                         }
 326                 }
 327                 if (nicps > 0) {
 328                         tnicps += nicps;
 329                         nilfs_mdt_mark_buffer_dirty(cp_bh);
 330                         nilfs_mdt_mark_dirty(cpfile);
 331                         if (!nilfs_cpfile_is_in_first(cpfile, cno)) {
 332                                 count =
 333                                   nilfs_cpfile_block_sub_valid_checkpoints(
 334                                                 cpfile, cp_bh, kaddr, nicps);
 335                                 if (count == 0) {
 336                                         /* make hole */
 337                                         kunmap_atomic(kaddr, KM_USER0);
 338                                         brelse(cp_bh);
 339                                         ret =
 340                                           nilfs_cpfile_delete_checkpoint_block(
 341                                                                    cpfile, cno);
 342                                         if (ret == 0)
 343                                                 continue;
 344                                         printk(KERN_ERR
 345                                                "%s: cannot delete block\n",
 346                                                __func__);
 347                                         break;
 348                                 }
 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
 366         brelse(header_bh);
 367
 368  out_sem:
 369         up_write(&NILFS_MDT(cpfile)->mi_sem);
 370         return ret;
 371 }
 372
 373 static void nilfs_cpfile_checkpoint_to_cpinfo(struct inode *cpfile,
 374                                               struct nilfs_checkpoint *cp,
 375                                               struct nilfs_cpinfo *ci)
 376 {
 377         ci->ci_flags = le32_to_cpu(cp->cp_flags);
 378         ci->ci_cno = le64_to_cpu(cp->cp_cno);
 379         ci->ci_create = le64_to_cpu(cp->cp_create);
 380         ci->ci_nblk_inc = le64_to_cpu(cp->cp_nblk_inc);
 381         ci->ci_inodes_count = le64_to_cpu(cp->cp_inodes_count);
 382         ci->ci_blocks_count = le64_to_cpu(cp->cp_blocks_count);
 383         ci->ci_next = le64_to_cpu(cp->cp_snapshot_list.ssl_next);
 384 }
 385
 386 static ssize_t nilfs_cpfile_do_get_cpinfo(struct inode *cpfile, __u64 *cnop,
 387                                           void *buf, unsigned cisz, size_t nci)
 388 {
 389         struct nilfs_checkpoint *cp;
 390         struct nilfs_cpinfo *ci = buf;
 391         struct buffer_head *bh;
 392         size_t cpsz = NILFS_MDT(cpfile)->mi_entry_size;
 393         __u64 cur_cno = nilfs_mdt_cno(cpfile), cno = *cnop;
 394         void *kaddr;
 395         int n, ret;
 396         int ncps, i;
 397
 398         if (cno == 0)
 399                 return -ENOENT; /* checkpoint number 0 is invalid */
 400         down_read(&NILFS_MDT(cpfile)->mi_sem);
 401
 402         for (n = 0; cno < cur_cno && n < nci; cno += ncps) {
 403                 ncps = nilfs_cpfile_checkpoints_in_block(cpfile, cno, cur_cno);
 404                 ret = nilfs_cpfile_get_checkpoint_block(cpfile, cno, 0, &bh);
 405                 if (ret < 0) {
 406                         if (ret != -ENOENT)
 407                                 goto out;
 408                         continue; /* skip hole */
 409                 }
 410
 411                 kaddr = kmap_atomic(bh->b_page, KM_USER0);
