linux/fs/nilfs2/cpfile.c
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   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
  33static inline unsigned long
  34nilfs_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 */
  40static unsigned long
  41nilfs_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 */
  49static unsigned long
  50nilfs_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
  56static unsigned long
  57nilfs_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
  67static 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
  73static unsigned int
  74nilfs_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
  87static unsigned int
  88nilfs_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
 102static inline struct nilfs_cpfile_header *
 103nilfs_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
 110static struct nilfs_checkpoint *
 111nilfs_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
 119static 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
 133static 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
 139static 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
 149static 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 */
 181int 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                mark_buffer_dirty(cp_bh);
 220
 221                kaddr = kmap_atomic(header_bh->b_page);
 222                header = nilfs_cpfile_block_get_header(cpfile, header_bh,
 223                                                       kaddr);
 224                le64_add_cpu(&header->ch_ncheckpoints, 1);
 225                kunmap_atomic(kaddr);
 226                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 */
 252void 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 */
 278int 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, nss, 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        nss = 0;
 305
 306        for (cno = start; cno < end; cno += ncps) {
 307                ncps = nilfs_cpfile_checkpoints_in_block(cpfile, cno, end);
 308                ret = nilfs_cpfile_get_checkpoint_block(cpfile, cno, 0, &cp_bh);
 309                if (ret < 0) {
 310                        if (ret != -ENOENT)
 311                                break;
 312                        /* skip hole */
 313                        ret = 0;
 314                        continue;
 315                }
 316
 317                kaddr = kmap_atomic(cp_bh->b_page);
 318                cp = nilfs_cpfile_block_get_checkpoint(
 319                        cpfile, cno, cp_bh, kaddr);
 320                nicps = 0;
 321                for (i = 0; i < ncps; i++, cp = (void *)cp + cpsz) {
 322                        if (nilfs_checkpoint_snapshot(cp)) {
 323                                nss++;
 324                        } else if (!nilfs_checkpoint_invalid(cp)) {
 325                                nilfs_checkpoint_set_invalid(cp);
 326                                nicps++;
 327                        }
 328                }
 329                if (nicps > 0) {
 330                        tnicps += nicps;
 331                        mark_buffer_dirty(cp_bh);
 332                        nilfs_mdt_mark_dirty(cpfile);
 333                        if (!nilfs_cpfile_is_in_first(cpfile, cno)) {
 334                                count =
 335                                  nilfs_cpfile_block_sub_valid_checkpoints(
 336                                                cpfile, cp_bh, kaddr, nicps);
 337                                if (count == 0) {
 338                                        /* make hole */
 339                                        kunmap_atomic(kaddr);
 340                                        brelse(cp_bh);
 341                                        ret =
 342                                          nilfs_cpfile_delete_checkpoint_block(
