nbd_clear_meta_contexts - Man Page

 #include <libnbd.h>

 int nbd_clear_meta_contexts (
       struct nbd_handle *h
     );

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_64(3) command (for "base:allocation" this is whether blocks of data are allocated, zero or sparse).

This command resets the list of meta contexts to request back to an empty list, for re-population by further use of nbd_add_meta_context(3).  It is primarily useful when option negotiation mode is selected (see nbd_set_opt_mode(3)), for altering the list of attempted contexts between subsequent export queries.

If the call is successful the function returns 0.

On error -1 is returned.

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

The following parameters must not be NULL: h. For more information see "Non-NULL parameters" in libnbd(3).

nbd_clear_meta_contexts can be called when the handle is in the following states:

 ┌─────────────────────────────────────┬─────────────────────────┐
 │ Handle created, before connecting   │ ✅ allowed              │
 │ Connecting                          │ ❌ error                │
 │ Connecting & handshaking (opt_mode) │ ✅ allowed              │
 │ Connected to the server             │ ❌ error                │
 │ Connection shut down                │ ❌ error                │
 │ Handle dead                         │ ❌ error                │
 └─────────────────────────────────────┴─────────────────────────┘

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_CLEAR_META_CONTEXTS 1

nbd_add_meta_context(3), nbd_block_status_64(3), nbd_can_meta_context(3), nbd_create(3), nbd_get_meta_context(3), nbd_get_nr_meta_contexts(3), nbd_set_opt_mode(3), libnbd(3).

Eric Blake

Richard W.M. Jones

Copyright Red Hat

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

libnbd(3), libnbd-release-notes-1.6(1), NBD(3), nbd_add_meta_context(3), nbd_get_meta_context(3), nbd_get_nr_meta_contexts(3), nbd_opt_list_meta_context(3), nbd_opt_set_meta_context(3).