git.oblomov.eu Git - linux-2.6/blob - fs/nilfs2/sufile.c

   1 /*
   2  * sufile.c - NILFS segment usage 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  * Rivised by Ryusuke Konishi <ryusuke@osrg.net>.
  22  */
  23
  24 #include <linux/kernel.h>
  25 #include <linux/fs.h>
  26 #include <linux/string.h>
  27 #include <linux/buffer_head.h>
  28 #include <linux/errno.h>
  29 #include <linux/nilfs2_fs.h>
  30 #include "mdt.h"
  31 #include "sufile.h"
  32
  33
  34 static inline unsigned long
  35 nilfs_sufile_segment_usages_per_block(const struct inode *sufile)
  36 {
  37         return NILFS_MDT(sufile)->mi_entries_per_block;
  38 }
  39
  40 static unsigned long
  41 nilfs_sufile_get_blkoff(const struct inode *sufile, __u64 segnum)
  42 {
  43         __u64 t = segnum + NILFS_MDT(sufile)->mi_first_entry_offset;
  44         do_div(t, nilfs_sufile_segment_usages_per_block(sufile));
  45         return (unsigned long)t;
  46 }
  47
  48 static unsigned long
  49 nilfs_sufile_get_offset(const struct inode *sufile, __u64 segnum)
  50 {
  51         __u64 t = segnum + NILFS_MDT(sufile)->mi_first_entry_offset;
  52         return do_div(t, nilfs_sufile_segment_usages_per_block(sufile));
  53 }
  54
  55 static unsigned long
  56 nilfs_sufile_segment_usages_in_block(const struct inode *sufile, __u64 curr,
  57                                      __u64 max)
  58 {
  59         return min_t(unsigned long,
  60                      nilfs_sufile_segment_usages_per_block(sufile) -
  61                      nilfs_sufile_get_offset(sufile, curr),
  62                      max - curr + 1);
  63 }
  64
  65 static inline struct nilfs_sufile_header *
  66 nilfs_sufile_block_get_header(const struct inode *sufile,
  67                               struct buffer_head *bh,
  68                               void *kaddr)
  69 {
  70         return kaddr + bh_offset(bh);
  71 }
  72
  73 static struct nilfs_segment_usage *
  74 nilfs_sufile_block_get_segment_usage(const struct inode *sufile, __u64 segnum,
  75                                      struct buffer_head *bh, void *kaddr)
  76 {
  77         return kaddr + bh_offset(bh) +
  78                 nilfs_sufile_get_offset(sufile, segnum) *
  79                 NILFS_MDT(sufile)->mi_entry_size;
  80 }
  81
  82 static inline int nilfs_sufile_get_header_block(struct inode *sufile,
  83                                                 struct buffer_head **bhp)
  84 {
  85         return nilfs_mdt_get_block(sufile, 0, 0, NULL, bhp);
  86 }
  87
  88 static inline int
  89 nilfs_sufile_get_segment_usage_block(struct inode *sufile, __u64 segnum,
  90                                      int create, struct buffer_head **bhp)
  91 {
  92         return nilfs_mdt_get_block(sufile,
  93                                    nilfs_sufile_get_blkoff(sufile, segnum),
  94                                    create, NULL, bhp);
  95 }
  96
  97 static void nilfs_sufile_mod_counter(struct buffer_head *header_bh,
  98                                      u64 ncleanadd, u64 ndirtyadd)
  99 {
 100         struct nilfs_sufile_header *header;
 101         void *kaddr;
 102
 103         kaddr = kmap_atomic(header_bh->b_page, KM_USER0);
 104         header = kaddr + bh_offset(header_bh);
 105         le64_add_cpu(&header->sh_ncleansegs, ncleanadd);
 106         le64_add_cpu(&header->sh_ndirtysegs, ndirtyadd);
 107         kunmap_atomic(kaddr, KM_USER0);
 108
 109         nilfs_mdt_mark_buffer_dirty(header_bh);
 110 }
 111
 112 /**
 113  * nilfs_sufile_updatev - modify multiple segment usages at a time
 114  * @sufile: inode of segment usage file
 115  * @segnumv: array of segment numbers
 116  * @nsegs: size of @segnumv array
 117  * @create: creation flag
 118  * @ndone: place to store number of modified segments on @segnumv
 119  * @dofunc: primitive operation for the update
 120  *
 121  * Description: nilfs_sufile_updatev() repeatedly calls @dofunc
 122  * against the given array of segments.  The @dofunc is called with
 123  * buffers of a header block and the sufile block in which the target
 124  * segment usage entry is contained.  If @ndone is given, the number
 125  * of successfully modified segments from the head is stored in the
 126  * place @ndone points to.
