NAME

       nbd_trim - send trim command to the NBD server

SYNOPSIS

        #include <libnbd.h>

        int nbd_trim (
              struct nbd_handle *h, uint64_t count,
              uint64_t offset, uint32_t flags
            );

DESCRIPTION

       Issue a trim command to the NBD server, which if supported by the server causes a hole to
       be punched in the backing store starting at "offset" and ending at "offset" + "count" - 1.
       The call returns when the command has been acknowledged by the server, or there is an
       error.  Note this will generally return an error if nbd_can_trim(3) is false or
       nbd_is_read_only(3) is true.

       Note that not all servers can support a "count" of 4GiB or larger;
       nbd_get_extended_headers_negotiated(3) indicates which servers will parse a request larger
       than 32 bits.  The NBD protocol does not yet have a way for a client to learn if the
       server will enforce an even smaller maximum trim size, although a future extension may add
       a constraint visible in nbd_get_block_size(3).

       The "flags" parameter may be 0 for no flags, or may contain "LIBNBD_CMD_FLAG_FUA" meaning
       that the server should not return until the data has been committed to permanent storage
       (if that is supported - some servers cannot do this, see nbd_can_fua(3)).

       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_trim 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_TRIM 1

SEE ALSO

       nbd_aio_trim(3), nbd_can_fua(3), nbd_can_trim(3), nbd_create(3), nbd_get_block_size(3),
       nbd_get_extended_headers_negotiated(3), nbd_is_read_only(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