detect-renamed.diff

   1 This patch adds the --detect-renamed option which makes rsync notice files
   2 that either (1) match in size & modify-time (plus the basename, if possible)
   3 or (2) match in size & checksum (when --checksum was also specified) and use
   4 each match as an alternate basis file to speed up the transfer.
   5
   6 The algorithm attempts to scan the receiving-side's files in an efficient
   7 manner.  If --delete[-before] is enabled, we'll take advantage of the
   8 pre-transfer delete pass to prepare any alternate-basis-file matches we
   9 might find.  If --delete-before is not enabled, rsync does the rename scan
  10 during the regular file-sending scan (scanning each directory right before
  11 the generator starts updating files from that dir).  In this latter mode,
  12 rsync might delay the updating of a file (if no alternate-basis match was
  13 yet found) until the full scan of the receiving side is complete, at which
  14 point any delayed files are processed.
  15
  16 I chose to hard-link the alternate-basis files into a ".~tmp~" subdir that
  17 takes advantage of rsync's pre-existing partial-dir logic.  This uses less
  18 memory than trying to keep track of the matches internally, and also allows
  19 any deletions or file-updates to occur normally without interfering with
  20 these alternate-basis discoveries.
  21
  22 To use this patch, run these commands for a successful build:
  23
  24     patch -p1 <patches/detect-renamed.diff
  25     ./configure                                 (optional if already run)
  26     make
  27
  28 TODO:
  29
  30   We need to never return a match from fattr_find() that has a basis
  31   file.  This will ensure that we don't try to give a renamed file to
  32   a file that can't use it, while missing out on giving it to a file
  33   that could use it.
  34
  35 diff --git a/compat.c b/compat.c
  36 --- a/compat.c
  37 +++ b/compat.c
  38 @@ -41,6 +41,7 @@ extern int checksum_seed;
  39  extern int basis_dir_cnt;
  40  extern int prune_empty_dirs;
  41  extern int protocol_version;
  42 +extern int detect_renamed;
  43  extern int protect_args;
  44  extern int preserve_uid;
  45  extern int preserve_gid;
  46 @@ -117,6 +118,7 @@ void set_allow_inc_recurse(void)
  47                 allow_inc_recurse = 0;
  48         else if (!am_sender
  49          && (delete_before || delete_after
  50 +         || detect_renamed
  51           || delay_updates || prune_empty_dirs))
  52                 allow_inc_recurse = 0;
  53         else if (am_server && !local_server
  54 diff --git a/flist.c b/flist.c
  55 --- a/flist.c
  56 +++ b/flist.c
  57 @@ -63,6 +63,7 @@ extern int non_perishable_cnt;
  58  extern int prune_empty_dirs;
  59  extern int copy_links;
  60  extern int copy_unsafe_links;
  61 +extern int detect_renamed;
  62  extern int protocol_version;
  63  extern int sanitize_paths;
  64  extern int munge_symlinks;
  65 @@ -120,6 +121,8 @@ static int64 tmp_dev, tmp_ino;
  66  #endif
  67  static char tmp_sum[MAX_DIGEST_LEN];
  68
  69 +struct file_list the_fattr_list;
  70 +
  71  static char empty_sum[MAX_DIGEST_LEN];
  72  static int flist_count_offset; /* for --delete --progress */
  73  static int dir_count = 0;
  74 @@ -287,6 +290,45 @@ static int is_excluded(const char *fname, int is_dir, int filter_level)
  75         return 0;
  76  }
  77
  78 +static int fattr_compare(struct file_struct **file1, struct file_struct **file2)
  79 +{
  80 +       struct file_struct *f1 = *file1;
  81 +       struct file_struct *f2 = *file2;
  82 +       int64 len1 = F_LENGTH(f1), len2 = F_LENGTH(f2);
  83 +       int diff;
  84 +
  85 +       if (!f1->basename || !S_ISREG(f1->mode) || !len1) {
  86 +               if (!f2->basename || !S_ISREG(f2->mode) || !len2)
  87 +                       return 0;
  88 +               return 1;
  89 +       }
  90 +       if (!f2->basename || !S_ISREG(f2->mode) || !len2)
  91 +               return -1;
  92 +
  93 +       /* Don't use diff for values that are longer than an int. */
  94 +       if (len1 != len2)
