xref: /illumos-gate/usr/src/common/zfs/zfs_prop.c (revision bfed486ad8de8b8ebc6345a8e10accae08bf2f45)
1 /*
2  * CDDL HEADER START
3  *
4  * The contents of this file are subject to the terms of the
5  * Common Development and Distribution License (the "License").
6  * You may not use this file except in compliance with the License.
7  *
8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9  * or http://www.opensolaris.org/os/licensing.
10  * See the License for the specific language governing permissions
11  * and limitations under the License.
12  *
13  * When distributing Covered Code, include this CDDL HEADER in each
14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15  * If applicable, add the following below this CDDL HEADER, with the
16  * fields enclosed by brackets "[]" replaced with your own identifying
17  * information: Portions Copyright [yyyy] [name of copyright owner]
18  *
19  * CDDL HEADER END
20  */
21 /*
22  * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
23  * Use is subject to license terms.
24  */
25 
26 #include <sys/zio.h>
27 #include <sys/spa.h>
28 #include <sys/u8_textprep.h>
29 #include <sys/zfs_acl.h>
30 #include <sys/zfs_ioctl.h>
31 #include <sys/zfs_znode.h>
32 
33 #include "zfs_prop.h"
34 #include "zfs_deleg.h"
35 
36 #if defined(_KERNEL)
37 #include <sys/systm.h>
38 #else
39 #include <stdlib.h>
40 #include <string.h>
41 #include <ctype.h>
42 #endif
43 
44 static zprop_desc_t zfs_prop_table[ZFS_NUM_PROPS];
45 
46 zprop_desc_t *
47 zfs_prop_get_table(void)
48 {
49 	return (zfs_prop_table);
50 }
51 
52 void
53 zfs_prop_init(void)
54 {
55 	static zprop_index_t checksum_table[] = {
56 		{ "on",		ZIO_CHECKSUM_ON },
57 		{ "off",	ZIO_CHECKSUM_OFF },
58 		{ "fletcher2",	ZIO_CHECKSUM_FLETCHER_2 },
59 		{ "fletcher4",	ZIO_CHECKSUM_FLETCHER_4 },
60 		{ "sha256",	ZIO_CHECKSUM_SHA256 },
61 		{ NULL }
62 	};
63 
64 	static zprop_index_t compress_table[] = {
65 		{ "on",		ZIO_COMPRESS_ON },
66 		{ "off",	ZIO_COMPRESS_OFF },
67 		{ "lzjb",	ZIO_COMPRESS_LZJB },
68 		{ "gzip",	ZIO_COMPRESS_GZIP_6 },	/* gzip default */
69 		{ "gzip-1",	ZIO_COMPRESS_GZIP_1 },
70 		{ "gzip-2",	ZIO_COMPRESS_GZIP_2 },
71 		{ "gzip-3",	ZIO_COMPRESS_GZIP_3 },
72 		{ "gzip-4",	ZIO_COMPRESS_GZIP_4 },
73 		{ "gzip-5",	ZIO_COMPRESS_GZIP_5 },
74 		{ "gzip-6",	ZIO_COMPRESS_GZIP_6 },
75 		{ "gzip-7",	ZIO_COMPRESS_GZIP_7 },
76 		{ "gzip-8",	ZIO_COMPRESS_GZIP_8 },
77 		{ "gzip-9",	ZIO_COMPRESS_GZIP_9 },
78 		{ NULL }
79 	};
80 
81 	static zprop_index_t snapdir_table[] = {
82 		{ "hidden",	ZFS_SNAPDIR_HIDDEN },
83 		{ "visible",	ZFS_SNAPDIR_VISIBLE },
84 		{ NULL }
85 	};
86 
87 	static zprop_index_t acl_mode_table[] = {
88 		{ "discard",	ZFS_ACL_DISCARD },
89 		{ "groupmask",	ZFS_ACL_GROUPMASK },
90 		{ "passthrough", ZFS_ACL_PASSTHROUGH },
91 		{ NULL }
92 	};
93 
94 	static zprop_index_t acl_inherit_table[] = {
95 		{ "discard",	ZFS_ACL_DISCARD },
96 		{ "noallow",	ZFS_ACL_NOALLOW },
97 		{ "restricted",	ZFS_ACL_RESTRICTED },
98 		{ "passthrough", ZFS_ACL_PASSTHROUGH },
99 		{ "secure",	ZFS_ACL_RESTRICTED }, /* bkwrd compatability */
100 		{ "passthrough-x", ZFS_ACL_PASSTHROUGH_X },
101 		{ NULL }
102 	};
103 
104 	static zprop_index_t case_table[] = {
105 		{ "sensitive",		ZFS_CASE_SENSITIVE },
106 		{ "insensitive",	ZFS_CASE_INSENSITIVE },
107 		{ "mixed",		ZFS_CASE_MIXED },
108 		{ NULL }
109 	};
110 
111 	static zprop_index_t copies_table[] = {
112 		{ "1",		1 },
113 		{ "2",		2 },
114 		{ "3",		3 },
115 		{ NULL }
116 	};
117 
118 	/*
119 	 * Use the unique flags we have to send to u8_strcmp() and/or
120 	 * u8_textprep() to represent the various normalization property
121 	 * values.
