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22 * Copyright 2009 Sun Microsystems, Inc. All rights reserved.
23 * Use is subject to license terms.
30 * ZAP - ZFS Attribute Processor
32 * The ZAP is a module which sits on top of the DMU (Data Management
33 * Unit) and implements a higher-level storage primitive using DMU
34 * objects. Its primary consumer is the ZPL (ZFS Posix Layer).
36 * A "zapobj" is a DMU object which the ZAP uses to stores attributes.
37 * Users should use only zap routines to access a zapobj - they should
38 * not access the DMU object directly using DMU routines.
40 * The attributes stored in a zapobj are name-value pairs. The name is
41 * a zero-terminated string of up to ZAP_MAXNAMELEN bytes (including
42 * terminating NULL). The value is an array of integers, which may be
43 * 1, 2, 4, or 8 bytes long. The total space used by the array (number
44 * of integers * integer length) can be up to ZAP_MAXVALUELEN bytes.
45 * Note that an 8-byte integer value can be used to store the location
46 * (object number) of another dmu object (which may be itself a zapobj).
47 * Note that you can use a zero-length attribute to store a single bit
48 * of information - the attribute is present or not.
50 * The ZAP routines are thread-safe. However, you must observe the
51 * DMU's restriction that a transaction may not be operated on
54 * Any of the routines that return an int may return an I/O error (EIO
58 * Implementation / Performance Notes:
60 * The ZAP is intended to operate most efficiently on attributes with
61 * short (49 bytes or less) names and single 8-byte values, for which
62 * the microzap will be used. The ZAP should be efficient enough so
63 * that the user does not need to cache these attributes.
65 * The ZAP's locking scheme makes its routines thread-safe. Operations
66 * on different zapobjs will be processed concurrently. Operations on
67 * the same zapobj which only read data will be processed concurrently.
68 * Operations on the same zapobj which modify data will be processed
69 * concurrently when there are many attributes in the zapobj (because
70 * the ZAP uses per-block locking - more than 128 * (number of cpus)
71 * small attributes will suffice).
75 * We're using zero-terminated byte strings (ie. ASCII or UTF-8 C
76 * strings) for the names of attributes, rather than a byte string
77 * bounded by an explicit length. If some day we want to support names
78 * in character sets which have embedded zeros (eg. UTF-16, UTF-32),
79 * we'll have to add routines for using length-bounded strings.
89 * The matchtype specifies which entry will be accessed.
90 * MT_EXACT: only find an exact match (non-normalized)
91 * MT_FIRST: find the "first" normalized (case and Unicode
92 * form) match; the designated "first" match will not change as long
93 * as the set of entries with this normalization doesn't change
94 * MT_BEST: if there is an exact match, find that, otherwise find the
95 * first normalized match
97 typedef enum matchtype
105 * Create a new zapobj with no attributes and return its object number.
106 * MT_EXACT will cause the zap object to only support MT_EXACT lookups,
107 * otherwise any matchtype can be used for lookups.
109 * normflags specifies what normalization will be done. values are:
110 * 0: no normalization (legacy on-disk format, supports MT_EXACT matching
112 * U8_TEXTPREP_TOLOWER: case normalization will be performed.
113 * MT_FIRST/MT_BEST matching will find entries that match without
114 * regard to case (eg. looking for "foo" can find an entry "Foo").
115 * Eventually, other flags will permit unicode normalization as well.
117 uint64_t zap_create(objset_t *ds, dmu_object_type_t ot,
118 dmu_object_type_t bonustype, int bonuslen, dmu_tx_t *tx);
119 uint64_t zap_create_norm(objset_t *ds, int normflags, dmu_object_type_t ot,
120 dmu_object_type_t bonustype, int bonuslen, dmu_tx_t *tx);
123 * Create a new zapobj with no attributes from the given (unallocated)
126 int zap_create_claim(objset_t *ds, uint64_t obj, dmu_object_type_t ot,
127 dmu_object_type_t bonustype, int bonuslen, dmu_tx_t *tx);
128 int zap_create_claim_norm(objset_t *ds, uint64_t obj,
129 int normflags, dmu_object_type_t ot,
130 dmu_object_type_t bonustype, int bonuslen, dmu_tx_t *tx);
133 * The zapobj passed in must be a valid ZAP object for all of the
134 * following routines.
138 * Destroy this zapobj and all its attributes.
140 * Frees the object number using dmu_object_free.
142 int zap_destroy(objset_t *ds, uint64_t zapobj, dmu_tx_t *tx);
145 * Manipulate attributes.
147 * 'integer_size' is in bytes, and must be 1, 2, 4, or 8.
151 * Retrieve the contents of the attribute with the given name.
153 * If the requested attribute does not exist, the call will fail and
156 * If 'integer_size' is smaller than the attribute's integer size, the
157 * call will fail and return EINVAL.
