zap.h revision fa9e4066f08beec538e775443c5be79dd423fcab
/*
* CDDL HEADER START
*
* The contents of this file are subject to the terms of the
* Common Development and Distribution License, Version 1.0 only
* (the "License"). You may not use this file except in compliance
* with the License.
*
* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
* or http://www.opensolaris.org/os/licensing.
* See the License for the specific language governing permissions
* and limitations under the License.
*
* When distributing Covered Code, include this CDDL HEADER in each
* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
* If applicable, add the following below this CDDL HEADER, with the
* fields enclosed by brackets "[]" replaced with your own identifying
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*/
/*
* Copyright 2005 Sun Microsystems, Inc. All rights reserved.
* Use is subject to license terms.
*/
#ifndef _SYS_ZAP_H
#define _SYS_ZAP_H
#pragma ident "%Z%%M% %I% %E% SMI"
/*
* ZAP - ZFS Attribute Processor
*
* The ZAP is a module which sits on top of the DMU (Data Managemnt
* Unit) and implements a higher-level storage primitive using DMU
* objects. Its primary consumer is the ZPL (ZFS Posix Layer).
*
* A "zapobj" is a DMU object which the ZAP uses to stores attributes.
* Users should use only zap routines to access a zapobj - they should
* not access the DMU object directly using DMU routines.
*
* The attributes stored in a zapobj are name-value pairs. The name is
* a zero-terminated string of up to 256 bytes (including terminating
* NULL). The value is an array of integers (whose length is limited
* only by the size of the zapobj). The integers may be 1, 2, 4, or 8
* bytes long. Note that an 8-byte integer value can be used to store
* the location (object number) of another dmu object (which may be
* itself a zapobj). Note that you can use a zero-length attribute to
* store a single bit of information - the attribute is present or not.
*
* The ZAP routines are thread-safe. However, you must observe the
* DMU's restriction that a transaction may not be operated on
* concurrently.
*
* Any of the routines that return an int may return an I/O error (EIO
* or ECHECKSUM).
*
*
* Implementation / Performance Notes:
*
* The ZAP is intended to operate most efficiently on attributes with
* short (23 bytes or less) names and short (23 bytes or less) values.
* The ZAP should be efficient enough so that the user does not need to
* cache these attributes.
*
* Using extremely long (~256 bytes or more) attribute names or values
* values will result in poor performance, due to the memcpy from the
* user's buffer into the ZAP object. This penalty can be avoided by
* creating an integer-type attribute to store an object number, and
* accessing that object using the DMU directly.
*
* The ZAP's locking scheme makes its routines thread-safe. Operations
* on different zapobjs will be processed concurrently. Operations on
* the same zapobj which only read data will be processed concurrently.
* Operations on the same zapobj which modify data will be processed
* concurrently when there are many attributes in the zapobj (because
* the ZAP uses per-block locking - more than 32 * (number of cpus)
* small attributes will suffice).
*/
/*
* We're using zero-terminated byte strings (ie. ASCII or UTF-8 C
* strings) for the names of attributes, rather than a byte string
* bounded by an explicit length. If some day we want to support names
* in character sets which have embedded zeros (eg. UTF-16, UTF-32),
* we'll have to add routines for using length-bounded strings.
*/
#include <sys/dmu.h>
#ifdef __cplusplus
extern "C" {
#endif
/*
* Create a new zapobj with no attributes and return its object number.
*/
uint64_t zap_create(objset_t *ds, dmu_object_type_t ot,
dmu_object_type_t bonustype, int bonuslen, dmu_tx_t *tx);
/*
* Create a new zapobj with no attributes from the given (unallocated)
* object number.
*/
int zap_create_claim(objset_t *ds, uint64_t obj, dmu_object_type_t ot,
dmu_object_type_t bonustype, int bonuslen, dmu_tx_t *tx);
/*
* The zapobj passed in must be a valid ZAP object for all of the
* following routines.
*/
/*
* Destroy this zapobj and all its attributes.
*
* Frees the object number using dmu_object_free.