122 	 */
123 	static zprop_index_t normalize_table[] = {
124 		{ "none",	0 },
125 		{ "formD",	U8_TEXTPREP_NFD },
126 		{ "formKC",	U8_TEXTPREP_NFKC },
127 		{ "formC",	U8_TEXTPREP_NFC },
128 		{ "formKD",	U8_TEXTPREP_NFKD },
129 		{ NULL }
130 	};
131 
132 	static zprop_index_t version_table[] = {
133 		{ "1",		1 },
134 		{ "2",		2 },
135 		{ "3",		3 },
136 		{ "current",	ZPL_VERSION },
137 		{ NULL }
138 	};
139 
140 	static zprop_index_t boolean_table[] = {
141 		{ "off",	0 },
142 		{ "on",		1 },
143 		{ NULL }
144 	};
145 
146 	static zprop_index_t canmount_table[] = {
147 		{ "off",	ZFS_CANMOUNT_OFF },
148 		{ "on",		ZFS_CANMOUNT_ON },
149 		{ "noauto",	ZFS_CANMOUNT_NOAUTO },
150 		{ NULL }
151 	};
152 
153 	static zprop_index_t cache_table[] = {
154 		{ "none",	ZFS_CACHE_NONE },
155 		{ "metadata",	ZFS_CACHE_METADATA },
156 		{ "all",	ZFS_CACHE_ALL },
157 		{ NULL }
158 	};
159 
160 	/* inherit index properties */
161 	register_index(ZFS_PROP_CHECKSUM, "checksum", ZIO_CHECKSUM_DEFAULT,
162 	    PROP_INHERIT, ZFS_TYPE_FILESYSTEM | ZFS_TYPE_VOLUME,
163 	    "on | off | fletcher2 | fletcher4 | sha256", "CHECKSUM",
164 	    checksum_table);
165 	register_index(ZFS_PROP_COMPRESSION, "compression",
166 	    ZIO_COMPRESS_DEFAULT, PROP_INHERIT,
167 	    ZFS_TYPE_FILESYSTEM | ZFS_TYPE_VOLUME,
168 	    "on | off | lzjb | gzip | gzip-[1-9]", "COMPRESS", compress_table);
169 	register_index(ZFS_PROP_SNAPDIR, "snapdir", ZFS_SNAPDIR_HIDDEN,
170 	    PROP_INHERIT, ZFS_TYPE_FILESYSTEM,
171 	    "hidden | visible", "SNAPDIR", snapdir_table);
172 	register_index(ZFS_PROP_ACLMODE, "aclmode", ZFS_ACL_GROUPMASK,
173 	    PROP_INHERIT, ZFS_TYPE_FILESYSTEM,
174 	    "discard | groupmask | passthrough", "ACLMODE", acl_mode_table);
175 	register_index(ZFS_PROP_ACLINHERIT, "aclinherit", ZFS_ACL_RESTRICTED,
176 	    PROP_INHERIT, ZFS_TYPE_FILESYSTEM,
177 	    "discard | noallow | restricted | passthrough | passthrough-x",
178 	    "ACLINHERIT", acl_inherit_table);
179 	register_index(ZFS_PROP_COPIES, "copies", 1,
180 	    PROP_INHERIT, ZFS_TYPE_FILESYSTEM | ZFS_TYPE_VOLUME,
181 	    "1 | 2 | 3", "COPIES", copies_table);
182 	register_index(ZFS_PROP_PRIMARYCACHE, "primarycache",
183 	    ZFS_CACHE_ALL, PROP_INHERIT,
184 	    ZFS_TYPE_FILESYSTEM | ZFS_TYPE_SNAPSHOT | ZFS_TYPE_VOLUME,
185 	    "all | none | metadata", "PRIMARYCACHE", cache_table);
186 	register_index(ZFS_PROP_SECONDARYCACHE, "secondarycache",
187 	    ZFS_CACHE_ALL, PROP_INHERIT,
188 	    ZFS_TYPE_FILESYSTEM | ZFS_TYPE_SNAPSHOT | ZFS_TYPE_VOLUME,
189 	    "all | none | metadata", "SECONDARYCACHE", cache_table);
190 
191 	/* inherit index (boolean) properties */