 343                                                                   cpfile, cno);
 344                                        if (ret == 0)
 345                                                continue;
 346                                        printk(KERN_ERR
 347                                               "%s: cannot delete block\n",
 348                                               __func__);
 349                                        break;
 350                                }
 351                        }
 352                }
 353
 354                kunmap_atomic(kaddr);
 355                brelse(cp_bh);
 356        }
 357
 358        if (tnicps > 0) {
 359                kaddr = kmap_atomic(header_bh->b_page);
 360                header = nilfs_cpfile_block_get_header(cpfile, header_bh,
 361                                                       kaddr);
 362                le64_add_cpu(&header->ch_ncheckpoints, -(u64)tnicps);
 363                mark_buffer_dirty(header_bh);
 364                nilfs_mdt_mark_dirty(cpfile);
 365                kunmap_atomic(kaddr);
 366        }
 367
 368        brelse(header_bh);
 369        if (nss > 0)
 370                ret = -EBUSY;
 371
 372 out_sem:
 373        up_write(&NILFS_MDT(cpfile)->mi_sem);
 374        return ret;
 375}
 376
 377static void nilfs_cpfile_checkpoint_to_cpinfo(struct inode *cpfile,
 378                                              struct nilfs_checkpoint *cp,
 379                                              struct nilfs_cpinfo *ci)
 380{
 381        ci->ci_flags = le32_to_cpu(cp->cp_flags);
 382        ci->ci_cno = le64_to_cpu(cp->cp_cno);
 383        ci->ci_create = le64_to_cpu(cp->cp_create);
 384        ci->ci_nblk_inc = le64_to_cpu(cp->cp_nblk_inc);
 385        ci->ci_inodes_count = le64_to_cpu(cp->cp_inodes_count);
 386        ci->ci_blocks_count = le64_to_cpu(cp->cp_blocks_count);
 387        ci->ci_next = le64_to_cpu(cp->cp_snapshot_list.ssl_next);
 388}
 389
 390static ssize_t nilfs_cpfile_do_get_cpinfo(struct inode *cpfile, __u64 *cnop,
 391                                          void *buf, unsigned cisz, size_t nci)
 392{
 393        struct nilfs_checkpoint *cp;
 394        struct nilfs_cpinfo *ci = buf;
 395        struct buffer_head *bh;
 396        size_t cpsz = NILFS_MDT(cpfile)->mi_entry_size;
 397        __u64 cur_cno = nilfs_mdt_cno(cpfile), cno = *cnop;
 398        void *kaddr;
 399        int n, ret;
 400        int ncps, i;
 401
 402        if (cno == 0)
 403                return -ENOENT; /* checkpoint number 0 is invalid */
 404        down_read(&NILFS_MDT(cpfile)->mi_sem);
 405
 406        for (n = 0; cno < cur_cno && n < nci; cno += ncps) {
 407                ncps = nilfs_cpfile_checkpoints_in_block(cpfile, cno, cur_cno);
 408                ret = nilfs_cpfile_get_checkpoint_block(cpfile, cno, 0, &bh);
 409                if (ret < 0) {
 410                        if (ret != -ENOENT)
 411                                goto out;
 412                        continue; /* skip hole */
 413                }
 414
 415                kaddr = kmap_atomic(bh->b_page);
 416                cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, bh, kaddr);
 417                for (i = 0; i < ncps && n < nci; i++, cp = (void *)cp + cpsz) {
 418                        if (!nilfs_checkpoint_invalid(cp)) {
 419                                nilfs_cpfile_checkpoint_to_cpinfo(cpfile, cp,
 420                                                                  ci);
 421                                ci = (void *)ci + cisz;
 422                                n++;
 423                        }
 424                }
 425                kunmap_atomic(kaddr);
 426                brelse(bh);
 427        }
 428
 429        ret = n;
 430        if (n > 0) {
 431                ci = (void *)ci - cisz;
 432                *cnop = ci->ci_cno + 1;
 433        }
 434
 435 out:
 436        up_read(&NILFS_MDT(cpfile)->mi_sem);