  95 +               return len1 < len2 ? -1 : 1;
  96 +
  97 +       if (always_checksum) {
  98 +               diff = u_memcmp(F_SUM(f1), F_SUM(f2), checksum_len);
  99 +               if (diff)
 100 +                       return diff;
 101 +       } else if (f1->modtime != f2->modtime)
 102 +               return f1->modtime < f2->modtime ? -1 : 1;
 103 +
 104 +       diff = u_strcmp(f1->basename, f2->basename);
 105 +       if (diff)
 106 +               return diff;
 107 +
 108 +       if (f1->dirname == f2->dirname)
 109 +               return 0;
 110 +       if (!f1->dirname)
 111 +               return -1;
 112 +       if (!f2->dirname)
 113 +               return 1;
 114 +       return u_strcmp(f1->dirname, f2->dirname);
 115 +}
 116 +
 117  static void send_directory(int f, struct file_list *flist,
 118                            char *fbuf, int len, int flags);
 119
 120 @@ -2263,6 +2305,25 @@ struct file_list *recv_file_list(int f)
 121
 122         flist_sort_and_clean(flist, relative_paths);
 123
 124 +       if (detect_renamed) {
 125 +               int j = flist->used;
 126 +               the_fattr_list.used = j;
 127 +               the_fattr_list.files = new_array(struct file_struct *, j);
 128 +               if (!the_fattr_list.files)
 129 +                       out_of_memory("recv_file_list");
 130 +               memcpy(the_fattr_list.files, flist->files,
 131 +                      j * sizeof (struct file_struct *));
 132 +               qsort(the_fattr_list.files, j,
 133 +                     sizeof the_fattr_list.files[0], (int (*)())fattr_compare);
 134 +               the_fattr_list.low = 0;
 135 +               while (j-- > 0) {
 136 +                       struct file_struct *fp = the_fattr_list.files[j];
 137 +                       if (fp->basename && S_ISREG(fp->mode) && F_LENGTH(fp))
 138 +                               break;
 139 +               }
 140 +               the_fattr_list.high = j;
 141 +       }
 142 +
 143         if (protocol_version < 30) {
 144                 /* Recv the io_error flag */
 145                 if (ignore_errors)
 146 diff --git a/generator.c b/generator.c
 147 --- a/generator.c
 148 +++ b/generator.c
 149 @@ -80,6 +80,7 @@ extern char *basis_dir[];
 150  extern int compare_dest;
 151  extern int copy_dest;
 152  extern int link_dest;
 153 +extern int detect_renamed;
 154  extern int whole_file;
 155  extern int list_only;
 156  extern int read_batch;
 157 @@ -98,6 +99,7 @@ extern char *backup_suffix;
 158  extern int backup_suffix_len;
 159  extern struct file_list *cur_flist, *first_flist, *dir_flist;
 160  extern struct filter_list_struct daemon_filter_list;
 161 +extern struct file_list the_fattr_list;
 162
 163  int ignore_perishable = 0;
 164  int non_perishable_cnt = 0;
 165 @@ -105,6 +107,7 @@ int maybe_ATTRS_REPORT = 0;
 166
 167  static dev_t dev_zero;
 168  static int deletion_count = 0; /* used to implement --max-delete */
 169 +static int unexplored_dirs = 1;
 170  static int deldelay_size = 0, deldelay_cnt = 0;
 171  static char *deldelay_buf = NULL;
 172  static int deldelay_fd = -1;
 173 @@ -115,7 +118,7 @@ static int need_retouch_dir_times;
 174  static int need_retouch_dir_perms;
 175  static const char *solo_file = NULL;
 176
 177 -/* For calling delete_item() and delete_dir_contents(). */
 178 +/* For calling delete_item(), delete_dir_contents(), and delete_in_dir(). */
 179  #define DEL_NO_UID_WRITE       (1<<0) /* file/dir has our uid w/o write perm */
 180  #define DEL_RECURSE            (1<<1) /* if dir, delete all contents */
 181  #define DEL_DIR_IS_EMPTY       (1<<2) /* internal delete_FUNCTIONS use only */
 182 @@ -124,6 +127,7 @@ static const char *solo_file = NULL;
 183  #define DEL_FOR_SYMLINK        (1<<5) /* making room for a replacement symlink */
 184  #define DEL_FOR_DEVICE         (1<<6) /* making room for a replacement device */
 185  #define DEL_FOR_SPECIAL        (1<<7) /* making room for a replacement special */
 186 +#define DEL_NO_DELETIONS       (1<<9) /* just check for renames w/o deleting */
