nbd_get_nr_meta_contexts - Man Page

return the current number of requested meta contexts

Synopsis

 #include <libnbd.h>

 ssize_t nbd_get_nr_meta_contexts (struct nbd_handle *h);

Description

During connection libnbd can negotiate zero or more metadata contexts with the server.  Metadata contexts are features (such as "base:allocation") which describe information returned by the nbd_block_status(3) command (for "base:allocation" this is whether blocks of data are allocated, zero or sparse).

This command returns how many meta contexts have been added to the list to request from the server via nbd_add_meta_context(3). The server is not obligated to honor all of the requests; to see what it actually supports, see nbd_can_meta_context(3).

Return Value

This call returns an integer size ≥ 0.

Errors

On error -1 is returned.

Refer to “ERROR HANDLING” in libnbd(3) for how to get further details of the error.

Version

This function first appeared in libnbd 1.6.

If you need to test if this function is available at compile time check if the following macro is defined:

 #define LIBNBD_HAVE_NBD_GET_NR_META_CONTEXTS 1

See Also

nbd_add_meta_context(3), nbd_block_status(3), nbd_can_meta_context(3), nbd_clear_meta_contexts(3), nbd_create(3), nbd_get_meta_context(3), libnbd(3).

Authors

Eric Blake

Richard W.M. Jones

License

This library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.

This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License along with this library; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

Referenced By

libnbd(3), libnbd-release-notes-1.6(1), NBD(3), nbd_add_meta_context(3), nbd_clear_meta_contexts(3), nbd_get_meta_context(3).

2021-04-03 libnbd-1.7.5