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vol_pattern

Section: Devices and Network Interfaces (4)
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NAME

vol_pattern - Logical Storage Manager (LSM) disk group search specifications  

DESCRIPTION

The vol_pattern search expression language can be used in volprint and voledit, and with some Logical Storage Manager support library functions, to locate Logical Storage Manager configuration records with particular characteristics. Searches are limited to operation on one disk group at a time. In the current release, search expressions are limited to volume, plex, and subdisk recods. Search expressions cannot be applied to disk group, disk media, or disk access records.

Search patterns provide an expression-based language for specifying record attributes. In simple cases, patterns can be specified that match records whose fields have specific values. In more complex cases, records can be matched based on attributes of associated records.

Search patterns are expressions that do not have side effects (for example, variables cannot be set or changed). Expressions evaluate either to true or false. If evaluation of an expression within the context of a configuration record yields a value of true, then the expression matches the record; otherwise the expression does not match the record.

The search pattern language does not have operators that cause changes to be made, and does not have a concept of local variables that can be set and used within or between expressions.
 

Types of Expressions

Expressions in the pattern language are similar to expressions in awk(1). Expressions can have the following types for constants, variables, and subexpressions: A boolean variable or expression is either true or false. Numbers and strings can be used as truth values if the context requires a boolean value. For a number, zero implies false and nonzero implies true. For a string, an empty string implies false and a nonempty string implies true. A string is a literal string in quotes or a character array field from a configuration record. Strings can be implicitly promoted to boolean, but are never promoted to other types. For example, a string-valued field in a record that contains only digits cannot be compared with a number. String literals are described later. A number is an integer quantity. The maximum size for a number is the largest size that may be used for values in configuration records. In the reference porting base for the Logical Storage Manager, these numbers are 32 bit signed numbers.

Numbers can be specified in decimal, octal, or hexadecimal with a suffix to indicate the unit of the number when it indicates an object length or offset. Hexadecimal numbers begin with 0x, octal numbers begin with 0; otherwise numbers are in decimal. When used as a length, numbers with no suffix are taken as sectors.
Defined suffix characters are: b for 512-byte blocks, s for sectors (typically 512 bytes), k for kilobytes, m for megabytes, and g for gigabytes. Suffix characters also can be specified in upper case.
Length numbers are actually defined in terms of sectors. As a result, on a system with 512 byte sectors, 1k is the same as 2. Thus, the expression:
nassoc=1k
tests for a record with 2 associated records, rather than 1024 associated records. An enumeration field is a number that represents one of the values for a field that has symbolic names. The vol_pattern expression grammar handles enumeration values exactly like numbers. Enumerations are usually only useful for comparing compatible enumeration field and enumeration constants. For example, the enumeration field pl_layout enumeration field is a number whose possible values are represented by the symbols CONCAT and STRIPE. A regular expression is a value, much like a regular expression in awk or ed, that can be used to specify a pattern for matching strings. Regular expressions can only be used in the context of the boolean ~ and !~ operators. Each time a transaction is issued against a disk group configuration, a 64-bit configuration sequence number is increased. When a configuration records is created or changed in a transaction, the record is stamped with the configuration sequence number associated with that transaction.
When a record is created, it is given a 64-bit record ID. These record IDs are never reused within a disk group configuration.
Configuration sequence numbers and record IDs can be specified as constants of the form number.number, where both numbers are specified in decimal.

Two higher-level types are also included, which can represent multiple values of the same base type. These higher-level types are: A set is a multi-valued variable (an array). Sets are normally used within the right-hand expression for the any and in operators. Reference to a set expression yields all of the currently valid members of the set, of which there may be none. A list is a set of expressions and sets within parenthesis that are separated by commas. List expressions can only be used for the right-hand expression of the in operator.
 

Expression Grammar

A pattern is an expression with the following components and operators, in increasing order of precedence. Groups of operators described together have the same precedence. This is a conditional expression. Expression expr1 is evaluated as a boolean value. If it has a truth value of true, then the value for the conditional expression is the value of expr2, otherwise the value for the conditional expression is the value of expr3. The logical or operator. expr1 and expr2 are evaluated as boolean expressions. If either expr1 or expr2 have a truth value of true, the expression is true; otherwise, the value of the expression is false. The logical and operator. expr1 and expr2 are evaluated as boolean expressions. If both expr1 and expr2 have a truth value of true, the expression is true; otherwise, the value of the expression is false. The expression expr is evaluated as a boolean expression for all combinations of elements for all sets within expr that represent sets. If any of these combinations yields a truth value of true, then the value of the any expression is true; otherwise, the value is false.

