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 based-on: 40afd365cc8ca968fd16e161d24df5b8a8a520cc
  36 diff --git a/compat.c b/compat.c
  37 --- a/compat.c
  38 +++ b/compat.c
  39 @@ -41,6 +41,7 @@ extern int read_batch;
  40  extern int delay_updates;
  41  extern int checksum_seed;
  42  extern int basis_dir_cnt;
  43 +extern int detect_renamed;
  44  extern int prune_empty_dirs;
  45  extern int protocol_version;
  46  extern int protect_args;
  47 @@ -123,6 +124,7 @@ void set_allow_inc_recurse(void)
  48                 allow_inc_recurse = 0;
  49         else if (!am_sender
  50          && (delete_before || delete_after
  51 +         || detect_renamed
  52           || delay_updates || prune_empty_dirs))
  53                 allow_inc_recurse = 0;
  54         else if (am_server && !local_server
  55 diff --git a/flist.c b/flist.c
  56 --- a/flist.c
  57 +++ b/flist.c
  58 @@ -60,6 +60,7 @@ extern int non_perishable_cnt;
  59  extern int prune_empty_dirs;
  60  extern int copy_links;
  61  extern int copy_unsafe_links;
  62 +extern int detect_renamed;
  63  extern int protocol_version;
  64  extern int sanitize_paths;
  65  extern int munge_symlinks;
  66 @@ -120,6 +121,8 @@ static int64 tmp_dev = -1, tmp_ino;
  67  #endif
  68  static char tmp_sum[MAX_DIGEST_LEN];
  69
  70 +struct file_list the_fattr_list;
  71 +
  72  static char empty_sum[MAX_DIGEST_LEN];
  73  static int flist_count_offset; /* for --delete --progress */
  74  static int dir_count = 0;
  75 @@ -287,6 +290,45 @@ static int is_excluded(const char *fname, int is_dir, int filter_level)
  76         return 0;
  77  }
  78
  79 +static int fattr_compare(struct file_struct **file1, struct file_struct **file2)
  80 +{
  81 +       struct file_struct *f1 = *file1;
  82 +       struct file_struct *f2 = *file2;
  83 +       int64 len1 = F_LENGTH(f1), len2 = F_LENGTH(f2);
  84 +       int diff;
  85 +
  86 +       if (!f1->basename || !S_ISREG(f1->mode) || !len1) {
  87 +               if (!f2->basename || !S_ISREG(f2->mode) || !len2)
  88 +                       return 0;
  89 +               return 1;
  90 +       }
  91 +       if (!f2->basename || !S_ISREG(f2->mode) || !len2)
  92 +               return -1;
  93 +
  94 +       /* Don't use diff for values that are longer than an int. */
  95 +       if (len1 != len2)
  96 +               return len1 < len2 ? -1 : 1;
  97 +
  98 +       if (always_checksum) {
  99 +               diff = u_memcmp(F_SUM(f1), F_SUM(f2), checksum_len);
 100 +               if (diff)
 101 +                       return diff;
 102 +       } else if (f1->modtime != f2->modtime)
 103 +               return f1->modtime < f2->modtime ? -1 : 1;
 104 +
 105 +       diff = u_strcmp(f1->basename, f2->basename);
 106 +       if (diff)
 107 +               return diff;
 108 +
 109 +       if (f1->dirname == f2->dirname)
 110 +               return 0;
 111 +       if (!f1->dirname)
 112 +               return -1;
 113 +       if (!f2->dirname)
 114 +               return 1;
 115 +       return u_strcmp(f1->dirname, f2->dirname);
 116 +}
 117 +
 118  static void send_directory(int f, struct file_list *flist,
 119                            char *fbuf, int len, int flags);
 120
 121 @@ -2427,6 +2469,25 @@ struct file_list *recv_file_list(int f)
 122
 123         flist_sort_and_clean(flist, relative_paths);
 124
 125 +       if (detect_renamed) {
 126 +               int j = flist->used;
 127 +               the_fattr_list.used = j;
 128 +               the_fattr_list.files = new_array(struct file_struct *, j);
 129 +               if (!the_fattr_list.files)
 130 +                       out_of_memory("recv_file_list");
 131 +               memcpy(the_fattr_list.files, flist->files,
 132 +                      j * sizeof (struct file_struct *));
 133 +               qsort(the_fattr_list.files, j,
 134 +                     sizeof the_fattr_list.files[0], (int (*)())fattr_compare);