 412                 cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, bh, kaddr);
 413                 for (i = 0; i < ncps && n < nci; i++, cp = (void *)cp + cpsz) {
 414                         if (!nilfs_checkpoint_invalid(cp)) {
 415                                 nilfs_cpfile_checkpoint_to_cpinfo(cpfile, cp,
 416                                                                   ci);
 417                                 ci = (void *)ci + cisz;
 418                                 n++;
 419                         }
 420                 }
 421                 kunmap_atomic(kaddr, KM_USER0);
 422                 brelse(bh);
 423         }
 424
 425         ret = n;
 426         if (n > 0) {
 427                 ci = (void *)ci - cisz;
 428                 *cnop = ci->ci_cno + 1;
 429         }
 430
 431  out:
 432         up_read(&NILFS_MDT(cpfile)->mi_sem);
 433         return ret;
 434 }
 435
 436 static ssize_t nilfs_cpfile_do_get_ssinfo(struct inode *cpfile, __u64 *cnop,
 437                                           void *buf, unsigned cisz, size_t nci)
 438 {
 439         struct buffer_head *bh;
 440         struct nilfs_cpfile_header *header;
 441         struct nilfs_checkpoint *cp;
 442         struct nilfs_cpinfo *ci = buf;
 443         __u64 curr = *cnop, next;
 444         unsigned long curr_blkoff, next_blkoff;
 445         void *kaddr;
 446         int n = 0, ret;
 447
 448         down_read(&NILFS_MDT(cpfile)->mi_sem);
 449
 450         if (curr == 0) {
 451                 ret = nilfs_cpfile_get_header_block(cpfile, &bh);
 452                 if (ret < 0)
 453                         goto out;
 454                 kaddr = kmap_atomic(bh->b_page, KM_USER0);
 455                 header = nilfs_cpfile_block_get_header(cpfile, bh, kaddr);
 456                 curr = le64_to_cpu(header->ch_snapshot_list.ssl_next);
 457                 kunmap_atomic(kaddr, KM_USER0);
 458                 brelse(bh);
 459                 if (curr == 0) {
 460                         ret = 0;
 461                         goto out;
 462                 }
 463         } else if (unlikely(curr == ~(__u64)0)) {
 464                 ret = 0;
 465                 goto out;
 466         }
 467
 468         curr_blkoff = nilfs_cpfile_get_blkoff(cpfile, curr);
 469         ret = nilfs_cpfile_get_checkpoint_block(cpfile, curr, 0, &bh);
 470         if (unlikely(ret < 0)) {
 471                 if (ret == -ENOENT)
 472                         ret = 0; /* No snapshots (started from a hole block) */
 473                 goto out;
 474         }
 475         kaddr = kmap_atomic(bh->b_page, KM_USER0);
 476         while (n < nci) {
 477                 cp = nilfs_cpfile_block_get_checkpoint(cpfile, curr, bh, kaddr);
 478                 curr = ~(__u64)0; /* Terminator */
 479                 if (unlikely(nilfs_checkpoint_invalid(cp) ||
 480                              !nilfs_checkpoint_snapshot(cp)))
 481                         break;
 482                 nilfs_cpfile_checkpoint_to_cpinfo(cpfile, cp, ci);
 483                 ci = (void *)ci + cisz;
 484                 n++;
 485                 next = le64_to_cpu(cp->cp_snapshot_list.ssl_next);
 486                 if (next == 0)
 487                         break; /* reach end of the snapshot list */
 488
 489                 next_blkoff = nilfs_cpfile_get_blkoff(cpfile, next);
 490                 if (curr_blkoff != next_blkoff) {
 491                         kunmap_atomic(kaddr, KM_USER0);
