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.
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.
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.
22 To use this patch, run these commands for a successful build:
24 patch -p1 <patches/detect-renamed.diff
25 ./configure (optional if already run)
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
35 diff --git a/compat.c 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 @@ -120,6 +121,7 @@ void set_allow_inc_recurse(void)
47 allow_inc_recurse = 0;
49 && (delete_before || delete_after
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
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 @@ -121,6 +122,8 @@ static int64 tmp_dev, tmp_ino;
67 static char tmp_sum[MAX_DIGEST_LEN];
69 +struct file_list the_fattr_list;
71 static char empty_sum[MAX_DIGEST_LEN];
72 static int flist_count_offset; /* for --delete --progress */
73 static int dir_count = 0;
74 @@ -288,6 +291,45 @@ static int is_excluded(const char *fname, int is_dir, int filter_level)
78 +static int fattr_compare(struct file_struct **file1, struct file_struct **file2)
80 + struct file_struct *f1 = *file1;
81 + struct file_struct *f2 = *file2;
82 + int64 len1 = F_LENGTH(f1), len2 = F_LENGTH(f2);
85 + if (!f1->basename || !S_ISREG(f1->mode) || !len1) {
86 + if (!f2->basename || !S_ISREG(f2->mode) || !len2)
90 + if (!f2->basename || !S_ISREG(f2->mode) || !len2)
93 + /* Don't use diff for values that are longer than an int. */
95 + return len1 < len2 ? -1 : 1;
97 + if (always_checksum) {
98 + diff = u_memcmp(F_SUM(f1), F_SUM(f2), checksum_len);
101 + } else if (f1->modtime != f2->modtime)
102 + return f1->modtime < f2->modtime ? -1 : 1;
104 + diff = u_strcmp(f1->basename, f2->basename);
108 + if (f1->dirname == f2->dirname)
114 + return u_strcmp(f1->dirname, f2->dirname);
117 static void send_directory(int f, struct file_list *flist,
118 char *fbuf, int len, int flags);
120 @@ -2357,6 +2399,25 @@ struct file_list *recv_file_list(int f)
122 flist_sort_and_clean(flist, relative_paths);
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;
136 + struct file_struct *fp = the_fattr_list.files[j];
137 + if (fp->basename && S_ISREG(fp->mode) && F_LENGTH(fp))
140 + the_fattr_list.high = j;
143 if (protocol_version < 30) {
144 /* Recv the io_error flag */
146 diff --git a/generator.c 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;
163 int ignore_perishable = 0;
164 int non_perishable_cnt = 0;
165 @@ -105,6 +107,7 @@ int maybe_ATTRS_REPORT = 0;
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;
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 */
188 #define DEL_MAKE_ROOM (DEL_FOR_FILE|DEL_FOR_DIR|DEL_FOR_SYMLINK|DEL_FOR_DEVICE|DEL_FOR_SPECIAL)
190 @@ -148,11 +152,121 @@ static int is_backup_file(char *fn)
191 return k > 0 && strcmp(fn+k, backup_suffix) == 0;
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)
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;
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))
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;
225 + diff = u_memcmp(F_SUM(fmid), F_SUM(f), checksum_len);
234 + if (fmid->modtime != f->modtime) {
235 + if (fmid->modtime < f->modtime)
243 + diff = u_strcmp(fmid->basename, f->basename);
246 + if (fmid->dirname == f->dirname)
247 + return -1; /* file is up-to-date */
248 + if (!fmid->dirname) {
256 + diff = u_strcmp(fmid->dirname, f->dirname);
258 + return -1; /* file is up-to-date */
266 + return good_match >= 0 ? good_match : ok_match;
269 +static void look_for_rename(struct file_struct *file, char *fname)
271 + struct file_struct *fp;
272 + char *partialptr, *fn;
276 + if (!partial_dir || (ndx = fattr_find(file, fname)) < 0)
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)
286 + if ((partialptr = partial_dir_fname(fn)) == NULL
287 + || !handle_partial_dir(partialptr, PDIR_CREATE))
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);
297 + /* I think this falls into the -vv category with "%s is uptodate", etc. */
299 + rprintf(FINFO, "found renamed: %s => %s\n", fname, fn);
302 /* Delete a file or directory. If DEL_RECURSE is set in the flags, this will
303 * delete recursively.