 135 +               the_fattr_list.low = 0;
 136 +               while (j-- > 0) {
 137 +                       struct file_struct *fp = the_fattr_list.files[j];
 138 +                       if (fp->basename && S_ISREG(fp->mode) && F_LENGTH(fp))
 139 +                               break;
 140 +               }
 141 +               the_fattr_list.high = j;
 142 +       }
 143 +
 144         if (protocol_version < 30) {
 145                 /* Recv the io_error flag */
 146                 if (ignore_errors)
 147 diff --git a/generator.c b/generator.c
 148 --- a/generator.c
 149 +++ b/generator.c
 150 @@ -78,6 +78,7 @@ extern char *basis_dir[MAX_BASIS_DIRS+1];
 151  extern int compare_dest;
 152  extern int copy_dest;
 153  extern int link_dest;
 154 +extern int detect_renamed;
 155  extern int whole_file;
 156  extern int list_only;
 157  extern int read_batch;
 158 @@ -96,6 +97,7 @@ extern char *backup_suffix;
 159  extern int backup_suffix_len;
 160  extern struct file_list *cur_flist, *first_flist, *dir_flist;
 161  extern struct filter_list_struct daemon_filter_list;
 162 +extern struct file_list the_fattr_list;
 163
 164  int ignore_perishable = 0;
 165  int non_perishable_cnt = 0;
 166 @@ -103,6 +105,7 @@ int maybe_ATTRS_REPORT = 0;
 167
 168  static dev_t dev_zero;
 169  static int deletion_count = 0; /* used to implement --max-delete */
 170 +static int unexplored_dirs = 1;
 171  static int deldelay_size = 0, deldelay_cnt = 0;
 172  static char *deldelay_buf = NULL;
 173  static int deldelay_fd = -1;
 174 @@ -113,7 +116,7 @@ static int need_retouch_dir_times;
 175  static int need_retouch_dir_perms;
 176  static const char *solo_file = NULL;
 177
 178 -/* For calling delete_item() and delete_dir_contents(). */
 179 +/* For calling delete_item(), delete_dir_contents(), and delete_in_dir(). */
 180  #define DEL_NO_UID_WRITE       (1<<0) /* file/dir has our uid w/o write perm */
 181  #define DEL_RECURSE            (1<<1) /* if dir, delete all contents */
 182  #define DEL_DIR_IS_EMPTY       (1<<2) /* internal delete_FUNCTIONS use only */
 183 @@ -122,6 +125,7 @@ static const char *solo_file = NULL;
 184  #define DEL_FOR_SYMLINK        (1<<5) /* making room for a replacement symlink */
 185  #define DEL_FOR_DEVICE         (1<<6) /* making room for a replacement device */
 186  #define DEL_FOR_SPECIAL        (1<<7) /* making room for a replacement special */
 187 +#define DEL_NO_DELETIONS       (1<<9) /* just check for renames w/o deleting */
 188
 189  #define DEL_MAKE_ROOM (DEL_FOR_FILE|DEL_FOR_DIR|DEL_FOR_SYMLINK|DEL_FOR_DEVICE|DEL_FOR_SPECIAL)
 190
 191 @@ -146,11 +150,121 @@ static int is_backup_file(char *fn)
 192         return k > 0 && strcmp(fn+k, backup_suffix) == 0;
 193  }
 194
 195 +/* Search for a regular file that matches either (1) the size & modified
 196 + * time (plus the basename, if possible) or (2) the size & checksum.  If
 197 + * we find an exact match down to the dirname, return -1 because we found
 198 + * an up-to-date file in the transfer, not a renamed file. */
 199 +static int fattr_find(struct file_struct *f, char *fname)
 200 +{
 201 +       int low = the_fattr_list.low, high = the_fattr_list.high;
 202 +       int mid, ok_match = -1, good_match = -1;
 203 +       struct file_struct *fmid;
 204 +       int diff;
 205 +
 206 +       while (low <= high) {
 207 +               mid = (low + high) / 2;
 208 +               fmid = the_fattr_list.files[mid];
 209 +               if (F_LENGTH(fmid) != F_LENGTH(f)) {
 210 +                       if (F_LENGTH(fmid) < F_LENGTH(f))
 211 +                               low = mid + 1;
 212 +                       else
 213 +                               high = mid - 1;
 214 +                       continue;
 215 +               }
 216 +               if (always_checksum) {
 217 +                       /* We use the FLAG_FILE_SENT flag to indicate when we
 218 +                        * have computed the checksum for an entry. */