192 	register_index(ZFS_PROP_ATIME, "atime", 1, PROP_INHERIT,
193 	    ZFS_TYPE_FILESYSTEM, "on | off", "ATIME", boolean_table);
194 	register_index(ZFS_PROP_DEVICES, "devices", 1, PROP_INHERIT,
195 	    ZFS_TYPE_FILESYSTEM | ZFS_TYPE_SNAPSHOT, "on | off", "DEVICES",
196 	    boolean_table);
197 	register_index(ZFS_PROP_EXEC, "exec", 1, PROP_INHERIT,
198 	    ZFS_TYPE_FILESYSTEM | ZFS_TYPE_SNAPSHOT, "on | off", "EXEC",
199 	    boolean_table);
200 	register_index(ZFS_PROP_SETUID, "setuid", 1, PROP_INHERIT,
201 	    ZFS_TYPE_FILESYSTEM | ZFS_TYPE_SNAPSHOT, "on | off", "SETUID",
202 	    boolean_table);
203 	register_index(ZFS_PROP_READONLY, "readonly", 0, PROP_INHERIT,
204 	    ZFS_TYPE_FILESYSTEM | ZFS_TYPE_VOLUME, "on | off", "RDONLY",
205 	    boolean_table);
206 	register_index(ZFS_PROP_ZONED, "zoned", 0, PROP_INHERIT,
207 	    ZFS_TYPE_FILESYSTEM, "on | off", "ZONED", boolean_table);
208 	register_index(ZFS_PROP_XATTR, "xattr", 1, PROP_INHERIT,
209 	    ZFS_TYPE_FILESYSTEM | ZFS_TYPE_SNAPSHOT, "on | off", "XATTR",
210 	    boolean_table);
211 	register_index(ZFS_PROP_VSCAN, "vscan", 0, PROP_INHERIT,
212 	    ZFS_TYPE_FILESYSTEM, "on | off", "VSCAN",
213 	    boolean_table);
214 	register_index(ZFS_PROP_NBMAND, "nbmand", 0, PROP_INHERIT,
215 	    ZFS_TYPE_FILESYSTEM | ZFS_TYPE_SNAPSHOT, "on | off", "NBMAND",
216 	    boolean_table);
217 
218 	/* default index properties */
219 	register_index(ZFS_PROP_VERSION, "version", 0, PROP_DEFAULT,
220 	    ZFS_TYPE_FILESYSTEM | ZFS_TYPE_SNAPSHOT,
221 	    "1 | 2 | 3 | current", "VERSION", version_table);
222 	register_index(ZFS_PROP_CANMOUNT, "canmount", ZFS_CANMOUNT_ON,
223 	    PROP_DEFAULT, ZFS_TYPE_FILESYSTEM, "on | off | noauto",
224 	    "CANMOUNT", canmount_table);
225 
226 	/* readonly index (boolean) properties */
227 	register_index(ZFS_PROP_MOUNTED, "mounted", 0, PROP_READONLY,
228 	    ZFS_TYPE_FILESYSTEM, "yes | no", "MOUNTED", boolean_table);
229 
230 	/* set once index properties */
231 	register_index(ZFS_PROP_NORMALIZE, "normalization", 0,
232 	    PROP_ONETIME, ZFS_TYPE_FILESYSTEM | ZFS_TYPE_SNAPSHOT,
233 	    "none | formC | formD | formKC | formKD", "NORMALIZATION",
234 	    normalize_table);
235 	register_index(ZFS_PROP_CASE, "casesensitivity", ZFS_CASE_SENSITIVE,
236 	    PROP_ONETIME, ZFS_TYPE_FILESYSTEM | ZFS_TYPE_SNAPSHOT,
237 	    "sensitive | insensitive | mixed", "CASE", case_table);
238 
239 	/* set once index (boolean) properties */
240 	register_index(ZFS_PROP_UTF8ONLY, "utf8only", 0, PROP_ONETIME,
241 	    ZFS_TYPE_FILESYSTEM | ZFS_TYPE_SNAPSHOT,
242 	    "on | off", "UTF8ONLY", boolean_table);
243 
244 	/* string properties */