 187
 188  #define DEL_MAKE_ROOM (DEL_FOR_FILE|DEL_FOR_DIR|DEL_FOR_SYMLINK|DEL_FOR_DEVICE|DEL_FOR_SPECIAL)
 189
 190 @@ -148,11 +152,121 @@ static int is_backup_file(char *fn)
 191         return k > 0 && strcmp(fn+k, backup_suffix) == 0;
 192  }
 193
 194 +/* Search for a regular file that matches either (1) the size & modified
 195 + * time (plus the basename, if possible) or (2) the size & checksum.  If
 196 + * we find an exact match down to the dirname, return -1 because we found
 197 + * an up-to-date file in the transfer, not a renamed file. */
 198 +static int fattr_find(struct file_struct *f, char *fname)
 199 +{
 200 +       int low = the_fattr_list.low, high = the_fattr_list.high;
 201 +       int mid, ok_match = -1, good_match = -1;
 202 +       struct file_struct *fmid;
 203 +       int diff;
 204 +
 205 +       while (low <= high) {
 206 +               mid = (low + high) / 2;
 207 +               fmid = the_fattr_list.files[mid];
 208 +               if (F_LENGTH(fmid) != F_LENGTH(f)) {
 209 +                       if (F_LENGTH(fmid) < F_LENGTH(f))
 210 +                               low = mid + 1;
 211 +                       else
 212 +                               high = mid - 1;
 213 +                       continue;
 214 +               }
 215 +               if (always_checksum) {
 216 +                       /* We use the FLAG_FILE_SENT flag to indicate when we
 217 +                        * have computed the checksum for an entry. */
 218 +                       if (!(f->flags & FLAG_FILE_SENT)) {
 219 +                               if (fmid->modtime == f->modtime
 220 +                                && f_name_cmp(fmid, f) == 0)
 221 +                                       return -1; /* assume we can't help */
 222 +                               file_checksum(fname, F_SUM(f), F_LENGTH(f));
 223 +                               f->flags |= FLAG_FILE_SENT;
 224 +                       }
 225 +                       diff = u_memcmp(F_SUM(fmid), F_SUM(f), checksum_len);
 226 +                       if (diff) {
 227 +                               if (diff < 0)
 228 +                                       low = mid + 1;
 229 +                               else
 230 +                                       high = mid - 1;
 231 +                               continue;
 232 +                       }
 233 +               } else {
 234 +                       if (fmid->modtime != f->modtime) {
 235 +                               if (fmid->modtime < f->modtime)
 236 +                                       low = mid + 1;
 237 +                               else
 238 +                                       high = mid - 1;
 239 +                               continue;
 240 +                       }
 241 +               }
 242 +               ok_match = mid;
 243 +               diff = u_strcmp(fmid->basename, f->basename);
 244 +               if (diff == 0) {
 245 +                       good_match = mid;
 246 +                       if (fmid->dirname == f->dirname)
 247 +                               return -1; /* file is up-to-date */
 248 +                       if (!fmid->dirname) {
 249 +                               low = mid + 1;
 250 +                               continue;
 251 +                       }
 252 +                       if (!f->dirname) {
 253 +                               high = mid - 1;
 254 +                               continue;
 255 +                       }
 256 +                       diff = u_strcmp(fmid->dirname, f->dirname);
 257 +                       if (diff == 0)
 258 +                               return -1; /* file is up-to-date */
 259 +               }
 260 +               if (diff < 0)
 261 +                       low = mid + 1;
 262 +               else
 263 +                       high = mid - 1;
 264 +       }
 265 +
 266 +       return good_match >= 0 ? good_match : ok_match;
 267 +}
 268 +
 269 +static void look_for_rename(struct file_struct *file, char *fname)
 270 +{
 271 +       struct file_struct *fp;
 272 +       char *partialptr, *fn;