 127  *
 128  * Return Value: On success, zero is returned.  On error, one of the
 129  * following negative error codes is returned.
 130  *
 131  * %-EIO - I/O error.
 132  *
 133  * %-ENOMEM - Insufficient amount of memory available.
 134  *
 135  * %-ENOENT - Given segment usage is in hole block (may be returned if
 136  *            @create is zero)
 137  *
 138  * %-EINVAL - Invalid segment usage number
 139  */
 140 int nilfs_sufile_updatev(struct inode *sufile, __u64 *segnumv, size_t nsegs,
 141                          int create, size_t *ndone,
 142                          void (*dofunc)(struct inode *, __u64,
 143                                         struct buffer_head *,
 144                                         struct buffer_head *))
 145 {
 146         struct buffer_head *header_bh, *bh;
 147         unsigned long blkoff, prev_blkoff;
 148         __u64 *seg;
 149         size_t nerr = 0, n = 0;
 150         int ret = 0;
 151
 152         if (unlikely(nsegs == 0))
 153                 goto out;
 154
 155         down_write(&NILFS_MDT(sufile)->mi_sem);
 156         for (seg = segnumv; seg < segnumv + nsegs; seg++) {
 157                 if (unlikely(*seg >= nilfs_sufile_get_nsegments(sufile))) {
 158                         printk(KERN_WARNING
 159                                "%s: invalid segment number: %llu\n", __func__,
 160                                (unsigned long long)*seg);
 161                         nerr++;
 162                 }
 163         }
 164         if (nerr > 0) {
 165                 ret = -EINVAL;
 166                 goto out_sem;
 167         }
 168
 169         ret = nilfs_sufile_get_header_block(sufile, &header_bh);
 170         if (ret < 0)
 171                 goto out_sem;
 172
 173         seg = segnumv;
 174         blkoff = nilfs_sufile_get_blkoff(sufile, *seg);
 175         ret = nilfs_mdt_get_block(sufile, blkoff, create, NULL, &bh);
 176         if (ret < 0)
 177                 goto out_header;
 178
 179         for (;;) {
 180                 dofunc(sufile, *seg, header_bh, bh);
 181
 182                 if (++seg >= segnumv + nsegs)
 183                         break;
 184                 prev_blkoff = blkoff;
 185                 blkoff = nilfs_sufile_get_blkoff(sufile, *seg);
 186                 if (blkoff == prev_blkoff)
 187                         continue;
 188
 189                 /* get different block */
 190                 brelse(bh);
 191                 ret = nilfs_mdt_get_block(sufile, blkoff, create, NULL, &bh);
 192                 if (unlikely(ret < 0))
 193                         goto out_header;
 194         }
 195         brelse(bh);
 196
 197  out_header:
 198         n = seg - segnumv;
 199         brelse(header_bh);
 200  out_sem:
 201         up_write(&NILFS_MDT(sufile)->mi_sem);
 202  out:
 203         if (ndone)
 204                 *ndone = n;
 205         return ret;
 206 }
 207
 208 int nilfs_sufile_update(struct inode *sufile, __u64 segnum, int create,
 209                         void (*dofunc)(struct inode *, __u64,
 210                                        struct buffer_head *,
 211                                        struct buffer_head *))
 212 {
 213         struct buffer_head *header_bh, *bh;
 214         int ret;
 215
 216         if (unlikely(segnum >= nilfs_sufile_get_nsegments(sufile))) {
 217                 printk(KERN_WARNING "%s: invalid segment number: %llu\n",
 218                        __func__, (unsigned long long)segnum);
 219                 return -EINVAL;
 220         }
 221         down_write(&NILFS_MDT(sufile)->mi_sem);
 222
 223         ret = nilfs_sufile_get_header_block(sufile, &header_bh);
 224         if (ret < 0)
 225                 goto out_sem;
 226
 227         ret = nilfs_sufile_get_segment_usage_block(sufile, segnum, create, &bh);
 228         if (!ret) {
 229                 dofunc(sufile, segnum, header_bh, bh);
 230                 brelse(bh);
 231         }
 232         brelse(header_bh);
 233
 234  out_sem:
 235         up_write(&NILFS_MDT(sufile)->mi_sem);
 236         return ret;
 237 }
 238
 239 /**
 240  * nilfs_sufile_alloc - allocate a segment
 241  * @sufile: inode of segment usage file
 242  * @segnump: pointer to segment number
 243  *
 244  * Description: nilfs_sufile_alloc() allocates a clean segment.