245 	register_string(ZFS_PROP_ORIGIN, "origin", NULL, PROP_READONLY,
246 	    ZFS_TYPE_FILESYSTEM | ZFS_TYPE_VOLUME, "<snapshot>", "ORIGIN");
247 	register_string(ZFS_PROP_MOUNTPOINT, "mountpoint", "/", PROP_INHERIT,
248 	    ZFS_TYPE_FILESYSTEM, "<path> | legacy | none", "MOUNTPOINT");
249 	register_string(ZFS_PROP_SHARENFS, "sharenfs", "off", PROP_INHERIT,
250 	    ZFS_TYPE_FILESYSTEM, "on | off | share(1M) options", "SHARENFS");
251 	register_string(ZFS_PROP_SHAREISCSI, "shareiscsi", "off", PROP_INHERIT,
252 	    ZFS_TYPE_DATASET, "on | off | type=<type>", "SHAREISCSI");
253 	register_string(ZFS_PROP_TYPE, "type", NULL, PROP_READONLY,
254 	    ZFS_TYPE_DATASET, "filesystem | volume | snapshot", "TYPE");
255 	register_string(ZFS_PROP_SHARESMB, "sharesmb", "off", PROP_INHERIT,
256 	    ZFS_TYPE_FILESYSTEM, "on | off | sharemgr(1M) options", "SHARESMB");
257 
258 	/* readonly number properties */
259 	register_number(ZFS_PROP_USED, "used", 0, PROP_READONLY,
260 	    ZFS_TYPE_DATASET, "<size>", "USED");
261 	register_number(ZFS_PROP_AVAILABLE, "available", 0, PROP_READONLY,
262 	    ZFS_TYPE_FILESYSTEM | ZFS_TYPE_VOLUME, "<size>", "AVAIL");
263 	register_number(ZFS_PROP_REFERENCED, "referenced", 0, PROP_READONLY,
264 	    ZFS_TYPE_DATASET, "<size>", "REFER");
265 	register_number(ZFS_PROP_COMPRESSRATIO, "compressratio", 0,
266 	    PROP_READONLY, ZFS_TYPE_DATASET,
267 	    "<1.00x or higher if compressed>", "RATIO");
268 	register_number(ZFS_PROP_VOLBLOCKSIZE, "volblocksize", 8192,
269 	    PROP_ONETIME,
270 	    ZFS_TYPE_VOLUME, "512 to 128k, power of 2",	"VOLBLOCK");
271 	register_number(ZFS_PROP_USEDSNAP, "usedbysnapshots", 0, PROP_READONLY,
272 	    ZFS_TYPE_FILESYSTEM | ZFS_TYPE_VOLUME, "<size>", "USEDSNAP");
273 	register_number(ZFS_PROP_USEDDS, "usedbydataset", 0, PROP_READONLY,
274 	    ZFS_TYPE_FILESYSTEM | ZFS_TYPE_VOLUME, "<size>", "USEDDS");
275 	register_number(ZFS_PROP_USEDCHILD, "usedbychildren", 0, PROP_READONLY,
276 	    ZFS_TYPE_FILESYSTEM | ZFS_TYPE_VOLUME, "<size>", "USEDCHILD");
277 	register_number(ZFS_PROP_USEDREFRESERV, "usedbyrefreservation", 0,
278 	    PROP_READONLY,
279 	    ZFS_TYPE_FILESYSTEM | ZFS_TYPE_VOLUME, "<size>", "USEDREFRESERV");
280 
281 	/* default number properties */
282 	register_number(ZFS_PROP_QUOTA, "quota", 0, PROP_DEFAULT,
283 	    ZFS_TYPE_FILESYSTEM, "<size> | none", "QUOTA");
284 	register_number(ZFS_PROP_RESERVATION, "reservation", 0, PROP_DEFAULT,
285 	    ZFS_TYPE_FILESYSTEM | ZFS_TYPE_VOLUME, "<size> | none", "RESERV");
286 	register_number(ZFS_PROP_VOLSIZE, "volsize", 0, PROP_DEFAULT,
287 	    ZFS_TYPE_VOLUME, "<size>", "VOLSIZE");
288 	register_number(ZFS_PROP_REFQUOTA, "refquota", 0, PROP_DEFAULT,