 219 +                       if (!(f->flags & FLAG_FILE_SENT)) {
 220 +                               if (fmid->modtime == f->modtime
 221 +                                && f_name_cmp(fmid, f) == 0)
 222 +                                       return -1; /* assume we can't help */
 223 +                               file_checksum(fname, F_SUM(f), F_LENGTH(f));
 224 +                               f->flags |= FLAG_FILE_SENT;
 225 +                       }
 226 +                       diff = u_memcmp(F_SUM(fmid), F_SUM(f), checksum_len);
 227 +                       if (diff) {
 228 +                               if (diff < 0)
 229 +                                       low = mid + 1;
 230 +                               else
 231 +                                       high = mid - 1;
 232 +                               continue;
 233 +                       }
 234 +               } else {
 235 +                       if (fmid->modtime != f->modtime) {
 236 +                               if (fmid->modtime < f->modtime)
 237 +                                       low = mid + 1;
 238 +                               else
 239 +                                       high = mid - 1;
 240 +                               continue;
 241 +                       }
 242 +               }
 243 +               ok_match = mid;
 244 +               diff = u_strcmp(fmid->basename, f->basename);
 245 +               if (diff == 0) {
 246 +                       good_match = mid;
 247 +                       if (fmid->dirname == f->dirname)
 248 +                               return -1; /* file is up-to-date */
 249 +                       if (!fmid->dirname) {
 250 +                               low = mid + 1;
 251 +                               continue;
 252 +                       }
 253 +                       if (!f->dirname) {
 254 +                               high = mid - 1;
 255 +                               continue;
 256 +                       }
 257 +                       diff = u_strcmp(fmid->dirname, f->dirname);
 258 +                       if (diff == 0)
 259 +                               return -1; /* file is up-to-date */
 260 +               }
 261 +               if (diff < 0)
 262 +                       low = mid + 1;
 263 +               else
 264 +                       high = mid - 1;
 265 +       }
 266 +
 267 +       return good_match >= 0 ? good_match : ok_match;
 268 +}
 269 +
 270 +static void look_for_rename(struct file_struct *file, char *fname)
 271 +{
 272 +       struct file_struct *fp;
 273 +       char *partialptr, *fn;
 274 +       STRUCT_STAT st;
 275 +       int ndx;
 276 +
 277 +       if (!partial_dir || (ndx = fattr_find(file, fname)) < 0)
 278 +               return;
 279 +
 280 +       fp = the_fattr_list.files[ndx];
 281 +       fn = f_name(fp, NULL);
 282 +       /* We don't provide an alternate-basis file if there is a basis file. */
 283 +       if (link_stat(fn, &st, 0) == 0)
 284 +               return;
 285 +
 286 +       if (!dry_run) {
 287 +               if ((partialptr = partial_dir_fname(fn)) == NULL
 288 +                || !handle_partial_dir(partialptr, PDIR_CREATE))
 289 +                       return;
 290 +               /* We only use the file if we can hard-link it into our tmp dir. */
 291 +               if (link(fname, partialptr) != 0) {
 292 +                       if (errno != EEXIST)
 293 +                               handle_partial_dir(partialptr, PDIR_DELETE);
 294 +                       return;
 295 +               }
 296 +       }
 297 +
 298 +       /* I think this falls into the -vv category with "%s is uptodate", etc. */
 299 +       if (verbose > 1)
 300 +               rprintf(FINFO, "found renamed: %s => %s\n", fname, fn);
 301 +}
 302 +
 303  /* Delete a file or directory.  If DEL_RECURSE is set in the flags, this will
 304   * delete recursively.