 437        return ret;
 438}
 439
 440static ssize_t nilfs_cpfile_do_get_ssinfo(struct inode *cpfile, __u64 *cnop,
 441                                          void *buf, unsigned cisz, size_t nci)
 442{
 443        struct buffer_head *bh;
 444        struct nilfs_cpfile_header *header;
 445        struct nilfs_checkpoint *cp;
 446        struct nilfs_cpinfo *ci = buf;
 447        __u64 curr = *cnop, next;
 448        unsigned long curr_blkoff, next_blkoff;
 449        void *kaddr;
 450        int n = 0, ret;
 451
 452        down_read(&NILFS_MDT(cpfile)->mi_sem);
 453
 454        if (curr == 0) {
 455                ret = nilfs_cpfile_get_header_block(cpfile, &bh);
 456                if (ret < 0)
 457                        goto out;
 458                kaddr = kmap_atomic(bh->b_page);
 459                header = nilfs_cpfile_block_get_header(cpfile, bh, kaddr);
 460                curr = le64_to_cpu(header->ch_snapshot_list.ssl_next);
 461                kunmap_atomic(kaddr);
 462                brelse(bh);
 463                if (curr == 0) {
 464                        ret = 0;
 465                        goto out;
 466                }
 467        } else if (unlikely(curr == ~(__u64)0)) {
 468                ret = 0;
 469                goto out;
 470        }
 471
 472        curr_blkoff = nilfs_cpfile_get_blkoff(cpfile, curr);
 473        ret = nilfs_cpfile_get_checkpoint_block(cpfile, curr, 0, &bh);
 474        if (unlikely(ret < 0)) {
 475                if (ret == -ENOENT)
 476                        ret = 0; /* No snapshots (started from a hole block) */
 477                goto out;
 478        }
 479        kaddr = kmap_atomic(bh->b_page);
 480        while (n < nci) {
 481                cp = nilfs_cpfile_block_get_checkpoint(cpfile, curr, bh, kaddr);
 482                curr = ~(__u64)0; /* Terminator */
 483                if (unlikely(nilfs_checkpoint_invalid(cp) ||
 484                             !nilfs_checkpoint_snapshot(cp)))
 485                        break;
 486                nilfs_cpfile_checkpoint_to_cpinfo(cpfile, cp, ci);
 487                ci = (void *)ci + cisz;
 488                n++;
 489                next = le64_to_cpu(cp->cp_snapshot_list.ssl_next);
 490                if (next == 0)
 491                        break; /* reach end of the snapshot list */
 492
 493                next_blkoff = nilfs_cpfile_get_blkoff(cpfile, next);
 494                if (curr_blkoff != next_blkoff) {
 495                        kunmap_atomic(kaddr);
 496                        brelse(bh);
 497                        ret = nilfs_cpfile_get_checkpoint_block(cpfile, next,
 498                                                                0, &bh);
 499                        if (unlikely(ret < 0)) {
 500                                WARN_ON(ret == -ENOENT);
 501                                goto out;
 502                        }
 503                        kaddr = kmap_atomic(bh->b_page);
 504                }
 505                curr = next;
 506                curr_blkoff = next_blkoff;
 507        }
 508        kunmap_atomic(kaddr);
 509        brelse(bh);
 510        *cnop = curr;
 511        ret = n;
 512
 513 out:
 514        up_read(&NILFS_MDT(cpfile)->mi_sem);
 515        return ret;
 516}
 517
 518/**
 519 * nilfs_cpfile_get_cpinfo -
 520 * @cpfile:
 521 * @cno:
 522 * @ci:
 523 * @nci:
 524 */
 525
 526ssize_t nilfs_cpfile_get_cpinfo(struct inode *cpfile, __u64 *cnop, int mode,
 527                                void *buf, unsigned cisz, size_t nci)
 528{
 529        switch (mode) {
 530        case NILFS_CHECKPOINT:
 531                return nilfs_cpfile_do_get_cpinfo(cpfile, cnop, buf, cisz, nci);
 532        case NILFS_SNAPSHOT:
 533                return nilfs_cpfile_do_get_ssinfo(cpfile, cnop, buf, cisz, nci);
 534        default:
 535                return -EINVAL;
 536        }
 537}
 538
 539/**
