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>
10
11        int nbd_trim (struct nbd_handle *h, uint64_t count,
12                      uint64_t offset, uint32_t flags);
13

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.
21
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).
26
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)).
31
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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47       The following parameters must not be NULL: "h".  For more information
48       see "Non-NULL parameters" in libnbd(3).
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HANDLE STATE

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

55       This function first appeared in libnbd 1.0.
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57       If you need to test if this function is available at compile time check
58       if the following macro is defined:
59
60        #define LIBNBD_HAVE_NBD_TRIM 1
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SEE ALSO

63       nbd_aio_trim(3), nbd_can_fua(3), nbd_can_trim(3), nbd_create(3),
64       nbd_get_block_size(3), nbd_is_read_only(3), nbd_set_strict_mode(3),
65       libnbd(3).
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AUTHORS

68       Eric Blake
69
70       Richard W.M. Jones
71

73       Copyright (C) 2019-2021 Red Hat Inc.
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LICENSE

76       This library is free software; you can redistribute it and/or modify it
77       under the terms of the GNU Lesser General Public License as published
78       by the Free Software Foundation; either version 2 of the License, or
79       (at your option) any later version.
80
81       This library is distributed in the hope that it will be useful, but
82       WITHOUT ANY WARRANTY; without even the implied warranty of
83       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
84       Lesser General Public License for more details.
85
86       You should have received a copy of the GNU Lesser General Public
87       License along with this library; if not, write to the Free Software
88       Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
89       02110-1301 USA
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93libnbd-1.14.2                     2023-01-03                       nbd_trim(3)
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