*/
int zap_destroy(objset_t *ds, uint64_t zapobj, dmu_tx_t *tx);
/*
* Manipulate attributes.
*
* 'integer_size' is in bytes, and must be 1, 2, 4, or 8.
*/
/*
* Retrieve the contents of the attribute with the given name.
*
* If the requested attribute does not exist, the call will fail and
* return ENOENT.
*
* If 'integer_size' is smaller than the attribute's integer size, the
* call will fail and return EINVAL.
*
* If 'integer_size' is equal to or larger than the attribute's integer
* size, the call will succeed and return 0. * When converting to a
* larger integer size, the integers will be treated as unsigned (ie. no
* sign-extension will be performed).
*
* 'num_integers' is the length (in integers) of 'buf'.
*
* If the attribute is longer than the buffer, as many integers as will
* fit will be transferred to 'buf'. If the entire attribute was not
* transferred, the call will return EOVERFLOW.
*/
int zap_lookup(objset_t *ds, uint64_t zapobj, const char *name,
uint64_t integer_size, uint64_t num_integers, void *buf);
/*
* Create an attribute with the given name and value.
*
* If an attribute with the given name already exists, the call will
* fail and return EEXIST.
*/
int zap_add(objset_t *ds, uint64_t zapobj, const char *name,
int integer_size, uint64_t num_integers,
const void *val, dmu_tx_t *tx);
/*
* Set the attribute with the given name to the given value. If an
* attribute with the given name does not exist, it will be created. If
* an attribute with the given name already exists, the previous value
* will be overwritten. The integer_size may be different from the
* existing attribute's integer size, in which case the attribute's
* integer size will be updated to the new value.
*/
int zap_update(objset_t *ds, uint64_t zapobj, const char *name,
int integer_size, uint64_t num_integers, const void *val, dmu_tx_t *tx);
/*
* Get the length (in integers) and the integer size of the specified
* attribute.
*
* If the requested attribute does not exist, the call will fail and
* return ENOENT.
*/
int zap_length(objset_t *ds, uint64_t zapobj, const char *name,
uint64_t *integer_size, uint64_t *num_integers);
/*
* Remove the specified attribute.
*
* If the specified attribute does not exist, the call will fail and
* return ENOENT.
*/
int zap_remove(objset_t *ds, uint64_t zapobj, const char *name, dmu_tx_t *tx);
/*
* Returns (in *count) the number of attributes in the specified zap
* object.
*/
int zap_count(objset_t *ds, uint64_t zapobj, uint64_t *count);
/*
* Returns (in name) the name of the entry whose value
* (za_first_integer) is value, or ENOENT if not found. The string
* pointed to by name must be at least 256 bytes long.
*/
int zap_value_search(objset_t *os, uint64_t zapobj, uint64_t value, char *name);
typedef struct zap_cursor {
/* This structure is opaque! */
objset_t *zc_objset;
uint64_t zc_zapobj;
uint64_t zc_hash;
uint32_t zc_cd;
} zap_cursor_t;
typedef struct {
int za_integer_length;
uint64_t za_num_integers;
uint64_t za_first_integer; /* no sign extension for <8byte ints */
char za_name[MAXNAMELEN];
} zap_attribute_t;
/*
* The interface for listing all the attributes of a zapobj can be
* thought of as cursor moving down a list of the attributes one by
* one. The cookie returned by the zap_cursor_serialize routine is
* persistent across system calls (and across reboot, even).
*/
/*
* Initialize a zap cursor, pointing to the "first" attribute of the
* zapobj.
*/
void zap_cursor_init(zap_cursor_t *zc, objset_t *ds, uint64_t zapobj);
/*
* Get the attribute currently pointed to by the cursor. Returns
* ENOENT if at the end of the attributes.
*/
int zap_cursor_retrieve(zap_cursor_t *zc, zap_attribute_t *za);
/*
* Advance the cursor to the next attribute.
