1 .\" Copyright (c) 2003 Poul-Henning Kamp
2 .\" Copyright (c) 2007 Pawel Jakub Dawidek <pjd@FreeBSD.org>
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36 .Nm geom_stats_close ,
37 .Nm geom_stats_resync ,
38 .Nm geom_stats_snapshot_get ,
39 .Nm geom_stats_snapshot_free ,
40 .Nm geom_stats_snapshot_timestamp ,
41 .Nm geom_stats_snapshot_reset ,
42 .Nm geom_stats_snapshot_next ,
58 .Nd userland API library for kernel GEOM subsystem
63 .Ss "Statistics Functions"
65 .Fn geom_stats_close void
67 .Fn geom_stats_open void
69 .Fn geom_stats_resync void
71 .Fn geom_stats_snapshot_get void
73 .Fn geom_stats_snapshot_free "void *arg"
75 .Fn geom_stats_snapshot_timestamp "void *arg" "struct timespec *tp"
77 .Fn geom_stats_snapshot_reset "void *arg"
78 .Ft "struct devstat *"
79 .Fn geom_stats_snapshot_next "void *arg"
80 .Ss "Control Functions"
81 .Ft "struct gctl_req *"
82 .Fn gctl_get_handle "void"
84 .Fn gctl_ro_param "struct gctl_req *req" "const char *name" "int len" "const void *value"
86 .Fn gctl_rw_param "struct gctl_req *req" "const char *name" "int len" "void *value"
88 .Fn gctl_issue "struct gctl_req *req"
90 .Fn gctl_free "struct gctl_req *req"
92 .Fn gctl_dump "struct gctl_req *req" "FILE *f"
93 .Ss "Utility Functions"
95 .Fn g_open "const char *name" "int write"
99 .Fn g_mediasize "int fd"
101 .Fn g_sectorsize "int fd"
105 .Fn g_delete "int fd" "off_t offset" "off_t length"
107 .Fn g_get_ident "int fd" "char *ident" "size_t size"
109 .Fn g_get_name "const char *ident" "char *name" "size_t size"
111 .Fn g_open_by_ident "const char *ident" "int write" "char *name" "size_t size"
115 library contains the official and publicized API for
116 interacting with the GEOM subsystem in the kernel.
117 .Ss "Statistics Functions"
118 GEOM collects statistics data for all consumers and providers, but does
119 not perform any normalization or presentation on the raw data, this is
120 left as an exercise for user-land presentation utilities.
126 functions open and close the necessary pathways to access the raw
127 statistics information in the kernel.
128 These functions are likely to
129 open one or more files and cache the file descriptors locally.
132 function returns zero on success, and sets
137 .Fn geom_stats_resync
138 function will check if more statistics collection points have been
139 added in the kernel since
141 or the previous call to
142 .Fn geom_stats_resync .
145 .Fn geom_stats_snapshot_get
147 will acquire a snapshot of the raw data from the kernel, and while a
148 reasonable effort is made to make this snapshot as atomic and consistent
149 as possible, no guarantee is given that it will actually be so.
150 The snapshot must be freed again using the
151 .Fn geom_stats_snapshot_free
154 .Fn geom_stats_snapshot_get
160 .Fn geom_stats_snapshot_timestamp
162 provides access to the timestamp acquired in the snapshot.
165 .Fn geom_stats_snapshot_reset
167 .Fn geom_stats_snapshot_next
169 provide an iterator over the statistics slots in the snapshot.
171 .Fn geom_stats_snapshot_reset
173 forces the internal pointer in the snapshot back to before the first item.
175 .Fn geom_stats_snapshot_next
177 returns the next item, and
179 if there are no more items in the snapshot.
180 .Ss "Control Functions"
183 functions are used to send requests to GEOM classes.
185 class to actually be able to receive these requests, it must have defined a
189 .Vt "struct gctl_req *" ,
191 .Fn gctl_get_handle ,
192 can hold any number of parameters, which must be added to it with
194 (for read-only parameters) or
196 (for read/write parameters).
204 which is used to identify the parameter, and a
206 which contains, in the read-only case, the data to be passed to the
207 GEOM class, or, in the read/write case, a pointer to preallocated memory
208 that the GEOM class should fill with the desired data.
211 is negative, it is assumed that
215 string and the actual length is taken from the string length of
217 otherwise it must hold the size of
222 containing the string
224 is mandatory for each request, and the
227 must hold the name of the GEOM class where the request should be sent to.
229 Also mandatory for each request is a parameter with a
233 and the corresponding
235 needs to hold the command string that the GEOM class should react upon.
237 Once all desired parameters are filled in, the request must be sent to
238 the GEOM subsystem with
242 on success, or a string containing the error message
245 After the request is finished, the allocated memory should be released with
251 can be used to format the contents of
253 to the open file handle pointed to by
255 for debugging purposes.
257 Error handling for the control functions is postponed until the call
262 on success, or an error message corresponding to the
263 first error which happened.
264 .Ss "Utility Functions"
267 functions are used to communicate with GEOM providers.
271 function opens the given provider and returns file descriptor number, which can
272 be used with other functions.
275 argument indicates if operations that modify the provider (like
279 are going to be called.
283 function closes the provider.
287 function returns size of the given provider.
291 function returns sector size of the given provider.
297 request to flush write cache of the provider.
301 function tells the provider that the given data range is no longer used.
305 function returns provider's fixed and unique identifier.
308 argument should be at least
314 function returns name of the provider, which identifier is equal to the
320 function opens provider using its ident, unlike
322 which uses provider's name.
327 the function will store provider's name there.
329 All functions return value greater than or equal to
335 Create a request that is to be sent to the CCD class, and tell
336 it to destroy a specific geom:
337 .Bd -literal -offset indent
338 H = gctl_get_handle();
339 gctl_ro_param(H, "verb", -1, "destroy geom");
340 gctl_ro_param(H, "class", -1, "CCD");
341 sprintf(buf, "ccd%d", ccd);
342 gctl_ro_param(H, "geom", -1, buf);
343 errstr = gctl_issue(H);
345 err(1, "could not destroy ccd: %s", errstr);
349 .Pa http://ezine.daemonnews.org/200308/blueprints.html
356 .An Poul-Henning Kamp Aq phk@FreeBSD.org
357 .An Lukas Ertl Aq le@FreeBSD.org
358 .An Pawel Jakub Dawidek pjd@FreeBSD.org