 305   *
 306   * Note that fbuf must point to a MAXPATHLEN buffer if the mode indicates it's
 307   * a directory! (The buffer is used for recursion, but returned unchanged.)
 308 + *
 309 + * Also note: --detect-rename may use this routine with DEL_NO_DELETIONS set!
 310   */
 311  static enum delret delete_item(char *fbuf, uint16 mode, uint16 flags)
 312  {
 313 @@ -177,6 +291,8 @@ static enum delret delete_item(char *fbuf, uint16 mode, uint16 flags)
 314                         goto check_ret;
 315                 /* OK: try to delete the directory. */
 316         }
 317 +       if (flags & DEL_NO_DELETIONS)
 318 +               return DR_SUCCESS;
 319
 320         if (!(flags & DEL_MAKE_ROOM) && max_delete >= 0 && ++deletion_count > max_delete)
 321                 return DR_AT_LIMIT;
 322 @@ -232,6 +348,8 @@ static enum delret delete_item(char *fbuf, uint16 mode, uint16 flags)
 323   * its contents, otherwise just checks for content.  Returns DR_SUCCESS or
 324   * DR_NOT_EMPTY.  Note that fname must point to a MAXPATHLEN buffer!  (The
 325   * buffer is used for recursion, but returned unchanged.)
 326 + *
 327 + * Note: --detect-rename may use this routine with DEL_NO_DELETIONS set!
 328   */
 329  static enum delret delete_dir_contents(char *fname, uint16 flags)
 330  {
 331 @@ -251,7 +369,9 @@ static enum delret delete_dir_contents(char *fname, uint16 flags)
 332         save_filters = push_local_filters(fname, dlen);
 333
 334         non_perishable_cnt = 0;
 335 +       file_extra_cnt += SUM_EXTRA_CNT;
 336         dirlist = get_dirlist(fname, dlen, 0);
 337 +       file_extra_cnt -= SUM_EXTRA_CNT;
 338         ret = non_perishable_cnt ? DR_NOT_EMPTY : DR_SUCCESS;
 339
 340         if (!dirlist->used)
 341 @@ -291,7 +411,8 @@ static enum delret delete_dir_contents(char *fname, uint16 flags)
 342                 if (S_ISDIR(fp->mode)) {
 343                         if (delete_dir_contents(fname, flags | DEL_RECURSE) != DR_SUCCESS)
 344                                 ret = DR_NOT_EMPTY;
 345 -               }
 346 +               } else if (detect_renamed && S_ISREG(fp->mode))
 347 +                       look_for_rename(fp, fname);
 348                 if (delete_item(fname, fp->mode, flags) != DR_SUCCESS)
 349                         ret = DR_NOT_EMPTY;
 350         }
 351 @@ -456,13 +577,18 @@ static void do_delayed_deletions(char *delbuf)
 352   * all the --delete-WHEN options.  Note that the fbuf pointer must point to a
 353   * MAXPATHLEN buffer with the name of the directory in it (the functions we
 354   * call will append names onto the end, but the old dir value will be restored
 355 - * on exit). */
 356 -static void delete_in_dir(char *fbuf, struct file_struct *file, dev_t *fs_dev)
 357 + * on exit).
 358 + *
 359 + * Note:  --detect-rename may use this routine with DEL_NO_DELETIONS set!