289 	    ZFS_TYPE_FILESYSTEM, "<size> | none", "REFQUOTA");
290 	register_number(ZFS_PROP_REFRESERVATION, "refreservation", 0,
291 	    PROP_DEFAULT, ZFS_TYPE_FILESYSTEM | ZFS_TYPE_VOLUME,
292 	    "<size> | none", "REFRESERV");
293 
294 	/* inherit number properties */
295 	register_number(ZFS_PROP_RECORDSIZE, "recordsize", SPA_MAXBLOCKSIZE,
296 	    PROP_INHERIT,
297 	    ZFS_TYPE_FILESYSTEM, "512 to 128k, power of 2", "RECSIZE");
298 
299 	/* hidden properties */
300 	register_hidden(ZFS_PROP_CREATETXG, "createtxg", PROP_TYPE_NUMBER,
301 	    PROP_READONLY, ZFS_TYPE_DATASET, NULL);
302 	register_hidden(ZFS_PROP_NUMCLONES, "numclones", PROP_TYPE_NUMBER,
303 	    PROP_READONLY, ZFS_TYPE_SNAPSHOT, NULL);
304 	register_hidden(ZFS_PROP_NAME, "name", PROP_TYPE_STRING,
305 	    PROP_READONLY, ZFS_TYPE_DATASET, "NAME");
306 	register_hidden(ZFS_PROP_ISCSIOPTIONS, "iscsioptions", PROP_TYPE_STRING,
307 	    PROP_INHERIT, ZFS_TYPE_VOLUME, "ISCSIOPTIONS");
308 	register_hidden(ZFS_PROP_GUID, "guid", PROP_TYPE_NUMBER, PROP_READONLY,
309 	    ZFS_TYPE_DATASET, "GUID");
310 
311 	/* oddball properties */
312 	register_impl(ZFS_PROP_CREATION, "creation", PROP_TYPE_NUMBER, 0, NULL,
313 	    PROP_READONLY, ZFS_TYPE_DATASET,
314 	    "<date>", "CREATION", B_FALSE, B_TRUE, NULL);
315 }
316 
317 boolean_t
318 zfs_prop_delegatable(zfs_prop_t prop)
319 {
320 	zprop_desc_t *pd = &zfs_prop_table[prop];
321 	return (pd->pd_attr != PROP_READONLY);
322 }
323 
324 /*
325  * Given a zfs dataset property name, returns the corresponding property ID.
326  */
327 zfs_prop_t
328 zfs_name_to_prop(const char *propname)
329 {
330 	return (zprop_name_to_prop(propname, ZFS_TYPE_DATASET));
331 }
332 
333 
334 /*
335  * For user property names, we allow all lowercase alphanumeric characters, plus
336  * a few useful punctuation characters.
337  */
338 static int
339 valid_char(char c)
340 {
341 	return ((c >= 'a' && c <= 'z') ||
342 	    (c >= '0' && c <= '9') ||
343 	    c == '-' || c == '_' || c == '.' || c == ':');
344 }
345 
346 /*
347  * Returns true if this is a valid user-defined property (one with a ':').
348  */
349 boolean_t
350 zfs_prop_user(const char *name)
351 {
352 	int i;
353 	char c;
354 	boolean_t foundsep = B_FALSE;
355 
356 	for (i = 0; i < strlen(name); i++) {
357 		c = name[i];
358 		if (!valid_char(c))
359 			return (B_FALSE);
360 		if (c == ':')
361 			foundsep = B_TRUE;
362 	}
363 
364 	if (!foundsep)
365 		return (B_FALSE);
366 
367 	return (B_TRUE);
368 }
369 
370 /*
371  * Tables of index types, plus functions to convert between the user view
372  * (strings) and internal representation (uint64_t).