For example, pl_sd is a set defining the names of subdisk records that are associated with a plex. The following expression searches for plex records that have an associated subdisk on disk disk01:
any pl_sd.sd_disk=""disk01""
Each name in the pl_sd_name set is referenced as a subdisk and checked to see if that subdisk is on disk disk01. The expression is true if it is true for any subdisk. Expression expr is evaluated, and the resulting value is compared to all of the values in list. If any of the values in list match expr, then the value of the in expression is true; otherwise, the value is false. The list can either be a list of expressions within parentheses that are separated by commas, or it can be a single expression. If any of the expressions in list represent sets, then the comparison is made against all combinations of values in that set.
Type promotions are not performed on the expressions in list, or on expr. Types for all these expression*Os must match exactly.
For example, the following expression searches for plexes that have either a regular subdisk or a subdisk on disk disk01:
""disk01"" in (pl_sd.sd_disk,pl_log_sd.sd_disk) The binary ~ and !~ operators are used to match string values against a regular expression. The value of expr must be a string. For the ~ operator, if the value of expr matches the regular expression regexp, then the value for the match expression is true; otherwise the value is false. For the !~ operator, if expr matches regexp the result is false; otherwise the result is true.
The / character in the regular expression must be escaped with \ if it does not occur within a character range.
For example, to search for subdisks that are defined on a partition of any device, use the following expressions:
sd_path ~ /^\/dev\/[^/]*e/ These expressions compare string, number, sequence number, record ID, or boolean values. If either expr1 or expr2 is a boolean value, then the other is promoted to a boolean as well. For the = operator, if the two values are equal then the result is true; otherwise, the result is false. For the != operator, if the two values are equal, then the result is false; otherwise, the result is true.
For consistency with awk(1) and many other languages, == is allowed as an alias for the = operator. These expressions compare the magnitudes of numbers or sequence numbers. They cannot be applied to any other types of expressions. The result is a boolean. These expressions add or subtract two numbers, yielding another number. These expressions multiply, divide, or take the modulo of two numbers, yielding another number. The unary (pl operator applied to any expression yields the value of that expression. The unary - operator negates the value of a number-valued expression expr. expr is evaluated as a boolean expression. If its value is true, then the value for the ! expression is false; otherwise, the value for the ! expression is true. expr is evaluated as a string expression. Its value is used as the name of a record in the disk group configuration. If the record exists, and if that record contains a field named field-name, then the value of this expression is the value in that field within the referenced record. If the record does not exist, or if the record does not contain a field named field-name, then the behavior is context-dependent.
If this occurs within the context of an any or 4in operator, then the next combination of values for the right-hand side of the any or in operator is evaluated. If this occurs within the context of an && or || operator, then the left or right-hand expression of that operator yields false, whichever side the . operator occurs on. The innermost any, in, &&, or || operator determines the context. If no such context exists, then the result of the entire search pattern is that the record being tested does not match the pattern.
The effect of this short-circuiting behavior is that an expression which is found not to make sense because a record does not exist, or does not contain a specific field, will cause that expression to be false. The effect is similar to implicit asserts, which are described later in this section under field name. Parentheses can be used to override precedence rules. A string, number, sequence number, or record ID literal, as defined in the section Types of Expressions. An assert is a special type of variable name that is true within the context of a specific type of record. Outside of that context, an assert causes the expression that it is in to be false. The scope of an assert is the right or left-hand side of the smallest expression within a || or && operator. If an assert does not occur within a || or && operator, then the search pattern does not match the record being evaluated. The names that specify asserts are vol, plex and sd which specify volume, plex and subdisk records, respectively. There is a set of symbolic constants that can be specified in search patterns. For example, true and false are the two truth values. Also, if a field within a record has a specific set of symbolic values, then these symbolic values are available as numeric constants. See the section titled Constants. There is a small set of global variables that can be referenced in search patterns. Such variables can be used within any context. See the section titled Global Variables. Referencing the name of a field in a configuration record yields the value of that field within the configuration record being evaluated.
Not all field names are defined for all record types. If a field name is referenced that is not valid in the context of the record type, then the smallest expression on either side of a && or || operator becomes false. This is an implicit assert. For example, the following expression matches only volume records because the v_kstate field is only defined for volume records:
v_kstate!=V_ENABLED
Some fields in a record only make sense if another field contains a specific value. For example, the pl_st_width field in plex records is not defined unless the value of the pl_layout field is PL_STRIPE. These cases are treated as implicit asserts.
 