 360 + */
 361 +static void delete_in_dir(char *fbuf, struct file_struct *file, dev_t *fs_dev,
 362 +                         int del_flags)
 363  {
 364         static int already_warned = 0;
 365         struct file_list *dirlist;
 366 -       char delbuf[MAXPATHLEN];
 367 -       int dlen, i;
 368 +       char *p, delbuf[MAXPATHLEN];
 369 +       unsigned remainder;
 370 +       int dlen, i, restore_dot = 0;
 371
 372         if (!fbuf) {
 373                 change_local_filter_dir(NULL, 0, 0);
 374 @@ -476,17 +602,22 @@ static void delete_in_dir(char *fbuf, struct file_struct *file, dev_t *fs_dev)
 375                 maybe_send_keepalive();
 376
 377         if (io_error && !ignore_errors) {
 378 -               if (already_warned)
 379 +               if (!already_warned) {
 380 +                       rprintf(FINFO,
 381 +                           "IO error encountered -- skipping file deletion\n");
 382 +                       already_warned = 1;
 383 +               }
 384 +               if (!detect_renamed)
 385                         return;
 386 -               rprintf(FINFO,
 387 -                       "IO error encountered -- skipping file deletion\n");
 388 -               already_warned = 1;
 389 -               return;
 390 +               del_flags |= DEL_NO_DELETIONS;
 391         }
 392
 393         dlen = strlen(fbuf);
 394         change_local_filter_dir(fbuf, dlen, F_DEPTH(file));
 395
 396 +       if (detect_renamed)
 397 +               unexplored_dirs--;
 398 +
 399         if (one_file_system) {
 400                 if (file->flags & FLAG_TOP_DIR)
 401                         filesystem_dev = *fs_dev;
 402 @@ -496,6 +627,14 @@ static void delete_in_dir(char *fbuf, struct file_struct *file, dev_t *fs_dev)
 403
 404         dirlist = get_dirlist(fbuf, dlen, 0);
 405
 406 +       p = fbuf + dlen;
 407 +       if (dlen == 1 && *fbuf == '.') {
 408 +               restore_dot = 1;
 409 +               p = fbuf;
 410 +       } else if (dlen != 1 || *fbuf != '/')
 411 +               *p++ = '/';
 412 +       remainder = MAXPATHLEN - (p - fbuf);
 413 +
 414         /* If an item in dirlist is not found in flist, delete it
 415          * from the filesystem. */
 416         for (i = dirlist->used; i--; ) {
 417 @@ -508,6 +647,10 @@ static void delete_in_dir(char *fbuf, struct file_struct *file, dev_t *fs_dev)
 418                                         f_name(fp, NULL));
 419                         continue;
 420                 }
 421 +               if (detect_renamed && S_ISREG(fp->mode)) {
 422 +                       strlcpy(p, fp->basename, remainder);
 423 +                       look_for_rename(fp, fbuf);
 424 +               }
 425                 /* Here we want to match regardless of file type.  Replacement
 426                  * of a file with one of another type is handled separately by
 427                  * a delete_item call with a DEL_MAKE_ROOM flag. */
 428 @@ -516,14 +659,19 @@ static void delete_in_dir(char *fbuf, struct file_struct *file, dev_t *fs_dev)
 429                         if (!(fp->mode & S_IWUSR) && !am_root && fp->flags & FLAG_OWNED_BY_US)
 430                                 flags |= DEL_NO_UID_WRITE;
 431                         f_name(fp, delbuf);
 432 -                       if (delete_during == 2) {
 433 -                               if (!remember_delete(fp, delbuf, flags))
 434 +                       if (delete_during == 2 && !(del_flags & DEL_NO_DELETIONS)) {
 435 +                               if (!remember_delete(fp, delbuf, del_flags | flags))
 436                                         break;
 437                         } else
 438 -                               delete_item(delbuf, fp->mode, flags);
 439 -               }
 440 +                               delete_item(delbuf, fp->mode, del_flags | flags);
 441 +               } else if (detect_renamed && S_ISDIR(fp->mode))
 442 +                       unexplored_dirs++;