 492                         brelse(bh);
 493                         ret = nilfs_cpfile_get_checkpoint_block(cpfile, next,
 494                                                                 0, &bh);
 495                         if (unlikely(ret < 0)) {
 496                                 WARN_ON(ret == -ENOENT);
 497                                 goto out;
 498                         }
 499                         kaddr = kmap_atomic(bh->b_page, KM_USER0);
 500                 }
 501                 curr = next;
 502                 curr_blkoff = next_blkoff;
 503         }
 504         kunmap_atomic(kaddr, KM_USER0);
 505         brelse(bh);
 506         *cnop = curr;
 507         ret = n;
 508
 509  out:
 510         up_read(&NILFS_MDT(cpfile)->mi_sem);
 511         return ret;
 512 }
 513
 514 /**
 515  * nilfs_cpfile_get_cpinfo -
 516  * @cpfile:
 517  * @cno:
 518  * @ci:
 519  * @nci:
 520  */
 521
 522 ssize_t nilfs_cpfile_get_cpinfo(struct inode *cpfile, __u64 *cnop, int mode,
 523                                 void *buf, unsigned cisz, size_t nci)
 524 {
 525         switch (mode) {
 526         case NILFS_CHECKPOINT:
 527                 return nilfs_cpfile_do_get_cpinfo(cpfile, cnop, buf, cisz, nci);
 528         case NILFS_SNAPSHOT:
 529                 return nilfs_cpfile_do_get_ssinfo(cpfile, cnop, buf, cisz, nci);
 530         default:
 531                 return -EINVAL;
 532         }
 533 }
 534
 535 /**
 536  * nilfs_cpfile_delete_checkpoint -
 537  * @cpfile:
 538  * @cno:
 539  */
 540 int nilfs_cpfile_delete_checkpoint(struct inode *cpfile, __u64 cno)
 541 {
 542         struct nilfs_cpinfo ci;
 543         __u64 tcno = cno;
 544         ssize_t nci;
 545
 546         nci = nilfs_cpfile_do_get_cpinfo(cpfile, &tcno, &ci, sizeof(ci), 1);
 547         if (nci < 0)
 548                 return nci;
 549         else if (nci == 0 || ci.ci_cno != cno)
 550                 return -ENOENT;
 551         else if (nilfs_cpinfo_snapshot(&ci))
 552                 return -EBUSY;
 553
 554         return nilfs_cpfile_delete_checkpoints(cpfile, cno, cno + 1);
 555 }
 556
 557 static struct nilfs_snapshot_list *
 558 nilfs_cpfile_block_get_snapshot_list(const struct inode *cpfile,
 559                                      __u64 cno,
 560                                      struct buffer_head *bh,
 561                                      void *kaddr)
 562 {
 563         struct nilfs_cpfile_header *header;
 564         struct nilfs_checkpoint *cp;
 565         struct nilfs_snapshot_list *list;
 566
 567         if (cno != 0) {
 568                 cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, bh, kaddr);
 569                 list = &cp->cp_snapshot_list;
 570         } else {
 571                 header = nilfs_cpfile_block_get_header(cpfile, bh, kaddr);
 572                 list = &header->ch_snapshot_list;
 573         }
 574         return list;
 575 }
 576
 577 static int nilfs_cpfile_set_snapshot(struct inode *cpfile, __u64 cno)
 578 {
 579         struct buffer_head *header_bh, *curr_bh, *prev_bh, *cp_bh;
 580         struct nilfs_cpfile_header *header;
 581         struct nilfs_checkpoint *cp;
 582         struct nilfs_snapshot_list *list;
 583         __u64 curr, prev;
 584         unsigned long curr_blkoff, prev_blkoff;
 585         void *kaddr;
 586         int ret;
 587
 588         if (cno == 0)
 589                 return -ENOENT; /* checkpoint number 0 is invalid */