 273 +       STRUCT_STAT st;
 274 +       int ndx;
 275 +
 276 +       if (!partial_dir || (ndx = fattr_find(file, fname)) < 0)
 277 +               return;
 278 +
 279 +       fp = the_fattr_list.files[ndx];
 280 +       fn = f_name(fp, NULL);
 281 +       /* We don't provide an alternate-basis file if there is a basis file. */
 282 +       if (link_stat(fn, &st, 0) == 0)
 283 +               return;
 284 +
 285 +       if (!dry_run) {
 286 +               if ((partialptr = partial_dir_fname(fn)) == NULL
 287 +                || !handle_partial_dir(partialptr, PDIR_CREATE))
 288 +                       return;
 289 +               /* We only use the file if we can hard-link it into our tmp dir. */
 290 +               if (link(fname, partialptr) != 0) {
 291 +                       if (errno != EEXIST)
 292 +                               handle_partial_dir(partialptr, PDIR_DELETE);
 293 +                       return;
 294 +               }
 295 +       }
 296 +
 297 +       /* I think this falls into the -vv category with "%s is uptodate", etc. */
 298 +       if (verbose > 1)
 299 +               rprintf(FINFO, "found renamed: %s => %s\n", fname, fn);
 300 +}
 301 +
 302  /* Delete a file or directory.  If DEL_RECURSE is set in the flags, this will
 303   * delete recursively.
 304   *
 305   * Note that fbuf must point to a MAXPATHLEN buffer if the mode indicates it's
 306   * a directory! (The buffer is used for recursion, but returned unchanged.)
 307 + *
 308 + * Also note: --detect-rename may use this routine with DEL_NO_DELETIONS set!
 309   */
 310  static enum delret delete_item(char *fbuf, uint16 mode, uint16 flags)
 311  {
 312 @@ -186,6 +300,8 @@ static enum delret delete_item(char *fbuf, uint16 mode, uint16 flags)
 313                         goto check_ret;
 314                 /* OK: try to delete the directory. */
 315         }
 316 +       if (flags & DEL_NO_DELETIONS)
 317 +               return DR_SUCCESS;
 318
 319         if (!(flags & DEL_MAKE_ROOM) && max_delete >= 0 && ++deletion_count > max_delete)
 320                 return DR_AT_LIMIT;
 321 @@ -241,6 +357,8 @@ static enum delret delete_item(char *fbuf, uint16 mode, uint16 flags)
 322   * its contents, otherwise just checks for content.  Returns DR_SUCCESS or
 323   * DR_NOT_EMPTY.  Note that fname must point to a MAXPATHLEN buffer!  (The
 324   * buffer is used for recursion, but returned unchanged.)
 325 + *
 326 + * Note: --detect-rename may use this routine with DEL_NO_DELETIONS set!
 327   */
 328  static enum delret delete_dir_contents(char *fname, uint16 flags)
 329  {
 330 @@ -260,7 +378,9 @@ static enum delret delete_dir_contents(char *fname, uint16 flags)
 331         save_filters = push_local_filters(fname, dlen);
 332
 333         non_perishable_cnt = 0;
 334 +       file_extra_cnt += SUM_EXTRA_CNT;
 335         dirlist = get_dirlist(fname, dlen, 0);
 336 +       file_extra_cnt -= SUM_EXTRA_CNT;
 337         ret = non_perishable_cnt ? DR_NOT_EMPTY : DR_SUCCESS;
 338
 339         if (!dirlist->used)
 340 @@ -300,7 +420,8 @@ static enum delret delete_dir_contents(char *fname, uint16 flags)
 341                 if (S_ISDIR(fp->mode)) {
 342                         if (delete_dir_contents(fname, flags | DEL_RECURSE) != DR_SUCCESS)
 343                                 ret = DR_NOT_EMPTY;
 344 -               }
 345 +               } else if (detect_renamed && S_ISREG(fp->mode))
 346 +                       look_for_rename(fp, fname);
 347                 if (delete_item(fname, fp->mode, flags) != DR_SUCCESS)
 348                         ret = DR_NOT_EMPTY;
 349         }
 350 @@ -465,13 +586,18 @@ static void do_delayed_deletions(char *delbuf)
 351   * all the --delete-WHEN options.  Note that the fbuf pointer must point to a
 352   * MAXPATHLEN buffer with the name of the directory in it (the functions we
 353   * call will append names onto the end, but the old dir value will be restored
 354 - * on exit). */
 355 -static void delete_in_dir(char *fbuf, struct file_struct *file, dev_t *fs_dev)
 356 + * on exit).