 443         }
 444
 445 +       if (restore_dot)
 446 +               fbuf[0] = '.';
 447 +       fbuf[dlen] = '\0';
 448 +
 449         flist_free(dirlist);
 450  }
 451
 452 @@ -556,9 +704,9 @@ static void do_delete_pass(void)
 453                  || !S_ISDIR(st.st_mode))
 454                         continue;
 455
 456 -               delete_in_dir(fbuf, file, &st.st_dev);
 457 +               delete_in_dir(fbuf, file, &st.st_dev, 0);
 458         }
 459 -       delete_in_dir(NULL, NULL, &dev_zero);
 460 +       delete_in_dir(NULL, NULL, &dev_zero, 0);
 461
 462         if (do_progress && !am_server)
 463                 rprintf(FINFO, "                    \r");
 464 @@ -1269,6 +1417,7 @@ static void list_file_entry(struct file_struct *f)
 465         }
 466  }
 467
 468 +static struct bitbag *delayed_bits = NULL;
 469  static int phase = 0;
 470  static int dflt_perms;
 471
 472 @@ -1558,9 +1707,12 @@ static void recv_generator(char *fname, struct file_struct *file, int ndx,
 473                 }
 474                 else if (delete_during && f_out != -1 && !phase
 475                     && !(file->flags & FLAG_MISSING_DIR)) {
 476 -                       if (file->flags & FLAG_CONTENT_DIR)
 477 -                               delete_in_dir(fname, file, &real_sx.st.st_dev);
 478 -                       else
 479 +                       if (file->flags & FLAG_CONTENT_DIR) {
 480 +                               if (detect_renamed && real_ret != 0)
 481 +                                       unexplored_dirs++;
 482 +                               delete_in_dir(fname, file, &real_sx.st.st_dev,
 483 +                                             delete_during < 0 ? DEL_NO_DELETIONS : 0);
 484 +                       } else
 485                                 change_local_filter_dir(fname, strlen(fname), F_DEPTH(file));
 486                 }
 487                 goto cleanup;
 488 @@ -1844,8 +1996,14 @@ static void recv_generator(char *fname, struct file_struct *file, int ndx,
 489                         goto cleanup;
 490                 }
 491  #endif
 492 -               if (stat_errno == ENOENT)
 493 +               if (stat_errno == ENOENT) {
 494 +                       if (detect_renamed && unexplored_dirs > 0
 495 +                        && F_LENGTH(file)) {
 496 +                               bitbag_set_bit(delayed_bits, ndx);
 497 +                               return;
 498 +                       }
 499                         goto notify_others;
 500 +               }
 501                 rsyserr(FERROR_XFER, stat_errno, "recv_generator: failed to stat %s",
 502                         full_fname(fname));
 503                 goto cleanup;
 504 @@ -2254,6 +2412,12 @@ void generate_files(int f_out, const char *local_name)
 505         if (verbose > 2)
 506                 rprintf(FINFO, "generator starting pid=%ld\n", (long)getpid());
 507
 508 +       if (detect_renamed) {
 509 +               delayed_bits = bitbag_create(cur_flist->used);
 510 +               if (!delete_before && !delete_during)
 511 +                       delete_during = -1;
 512 +       }
 513 +
 514         if (delete_before && !solo_file && cur_flist->used > 0)
 515                 do_delete_pass();
 516         if (delete_during == 2) {
 517 @@ -2264,7 +2428,7 @@ void generate_files(int f_out, const char *local_name)
 518         }
 519         do_progress = 0;
 520
 521 -       if (append_mode > 0 || whole_file < 0)
 522 +       if (append_mode > 0 || detect_renamed || whole_file < 0)
 523                 whole_file = 0;
 524         if (verbose >= 2) {
 525                 rprintf(FINFO, "delta-transmission %s\n",
 526 @@ -2306,7 +2470,7 @@ void generate_files(int f_out, const char *local_name)
 527                                                 dirdev = MAKEDEV(DEV_MAJOR(devp), DEV_MINOR(devp));
 528                                         } else
