1nbd_trim(3)                         LIBNBD                         nbd_trim(3)
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NAME

6       nbd_trim - send trim command to the NBD server
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SYNOPSIS

9        #include <libnbd.h>
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11        int nbd_trim (struct nbd_handle *h, uint64_t count,
12                      uint64_t offset, uint32_t flags);
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DESCRIPTION

15       Issue a trim command to the NBD server, which if supported by the
16       server causes a hole to be punched in the backing store starting at
17       "offset" and ending at "offset" + "count" - 1.  The call returns when
18       the command has been acknowledged by the server, or there is an error.
19       Note this will generally return an error if nbd_can_trim(3) is false or
20       nbd_is_read_only(3) is true.
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22       Note that not all servers can support a "count" of 4GiB or larger.  The
23       NBD protocol does not yet have a way for a client to learn if the
24       server will enforce an even smaller maximum trim size, although a
25       future extension may add a constraint visible in nbd_get_block_size(3).
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27       The "flags" parameter may be 0 for no flags, or may contain
28       "LIBNBD_CMD_FLAG_FUA" meaning that the server should not return until
29       the data has been committed to permanent storage (if that is supported
30       - some servers cannot do this, see nbd_can_fua(3)).
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32       By default, libnbd will reject attempts to use this function with
33       parameters that are likely to result in server failure, such as
34       requesting an unknown command flag.  The nbd_set_strict_mode(3)
35       function can be used to alter which scenarios should await a server
36       reply rather than failing fast.
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RETURN VALUE

39       If the call is successful the function returns 0.
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ERRORS

42       On error "-1" is returned.
43
44       Refer to "ERROR HANDLING" in libnbd(3) for how to get further details
45       of the error.
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HANDLE STATE

48       The handle must be connected with the server, otherwise this call will
49       return an error.
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VERSION

52       This function first appeared in libnbd 1.0.
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54       If you need to test if this function is available at compile time check
55       if the following macro is defined:
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57        #define LIBNBD_HAVE_NBD_TRIM 1
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SEE ALSO

60       nbd_aio_trim(3), nbd_can_fua(3), nbd_can_trim(3), nbd_create(3),
61       nbd_get_block_size(3), nbd_is_read_only(3), nbd_set_strict_mode(3),
62       libnbd(3).
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AUTHORS

65       Eric Blake
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67       Richard W.M. Jones
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70       Copyright (C) 2019-2021 Red Hat Inc.
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LICENSE

73       This library is free software; you can redistribute it and/or modify it
74       under the terms of the GNU Lesser General Public License as published
75       by the Free Software Foundation; either version 2 of the License, or
76       (at your option) any later version.
77
78       This library is distributed in the hope that it will be useful, but
79       WITHOUT ANY WARRANTY; without even the implied warranty of
80       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
81       Lesser General Public License for more details.
82
83       You should have received a copy of the GNU Lesser General Public
84       License along with this library; if not, write to the Free Software
85       Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
86       02110-1301 USA
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90libnbd-1.12.5                     2022-07-10                       nbd_trim(3)
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