*/
void zap_cursor_advance(zap_cursor_t *zc);
/*
* Get a persistent cookie pointing to the current position of the zap
* cursor. The low 4 bits in the cookie are always zero, and thus can
* be used as to differentiate a serialized cookie from a different type
* of value. The cookie will be less than 2^32 as long as there are
* fewer than 2^22 (4.2 million) entries in the zap object.
*/
uint64_t zap_cursor_serialize(zap_cursor_t *zc);
/*
* Initialize a zap cursor pointing to the position recorded by
* zap_cursor_serialize (in the "serialized" argument). You can also
* use a "serialized" argument of 0 to start at the beginning of the
* zapobj (ie. zap_cursor_init_serialized(..., 0) is equivalent to
* zap_cursor_init(...).)
*/
void zap_cursor_init_serialized(zap_cursor_t *zc, objset_t *ds,
uint64_t zapobj, uint64_t serialized);
#define ZAP_HISTOGRAM_SIZE 10
typedef struct zap_stats {
/*
* Size of the pointer table (in number of entries).
* This is always a power of 2, or zero if it's a microzap.
* In general, it should be considerably greater than zs_num_leafs.
*/
uint64_t zs_ptrtbl_len;
uint64_t zs_blocksize; /* size of zap blocks */
uint64_t zs_num_leafs; /* The number of leaf blocks */
uint64_t zs_num_entries; /* The number of zap entries */
/*
* The number of blocks used. Note that some blocks may be
* wasted because old ptrtbl's and large name/value blocks are
* not reused. (Although their space is reclaimed, we don't
* reuse those offsets in the object.)
*/
uint64_t zs_num_blocks;
/* The number of blocks used for large names or values */
uint64_t zs_num_blocks_large;
/*
* Histograms. For all histograms, the last index
* (ZAP_HISTOGRAM_SIZE-1) includes any values which are greater
* than what can be represented. For example
* zs_leafs_with_n5_entries[ZAP_HISTOGRAM_SIZE-1] is the number
* of leafs with more than 45 entries.
*/
/*
* zs_leafs_with_n_pointers[n] is the number of leafs with
* 2^n pointers to it.
*/
uint64_t zs_leafs_with_2n_pointers[ZAP_HISTOGRAM_SIZE];
/*
* zs_leafs_with_n_chained[n] is the number of leafs with n
* chained blocks. zs_leafs_with_n_chained[0] (leafs with no
* chained blocks) should be very close to zs_num_leafs.
*/
uint64_t zs_leafs_with_n_chained[ZAP_HISTOGRAM_SIZE];
/*
* zs_leafs_with_n_entries[n] is the number of leafs with
* [n*5, (n+1)*5) entries. In the current implementation, there
* can be at most 55 entries in any block, but there may be
* fewer if the name or value is large, or the block is not
* completely full.
*/
uint64_t zs_blocks_with_n5_entries[ZAP_HISTOGRAM_SIZE];
/*
* zs_leafs_n_tenths_full[n] is the number of leafs whose
* fullness is in the range [n/10, (n+1)/10).
*/
uint64_t zs_blocks_n_tenths_full[ZAP_HISTOGRAM_SIZE];
/*
* zs_entries_using_n_chunks[n] is the number of entries which
* consume n 24-byte chunks. (Note, large names/values only use
* one chunk, but contribute to zs_num_blocks_large.)
*/
uint64_t zs_entries_using_n_chunks[ZAP_HISTOGRAM_SIZE];
/*
* zs_buckets_with_n_entries[n] is the number of buckets (each
* leaf has 64 buckets) with n entries.
* zs_buckets_with_n_entries[1] should be very close to
* zs_num_entries.
*/
uint64_t zs_buckets_with_n_entries[ZAP_HISTOGRAM_SIZE];
} zap_stats_t;
/*
* Get statistics about a ZAP object. Note: you need to be aware of the
* internal implementation of the ZAP to correctly interpret some of the
* statistics. This interface shouldn't be relied on unless you really
* know what you're doing.
*/
int zap_get_stats(objset_t *ds, uint64_t zapobj, zap_stats_t *zs);
#ifdef __cplusplus
}
#endif
#endif /* _SYS_ZAP_H */