 529                                                 dirdev = MAKEDEV(0, 0);
 530 -                                       delete_in_dir(fbuf, fp, &dirdev);
 531 +                                       delete_in_dir(fbuf, fp, &dirdev, 0);
 532                                 } else
 533                                         change_local_filter_dir(fbuf, strlen(fbuf), F_DEPTH(fp));
 534                         }
 535 @@ -2353,7 +2517,21 @@ void generate_files(int f_out, const char *local_name)
 536         } while ((cur_flist = cur_flist->next) != NULL);
 537
 538         if (delete_during)
 539 -               delete_in_dir(NULL, NULL, &dev_zero);
 540 +               delete_in_dir(NULL, NULL, &dev_zero, 0);
 541 +       if (detect_renamed) {
 542 +               if (delete_during < 0)
 543 +                       delete_during = 0;
 544 +               detect_renamed = 0;
 545 +
 546 +               for (i = -1; (i = bitbag_next_bit(delayed_bits, i)) >= 0; ) {
 547 +                       struct file_struct *file = cur_flist->files[i];
 548 +                       if (local_name)
 549 +                               strlcpy(fbuf, local_name, sizeof fbuf);
 550 +                       else
 551 +                               f_name(file, fbuf);
 552 +                       recv_generator(fbuf, file, i, itemizing, code, f_out);
 553 +               }
 554 +       }
 555         phase++;
 556         if (verbose > 2)
 557                 rprintf(FINFO, "generate_files phase=%d\n", phase);
 558 diff --git a/options.c b/options.c
 559 --- a/options.c
 560 +++ b/options.c
 561 @@ -81,6 +81,7 @@ int am_sender = 0;
 562  int am_starting_up = 1;
 563  int relative_paths = -1;
 564  int implied_dirs = 1;
 565 +int detect_renamed = 0;
 566  int numeric_ids = 0;
 567  int allow_8bit_chars = 0;
 568  int force_delete = 0;
 569 @@ -390,6 +391,7 @@ void usage(enum logcode F)
 570    rprintf(F,"     --modify-window=NUM     compare mod-times with reduced accuracy\n");
 571    rprintf(F," -T, --temp-dir=DIR          create temporary files in directory DIR\n");
 572    rprintf(F," -y, --fuzzy                 find similar file for basis if no dest file\n");
 573 +  rprintf(F,"     --detect-renamed        try to find renamed files to speed up the transfer\n");
 574    rprintf(F,"     --compare-dest=DIR      also compare destination files relative to DIR\n");
 575    rprintf(F,"     --copy-dest=DIR         ... and include copies of unchanged files\n");
 576    rprintf(F,"     --link-dest=DIR         hardlink to files in DIR when unchanged\n");
 577 @@ -577,6 +579,7 @@ static struct poptOption long_options[] = {
 578    {"compare-dest",     0,  POPT_ARG_STRING, 0, OPT_COMPARE_DEST, 0, 0 },
 579    {"copy-dest",        0,  POPT_ARG_STRING, 0, OPT_COPY_DEST, 0, 0 },
 580    {"link-dest",        0,  POPT_ARG_STRING, 0, OPT_LINK_DEST, 0, 0 },
 581 +  {"detect-renamed",   0,  POPT_ARG_NONE,   &detect_renamed, 0, 0, 0 },
 582    {"fuzzy",           'y', POPT_ARG_VAL,    &fuzzy_basis, 1, 0, 0 },
 583    {"no-fuzzy",         0,  POPT_ARG_VAL,    &fuzzy_basis, 0, 0, 0 },
 584    {"no-y",             0,  POPT_ARG_VAL,    &fuzzy_basis, 0, 0, 0 },
 585 @@ -1601,7 +1604,7 @@ int parse_arguments(int *argc_p, const char ***argv_p)
 586                 inplace = 1;
 587         }
 588
 589 -       if (delay_updates && !partial_dir)
 590 +       if ((delay_updates || detect_renamed) && !partial_dir)
 591                 partial_dir = tmp_partialdir;
 592
 593         if (inplace) {
 594 @@ -1610,6 +1613,7 @@ int parse_arguments(int *argc_p, const char ***argv_p)
 595                         snprintf(err_buf, sizeof err_buf,
 596                                  "--%s cannot be used with --%s\n",
 597                                  append_mode ? "append" : "inplace",
 598 +                                detect_renamed ? "detect-renamed" :
 599                                  delay_updates ? "delay-updates" : "partial-dir");