 540 * nilfs_cpfile_delete_checkpoint -
 541 * @cpfile:
 542 * @cno:
 543 */
 544int nilfs_cpfile_delete_checkpoint(struct inode *cpfile, __u64 cno)
 545{
 546        struct nilfs_cpinfo ci;
 547        __u64 tcno = cno;
 548        ssize_t nci;
 549
 550        nci = nilfs_cpfile_do_get_cpinfo(cpfile, &tcno, &ci, sizeof(ci), 1);
 551        if (nci < 0)
 552                return nci;
 553        else if (nci == 0 || ci.ci_cno != cno)
 554                return -ENOENT;
 555        else if (nilfs_cpinfo_snapshot(&ci))
 556                return -EBUSY;
 557
 558        return nilfs_cpfile_delete_checkpoints(cpfile, cno, cno + 1);
 559}
 560
 561static struct nilfs_snapshot_list *
 562nilfs_cpfile_block_get_snapshot_list(const struct inode *cpfile,
 563                                     __u64 cno,
 564                                     struct buffer_head *bh,
 565                                     void *kaddr)
 566{
 567        struct nilfs_cpfile_header *header;
 568        struct nilfs_checkpoint *cp;
 569        struct nilfs_snapshot_list *list;
 570
 571        if (cno != 0) {
 572                cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, bh, kaddr);
 573                list = &cp->cp_snapshot_list;
 574        } else {
 575                header = nilfs_cpfile_block_get_header(cpfile, bh, kaddr);
 576                list = &header->ch_snapshot_list;
 577        }
 578        return list;
 579}
 580
 581static int nilfs_cpfile_set_snapshot(struct inode *cpfile, __u64 cno)
 582{
 583        struct buffer_head *header_bh, *curr_bh, *prev_bh, *cp_bh;
 584        struct nilfs_cpfile_header *header;
 585        struct nilfs_checkpoint *cp;
 586        struct nilfs_snapshot_list *list;
 587        __u64 curr, prev;
 588        unsigned long curr_blkoff, prev_blkoff;
 589        void *kaddr;
 590        int ret;
 591
 592        if (cno == 0)
 593                return -ENOENT; /* checkpoint number 0 is invalid */
 594        down_write(&NILFS_MDT(cpfile)->mi_sem);
 595
 596        ret = nilfs_cpfile_get_checkpoint_block(cpfile, cno, 0, &cp_bh);
 597        if (ret < 0)
 598                goto out_sem;
 599        kaddr = kmap_atomic(cp_bh->b_page);
 600        cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, cp_bh, kaddr);
 601        if (nilfs_checkpoint_invalid(cp)) {
 602                ret = -ENOENT;
 603                kunmap_atomic(kaddr);
 604                goto out_cp;
 605        }
 606        if (nilfs_checkpoint_snapshot(cp)) {
 607                ret = 0;
 608                kunmap_atomic(kaddr);
 609                goto out_cp;
 610        }
 611        kunmap_atomic(kaddr);
 612
 613        ret = nilfs_cpfile_get_header_block(cpfile, &header_bh);
 614        if (ret < 0)
 615                goto out_cp;
 616        kaddr = kmap_atomic(header_bh->b_page);
 617        header = nilfs_cpfile_block_get_header(cpfile, header_bh, kaddr);
 618        list = &header->ch_snapshot_list;
 619        curr_bh = header_bh;
 620        get_bh(curr_bh);
 621        curr = 0;
 622        curr_blkoff = 0;
 623        prev = le64_to_cpu(list->ssl_prev);
 624        while (prev > cno) {
 625                prev_blkoff = nilfs_cpfile_get_blkoff(cpfile, prev);
 626                curr = prev;
 627                if (curr_blkoff != prev_blkoff) {
 628                        kunmap_atomic(kaddr);
 629                        brelse(curr_bh);
 630                        ret = nilfs_cpfile_get_checkpoint_block(cpfile, curr,
 631                                                                0, &curr_bh);
 632                        if (ret < 0)
 633                                goto out_header;
 634                        kaddr = kmap_atomic(curr_bh->b_page);
 635                }
 636                curr_blkoff = prev_blkoff;
 637                cp = nilfs_cpfile_block_get_checkpoint(
 638                        cpfile, curr, curr_bh, kaddr);