 590         down_write(&NILFS_MDT(cpfile)->mi_sem);
 591
 592         ret = nilfs_cpfile_get_checkpoint_block(cpfile, cno, 0, &cp_bh);
 593         if (ret < 0)
 594                 goto out_sem;
 595         kaddr = kmap_atomic(cp_bh->b_page, KM_USER0);
 596         cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, cp_bh, kaddr);
 597         if (nilfs_checkpoint_invalid(cp)) {
 598                 ret = -ENOENT;
 599                 kunmap_atomic(kaddr, KM_USER0);
 600                 goto out_cp;
 601         }
 602         if (nilfs_checkpoint_snapshot(cp)) {
 603                 ret = 0;
 604                 kunmap_atomic(kaddr, KM_USER0);
 605                 goto out_cp;
 606         }
 607         kunmap_atomic(kaddr, KM_USER0);
 608
 609         ret = nilfs_cpfile_get_header_block(cpfile, &header_bh);
 610         if (ret < 0)
 611                 goto out_cp;
 612         kaddr = kmap_atomic(header_bh->b_page, KM_USER0);
 613         header = nilfs_cpfile_block_get_header(cpfile, header_bh, kaddr);
 614         list = &header->ch_snapshot_list;
 615         curr_bh = header_bh;
 616         get_bh(curr_bh);
 617         curr = 0;
 618         curr_blkoff = 0;
 619         prev = le64_to_cpu(list->ssl_prev);
 620         while (prev > cno) {
 621                 prev_blkoff = nilfs_cpfile_get_blkoff(cpfile, prev);
 622                 curr = prev;
 623                 if (curr_blkoff != prev_blkoff) {
 624                         kunmap_atomic(kaddr, KM_USER0);
 625                         brelse(curr_bh);
 626                         ret = nilfs_cpfile_get_checkpoint_block(cpfile, curr,
 627                                                                 0, &curr_bh);
 628                         if (ret < 0)
 629                                 goto out_header;
 630                         kaddr = kmap_atomic(curr_bh->b_page, KM_USER0);
 631                 }
 632                 curr_blkoff = prev_blkoff;
 633                 cp = nilfs_cpfile_block_get_checkpoint(
 634                         cpfile, curr, curr_bh, kaddr);
 635                 list = &cp->cp_snapshot_list;
 636                 prev = le64_to_cpu(list->ssl_prev);
 637         }
 638         kunmap_atomic(kaddr, KM_USER0);
 639
 640         if (prev != 0) {
 641                 ret = nilfs_cpfile_get_checkpoint_block(cpfile, prev, 0,
 642                                                         &prev_bh);
 643                 if (ret < 0)
 644                         goto out_curr;
 645         } else {
 646                 prev_bh = header_bh;
 647                 get_bh(prev_bh);
 648         }
 649
 650         kaddr = kmap_atomic(curr_bh->b_page, KM_USER0);
 651         list = nilfs_cpfile_block_get_snapshot_list(
 652                 cpfile, curr, curr_bh, kaddr);
 653         list->ssl_prev = cpu_to_le64(cno);
 654         kunmap_atomic(kaddr, KM_USER0);
 655
 656         kaddr = kmap_atomic(cp_bh->b_page, KM_USER0);
 657         cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, cp_bh, kaddr);
 658         cp->cp_snapshot_list.ssl_next = cpu_to_le64(curr);
 659         cp->cp_snapshot_list.ssl_prev = cpu_to_le64(prev);
 660         nilfs_checkpoint_set_snapshot(cp);
 661         kunmap_atomic(kaddr, KM_USER0);
 662
 663         kaddr = kmap_atomic(prev_bh->b_page, KM_USER0);
 664         list = nilfs_cpfile_block_get_snapshot_list(
 665                 cpfile, prev, prev_bh, kaddr);
 666         list->ssl_next = cpu_to_le64(cno);
