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gctl_dump (3)

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NAME



geom_stats_open

 
geom_stats_close

 
geom_stats_resync

 
geom_stats_snapshot_get

 
geom_stats_snapshot_free

 
geom_stats_snapshot_timestamp

 
geom_stats_snapshot_reset

 
geom_stats_snapshot_next

 
gctl_get_handle

 
gctl_ro_param

 
gctl_rw_param

 
gctl_issue

 
gctl_free

 
gctl_dump

 
g_open

 
g_close

 
g_mediasize

 
g_sectorsize

 
g_flush

 
g_delete

 
g_get_ident

 
g_get_name

 
g_open_by_ident

 - userland API library for kernel GEOM subsystem

LIBRARY

Lb libgeom

SYNOPSIS

#include <libgeom.h>

Statistics Functions

void geom_stats_close (void);
int geom_stats_open (void);
void geom_stats_resync (void);
void * geom_stats_snapshot_get (void);
void geom_stats_snapshot_free (void *arg);
void geom_stats_snapshot_timestamp (void *arg struct timespec *tp);
void geom_stats_snapshot_reset (void *arg);
struct devstat * geom_stats_snapshot_next (void *arg);

Control Functions

struct gctl_req * gctl_get_handle (void);
void gctl_ro_param (struct gctl_req *req const char *name int len const void *value);
void gctl_rw_param (struct gctl_req *req const char *name int len void *value);
const char * gctl_issue (struct gctl_req *req);
void gctl_free (struct gctl_req *req);
void gctl_dump (struct gctl_req *req FILE *f);

Utility Functions

int g_open (const char *name int write);
int g_close (int fd);
off_t g_mediasize (int fd);
ssize_t g_sectorsize (int fd);
int g_flush (int fd);
int g_delete (int fd off_t offset off_t length);
int g_get_ident (int fd char *ident size_t size);
int g_get_name (const char *ident char *name size_t size);
int g_open_by_ident (const char *ident int write char *name size_t size);

DESCRIPTION

The geom library contains the official and publicized API for interacting with the GEOM subsystem in the kernel.

Statistics Functions

GEOM collects statistics data for all consumers and providers, but does not perform any normalization or presentation on the raw data, this is left as an exercise for user-land presentation utilities.

The geom_stats_open ();
and geom_stats_close ();
functions open and close the necessary pathways to access the raw statistics information in the kernel. These functions are likely to open one or more files and cache the file descriptors locally. The geom_stats_open ();
function returns zero on success, and sets errno if not.

The geom_stats_resync ();
function will check if more statistics collection points have been added in the kernel since geom_stats_open ();
or the previous call to geom_stats_resync (.);

The geom_stats_snapshot_get ();
function will acquire a snapshot of the raw data from the kernel, and while a reasonable effort is made to make this snapshot as atomic and consistent as possible, no guarantee is given that it will actually be so. The snapshot must be freed again using the geom_stats_snapshot_free ();
function. The geom_stats_snapshot_get ();
function returns NULL on failure.

The geom_stats_snapshot_timestamp ();
function provides access to the timestamp acquired in the snapshot.

The geom_stats_snapshot_reset ();
and geom_stats_snapshot_next ();
functions provide an iterator over the statistics slots in the snapshot. The geom_stats_snapshot_reset ();
function forces the internal pointer in the snapshot back to before the first item. The geom_stats_snapshot_next ();
function returns the next item, and NULL if there are no more items in the snapshot.

Control Functions

The gctl_ (*);
functions are used to send requests to GEOM classes. In order for a GEOM class to actually be able to receive these requests, it must have defined a "ctlreq" method.

A Vt struct gctl_req * , obtained with gctl_get_handle (,);
can hold any number of parameters, which must be added to it with gctl_ro_param ();
(for read-only parameters) or gctl_rw_param ();
(for read/write parameters).

Both gctl_ro_param ();
and gctl_rw_param ();
take a string Fa name , which is used to identify the parameter, and a Fa value , which contains, in the read-only case, the data to be passed to the GEOM class, or, in the read/write case, a pointer to preallocated memory that the GEOM class should fill with the desired data. If Fa len is negative, it is assumed that Fa value is an ASCII string and the actual length is taken from the string length of Fa value ; otherwise it must hold the size of Fa value .

A parameter with a Fa name containing the string Qq Li class is mandatory for each request, and the corresponding Fa value must hold the name of the GEOM class where the request should be sent to.

Also mandatory for each request is a parameter with a Fa name called Qq Li verb , and the corresponding Fa value needs to hold the command string that the GEOM class should react upon.

Once all desired parameters are filled in, the request must be sent to the GEOM subsystem with gctl_issue (,);
which returns NULL on success, or a string containing the error message on failure.

After the request is finished, the allocated memory should be released with gctl_free (.);

The gctl_dump ();
function can be used to format the contents of Fa req to the open file handle pointed to by Fa f , for debugging purposes.

Error handling for the control functions is postponed until the call to gctl_issue (,);
which returns NULL on success, or an error message corresponding to the first error which happened.

Utility Functions

The g_ (*);
functions are used to communicate with GEOM providers.

The g_open ();
function opens the given provider and returns file descriptor number, which can be used with other functions. The Fa write argument indicates if operations that modify the provider (like g_flush ();
or g_delete ());
are going to be called.

The g_close ();
function closes the provider.

The g_mediasize ();
function returns size of the given provider.

The g_sectorsize ();
function returns sector size of the given provider.

The g_flush ();
function sends BIO_FLUSH request to flush write cache of the provider.

The g_delete ();
function tells the provider that the given data range is no longer used.

The g_get_ident ();
function returns provider's fixed and unique identifier. The Fa ident argument should be at least DISK_IDENT_SIZE big.

The g_get_name ();
function returns name of the provider, which identifier is equal to the Fa ident string.

The g_open_by_ident ();
function opens provider using its ident, unlike g_open ();
which uses provider's name. If the Fa name argument is not NULL the function will store provider's name there.

All functions return value greater than or equal to 0 on success or -1 on failure.

EXAMPLES

Create a request that is to be sent to the CCD class, and tell it to destroy a specific geom:

H = gctl_get_handle();
gctl_ro_param(H, "verb", -1, "destroy geom");
gctl_ro_param(H, "class", -1, "CCD");
sprintf(buf, "ccd%d", ccd);
gctl_ro_param(H, "geom", -1, buf);
errstr = gctl_issue(H);
if (errstr != NULL)
    err(1, "could not destroy ccd: %s", errstr);
gctl_free(H);