 639                list = &cp->cp_snapshot_list;
 640                prev = le64_to_cpu(list->ssl_prev);
 641        }
 642        kunmap_atomic(kaddr);
 643
 644        if (prev != 0) {
 645                ret = nilfs_cpfile_get_checkpoint_block(cpfile, prev, 0,
 646                                                        &prev_bh);
 647                if (ret < 0)
 648                        goto out_curr;
 649        } else {
 650                prev_bh = header_bh;
 651                get_bh(prev_bh);
 652        }
 653
 654        kaddr = kmap_atomic(curr_bh->b_page);
 655        list = nilfs_cpfile_block_get_snapshot_list(
 656                cpfile, curr, curr_bh, kaddr);
 657        list->ssl_prev = cpu_to_le64(cno);
 658        kunmap_atomic(kaddr);
 659
 660        kaddr = kmap_atomic(cp_bh->b_page);
 661        cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, cp_bh, kaddr);
 662        cp->cp_snapshot_list.ssl_next = cpu_to_le64(curr);
 663        cp->cp_snapshot_list.ssl_prev = cpu_to_le64(prev);
 664        nilfs_checkpoint_set_snapshot(cp);
 665        kunmap_atomic(kaddr);
 666
 667        kaddr = kmap_atomic(prev_bh->b_page);
 668        list = nilfs_cpfile_block_get_snapshot_list(
 669                cpfile, prev, prev_bh, kaddr);
 670        list->ssl_next = cpu_to_le64(cno);
 671        kunmap_atomic(kaddr);
 672
 673        kaddr = kmap_atomic(header_bh->b_page);
 674        header = nilfs_cpfile_block_get_header(cpfile, header_bh, kaddr);
 675        le64_add_cpu(&header->ch_nsnapshots, 1);
 676        kunmap_atomic(kaddr);
 677
 678        mark_buffer_dirty(prev_bh);
 679        mark_buffer_dirty(curr_bh);
 680        mark_buffer_dirty(cp_bh);
 681        mark_buffer_dirty(header_bh);
 682        nilfs_mdt_mark_dirty(cpfile);
 683
 684        brelse(prev_bh);
 685
 686 out_curr:
 687        brelse(curr_bh);
 688
 689 out_header:
 690        brelse(header_bh);
 691
 692 out_cp:
 693        brelse(cp_bh);
 694
 695 out_sem:
 696        up_write(&NILFS_MDT(cpfile)->mi_sem);
 697        return ret;
 698}
 699
 700static int nilfs_cpfile_clear_snapshot(struct inode *cpfile, __u64 cno)
 701{
 702        struct buffer_head *header_bh, *next_bh, *prev_bh, *cp_bh;
 703        struct nilfs_cpfile_header *header;
 704        struct nilfs_checkpoint *cp;
 705        struct nilfs_snapshot_list *list;
 706        __u64 next, prev;
 707        void *kaddr;
 708        int ret;
 709
 710        if (cno == 0)
 711                return -ENOENT; /* checkpoint number 0 is invalid */
 712        down_write(&NILFS_MDT(cpfile)->mi_sem);
 713
 714        ret = nilfs_cpfile_get_checkpoint_block(cpfile, cno, 0, &cp_bh);
 715        if (ret < 0)
 716                goto out_sem;
 717        kaddr = kmap_atomic(cp_bh->b_page);
 718        cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, cp_bh, kaddr);
 719        if (nilfs_checkpoint_invalid(cp)) {
 720                ret = -ENOENT;
 721                kunmap_atomic(kaddr);
 722                goto out_cp;
 723        }
 724        if (!nilfs_checkpoint_snapshot(cp)) {
 725                ret = 0;
 726                kunmap_atomic(kaddr);
 727                goto out_cp;
 728        }
 729
 730        list = &cp->cp_snapshot_list;
 731        next = le64_to_cpu(list->ssl_next);
 732        prev = le64_to_cpu(list->ssl_prev);
 733        kunmap_atomic(kaddr);
 734
 735        ret = nilfs_cpfile_get_header_block(cpfile, &header_bh);
 736        if (ret < 0)
 737                goto out_cp;
 738        if (next != 0) {
 739                ret = nilfs_cpfile_get_checkpoint_block(cpfile, next, 0,
 740                                                        &next_bh);
 741                if (ret < 0)
 742                        goto out_header;
 743        } else {
 744                next_bh = header_bh;
 745                get_bh(next_bh);
 746        }
 747        if (prev != 0) {