 667         kunmap_atomic(kaddr, KM_USER0);
 668
 669         kaddr = kmap_atomic(header_bh->b_page, KM_USER0);
 670         header = nilfs_cpfile_block_get_header(cpfile, header_bh, kaddr);
 671         le64_add_cpu(&header->ch_nsnapshots, 1);
 672         kunmap_atomic(kaddr, KM_USER0);
 673
 674         nilfs_mdt_mark_buffer_dirty(prev_bh);
 675         nilfs_mdt_mark_buffer_dirty(curr_bh);
 676         nilfs_mdt_mark_buffer_dirty(cp_bh);
 677         nilfs_mdt_mark_buffer_dirty(header_bh);
 678         nilfs_mdt_mark_dirty(cpfile);
 679
 680         brelse(prev_bh);
 681
 682  out_curr:
 683         brelse(curr_bh);
 684
 685  out_header:
 686         brelse(header_bh);
 687
 688  out_cp:
 689         brelse(cp_bh);
 690
 691  out_sem:
 692         up_write(&NILFS_MDT(cpfile)->mi_sem);
 693         return ret;
 694 }
 695
 696 static int nilfs_cpfile_clear_snapshot(struct inode *cpfile, __u64 cno)
 697 {
 698         struct buffer_head *header_bh, *next_bh, *prev_bh, *cp_bh;
 699         struct nilfs_cpfile_header *header;
 700         struct nilfs_checkpoint *cp;
 701         struct nilfs_snapshot_list *list;
 702         __u64 next, prev;
 703         void *kaddr;
 704         int ret;
 705
 706         if (cno == 0)
 707                 return -ENOENT; /* checkpoint number 0 is invalid */
 708         down_write(&NILFS_MDT(cpfile)->mi_sem);
 709
 710         ret = nilfs_cpfile_get_checkpoint_block(cpfile, cno, 0, &cp_bh);
 711         if (ret < 0)
 712                 goto out_sem;
 713         kaddr = kmap_atomic(cp_bh->b_page, KM_USER0);
 714         cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, cp_bh, kaddr);
 715         if (nilfs_checkpoint_invalid(cp)) {
 716                 ret = -ENOENT;
 717                 kunmap_atomic(kaddr, KM_USER0);
 718                 goto out_cp;
 719         }
 720         if (!nilfs_checkpoint_snapshot(cp)) {
 721                 ret = 0;
 722                 kunmap_atomic(kaddr, KM_USER0);
 723                 goto out_cp;
 724         }
 725
 726         list = &cp->cp_snapshot_list;
 727         next = le64_to_cpu(list->ssl_next);
 728         prev = le64_to_cpu(list->ssl_prev);
 729         kunmap_atomic(kaddr, KM_USER0);
 730
 731         ret = nilfs_cpfile_get_header_block(cpfile, &header_bh);
 732         if (ret < 0)
 733                 goto out_cp;
 734         if (next != 0) {
 735                 ret = nilfs_cpfile_get_checkpoint_block(cpfile, next, 0,
 736                                                         &next_bh);
 737                 if (ret < 0)
 738                         goto out_header;
 739         } else {
 740                 next_bh = header_bh;
 741                 get_bh(next_bh);
 742         }
 743         if (prev != 0) {
 744                 ret = nilfs_cpfile_get_checkpoint_block(cpfile, prev, 0,
 745                                                         &prev_bh);
 746                 if (ret < 0)
 747                         goto out_next;
 748         } else {
 749                 prev_bh = header_bh;
 750                 get_bh(prev_bh);
 751         }
 752
 753         kaddr = kmap_atomic(next_bh->b_page, KM_USER0);
 754         list = nilfs_cpfile_block_get_snapshot_list(
 755                 cpfile, next, next_bh, kaddr);
 756         list->ssl_prev = cpu_to_le64(prev);
 757         kunmap_atomic(kaddr, KM_USER0);
 758
 759         kaddr = kmap_atomic(prev_bh->b_page, KM_USER0);
 760         list = nilfs_cpfile_block_get_snapshot_list(