 357 + *
 358 + * Note:  --detect-rename may use this routine with DEL_NO_DELETIONS set!
 359 + */
 360 +static void delete_in_dir(char *fbuf, struct file_struct *file, dev_t *fs_dev,
 361 +                         int del_flags)
 362  {
 363         static int already_warned = 0;
 364         struct file_list *dirlist;
 365 -       char delbuf[MAXPATHLEN];
 366 -       int dlen, i;
 367 +       char *p, delbuf[MAXPATHLEN];
 368 +       unsigned remainder;
 369 +       int dlen, i, restore_dot = 0;
 370         int save_uid_ndx = uid_ndx;
 371
 372         if (!fbuf) {
 373 @@ -486,17 +612,22 @@ static void delete_in_dir(char *fbuf, struct file_struct *file, dev_t *fs_dev)
 374                 maybe_send_keepalive();
 375
 376         if (io_error && !ignore_errors) {
 377 -               if (already_warned)
 378 +               if (!already_warned) {
 379 +                       rprintf(FINFO,
 380 +                           "IO error encountered -- skipping file deletion\n");
 381 +                       already_warned = 1;
 382 +               }
 383 +               if (!detect_renamed)
 384                         return;
 385 -               rprintf(FINFO,
 386 -                       "IO error encountered -- skipping file deletion\n");
 387 -               already_warned = 1;
 388 -               return;
 389 +               del_flags |= DEL_NO_DELETIONS;
 390         }
 391
 392         dlen = strlen(fbuf);
 393         change_local_filter_dir(fbuf, dlen, F_DEPTH(file));
 394
 395 +       if (detect_renamed)
 396 +               unexplored_dirs--;
 397 +
 398         if (one_file_system) {
 399                 if (file->flags & FLAG_TOP_DIR)
 400                         filesystem_dev = *fs_dev;
 401 @@ -509,6 +640,14 @@ static void delete_in_dir(char *fbuf, struct file_struct *file, dev_t *fs_dev)
 402
 403         dirlist = get_dirlist(fbuf, dlen, 0);
 404
 405 +       p = fbuf + dlen;
 406 +       if (dlen == 1 && *fbuf == '.') {
 407 +               restore_dot = 1;
 408 +               p = fbuf;
 409 +       } else if (dlen != 1 || *fbuf != '/')
 410 +               *p++ = '/';
 411 +       remainder = MAXPATHLEN - (p - fbuf);
 412 +
 413         /* If an item in dirlist is not found in flist, delete it
 414          * from the filesystem. */
 415         for (i = dirlist->used; i--; ) {
 416 @@ -521,19 +660,28 @@ static void delete_in_dir(char *fbuf, struct file_struct *file, dev_t *fs_dev)
 417                                         f_name(fp, NULL));
 418                         continue;
 419                 }
 420 +               if (detect_renamed && S_ISREG(fp->mode)) {
 421 +                       strlcpy(p, fp->basename, remainder);
 422 +                       look_for_rename(fp, fbuf);
 423 +               }
 424                 if (flist_find(cur_flist, fp) < 0) {
 425                         int flags = DEL_RECURSE;
 426                         if (!(fp->mode & S_IWUSR) && !am_root && (uid_t)F_OWNER(fp) == our_uid)
 427                                 flags |= DEL_NO_UID_WRITE;
 428                         f_name(fp, delbuf);
 429 -                       if (delete_during == 2) {
 430 -                               if (!remember_delete(fp, delbuf, flags))
 431 +                       if (delete_during == 2 && !(del_flags & DEL_NO_DELETIONS)) {
 432 +                               if (!remember_delete(fp, delbuf, del_flags | flags))
 433                                         break;
 434                         } else
 435 -                               delete_item(delbuf, fp->mode, flags);
 436 -               }
 437 +                               delete_item(delbuf, fp->mode, del_flags | flags);
 438 +               } else if (detect_renamed && S_ISDIR(fp->mode))
 439 +                       unexplored_dirs++;
 440         }
 441
 442 +       if (restore_dot)
 443 +               fbuf[0] = '.';