 748                ret = nilfs_cpfile_get_checkpoint_block(cpfile, prev, 0,
 749                                                        &prev_bh);
 750                if (ret < 0)
 751                        goto out_next;
 752        } else {
 753                prev_bh = header_bh;
 754                get_bh(prev_bh);
 755        }
 756
 757        kaddr = kmap_atomic(next_bh->b_page);
 758        list = nilfs_cpfile_block_get_snapshot_list(
 759                cpfile, next, next_bh, kaddr);
 760        list->ssl_prev = cpu_to_le64(prev);
 761        kunmap_atomic(kaddr);
 762
 763        kaddr = kmap_atomic(prev_bh->b_page);
 764        list = nilfs_cpfile_block_get_snapshot_list(
 765                cpfile, prev, prev_bh, kaddr);
 766        list->ssl_next = cpu_to_le64(next);
 767        kunmap_atomic(kaddr);
 768
 769        kaddr = kmap_atomic(cp_bh->b_page);
 770        cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, cp_bh, kaddr);
 771        cp->cp_snapshot_list.ssl_next = cpu_to_le64(0);
 772        cp->cp_snapshot_list.ssl_prev = cpu_to_le64(0);
 773        nilfs_checkpoint_clear_snapshot(cp);
 774        kunmap_atomic(kaddr);
 775
 776        kaddr = kmap_atomic(header_bh->b_page);
 777        header = nilfs_cpfile_block_get_header(cpfile, header_bh, kaddr);
 778        le64_add_cpu(&header->ch_nsnapshots, -1);
 779        kunmap_atomic(kaddr);
 780
 781        mark_buffer_dirty(next_bh);
 782        mark_buffer_dirty(prev_bh);
 783        mark_buffer_dirty(cp_bh);
 784        mark_buffer_dirty(header_bh);
 785        nilfs_mdt_mark_dirty(cpfile);
 786
 787        brelse(prev_bh);
 788
 789 out_next:
 790        brelse(next_bh);
 791
 792 out_header:
 793        brelse(header_bh);
 794
 795 out_cp:
 796        brelse(cp_bh);
 797
 798 out_sem:
 799        up_write(&NILFS_MDT(cpfile)->mi_sem);
 800        return ret;
 801}
 802
 803/**
 804 * nilfs_cpfile_is_snapshot -
 805 * @cpfile: inode of checkpoint file
 806 * @cno: checkpoint number
 807 *
 808 * Description:
 809 *
 810 * Return Value: On success, 1 is returned if the checkpoint specified by
 811 * @cno is a snapshot, or 0 if not. On error, one of the following negative
 812 * error codes is returned.
 813 *
 814 * %-EIO - I/O error.
 815 *
 816 * %-ENOMEM - Insufficient amount of memory available.
 817 *
 818 * %-ENOENT - No such checkpoint.
 819 */
 820int nilfs_cpfile_is_snapshot(struct inode *cpfile, __u64 cno)
 821{
 822        struct buffer_head *bh;
 823        struct nilfs_checkpoint *cp;
 824        void *kaddr;
 825        int ret;
 826
 827        /* CP number is invalid if it's zero or larger than the
 828        largest exist one.*/
 829        if (cno == 0 || cno >= nilfs_mdt_cno(cpfile))
 830                return -ENOENT;
 831        down_read(&NILFS_MDT(cpfile)->mi_sem);
 832
 833        ret = nilfs_cpfile_get_checkpoint_block(cpfile, cno, 0, &bh);
 834        if (ret < 0)
 835                goto out;
 836        kaddr = kmap_atomic(bh->b_page);
 837        cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, bh, kaddr);
 838        if (nilfs_checkpoint_invalid(cp))
 839                ret = -ENOENT;
 840        else
 841                ret = nilfs_checkpoint_snapshot(cp);
 842        kunmap_atomic(kaddr);
 843        brelse(bh);
 844
 845 out:
 846        up_read(&NILFS_MDT(cpfile)->mi_sem);
 847        return ret;
 848}
 849
 850/**
 851 * nilfs_cpfile_change_cpmode - change checkpoint mode
 852 * @cpfile: inode of checkpoint file
 853 * @cno: checkpoint number
 854 * @status: mode of checkpoint
 855 *
 856 * Description: nilfs_change_cpmode() changes the mode of the checkpoint
 857 * specified by @cno. The mode @mode is NILFS_CHECKPOINT or NILFS_SNAPSHOT.
 858 *
 859 * Return Value: On success, 0 is returned. On error, one of the following
 860 * negative error codes is returned.
 861 *
 862 * %-EIO - I/O error.
 863 *
 864 * %-ENOMEM - Insufficient amount of memory available.