 245  *
 246  * Return Value: On success, 0 is returned and the segment number of the
 247  * allocated segment is stored in the place pointed by @segnump. On error, one
 248  * of the following negative error codes is returned.
 249  *
 250  * %-EIO - I/O error.
 251  *
 252  * %-ENOMEM - Insufficient amount of memory available.
 253  *
 254  * %-ENOSPC - No clean segment left.
 255  */
 256 int nilfs_sufile_alloc(struct inode *sufile, __u64 *segnump)
 257 {
 258         struct buffer_head *header_bh, *su_bh;
 259         struct nilfs_sufile_header *header;
 260         struct nilfs_segment_usage *su;
 261         size_t susz = NILFS_MDT(sufile)->mi_entry_size;
 262         __u64 segnum, maxsegnum, last_alloc;
 263         void *kaddr;
 264         unsigned long nsegments, ncleansegs, nsus;
 265         int ret, i, j;
 266
 267         down_write(&NILFS_MDT(sufile)->mi_sem);
 268
 269         ret = nilfs_sufile_get_header_block(sufile, &header_bh);
 270         if (ret < 0)
 271                 goto out_sem;
 272         kaddr = kmap_atomic(header_bh->b_page, KM_USER0);
 273         header = nilfs_sufile_block_get_header(sufile, header_bh, kaddr);
 274         ncleansegs = le64_to_cpu(header->sh_ncleansegs);
 275         last_alloc = le64_to_cpu(header->sh_last_alloc);
 276         kunmap_atomic(kaddr, KM_USER0);
 277
 278         nsegments = nilfs_sufile_get_nsegments(sufile);
 279         segnum = last_alloc + 1;
 280         maxsegnum = nsegments - 1;
 281         for (i = 0; i < nsegments; i += nsus) {
 282                 if (segnum >= nsegments) {
 283                         /* wrap around */
 284                         segnum = 0;
 285                         maxsegnum = last_alloc;
 286                 }
 287                 ret = nilfs_sufile_get_segment_usage_block(sufile, segnum, 1,
 288                                                            &su_bh);
 289                 if (ret < 0)
 290                         goto out_header;
 291                 kaddr = kmap_atomic(su_bh->b_page, KM_USER0);
 292                 su = nilfs_sufile_block_get_segment_usage(
 293                         sufile, segnum, su_bh, kaddr);
 294
 295                 nsus = nilfs_sufile_segment_usages_in_block(
 296                         sufile, segnum, maxsegnum);
 297                 for (j = 0; j < nsus; j++, su = (void *)su + susz, segnum++) {
 298                         if (!nilfs_segment_usage_clean(su))
 299                                 continue;
 300                         /* found a clean segment */
 301                         nilfs_segment_usage_set_dirty(su);
 302                         kunmap_atomic(kaddr, KM_USER0);
 303
 304                         kaddr = kmap_atomic(header_bh->b_page, KM_USER0);
 305                         header = nilfs_sufile_block_get_header(
 306                                 sufile, header_bh, kaddr);
 307                         le64_add_cpu(&header->sh_ncleansegs, -1);
 308                         le64_add_cpu(&header->sh_ndirtysegs, 1);
 309                         header->sh_last_alloc = cpu_to_le64(segnum);
 310                         kunmap_atomic(kaddr, KM_USER0);
 311
 312                         nilfs_mdt_mark_buffer_dirty(header_bh);