Constants

The names of constants that are recognized within search patterns are: Constants representing boolean true. Constants representing boolean false. The enumeration constants that represent values for the v_read_pol field in volume records. The v_current_read_pol field can be set to ROUND or PREFER. These constants can also be specified with a prefix of V_ to match the enumeration values in the include file sys/vol.h. The enumeration constants that represent values for the v_kstate field in volume and plex records. These constants can also be specified with a prefix of V_ or PL_. GEN_DET, GEN_DET_SPARSE, GEN_FAIL, GEN_DET2

The enumeration constants that represent values for the v_r_all, v_r_some, v_w_all, and v_w_some fields in volume records. These constants can also be specified with a prefix of V_. The enumeration constants that represent values for the v_log_type field in volume records. These enumeration constants can also be specified with a prefix of V_PFLAG_ to match the enumeration values in the include file sys/vol.h. The enumeration constants that represent values for the pl_layout field in plex records. These constants can also be specified with a prefix of PL_. The enumeration constants that represent values for the pl_iomode field in plex records. These enumeration constants can also be specified with a prefix of PL_TFLAG_ to match the values in the include file sys/vol.h. The value for a device number field indicating that the device number is undefined.
 

Global Variables

The global variables that can be used within search patterns are: The configuration sequence number of the disk group configuration. The number of fields in a tutil or putil arrays in a volume, plex, or subdisk structure. This is always 3, but it is treated as a global variable anyway.
 

Generic Fields

Some fields can be found in all types of configuration records. These fields can be referenced without a v_, pl_, or sd_ suffix, and do not generate implicit asserts. These fields can be used either to name fields in the record being evaluated, or as a field name reference for the .1 operator.

A generic field name can be specified with a prefix of v_, pl_, or sd_ to indicate that implicit asserts should be used and that the field requires a context of a volume, plex, or subdisk record, respectively. Currently, use of a prefix for a generic field name is ignored for the right-hand side of a . operator.

The recognized generic field names are: A set of strings representing all of the temporary utility fields. A string representing the first temporary utility field. A string representing the second temporary utility field. A string representing the third temporary utility field. A set of strings representing all of the permanent utility fields. A string containing the first permanent utility field. A string containing the second permanent utility field. A string containing the third permanent utility field. A string containing the record name. A string containing the comment field. A number representing the length of the volume, plex or subdisk. A boolean value indicating whether the volume, plex, or subdisk is open. A subdisk is considered open of the volume or plex device for the subdisk is open. A plex is considered open only if the plex device is open. A volume is considered open if the volume or one of its plex devices is open. The record ID of the record being evaluated. The disk group configuration sequence number corresponding to the transaction that created or that last modified the record. A boolean value indicating whether the record is locked in the current transaction of the caller. This variable is not useful when used with volprint or voledit. It is useful for C programs only.

Special fields exist that do not obey the prefix convention, but which apply to more than one type of record. These are: This is the name of a field to which a record is associated. In the context of a plex or subdisk record, assoc yields the name of the volume or plex to which the record is associated. If the record is not associated, assoc yields an empty string. Use of assoc is not appropriate in the context of a volume record. This causes an implicit assert when applied to a volume. This is the set of associated record names. In the context of a volume or plex record, this yields the names of the associated plexes and subdisks, of which there may be none. This is not appropriate in the context of a subdisk record. This causes an implicit assert when applied to a subdisk. This is the number of records in the aslist set. This causes an implicit assert when applied to a subdisk.
 