159 * If 'integer_size' is equal to or larger than the attribute's integer
160 * size, the call will succeed and return 0. * When converting to a
161 * larger integer size, the integers will be treated as unsigned (ie. no
162 * sign-extension will be performed).
164 * 'num_integers' is the length (in integers) of 'buf'.
166 * If the attribute is longer than the buffer, as many integers as will
167 * fit will be transferred to 'buf'. If the entire attribute was not
168 * transferred, the call will return EOVERFLOW.
170 * If rn_len is nonzero, realname will be set to the name of the found
171 * entry (which may be different from the requested name if matchtype is
174 * If normalization_conflictp is not NULL, it will be set if there is
175 * another name with the same case/unicode normalized form.
177 int zap_lookup(objset_t *ds, uint64_t zapobj, const char *name,
178 uint64_t integer_size, uint64_t num_integers, void *buf);
179 int zap_lookup_norm(objset_t *ds, uint64_t zapobj, const char *name,
180 uint64_t integer_size, uint64_t num_integers, void *buf,
181 matchtype_t mt, char *realname, int rn_len,
182 boolean_t *normalization_conflictp);
184 int zap_count_write(objset_t *os, uint64_t zapobj, const char *name,
185 int add, uint64_t *towrite, uint64_t *tooverwrite);
188 * Create an attribute with the given name and value.
190 * If an attribute with the given name already exists, the call will
191 * fail and return EEXIST.
193 int zap_add(objset_t *ds, uint64_t zapobj, const char *name,
194 int integer_size, uint64_t num_integers,
195 const void *val, dmu_tx_t *tx);
198 * Set the attribute with the given name to the given value. If an
199 * attribute with the given name does not exist, it will be created. If
200 * an attribute with the given name already exists, the previous value
201 * will be overwritten. The integer_size may be different from the
202 * existing attribute's integer size, in which case the attribute's
203 * integer size will be updated to the new value.
205 int zap_update(objset_t *ds, uint64_t zapobj, const char *name,
206 int integer_size, uint64_t num_integers, const void *val, dmu_tx_t *tx);
209 * Get the length (in integers) and the integer size of the specified
212 * If the requested attribute does not exist, the call will fail and
215 int zap_length(objset_t *ds, uint64_t zapobj, const char *name,
216 uint64_t *integer_size, uint64_t *num_integers);
219 * Remove the specified attribute.
221 * If the specified attribute does not exist, the call will fail and
224 int zap_remove(objset_t *ds, uint64_t zapobj, const char *name, dmu_tx_t *tx);
225 int zap_remove_norm(objset_t *ds, uint64_t zapobj, const char *name,
226 matchtype_t mt, dmu_tx_t *tx);
229 * Returns (in *count) the number of attributes in the specified zap
232 int zap_count(objset_t *ds, uint64_t zapobj, uint64_t *count);
236 * Returns (in name) the name of the entry whose (value & mask)
237 * (za_first_integer) is value, or ENOENT if not found. The string
238 * pointed to by name must be at least 256 bytes long. If mask==0, the
239 * match must be exact (ie, same as mask=-1ULL).
241 int zap_value_search(objset_t *os, uint64_t zapobj,
242 uint64_t value, uint64_t mask, char *name);
245 * Transfer all the entries from fromobj into intoobj. Only works on
246 * int_size=8 num_integers=1 values. Fails if there are any duplicated
249 int zap_join(objset_t *os, uint64_t fromobj, uint64_t intoobj, dmu_tx_t *tx);
252 * Manipulate entries where the name + value are the "same" (the name is
253 * a stringified version of the value).
255 int zap_add_int(objset_t *os, uint64_t obj, uint64_t value, dmu_tx_t *tx);
256 int zap_remove_int(objset_t *os, uint64_t obj, uint64_t value, dmu_tx_t *tx);
257 int zap_lookup_int(objset_t *os, uint64_t obj, uint64_t value);
261 typedef struct zap_cursor {
262 /* This structure is opaque! */
265 struct zap_leaf *zc_leaf;
272 int za_integer_length;
274 * za_normalization_conflict will be set if there are additional
275 * entries with this normalized form (eg, "foo" and "Foo").
277 boolean_t za_normalization_conflict;
278 uint64_t za_num_integers;
279 uint64_t za_first_integer; /* no sign extension for <8byte ints */
280 char za_name[MAXNAMELEN];
284 * The interface for listing all the attributes of a zapobj can be
285 * thought of as cursor moving down a list of the attributes one by
286 * one. The cookie returned by the zap_cursor_serialize routine is
287 * persistent across system calls (and across reboot, even).
291 * Initialize a zap cursor, pointing to the "first" attribute of the
292 * zapobj. You must _fini the cursor when you are done with it.