 313                         nilfs_mdt_mark_buffer_dirty(su_bh);
 314                         nilfs_mdt_mark_dirty(sufile);
 315                         brelse(su_bh);
 316                         *segnump = segnum;
 317                         goto out_header;
 318                 }
 319
 320                 kunmap_atomic(kaddr, KM_USER0);
 321                 brelse(su_bh);
 322         }
 323
 324         /* no segments left */
 325         ret = -ENOSPC;
 326
 327  out_header:
 328         brelse(header_bh);
 329
 330  out_sem:
 331         up_write(&NILFS_MDT(sufile)->mi_sem);
 332         return ret;
 333 }
 334
 335 void nilfs_sufile_do_cancel_free(struct inode *sufile, __u64 segnum,
 336                                  struct buffer_head *header_bh,
 337                                  struct buffer_head *su_bh)
 338 {
 339         struct nilfs_segment_usage *su;
 340         void *kaddr;
 341
 342         kaddr = kmap_atomic(su_bh->b_page, KM_USER0);
 343         su = nilfs_sufile_block_get_segment_usage(sufile, segnum, su_bh, kaddr);
 344         if (unlikely(!nilfs_segment_usage_clean(su))) {
 345                 printk(KERN_WARNING "%s: segment %llu must be clean\n",
 346                        __func__, (unsigned long long)segnum);
 347                 kunmap_atomic(kaddr, KM_USER0);
 348                 return;
 349         }
 350         nilfs_segment_usage_set_dirty(su);
 351         kunmap_atomic(kaddr, KM_USER0);
 352
 353         nilfs_sufile_mod_counter(header_bh, -1, 1);
 354         nilfs_mdt_mark_buffer_dirty(su_bh);
 355         nilfs_mdt_mark_dirty(sufile);
 356 }
 357
 358 void nilfs_sufile_do_scrap(struct inode *sufile, __u64 segnum,
 359                            struct buffer_head *header_bh,
 360                            struct buffer_head *su_bh)
 361 {
 362         struct nilfs_segment_usage *su;
 363         void *kaddr;
 364         int clean, dirty;
 365
 366         kaddr = kmap_atomic(su_bh->b_page, KM_USER0);
 367         su = nilfs_sufile_block_get_segment_usage(sufile, segnum, su_bh, kaddr);
 368         if (su->su_flags == cpu_to_le32(1UL << NILFS_SEGMENT_USAGE_DIRTY) &&
 369             su->su_nblocks == cpu_to_le32(0)) {
 370                 kunmap_atomic(kaddr, KM_USER0);
 371                 return;
 372         }
 373         clean = nilfs_segment_usage_clean(su);
 374         dirty = nilfs_segment_usage_dirty(su);
 375
 376         /* make the segment garbage */
 377         su->su_lastmod = cpu_to_le64(0);
 378         su->su_nblocks = cpu_to_le32(0);
 379         su->su_flags = cpu_to_le32(1UL << NILFS_SEGMENT_USAGE_DIRTY);
 380         kunmap_atomic(kaddr, KM_USER0);
 381
 382         nilfs_sufile_mod_counter(header_bh, clean ? (u64)-1 : 0, dirty ? 0 : 1);
 383         nilfs_mdt_mark_buffer_dirty(su_bh);
 384         nilfs_mdt_mark_dirty(sufile);
 385 }
 386
 387 void nilfs_sufile_do_free(struct inode *sufile, __u64 segnum,
 388                           struct buffer_head *header_bh,
 389                           struct buffer_head *su_bh)
 390 {
 391         struct nilfs_segment_usage *su;
 392         void *kaddr;
 393         int sudirty;
 394
 395         kaddr = kmap_atomic(su_bh->b_page, KM_USER0);