Volume Record Fields

The fields that can be specified for volume records are: A boolean value indicating whether the record is locked within the current transaction of the caller. A boolean value indicating whether the volume is locked against I/O activity within the current transaction of the caller. An enumeration field for the kernel-enabled state for the volume. This can have one of the following values: DISABLED, DETACHED, or ENABLED. These are numbers that represent the exception policies for the volume. Each of these fields can have one of the following exception policy values: NO_OP, FAIL_OP, DET_PL, FAIL_DET_PL, DET_VOL, FAIL_DET_VOL, GEN_DET, GEN_DET_SPARSE, GEN_FAIL, or GEN_DET2. A number representing a sequence number for the last error that occurred on the volume. The sequence number of the last transaction that detached the volume due to a failure of some kind. This is also set when all copies of the block-change-log for the volume are detached by I/O failures. A string containing the usage type of the volume. A string containing the file system type for the volume, as set by the administrator. A string representing the usage-type-dependent state for the volume. A boolean value indicating whether the writeback-on-read-error policy is turned on for the volume. This policy is set by default and can be turned off or back on using voledit. See voledit(8) for more information. A boolean value indicating whether volume writes are copied to a private buffer in the kernel before being written to disk. See voledit(8) for more information. A boolean value indicating whether the value of v_writecopy was specified explicitly by the administrator using volmake or voledit. If v_specify_writecopy is false then the value for v_writecopy will be derived from the configuration of the volume: v_writecopy will be turned on if block-change-logging is in operation on the volume, and will be turned off otherwise. A number representing the number of plexes associated with the volume. The set of plex names that are associated with the volume. An enumeration representing the read policy for the volume. This can be one of the values ROUND, PREFER, or SELECT. The value SELECT indicates that read policy will be adjusted to match the configuration of the volume: if there is one associated striped plex, it will be preferred; otherwise the policy will be round-robin. An enumeration representing the current read policy that is in effect for the volume. This is the same as v_read_pol unless v_read_pol is SELECT, in which case v_current_read_pol matches the chosen policy. A string containing the preferred plex for the volume. This is only defined if the value for v_current_read_pol is PREFER. Otherwise, use of this variable causes an implicit assert. The record ID of the preferred plex. A number representing the minor number of the volume block and character devices. This is the persistent device number for the volume. If two volumes on the system have the same value for v_minor, then one of the volumes will be given a different device number, which will be reflected in v_bdev and v_cdev. The block and character device numbers for the volume. A boolean value indicating whether the volume can use one of the reserved minor numbers (minor numbers zero through four). The root and swap usage types set this flag to allow them to grab minor numbers 0 and 1 for the root and swap volumes. A number representing the user ID for the volume. There is currently no way to represent a user name in a search pattern. A number representing the group ID for the volume. There is currently no way to represent a group name in a search pattern. A number representing the file permission modes for the volume. There is currently no way to represent a symbolic mode in a search pattern. A number representing the length of logs associated with the volume, if any. An enumeration representing the logging type for the volume. This can have one of the following values: LOGUNDEF (no specific type specified), LOGNONE (no logging), or LOGBLKNO (block-change logging). A boolean value that is true if logging is enabled for the volume. Logging is enabled if the volume is enabled, and it has at least one associated, enabled plex with an enabled, associated log subdisk. Two numbers that together represent the most significant and least significant long values for the current log serial number for a volume. The log serial number, represented as a combined binary integer, is incremented every time a new log is written for a volume that has logging enabled. A boolean value indicating that all block-change-log copies for the value were detached due to I/O failures. A string value that is used by usage types to represent options to the volume start utility. See the usage-type-specific volume(8) reference pages for more information. A boolean value indicating whether the volume was in use at the time of a system failure. This will not be set if the volume was not written prior to the crash. This flag indicates that plex synchronization recovery is required for the volume. v_active is normally cleared during system startup when the volume is started. A boolean value indicating that read-writeback plex synchronization recovery has been started for the volume. This is normally set when a mirrored volume is started when the v_active flag was set. A boolean value indicating whether the read-writeback recovery mode is still enabled in the kernel. This flag is turned on when v_rwback is turned on, but is cleared by the kernel when recovery for the volume is complete. A number indicating the offset within the volume to where recovery has completed. A read operation on a volume performs a plex synchronization recovery if the read is after this point in the volume. A read that occurs at the current read-writeback offset advances the offset to the end of the read. When the offset reaches the end of the volume, recovery is complete and v_krwback is turned off. A number indicating the largest sector size, in bytes, of any disk associated with the volume.
 