 444 +       fbuf[dlen] = '\0';
 445 +
 446         flist_free(dirlist);
 447
 448         if (!save_uid_ndx) {
 449 @@ -571,9 +719,9 @@ static void do_delete_pass(void)
 450                  || !S_ISDIR(st.st_mode))
 451                         continue;
 452
 453 -               delete_in_dir(fbuf, file, &st.st_dev);
 454 +               delete_in_dir(fbuf, file, &st.st_dev, 0);
 455         }
 456 -       delete_in_dir(NULL, NULL, &dev_zero);
 457 +       delete_in_dir(NULL, NULL, &dev_zero, 0);
 458
 459         if (do_progress && !am_server)
 460                 rprintf(FINFO, "                    \r");
 461 @@ -1213,6 +1361,7 @@ static void list_file_entry(struct file_struct *f)
 462         }
 463  }
 464
 465 +static struct bitbag *delayed_bits = NULL;
 466  static int phase = 0;
 467  static int dflt_perms;
 468
 469 @@ -1484,9 +1633,12 @@ static void recv_generator(char *fname, struct file_struct *file, int ndx,
 470                 }
 471                 else if (delete_during && f_out != -1 && !phase
 472                     && !(file->flags & FLAG_MISSING_DIR)) {
 473 -                       if (file->flags & FLAG_CONTENT_DIR)
 474 -                               delete_in_dir(fname, file, &real_sx.st.st_dev);
 475 -                       else
 476 +                       if (file->flags & FLAG_CONTENT_DIR) {
 477 +                               if (detect_renamed && real_ret != 0)
 478 +                                       unexplored_dirs++;
 479 +                               delete_in_dir(fname, file, &real_sx.st.st_dev,
 480 +                                             delete_during < 0 ? DEL_NO_DELETIONS : 0);
 481 +                       } else
 482                                 change_local_filter_dir(fname, strlen(fname), F_DEPTH(file));
 483                 }
 484                 goto cleanup;
 485 @@ -1764,8 +1916,14 @@ static void recv_generator(char *fname, struct file_struct *file, int ndx,
 486                         goto cleanup;
 487                 }
 488  #endif
 489 -               if (stat_errno == ENOENT)
 490 +               if (stat_errno == ENOENT) {
 491 +                       if (detect_renamed && unexplored_dirs > 0
 492 +                        && F_LENGTH(file)) {
 493 +                               bitbag_set_bit(delayed_bits, ndx);
 494 +                               return;
 495 +                       }
 496                         goto notify_others;
 497 +               }
 498                 rsyserr(FERROR_XFER, stat_errno, "recv_generator: failed to stat %s",
 499                         full_fname(fname));
 500                 goto cleanup;
 501 @@ -2155,6 +2313,12 @@ void generate_files(int f_out, const char *local_name)
 502         if (verbose > 2)
 503                 rprintf(FINFO, "generator starting pid=%ld\n", (long)getpid());
 504
 505 +       if (detect_renamed) {
 506 +               delayed_bits = bitbag_create(cur_flist->used);
 507 +               if (!delete_before && !delete_during)
 508 +                       delete_during = -1;
 509 +       }
 510 +
 511         if (delete_before && !solo_file && cur_flist->used > 0)
 512                 do_delete_pass();
 513         if (delete_during == 2) {
 514 @@ -2165,7 +2329,7 @@ void generate_files(int f_out, const char *local_name)
 515         }
 516         do_progress = 0;
 517
 518 -       if (append_mode > 0 || whole_file < 0)
 519 +       if (append_mode > 0 || detect_renamed || whole_file < 0)
 520                 whole_file = 0;
 521         if (verbose >= 2) {
 522                 rprintf(FINFO, "delta-transmission %s\n",
 523 @@ -2204,7 +2368,7 @@ void generate_files(int f_out, const char *local_name)
 524                                                 dirdev = MAKEDEV(DEV_MAJOR(devp), DEV_MINOR(devp));
 525                                         } else
 526                                                 dirdev = MAKEDEV(0, 0);