 396         su = nilfs_sufile_block_get_segment_usage(sufile, segnum, su_bh, kaddr);
 397         if (nilfs_segment_usage_clean(su)) {
 398                 printk(KERN_WARNING "%s: segment %llu is already clean\n",
 399                        __func__, (unsigned long long)segnum);
 400                 kunmap_atomic(kaddr, KM_USER0);
 401                 return;
 402         }
 403         WARN_ON(nilfs_segment_usage_error(su));
 404         WARN_ON(!nilfs_segment_usage_dirty(su));
 405
 406         sudirty = nilfs_segment_usage_dirty(su);
 407         nilfs_segment_usage_set_clean(su);
 408         kunmap_atomic(kaddr, KM_USER0);
 409         nilfs_mdt_mark_buffer_dirty(su_bh);
 410
 411         nilfs_sufile_mod_counter(header_bh, 1, sudirty ? (u64)-1 : 0);
 412         nilfs_mdt_mark_dirty(sufile);
 413 }
 414
 415 /**
 416  * nilfs_sufile_get_segment_usage - get a segment usage
 417  * @sufile: inode of segment usage file
 418  * @segnum: segment number
 419  * @sup: pointer to segment usage
 420  * @bhp: pointer to buffer head
 421  *
 422  * Description: nilfs_sufile_get_segment_usage() acquires the segment usage
 423  * specified by @segnum.
 424  *
 425  * Return Value: On success, 0 is returned, and the segment usage and the
 426  * buffer head of the buffer on which the segment usage is located are stored
 427  * in the place pointed by @sup and @bhp, respectively. On error, one of the
 428  * following negative error codes is returned.
 429  *
 430  * %-EIO - I/O error.
 431  *
 432  * %-ENOMEM - Insufficient amount of memory available.
 433  *
 434  * %-EINVAL - Invalid segment usage number.
 435  */
 436 int nilfs_sufile_get_segment_usage(struct inode *sufile, __u64 segnum,
 437                                    struct nilfs_segment_usage **sup,
 438                                    struct buffer_head **bhp)
 439 {
 440         struct buffer_head *bh;
 441         struct nilfs_segment_usage *su;
 442         void *kaddr;
 443         int ret;
 444
 445         /* segnum is 0 origin */
 446         if (segnum >= nilfs_sufile_get_nsegments(sufile))
 447                 return -EINVAL;
 448         down_write(&NILFS_MDT(sufile)->mi_sem);
 449         ret = nilfs_sufile_get_segment_usage_block(sufile, segnum, 1, &bh);
 450         if (ret < 0)
 451                 goto out_sem;
 452         kaddr = kmap(bh->b_page);
 453         su = nilfs_sufile_block_get_segment_usage(sufile, segnum, bh, kaddr);
 454         if (nilfs_segment_usage_error(su)) {
 455                 kunmap(bh->b_page);
 456                 brelse(bh);
 457                 ret = -EINVAL;
 458                 goto out_sem;
 459         }
 460
 461         if (sup != NULL)
 462                 *sup = su;
 463         *bhp = bh;
 464
 465  out_sem:
 466         up_write(&NILFS_MDT(sufile)->mi_sem);
 467         return ret;
 468 }
 469
 470 /**
 471  * nilfs_sufile_put_segment_usage - put a segment usage
 472  * @sufile: inode of segment usage file
 473  * @segnum: segment number
 474  * @bh: buffer head
 475  *
 476  * Description: nilfs_sufile_put_segment_usage() releases the segment usage
 477  * specified by @segnum. @bh must be the buffer head which have been returned
 478  * by a previous call to nilfs_sufile_get_segment_usage() with @segnum.