Plex Record Fields

The fields that can be specified for plex records are: A boolean value that is true if the plex is compact. A plex is compact if its entire length is mapped by subdisks, leaving no holes. Note that the length of a plex is computed as the length to the end of the last block in the plex address space that is mapped by a subdisk. The offset to the first unmapped block in the plex. If the plex is compact, this will match the plex length. If the plex is not mapped, this will be the offset of the first hole in the plex. An enumeration representing the I/O mode of the plex. This can have one of the following values: RO (read-only), WO (write-only), or RW (read-write). A boolean value that is true if block-change-logging is enabled for the plex. A boolean value that is true if if one of the subdisks in the plex is defined on a volatile disk. Volatile disks are disks whose contents are not guaranteed to be preserved across a system reboot. Volatile disks can be created using the nopriv disk type [see voldisk(8)]. An enumeration for the kernel enabled state for the plex. This can have one of the values DISABLED, DETACHED or ENABLED. A number representing a sequence number for the last error that occurred on the plex. A number representing the minor number of the plex device. This will be -1 if the plex is dissociated. A number representing the device number of the plex device (a character device). This will be NODEV if the plex is dissociated. A boolean value that is true if the plex is accounted for in volume error handling. If this is set, then I/O errors on the plex are ignored if they result from normal volume I/O. The name of the associated volume. If the plex is not associated, this is an empty string. A number representing the count of subdisks that are associated with the plex. A set containing the names of subdisks that are associated with the plex. A string representing the usage-type-dependent state for the plex. An enumeration representing the subdisk layout policy for the plex. This can be one of the values CONCAT or STRIPE to represent concatenation or striping, respectively. A number representing the stripe width for the plex. This is only defined if the value for the pl_layout field in the plex is STRIPE. Otherwise, use of this variable causes an implicit assert. A string representing the name of a subdisk associated with the plex as a log subdisk. This string is empty if no log subdisk is associated with the plex. A boolean indicating whether any subdisk in the plex is defined on a removed disk. See voldg(8) for information on removed disks. A boolean indicating whether any subdisk in the plex is defined on a failed disk. A failed disk is one where the underlying physical disk could not be found, or was detached by an I/O failure. A boolean indicating whether a disk replacement or a temporary failure caused the plex to become disabled and out-of-date with respect to the volume contents. Such plexes require recovery either from other plexes in the volume or from a backup of the volume. A boolean indicating that the plex was detached by the kernel due to an I/O failure. The stale and kdetach flags are normally both cleared during a system reboot as part of starting the volume. The record ID of the volume to which the plex is associated. This will be 0.0 if the plex is not associated. The record ID of the log subdisk for the plex. This will be 0.0 if the plex has no log subdisk. The configuration sequence number of the disk group that was in effect when the plex was last detached or disabled due to an I/O failure or a disk failure.
 

Subdisk Record Fields

The fields that can be specified for subdisk records are: The name of the disk media record on which the subdisk is defined. The disk access record underlying the disk media record of the subdisk. This will be empty if the disk is currently failed or removed. The device number of the device that the subdisk resides on. This number is a combination of the major and minor number for the device. This will be NODEV if the underlying disk is removed or failed. A string containing the path to the device that the subdisk resides on. The name of the associated plex. If the subdisk is not associated, this is an empty string. A number representing the offset of the subdisk within the public region of the disk that the subdisk resides on. A number representing the offset of the subdisk within the disk partition containing the public region for the disk. This can differ from sd_dm_offset if the public region of the disk does not begin at the beginning of its partition. A number representing the offset of the subdisk within the address space of the plex to which it is associated. A boolean value that is true if the subdisk is defined on a volatile disk. The contents of a volatile disk are not guaranteed to be preserved across a reboot. Volatile disks can be created using the nopriv disk type [see voldisk(8)]. A boolean value indicating that this is a log subdisk for a plex. The record ID of the plex to which the subdisk is associated. The record ID of the disk media record on which the subdisk is defined.
 

EXAMPLES

The following example matches any plex or volume that does not have any associated subdisks or plexes. Because pl_nsd only applies to plexes, while v_nplex only applies to volumes, there is no ambiguity concerning which types of records can be matched by the expression.

pl_nsd = 0 || v_nplex = 0

The following example matches all plexes and subdisks that have a comment field beginning with the string "Henry ". For example, this could be a convention describing ownership.

(plex || sd) && comment ~ /^Henry/

The following example matches all volumes for which the preferred plex is striped:

v_pref_name.pl_layout = STRIPE

Because v_pref_name is only defined for volumes that have v_read_pol set to PREFER, the preceding expression is equivalent to:

vol && v_read_pol = PREFER && v_pref_name.pl_layout = STRIPE

The following expression matches any volume that contains a plex with a subdisk longer than 100 megabytes:

any v_plex.pl_subdisk.sd_len > 100M

If an expression contains a set but does not use the any or in operator, then an any operator is assumed to surround the expression. Thus, the preceding example can also be specified as:

v_plex.pl_subdisk.sd_len > 100M

The following example matches any record that was changed in the most recent set of changes to the disk group:

update_tid = config_tid

Alternatively, to get all records that have been changed since a past disk group configuration (with a configuration transaction ID of 0.23482), use:

update_tid > 0.23482


 

SEE ALSO

awk(1), volintro(8), voledit(8), volmake(8), volprint(8)


 

Index

NAME
DESCRIPTION
Types of Expressions
Expression Grammar
Constants
Global Variables
Generic Fields
Volume Record Fields
Plex Record Fields
Subdisk Record Fields
EXAMPLES
SEE ALSO

This document was created by man2html, using the manual pages.
Time: 02:40:04 GMT, October 02, 2010