 527 -                                       delete_in_dir(fbuf, fp, &dirdev);
 528 +                                       delete_in_dir(fbuf, fp, &dirdev, 0);
 529                                 } else
 530                                         change_local_filter_dir(fbuf, strlen(fbuf), F_DEPTH(fp));
 531                         }
 532 @@ -2248,7 +2412,21 @@ void generate_files(int f_out, const char *local_name)
 533         } while ((cur_flist = cur_flist->next) != NULL);
 534
 535         if (delete_during)
 536 -               delete_in_dir(NULL, NULL, &dev_zero);
 537 +               delete_in_dir(NULL, NULL, &dev_zero, 0);
 538 +       if (detect_renamed) {
 539 +               if (delete_during < 0)
 540 +                       delete_during = 0;
 541 +               detect_renamed = 0;
 542 +
 543 +               for (i = -1; (i = bitbag_next_bit(delayed_bits, i)) >= 0; ) {
 544 +                       struct file_struct *file = cur_flist->files[i];
 545 +                       if (local_name)
 546 +                               strlcpy(fbuf, local_name, sizeof fbuf);
 547 +                       else
 548 +                               f_name(file, fbuf);
 549 +                       recv_generator(fbuf, file, i, itemizing, code, f_out);
 550 +               }
 551 +       }
 552         phase++;
 553         if (verbose > 2)
 554                 rprintf(FINFO, "generate_files phase=%d\n", phase);
 555 diff --git a/options.c b/options.c
 556 --- a/options.c
 557 +++ b/options.c
 558 @@ -82,6 +82,7 @@ int am_generator = 0;
 559  int am_starting_up = 1;
 560  int relative_paths = -1;
 561  int implied_dirs = 1;
 562 +int detect_renamed = 0;
 563  int numeric_ids = 0;
 564  int allow_8bit_chars = 0;
 565  int force_delete = 0;
 566 @@ -391,6 +392,7 @@ void usage(enum logcode F)
 567    rprintf(F,"     --modify-window=NUM     compare mod-times with reduced accuracy\n");
 568    rprintf(F," -T, --temp-dir=DIR          create temporary files in directory DIR\n");
 569    rprintf(F," -y, --fuzzy                 find similar file for basis if no dest file\n");
 570 +  rprintf(F,"     --detect-renamed        try to find renamed files to speed up the transfer\n");
 571    rprintf(F,"     --compare-dest=DIR      also compare destination files relative to DIR\n");
 572    rprintf(F,"     --copy-dest=DIR         ... and include copies of unchanged files\n");
 573    rprintf(F,"     --link-dest=DIR         hardlink to files in DIR when unchanged\n");
 574 @@ -578,6 +580,7 @@ static struct poptOption long_options[] = {
 575    {"compare-dest",     0,  POPT_ARG_STRING, 0, OPT_COMPARE_DEST, 0, 0 },
 576    {"copy-dest",        0,  POPT_ARG_STRING, 0, OPT_COPY_DEST, 0, 0 },
 577    {"link-dest",        0,  POPT_ARG_STRING, 0, OPT_LINK_DEST, 0, 0 },
 578 +  {"detect-renamed",   0,  POPT_ARG_NONE,   &detect_renamed, 0, 0, 0 },
 579    {"fuzzy",           'y', POPT_ARG_VAL,    &fuzzy_basis, 1, 0, 0 },
 580    {"no-fuzzy",         0,  POPT_ARG_VAL,    &fuzzy_basis, 0, 0, 0 },
 581    {"no-y",             0,  POPT_ARG_VAL,    &fuzzy_basis, 0, 0, 0 },
 582 @@ -1590,7 +1593,7 @@ int parse_arguments(int *argc_p, const char ***argv_p)
 583                 inplace = 1;
 584         }
 585
 586 -       if (delay_updates && !partial_dir)
 587 +       if ((delay_updates || detect_renamed) && !partial_dir)
 588                 partial_dir = tmp_partialdir;
 589
 590         if (inplace) {
 591 @@ -1599,6 +1602,7 @@ int parse_arguments(int *argc_p, const char ***argv_p)
 592                         snprintf(err_buf, sizeof err_buf,
 593                                  "--%s cannot be used with --%s\n",
 594                                  append_mode ? "append" : "inplace",
 595 +                                detect_renamed ? "detect-renamed" :
 596                                  delay_updates ? "delay-updates" : "partial-dir");