373  */
374 int
375 zfs_prop_string_to_index(zfs_prop_t prop, const char *string, uint64_t *index)
376 {
377 	return (zprop_string_to_index(prop, string, index, ZFS_TYPE_DATASET));
378 }
379 
380 int
381 zfs_prop_index_to_string(zfs_prop_t prop, uint64_t index, const char **string)
382 {
383 	return (zprop_index_to_string(prop, index, string, ZFS_TYPE_DATASET));
384 }
385 
386 /*
387  * Returns TRUE if the property applies to any of the given dataset types.
388  */
389 boolean_t
390 zfs_prop_valid_for_type(int prop, zfs_type_t types)
391 {
392 	return (zprop_valid_for_type(prop, types));
393 }
394 
395 zprop_type_t
396 zfs_prop_get_type(zfs_prop_t prop)
397 {
398 	return (zfs_prop_table[prop].pd_proptype);
399 }
400 
401 /*
402  * Returns TRUE if the property is readonly.
403  */
404 boolean_t
405 zfs_prop_readonly(zfs_prop_t prop)
406 {
407 	return (zfs_prop_table[prop].pd_attr == PROP_READONLY ||
408 	    zfs_prop_table[prop].pd_attr == PROP_ONETIME);
409 }
410 
411 /*
412  * Returns TRUE if the property is only allowed to be set once.
413  */
414 boolean_t
415 zfs_prop_setonce(zfs_prop_t prop)
416 {
417 	return (zfs_prop_table[prop].pd_attr == PROP_ONETIME);
418 }
419 
420 const char *
421 zfs_prop_default_string(zfs_prop_t prop)
422 {
423 	return (zfs_prop_table[prop].pd_strdefault);
424 }
425 
426 uint64_t
427 zfs_prop_default_numeric(zfs_prop_t prop)
428 {
429 	return (zfs_prop_table[prop].pd_numdefault);
430 }
431 
432 /*
433  * Given a dataset property ID, returns the corresponding name.
434  * Assuming the zfs dataset property ID is valid.
435  */
436 const char *
437 zfs_prop_to_name(zfs_prop_t prop)
438 {
439 	return (zfs_prop_table[prop].pd_name);
440 }
441 
442 /*
443  * Returns TRUE if the property is inheritable.
444  */
445 boolean_t
446 zfs_prop_inheritable(zfs_prop_t prop)
447 {
448 	return (zfs_prop_table[prop].pd_attr == PROP_INHERIT ||
449 	    zfs_prop_table[prop].pd_attr == PROP_ONETIME);
450 }
451 
452 #ifndef _KERNEL
453 
454 /*
455  * Returns a string describing the set of acceptable values for the given
456  * zfs property, or NULL if it cannot be set.
457  */
458 const char *
459 zfs_prop_values(zfs_prop_t prop)
460 {
461 	return (zfs_prop_table[prop].pd_values);
462 }
463 
464 /*
465  * Returns TRUE if this property is a string type.  Note that index types
466  * (compression, checksum) are treated as strings in userland, even though they
467  * are stored numerically on disk.
468  */
469 int
470 zfs_prop_is_string(zfs_prop_t prop)
471 {
472 	return (zfs_prop_table[prop].pd_proptype == PROP_TYPE_STRING ||
473 	    zfs_prop_table[prop].pd_proptype == PROP_TYPE_INDEX);
474 }
475 
476 /*
477  * Returns the column header for the given property.  Used only in
478  * 'zfs list -o', but centralized here with the other property information.
479  */
480 const char *
481 zfs_prop_column_name(zfs_prop_t prop)
482 {
483 	return (zfs_prop_table[prop].pd_colname);
484 }
485 
486 /*
487  * Returns whether the given property should be displayed right-justified for
488  * 'zfs list'.
489  */
490 boolean_t
491 zfs_prop_align_right(zfs_prop_t prop)
492 {
493 	return (zfs_prop_table[prop].pd_rightalign);
494 }
495 
496 #endif
497