 761                 cpfile, prev, prev_bh, kaddr);
 762         list->ssl_next = cpu_to_le64(next);
 763         kunmap_atomic(kaddr, KM_USER0);
 764
 765         kaddr = kmap_atomic(cp_bh->b_page, KM_USER0);
 766         cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, cp_bh, kaddr);
 767         cp->cp_snapshot_list.ssl_next = cpu_to_le64(0);
 768         cp->cp_snapshot_list.ssl_prev = cpu_to_le64(0);
 769         nilfs_checkpoint_clear_snapshot(cp);
 770         kunmap_atomic(kaddr, KM_USER0);
 771
 772         kaddr = kmap_atomic(header_bh->b_page, KM_USER0);
 773         header = nilfs_cpfile_block_get_header(cpfile, header_bh, kaddr);
 774         le64_add_cpu(&header->ch_nsnapshots, -1);
 775         kunmap_atomic(kaddr, KM_USER0);
 776
 777         nilfs_mdt_mark_buffer_dirty(next_bh);
 778         nilfs_mdt_mark_buffer_dirty(prev_bh);
 779         nilfs_mdt_mark_buffer_dirty(cp_bh);
 780         nilfs_mdt_mark_buffer_dirty(header_bh);
 781         nilfs_mdt_mark_dirty(cpfile);
 782
 783         brelse(prev_bh);
 784
 785  out_next:
 786         brelse(next_bh);
 787
 788  out_header:
 789         brelse(header_bh);
 790
 791  out_cp:
 792         brelse(cp_bh);
 793
 794  out_sem:
 795         up_write(&NILFS_MDT(cpfile)->mi_sem);
 796         return ret;
 797 }
 798
 799 /**
 800  * nilfs_cpfile_is_snapshot -
 801  * @cpfile: inode of checkpoint file
 802  * @cno: checkpoint number
 803  *
 804  * Description:
 805  *
 806  * Return Value: On success, 1 is returned if the checkpoint specified by
 807  * @cno is a snapshot, or 0 if not. On error, one of the following negative
 808  * error codes is returned.
 809  *
 810  * %-EIO - I/O error.
 811  *
 812  * %-ENOMEM - Insufficient amount of memory available.
 813  *
 814  * %-ENOENT - No such checkpoint.
 815  */
 816 int nilfs_cpfile_is_snapshot(struct inode *cpfile, __u64 cno)
 817 {
 818         struct buffer_head *bh;
 819         struct nilfs_checkpoint *cp;
 820         void *kaddr;
 821         int ret;
 822
 823         /* CP number is invalid if it's zero or larger than the
 824         largest exist one.*/
 825         if (cno == 0 || cno >= nilfs_mdt_cno(cpfile))
 826                 return -ENOENT;
 827         down_read(&NILFS_MDT(cpfile)->mi_sem);
 828
 829         ret = nilfs_cpfile_get_checkpoint_block(cpfile, cno, 0, &bh);
 830         if (ret < 0)
 831                 goto out;
 832         kaddr = kmap_atomic(bh->b_page, KM_USER0);
 833         cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, bh, kaddr);
 834         if (nilfs_checkpoint_invalid(cp))
 835                 ret = -ENOENT;
 836         else
 837                 ret = nilfs_checkpoint_snapshot(cp);
 838         kunmap_atomic(kaddr, KM_USER0);
 839         brelse(bh);
 840
 841  out:
 842         up_read(&NILFS_MDT(cpfile)->mi_sem);
 843         return ret;
 844 }
 845
 846 /**
 847  * nilfs_cpfile_change_cpmode - change checkpoint mode
 848  * @cpfile: inode of checkpoint file
 849  * @cno: checkpoint number
 850  * @status: mode of checkpoint
 851  *
 852  * Description: nilfs_change_cpmode() changes the mode of the checkpoint
 853  * specified by @cno. The mode @mode is NILFS_CHECKPOINT or NILFS_SNAPSHOT.
 854  *
 855  * Return Value: On success, 0 is returned. On error, one of the following
 856  * negative error codes is returned.
 857  *
 858  * %-EIO - I/O error.
 859  *
 860  * %-ENOMEM - Insufficient amount of memory available.
 861  *
 862  * %-ENOENT - No such checkpoint.