 597                         return 0;
 598                 }
 599 @@ -1945,6 +1949,8 @@ void server_options(char **args, int *argc_p)
 600                         args[ac++] = "--super";
 601                 if (size_only)
 602                         args[ac++] = "--size-only";
 603 +               if (detect_renamed)
 604 +                       args[ac++] = "--detect-renamed";
 605         } else {
 606                 if (skip_compress) {
 607                         if (asprintf(&arg, "--skip-compress=%s", skip_compress) < 0)
 608 diff --git a/rsync.yo b/rsync.yo
 609 --- a/rsync.yo
 610 +++ b/rsync.yo
 611 @@ -385,6 +385,7 @@ to the detailed description below for a complete description.  verb(
 612       --modify-window=NUM     compare mod-times with reduced accuracy
 613   -T, --temp-dir=DIR          create temporary files in directory DIR
 614   -y, --fuzzy                 find similar file for basis if no dest file
 615 +     --detect-renamed        try to find renamed files to speed the xfer
 616       --compare-dest=DIR      also compare received files relative to DIR
 617       --copy-dest=DIR         ... and include copies of unchanged files
 618       --link-dest=DIR         hardlink to files in DIR when unchanged
 619 @@ -1480,6 +1481,21 @@ Note that the use of the bf(--delete) option might get rid of any potential
 620  fuzzy-match files, so either use bf(--delete-after) or specify some
 621  filename exclusions if you need to prevent this.
 622
 623 +dit(bf(--detect-renamed)) With this option, for each new source file
 624 +(call it em(src/S)), rsync looks for a file em(dest/D) anywhere in the
 625 +destination that passes the quick check with em(src/S).  If such a em(dest/D)
 626 +is found, rsync uses it as an alternate basis for transferring em(S).  The
 627 +idea is that if em(src/S) was renamed from em(src/D) (as opposed to em(src/S)
 628 +passing the quick check with em(dest/D) by coincidence), the delta-transfer
 629 +algorithm will find that all the data matches between em(src/S) and em(dest/D),
 630 +and the transfer will be really fast.
 631 +
 632 +By default, alternate-basis files are hard-linked into a directory named
 633 +".~tmp~" in each file's destination directory, but if you've specified
 634 +the bf(--partial-dir) option, that directory will be used instead.  These
 635 +potential alternate-basis files will be removed as the transfer progresses.
 636 +This option conflicts with bf(--inplace) and bf(--append).
 637 +
 638  dit(bf(--compare-dest=DIR)) This option instructs rsync to use em(DIR) on
 639  the destination machine as an additional hierarchy to compare destination
 640  files against doing transfers (if the files are missing in the destination
 641 diff --git a/util.c b/util.c
 642 --- a/util.c
 643 +++ b/util.c
 644 @@ -1125,6 +1125,32 @@ int handle_partial_dir(const char *fname, int create)
 645         return 1;
 646  }
 647
 648 +/* We need to supply our own strcmp function for file list comparisons
 649 + * to ensure that signed/unsigned usage is consistent between machines. */
 650 +int u_strcmp(const char *p1, const char *p2)
 651 +{
 652 +        for ( ; *p1; p1++, p2++) {
 653 +               if (*p1 != *p2)
 654 +                       break;
 655 +       }
 656 +
 657 +       return (int)*(uchar*)p1 - (int)*(uchar*)p2;
 658 +}
 659 +
 660 +/* We need a memcmp function compares unsigned-byte values. */
 661 +int u_memcmp(const void *p1, const void *p2, size_t len)
 662 +{
 663 +       const uchar *u1 = p1;
 664 +       const uchar *u2 = p2;
 665 +
 666 +       while (len--) {
 667 +               if (*u1 != *u2)
 668 +                       return (int)*u1 - (int)*u2;
 669 +       }
 670 +
 671 +       return 0;
 672 +}
 673 +
 674  /**
 675   * Determine if a symlink points outside the current directory tree.
 676   * This is considered "unsafe" because e.g. when mirroring somebody