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.)
308 + * Also note: --detect-rename may use this routine with DEL_NO_DELETIONS set!
310 static enum delret delete_item(char *fbuf, uint16 mode, uint16 flags)
312 @@ -186,6 +300,8 @@ static enum delret delete_item(char *fbuf, uint16 mode, uint16 flags)
314 /* OK: try to delete the directory. */
316 + if (flags & DEL_NO_DELETIONS)
319 if (!(flags & DEL_MAKE_ROOM) && max_delete >= 0 && ++deletion_count > max_delete)
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.)
326 + * Note: --detect-rename may use this routine with DEL_NO_DELETIONS set!
328 static enum delret delete_dir_contents(char *fname, uint16 flags)
330 @@ -260,7 +378,9 @@ static enum delret delete_dir_contents(char *fname, uint16 flags)
331 save_filters = push_local_filters(fname, dlen);
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;
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)
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)
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
355 -static void delete_in_dir(char *fbuf, struct file_struct *file, dev_t *fs_dev)
358 + * Note: --detect-rename may use this routine with DEL_NO_DELETIONS set!
360 +static void delete_in_dir(char *fbuf, struct file_struct *file, dev_t *fs_dev,
363 static int already_warned = 0;
364 struct file_list *dirlist;
365 - char delbuf[MAXPATHLEN];
367 + char *p, delbuf[MAXPATHLEN];
368 + unsigned remainder;
369 + int dlen, i, restore_dot = 0;
370 int save_uid_ndx = uid_ndx;
373 @@ -486,17 +612,22 @@ static void delete_in_dir(char *fbuf, struct file_struct *file, dev_t *fs_dev)
374 maybe_send_keepalive();
376 if (io_error && !ignore_errors) {
377 - if (already_warned)
378 + if (!already_warned) {
380 + "IO error encountered -- skipping file deletion\n");
381 + already_warned = 1;
383 + if (!detect_renamed)
386 - "IO error encountered -- skipping file deletion\n");
387 - already_warned = 1;
389 + del_flags |= DEL_NO_DELETIONS;
393 change_local_filter_dir(fbuf, dlen, F_DEPTH(file));
395 + if (detect_renamed)
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)
403 dirlist = get_dirlist(fbuf, dlen, 0);
406 + if (dlen == 1 && *fbuf == '.') {
409 + } else if (dlen != 1 || *fbuf != '/')
411 + remainder = MAXPATHLEN - (p - fbuf);
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)
420 + if (detect_renamed && S_ISREG(fp->mode)) {
421 + strlcpy(p, fp->basename, remainder);
422 + look_for_rename(fp, fbuf);
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;
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))
435 - delete_item(delbuf, fp->mode, flags);
437 + delete_item(delbuf, fp->mode, del_flags | flags);
438 + } else if (detect_renamed && S_ISDIR(fp->mode))
449 @@ -571,9 +719,9 @@ static void do_delete_pass(void)
450 || !S_ISDIR(st.st_mode))
453 - delete_in_dir(fbuf, file, &st.st_dev);
454 + delete_in_dir(fbuf, file, &st.st_dev, 0);
456 - delete_in_dir(NULL, NULL, &dev_zero);
457 + delete_in_dir(NULL, NULL, &dev_zero, 0);
459 if (do_progress && !am_server)
460 rprintf(FINFO, " \r");
461 @@ -1226,6 +1374,7 @@ static void list_file_entry(struct file_struct *f)
465 +static struct bitbag *delayed_bits = NULL;
466 static int phase = 0;
467 static int dflt_perms;
469 @@ -1502,9 +1651,12 @@ static void recv_generator(char *fname, struct file_struct *file, int ndx,
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);
476 + if (file->flags & FLAG_CONTENT_DIR) {