 600                         return 0;
 601                 }
 602 @@ -1972,6 +1976,8 @@ void server_options(char **args, int *argc_p)
 603                         args[ac++] = "--super";
 604                 if (size_only)
 605                         args[ac++] = "--size-only";
 606 +               if (detect_renamed)
 607 +                       args[ac++] = "--detect-renamed";
 608         } else {
 609                 if (skip_compress) {
 610                         if (asprintf(&arg, "--skip-compress=%s", skip_compress) < 0)
 611 diff --git a/rsync.yo b/rsync.yo
 612 --- a/rsync.yo
 613 +++ b/rsync.yo
 614 @@ -402,6 +402,7 @@ to the detailed description below for a complete description.  verb(
 615       --modify-window=NUM     compare mod-times with reduced accuracy
 616   -T, --temp-dir=DIR          create temporary files in directory DIR
 617   -y, --fuzzy                 find similar file for basis if no dest file
 618 +     --detect-renamed        try to find renamed files to speed the xfer
 619       --compare-dest=DIR      also compare received files relative to DIR
 620       --copy-dest=DIR         ... and include copies of unchanged files
 621       --link-dest=DIR         hardlink to files in DIR when unchanged
 622 @@ -1590,6 +1591,21 @@ Note that the use of the bf(--delete) option might get rid of any potential
 623  fuzzy-match files, so either use bf(--delete-after) or specify some
 624  filename exclusions if you need to prevent this.
 625
 626 +dit(bf(--detect-renamed)) With this option, for each new source file
 627 +(call it em(src/S)), rsync looks for a file em(dest/D) anywhere in the
 628 +destination that passes the quick check with em(src/S).  If such a em(dest/D)
 629 +is found, rsync uses it as an alternate basis for transferring em(S).  The
 630 +idea is that if em(src/S) was renamed from em(src/D) (as opposed to em(src/S)
 631 +passing the quick check with em(dest/D) by coincidence), the delta-transfer
 632 +algorithm will find that all the data matches between em(src/S) and em(dest/D),
 633 +and the transfer will be really fast.
 634 +
 635 +By default, alternate-basis files are hard-linked into a directory named
 636 +".~tmp~" in each file's destination directory, but if you've specified
 637 +the bf(--partial-dir) option, that directory will be used instead.  These
 638 +potential alternate-basis files will be removed as the transfer progresses.
 639 +This option conflicts with bf(--inplace) and bf(--append).
 640 +
 641  dit(bf(--compare-dest=DIR)) This option instructs rsync to use em(DIR) on
 642  the destination machine as an additional hierarchy to compare destination
 643  files against doing transfers (if the files are missing in the destination
 644 diff --git a/util.c b/util.c
 645 --- a/util.c
 646 +++ b/util.c
 647 @@ -1179,6 +1179,32 @@ int handle_partial_dir(const char *fname, int create)
 648         return 1;
 649  }
 650
 651 +/* We need to supply our own strcmp function for file list comparisons
 652 + * to ensure that signed/unsigned usage is consistent between machines. */
 653 +int u_strcmp(const char *p1, const char *p2)
 654 +{
 655 +        for ( ; *p1; p1++, p2++) {
 656 +               if (*p1 != *p2)
 657 +                       break;
 658 +       }
 659 +
 660 +       return (int)*(uchar*)p1 - (int)*(uchar*)p2;
 661 +}
 662 +
 663 +/* We need a memcmp function compares unsigned-byte values. */
 664 +int u_memcmp(const void *p1, const void *p2, size_t len)
 665 +{
 666 +       const uchar *u1 = p1;
 667 +       const uchar *u2 = p2;
 668 +
 669 +       while (len--) {
 670 +               if (*u1 != *u2)
 671 +                       return (int)*u1 - (int)*u2;
 672 +       }
 673 +
 674 +       return 0;
 675 +}
 676 +
 677  /* Determine if a symlink points outside the current directory tree.
 678   * This is considered "unsafe" because e.g. when mirroring somebody
 679   * else's machine it might allow them to establish a symlink to