294 void zap_cursor_init(zap_cursor_t *zc, objset_t *ds, uint64_t zapobj);
295 void zap_cursor_fini(zap_cursor_t *zc);
298 * Get the attribute currently pointed to by the cursor. Returns
299 * ENOENT if at the end of the attributes.
301 int zap_cursor_retrieve(zap_cursor_t *zc, zap_attribute_t *za);
304 * Advance the cursor to the next attribute.
306 void zap_cursor_advance(zap_cursor_t *zc);
309 * Get a persistent cookie pointing to the current position of the zap
310 * cursor. The low 4 bits in the cookie are always zero, and thus can
311 * be used as to differentiate a serialized cookie from a different type
312 * of value. The cookie will be less than 2^32 as long as there are
313 * fewer than 2^22 (4.2 million) entries in the zap object.
315 uint64_t zap_cursor_serialize(zap_cursor_t *zc);
318 * Initialize a zap cursor pointing to the position recorded by
319 * zap_cursor_serialize (in the "serialized" argument). You can also
320 * use a "serialized" argument of 0 to start at the beginning of the
321 * zapobj (ie. zap_cursor_init_serialized(..., 0) is equivalent to
322 * zap_cursor_init(...).)
324 void zap_cursor_init_serialized(zap_cursor_t *zc, objset_t *ds,
325 uint64_t zapobj, uint64_t serialized);
328 #define ZAP_HISTOGRAM_SIZE 10
330 typedef struct zap_stats {
332 * Size of the pointer table (in number of entries).
333 * This is always a power of 2, or zero if it's a microzap.
334 * In general, it should be considerably greater than zs_num_leafs.
336 uint64_t zs_ptrtbl_len;
338 uint64_t zs_blocksize; /* size of zap blocks */
341 * The number of blocks used. Note that some blocks may be
342 * wasted because old ptrtbl's and large name/value blocks are
343 * not reused. (Although their space is reclaimed, we don't
344 * reuse those offsets in the object.)
346 uint64_t zs_num_blocks;
349 * Pointer table values from zap_ptrtbl in the zap_phys_t
351 uint64_t zs_ptrtbl_nextblk; /* next (larger) copy start block */
352 uint64_t zs_ptrtbl_blks_copied; /* number source blocks copied */
353 uint64_t zs_ptrtbl_zt_blk; /* starting block number */
354 uint64_t zs_ptrtbl_zt_numblks; /* number of blocks */
355 uint64_t zs_ptrtbl_zt_shift; /* bits to index it */
358 * Values of the other members of the zap_phys_t
360 uint64_t zs_block_type; /* ZBT_HEADER */
361 uint64_t zs_magic; /* ZAP_MAGIC */
362 uint64_t zs_num_leafs; /* The number of leaf blocks */
363 uint64_t zs_num_entries; /* The number of zap entries */
364 uint64_t zs_salt; /* salt to stir into hash function */
367 * Histograms. For all histograms, the last index
368 * (ZAP_HISTOGRAM_SIZE-1) includes any values which are greater
369 * than what can be represented. For example
370 * zs_leafs_with_n5_entries[ZAP_HISTOGRAM_SIZE-1] is the number
371 * of leafs with more than 45 entries.
375 * zs_leafs_with_n_pointers[n] is the number of leafs with
376 * 2^n pointers to it.
378 uint64_t zs_leafs_with_2n_pointers[ZAP_HISTOGRAM_SIZE];
381 * zs_leafs_with_n_entries[n] is the number of leafs with
382 * [n*5, (n+1)*5) entries. In the current implementation, there
383 * can be at most 55 entries in any block, but there may be
384 * fewer if the name or value is large, or the block is not
387 uint64_t zs_blocks_with_n5_entries[ZAP_HISTOGRAM_SIZE];
390 * zs_leafs_n_tenths_full[n] is the number of leafs whose
391 * fullness is in the range [n/10, (n+1)/10).
393 uint64_t zs_blocks_n_tenths_full[ZAP_HISTOGRAM_SIZE];
396 * zs_entries_using_n_chunks[n] is the number of entries which
397 * consume n 24-byte chunks. (Note, large names/values only use
398 * one chunk, but contribute to zs_num_blocks_large.)
400 uint64_t zs_entries_using_n_chunks[ZAP_HISTOGRAM_SIZE];
403 * zs_buckets_with_n_entries[n] is the number of buckets (each
404 * leaf has 64 buckets) with n entries.
405 * zs_buckets_with_n_entries[1] should be very close to
408 uint64_t zs_buckets_with_n_entries[ZAP_HISTOGRAM_SIZE];
412 * Get statistics about a ZAP object. Note: you need to be aware of the
413 * internal implementation of the ZAP to correctly interpret some of the
414 * statistics. This interface shouldn't be relied on unless you really
415 * know what you're doing.
417 int zap_get_stats(objset_t *ds, uint64_t zapobj, zap_stats_t *zs);
423 #endif /* _SYS_ZAP_H */