 479  */
 480 void nilfs_sufile_put_segment_usage(struct inode *sufile, __u64 segnum,
 481                                     struct buffer_head *bh)
 482 {
 483         kunmap(bh->b_page);
 484         brelse(bh);
 485 }
 486
 487 /**
 488  * nilfs_sufile_get_stat - get segment usage statistics
 489  * @sufile: inode of segment usage file
 490  * @stat: pointer to a structure of segment usage statistics
 491  *
 492  * Description: nilfs_sufile_get_stat() returns information about segment
 493  * usage.
 494  *
 495  * Return Value: On success, 0 is returned, and segment usage information is
 496  * stored in the place pointed by @stat. On error, one of the following
 497  * negative error codes is returned.
 498  *
 499  * %-EIO - I/O error.
 500  *
 501  * %-ENOMEM - Insufficient amount of memory available.
 502  */
 503 int nilfs_sufile_get_stat(struct inode *sufile, struct nilfs_sustat *sustat)
 504 {
 505         struct buffer_head *header_bh;
 506         struct nilfs_sufile_header *header;
 507         struct the_nilfs *nilfs = NILFS_MDT(sufile)->mi_nilfs;
 508         void *kaddr;
 509         int ret;
 510
 511         down_read(&NILFS_MDT(sufile)->mi_sem);
 512
 513         ret = nilfs_sufile_get_header_block(sufile, &header_bh);
 514         if (ret < 0)
 515                 goto out_sem;
 516
 517         kaddr = kmap_atomic(header_bh->b_page, KM_USER0);
 518         header = nilfs_sufile_block_get_header(sufile, header_bh, kaddr);
 519         sustat->ss_nsegs = nilfs_sufile_get_nsegments(sufile);
 520         sustat->ss_ncleansegs = le64_to_cpu(header->sh_ncleansegs);
 521         sustat->ss_ndirtysegs = le64_to_cpu(header->sh_ndirtysegs);
 522         sustat->ss_ctime = nilfs->ns_ctime;
 523         sustat->ss_nongc_ctime = nilfs->ns_nongc_ctime;
 524         spin_lock(&nilfs->ns_last_segment_lock);
 525         sustat->ss_prot_seq = nilfs->ns_prot_seq;
 526         spin_unlock(&nilfs->ns_last_segment_lock);
 527         kunmap_atomic(kaddr, KM_USER0);
 528         brelse(header_bh);
 529
 530  out_sem:
 531         up_read(&NILFS_MDT(sufile)->mi_sem);
 532         return ret;
 533 }
 534
 535 /**
 536  * nilfs_sufile_get_ncleansegs - get the number of clean segments
 537  * @sufile: inode of segment usage file
 538  * @nsegsp: pointer to the number of clean segments
 539  *
 540  * Description: nilfs_sufile_get_ncleansegs() acquires the number of clean
 541  * segments.
 542  *
 543  * Return Value: On success, 0 is returned and the number of clean segments is
 544  * stored in the place pointed by @nsegsp. On error, one of the following
 545  * negative error codes is returned.
 546  *
 547  * %-EIO - I/O error.
 548  *
 549  * %-ENOMEM - Insufficient amount of memory available.