477 + if (detect_renamed && real_ret != 0)
479 + delete_in_dir(fname, file, &real_sx.st.st_dev,
480 + delete_during < 0 ? DEL_NO_DELETIONS : 0);
482 change_local_filter_dir(fname, strlen(fname), F_DEPTH(file));
485 @@ -1782,8 +1934,14 @@ static void recv_generator(char *fname, struct file_struct *file, int ndx,
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);
498 rsyserr(FERROR_XFER, stat_errno, "recv_generator: failed to stat %s",
501 @@ -2184,6 +2342,12 @@ void generate_files(int f_out, const char *local_name)
503 rprintf(FINFO, "generator starting pid=%ld\n", (long)getpid());
505 + if (detect_renamed) {
506 + delayed_bits = bitbag_create(cur_flist->used);
507 + if (!delete_before && !delete_during)
508 + delete_during = -1;
511 if (delete_before && !solo_file && cur_flist->used > 0)
513 if (delete_during == 2) {
514 @@ -2194,7 +2358,7 @@ void generate_files(int f_out, const char *local_name)
518 - if (append_mode > 0 || whole_file < 0)
519 + if (append_mode > 0 || detect_renamed || whole_file < 0)
522 rprintf(FINFO, "delta-transmission %s\n",
523 @@ -2236,7 +2400,7 @@ void generate_files(int f_out, const char *local_name)
524 dirdev = MAKEDEV(DEV_MAJOR(devp), DEV_MINOR(devp));
526 dirdev = MAKEDEV(0, 0);
527 - delete_in_dir(fbuf, fp, &dirdev);
528 + delete_in_dir(fbuf, fp, &dirdev, 0);
530 change_local_filter_dir(fbuf, strlen(fbuf), F_DEPTH(fp));
532 @@ -2283,7 +2447,21 @@ void generate_files(int f_out, const char *local_name)
533 } while ((cur_flist = cur_flist->next) != NULL);
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)
541 + detect_renamed = 0;
543 + for (i = -1; (i = bitbag_next_bit(delayed_bits, i)) >= 0; ) {
544 + struct file_struct *file = cur_flist->files[i];
546 + strlcpy(fbuf, local_name, sizeof fbuf);
548 + f_name(file, fbuf);
549 + recv_generator(fbuf, file, i, itemizing, code, f_out);
554 rprintf(FINFO, "generate_files phase=%d\n", phase);
555 diff --git a/options.c 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;
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)
586 - if (delay_updates && !partial_dir)
587 + if ((delay_updates || detect_renamed) && !partial_dir)
588 partial_dir = tmp_partialdir;
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");
599 @@ -1959,6 +1963,8 @@ void server_options(char **args, int *argc_p)
600 args[ac++] = "--super";
602 args[ac++] = "--size-only";
603 + if (detect_renamed)
604 + args[ac++] = "--detect-renamed";
607 if (asprintf(&arg, "--skip-compress=%s", skip_compress) < 0)
608 diff --git a/rsync.yo 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 @@ -1487,6 +1488,21 @@ 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.
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.
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).
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
644 @@ -1129,6 +1129,32 @@ int handle_partial_dir(const char *fname, int create)
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)
652 + for ( ; *p1; p1++, p2++) {
657 + return (int)*(uchar*)p1 - (int)*(uchar*)p2;
660 +/* We need a memcmp function compares unsigned-byte values. */
661 +int u_memcmp(const void *p1, const void *p2, size_t len)
663 + const uchar *u1 = p1;
664 + const uchar *u2 = p2;
668 + return (int)*u1 - (int)*u2;
675 * Determine if a symlink points outside the current directory tree.
676 * This is considered "unsafe" because e.g. when mirroring somebody