Provided by: libnbd-dev_1.2.2-1ubuntu2_amd64
nbd_cache - send cache (prefetch) command to the NBD server
#include <libnbd.h> int nbd_cache (struct nbd_handle *h, uint64_t count, uint64_t offset, uint32_t flags);
Issue the cache (prefetch) command to the NBD server, which if supported by the server causes data to be prefetched into faster storage by the server, speeding up a subsequent nbd_pread(3) call. The server can also silently ignore this command. Note this will return an error if nbd_can_cache(3) is false. The "flags" parameter must be 0 for now (it exists for future NBD protocol extensions).
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 handle must be connected and finished handshaking with the server, otherwise this call will return an error.
This function first appeared in libnbd 1.0. If you need to test if this function is available at compile time check if the following macro is defined: #define LIBNBD_HAVE_NBD_CACHE 1
nbd_can_cache(3), nbd_aio_cache(3), nbd_create(3), libnbd(3).
Eric Blake Richard W.M. Jones
Copyright (C) 2019 Red Hat Inc.
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