 863  */
 864 int nilfs_cpfile_change_cpmode(struct inode *cpfile, __u64 cno, int mode)
 865 {
 866         struct the_nilfs *nilfs;
 867         int ret;
 868
 869         nilfs = NILFS_MDT(cpfile)->mi_nilfs;
 870
 871         switch (mode) {
 872         case NILFS_CHECKPOINT:
 873                 /*
 874                  * Check for protecting existing snapshot mounts:
 875                  * ns_mount_mutex is used to make this operation atomic and
 876                  * exclusive with a new mount job.  Though it doesn't cover
 877                  * umount, it's enough for the purpose.
 878                  */
 879                 if (nilfs_checkpoint_is_mounted(nilfs, cno, 1)) {
 880                         /* Current implementation does not have to protect
 881                            plain read-only mounts since they are exclusive
 882                            with a read/write mount and are protected from the
 883                            cleaner. */
 884                         ret = -EBUSY;
 885                 } else
 886                         ret = nilfs_cpfile_clear_snapshot(cpfile, cno);
 887                 return ret;
 888         case NILFS_SNAPSHOT:
 889                 return nilfs_cpfile_set_snapshot(cpfile, cno);
 890         default:
 891                 return -EINVAL;
 892         }
 893 }
 894
 895 /**
 896  * nilfs_cpfile_get_stat - get checkpoint statistics
 897  * @cpfile: inode of checkpoint file
 898  * @stat: pointer to a structure of checkpoint statistics
 899  *
 900  * Description: nilfs_cpfile_get_stat() returns information about checkpoints.
 901  *
 902  * Return Value: On success, 0 is returned, and checkpoints information is
 903  * stored in the place pointed by @stat. On error, one of the following
 904  * negative error codes is returned.
 905  *
 906  * %-EIO - I/O error.
 907  *
 908  * %-ENOMEM - Insufficient amount of memory available.
 909  */
 910 int nilfs_cpfile_get_stat(struct inode *cpfile, struct nilfs_cpstat *cpstat)
 911 {
 912         struct buffer_head *bh;
 913         struct nilfs_cpfile_header *header;
 914         void *kaddr;
 915         int ret;
 916
 917         down_read(&NILFS_MDT(cpfile)->mi_sem);
 918
 919         ret = nilfs_cpfile_get_header_block(cpfile, &bh);
 920         if (ret < 0)
 921                 goto out_sem;
 922         kaddr = kmap_atomic(bh->b_page, KM_USER0);
 923         header = nilfs_cpfile_block_get_header(cpfile, bh, kaddr);
 924         cpstat->cs_cno = nilfs_mdt_cno(cpfile);
 925         cpstat->cs_ncps = le64_to_cpu(header->ch_ncheckpoints);
 926         cpstat->cs_nsss = le64_to_cpu(header->ch_nsnapshots);
 927         kunmap_atomic(kaddr, KM_USER0);
 928         brelse(bh);
 929
 930  out_sem:
 931         up_read(&NILFS_MDT(cpfile)->mi_sem);
 932         return ret;
 933 }
 934
 935 /**
 936  * nilfs_cpfile_read - read cpfile inode
 937  * @cpfile: cpfile inode
 938  * @raw_inode: on-disk cpfile inode
 939  */
 940 int nilfs_cpfile_read(struct inode *cpfile, struct nilfs_inode *raw_inode)
 941 {
 942         return nilfs_read_inode_common(cpfile, raw_inode);
 943 }
 944
 945 /**
 946  * nilfs_cpfile_new - create cpfile
 947  * @nilfs: nilfs object
 948  * @cpsize: size of a checkpoint entry
 949  */
 950 struct inode *nilfs_cpfile_new(struct the_nilfs *nilfs, size_t cpsize)
 951 {
 952         struct inode *cpfile;
 953
 954         cpfile = nilfs_mdt_new(nilfs, NULL, NILFS_CPFILE_INO, 0);
 955         if (cpfile)
 956                 nilfs_mdt_set_entry_size(cpfile, cpsize,
 957                                          sizeof(struct nilfs_cpfile_header));
 958         return cpfile;
 959 }