NAME

       nbd_block_status_filter - send filtered block status command, with 64-bit callback

SYNOPSIS

        #include <libnbd.h>

        typedef struct {
          int (*callback) (void *user_data,
                           const char *metacontext,
                           uint64_t offset, nbd_extent *entries,
                           size_t nr_entries, int *error);
          void *user_data;
          void (*free) (void *user_data);
        } nbd_extent64_callback;

        int nbd_block_status_filter (
              struct nbd_handle *h, uint64_t count,
              uint64_t offset, char **contexts,
              nbd_extent64_callback extent64_callback,
              uint32_t flags
            );

DESCRIPTION

       Issue a filtered block status command to the NBD server.  If supported by the server (see
       nbd_can_block_status_payload(3)), this causes metadata context information about blocks
       beginning from the specified offset to be returned, and with the result limited to just
       the contexts specified in "filter".  Note that all strings in "filter" must be supported
       by nbd_can_meta_context(3).

       All other parameters to this function have the same semantics as in
       nbd_block_status_64(3); except that for convenience, unless <nbd_set_strict_flags(3)> was
       used to disable "LIBNBD_STRICT_AUTO_FLAG", libnbd ignores the presence or absence of the
       flag "LIBNBD_CMD_FLAG_PAYLOAD_LEN" in "flags", while correctly using the flag over the
       wire.

       By default, libnbd will reject attempts to use this function with parameters that are
       likely to result in server failure, such as requesting an unknown command flag.  The
       nbd_set_strict_mode(3) function can be used to alter which scenarios should await a server
       reply rather than failing fast.

RETURN VALUE

       If the call is successful the function returns 0.

ERRORS

       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", "contexts".  For more information see
       "Non-NULL parameters" in libnbd(3).

HANDLE STATE

       nbd_block_status_filter can be called when the handle is in the following state:

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

VERSION

       This function first appeared in libnbd 1.18.

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

        #define LIBNBD_HAVE_NBD_BLOCK_STATUS_FILTER 1

SEE ALSO

       nbd_aio_block_status_filter(3), nbd_block_status_64(3), nbd_can_block_status_payload(3),
       nbd_can_meta_context(3), nbd_create(3), nbd_set_strict_mode(3), libnbd(3).

AUTHORS

       Eric Blake

       Richard W.M. Jones

COPYRIGHT

       Copyright Red Hat

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