 550  */
 551 int nilfs_sufile_get_ncleansegs(struct inode *sufile, unsigned long *nsegsp)
 552 {
 553         struct nilfs_sustat sustat;
 554         int ret;
 555
 556         ret = nilfs_sufile_get_stat(sufile, &sustat);
 557         if (ret == 0)
 558                 *nsegsp = sustat.ss_ncleansegs;
 559         return ret;
 560 }
 561
 562 void nilfs_sufile_do_set_error(struct inode *sufile, __u64 segnum,
 563                                struct buffer_head *header_bh,
 564                                struct buffer_head *su_bh)
 565 {
 566         struct nilfs_segment_usage *su;
 567         void *kaddr;
 568         int suclean;
 569
 570         kaddr = kmap_atomic(su_bh->b_page, KM_USER0);
 571         su = nilfs_sufile_block_get_segment_usage(sufile, segnum, su_bh, kaddr);
 572         if (nilfs_segment_usage_error(su)) {
 573                 kunmap_atomic(kaddr, KM_USER0);
 574                 return;
 575         }
 576         suclean = nilfs_segment_usage_clean(su);
 577         nilfs_segment_usage_set_error(su);
 578         kunmap_atomic(kaddr, KM_USER0);
 579
 580         if (suclean)
 581                 nilfs_sufile_mod_counter(header_bh, -1, 0);
 582         nilfs_mdt_mark_buffer_dirty(su_bh);
 583         nilfs_mdt_mark_dirty(sufile);
 584 }
 585
 586 /**
 587  * nilfs_sufile_get_suinfo -
 588  * @sufile: inode of segment usage file
 589  * @segnum: segment number to start looking
 590  * @buf: array of suinfo
 591  * @sisz: byte size of suinfo
 592  * @nsi: size of suinfo array
 593  *
 594  * Description:
 595  *
 596  * Return Value: On success, 0 is returned and .... On error, one of the
 597  * following negative error codes is returned.
 598  *
 599  * %-EIO - I/O error.
 600  *
 601  * %-ENOMEM - Insufficient amount of memory available.
 602  */
 603 ssize_t nilfs_sufile_get_suinfo(struct inode *sufile, __u64 segnum, void *buf,
 604                                 unsigned sisz, size_t nsi)
 605 {
 606         struct buffer_head *su_bh;
 607         struct nilfs_segment_usage *su;
 608         struct nilfs_suinfo *si = buf;
 609         size_t susz = NILFS_MDT(sufile)->mi_entry_size;
 610         struct the_nilfs *nilfs = NILFS_MDT(sufile)->mi_nilfs;
 611         void *kaddr;
 612         unsigned long nsegs, segusages_per_block;
 613         ssize_t n;
 614         int ret, i, j;
 615
 616         down_read(&NILFS_MDT(sufile)->mi_sem);
 617
 618         segusages_per_block = nilfs_sufile_segment_usages_per_block(sufile);
 619         nsegs = min_t(unsigned long,
 620                       nilfs_sufile_get_nsegments(sufile) - segnum,
 621                       nsi);
 622         for (i = 0; i < nsegs; i += n, segnum += n) {
 623                 n = min_t(unsigned long,
 624                           segusages_per_block -
 625                                   nilfs_sufile_get_offset(sufile, segnum),
 626                           nsegs - i);
 627                 ret = nilfs_sufile_get_segment_usage_block(sufile, segnum, 0,
 628                                                            &su_bh);
 629                 if (ret < 0) {
 630                         if (ret != -ENOENT)
 631                                 goto out;
 632                         /* hole */
 633                         memset(si, 0, sisz * n);
 634                         si = (void *)si + sisz * n;
 635                         continue;
 636                 }
 637
 638                 kaddr = kmap_atomic(su_bh->b_page, KM_USER0);
 639                 su = nilfs_sufile_block_get_segment_usage(
 640                         sufile, segnum, su_bh, kaddr);
 641                 for (j = 0; j < n;
 642                      j++, su = (void *)su + susz, si = (void *)si + sisz) {
 643                         si->sui_lastmod = le64_to_cpu(su->su_lastmod);
 644                         si->sui_nblocks = le32_to_cpu(su->su_nblocks);
 645                         si->sui_flags = le32_to_cpu(su->su_flags) &
 646                                 ~(1UL << NILFS_SEGMENT_USAGE_ACTIVE);
 647                         if (nilfs_segment_is_active(nilfs, segnum + j))
 648                                 si->sui_flags |=
 649                                         (1UL << NILFS_SEGMENT_USAGE_ACTIVE);
 650                 }
 651                 kunmap_atomic(kaddr, KM_USER0);
 652                 brelse(su_bh);
 653         }
 654         ret = nsegs;
 655
 656  out:
 657         up_read(&NILFS_MDT(sufile)->mi_sem);
 658         return ret;
 659 }