NAME

nbd_flush - send flush command to the NBD server

SYNOPSIS

#include <libnbd.h>
int nbd_flush (
      struct nbd_handle *h, uint32_t flags
    );

DESCRIPTION

Issue the flush command to the NBD server. The function should return when all write commands which have completed have been committed to permanent storage on the server. Note this will generally return an error if nbd_can_flush(3) is false.

The "flags" parameter must be 0 for now (it exists for future NBD protocol extensions).

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

HANDLE STATE

nbd_flush 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 1.0.

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

#define LIBNBD_HAVE_NBD_FLUSH 1

SEE ALSO

nbd_aio_flush(3), nbd_can_flush(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