 865 *
 866 * %-ENOENT - No such checkpoint.
 867 */
 868int nilfs_cpfile_change_cpmode(struct inode *cpfile, __u64 cno, int mode)
 869{
 870        int ret;
 871
 872        switch (mode) {
 873        case NILFS_CHECKPOINT:
 874                if (nilfs_checkpoint_is_mounted(cpfile->i_sb, cno))
 875                        /*
 876                         * Current implementation does not have to protect
 877                         * plain read-only mounts since they are exclusive
 878                         * with a read/write mount and are protected from the
 879                         * cleaner.
 880                         */
 881                        ret = -EBUSY;
 882                else
 883                        ret = nilfs_cpfile_clear_snapshot(cpfile, cno);
 884                return ret;
 885        case NILFS_SNAPSHOT:
 886                return nilfs_cpfile_set_snapshot(cpfile, cno);
 887        default:
 888                return -EINVAL;
 889        }
 890}
 891
 892/**
 893 * nilfs_cpfile_get_stat - get checkpoint statistics
 894 * @cpfile: inode of checkpoint file
 895 * @stat: pointer to a structure of checkpoint statistics
 896 *
 897 * Description: nilfs_cpfile_get_stat() returns information about checkpoints.
 898 *
 899 * Return Value: On success, 0 is returned, and checkpoints information is
 900 * stored in the place pointed by @stat. On error, one of the following
 901 * negative error codes is returned.
 902 *
 903 * %-EIO - I/O error.
 904 *
 905 * %-ENOMEM - Insufficient amount of memory available.
 906 */
 907int nilfs_cpfile_get_stat(struct inode *cpfile, struct nilfs_cpstat *cpstat)
 908{
 909        struct buffer_head *bh;
 910        struct nilfs_cpfile_header *header;
 911        void *kaddr;
 912        int ret;
 913
 914        down_read(&NILFS_MDT(cpfile)->mi_sem);
 915
 916        ret = nilfs_cpfile_get_header_block(cpfile, &bh);
 917        if (ret < 0)
 918                goto out_sem;
 919        kaddr = kmap_atomic(bh->b_page);
 920        header = nilfs_cpfile_block_get_header(cpfile, bh, kaddr);
 921        cpstat->cs_cno = nilfs_mdt_cno(cpfile);
 922        cpstat->cs_ncps = le64_to_cpu(header->ch_ncheckpoints);
 923        cpstat->cs_nsss = le64_to_cpu(header->ch_nsnapshots);
 924        kunmap_atomic(kaddr);
 925        brelse(bh);
 926
 927 out_sem:
 928        up_read(&NILFS_MDT(cpfile)->mi_sem);
 929        return ret;
 930}
 931
 932/**
 933 * nilfs_cpfile_read - read or get cpfile inode
 934 * @sb: super block instance
 935 * @cpsize: size of a checkpoint entry
 936 * @raw_inode: on-disk cpfile inode
 937 * @inodep: buffer to store the inode
 938 */
 939int nilfs_cpfile_read(struct super_block *sb, size_t cpsize,
 940                      struct nilfs_inode *raw_inode, struct inode **inodep)
 941{
 942        struct inode *cpfile;
 943        int err;
 944
 945        cpfile = nilfs_iget_locked(sb, NULL, NILFS_CPFILE_INO);
 946        if (unlikely(!cpfile))
 947                return -ENOMEM;
 948        if (!(cpfile->i_state & I_NEW))
 949                goto out;
 950
 951        err = nilfs_mdt_init(cpfile, NILFS_MDT_GFP, 0);
 952        if (err)
 953                goto failed;
 954
 955        nilfs_mdt_set_entry_size(cpfile, cpsize,
 956                                 sizeof(struct nilfs_cpfile_header));
 957
 958        err = nilfs_read_inode_common(cpfile, raw_inode);
 959        if (err)
 960                goto failed;
 961
 962        unlock_new_inode(cpfile);
 963 out:
 964        *inodep = cpfile;
 965        return 0;
 966 failed:
 967        iget_failed(cpfile);
 968        return err;
 969}
 970
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