1nbd_aio_cache(3)                    LIBNBD                    nbd_aio_cache(3)
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NAME

6       nbd_aio_cache - send cache (prefetch) command to the NBD server
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SYNOPSIS

9        #include <libnbd.h>
10
11        typedef struct {
12          int (*callback) (void *user_data, int *error);
13          void *user_data;
14          void (*free) (void *user_data);
15        } nbd_completion_callback;
16
17        int64_t nbd_aio_cache (struct nbd_handle *h,
18                               uint64_t count, uint64_t offset,
19                               nbd_completion_callback completion_callback,
20                               uint32_t flags);
21

DESCRIPTION

23       Issue the cache (prefetch) command to the NBD server.
24
25       To check if the command completed, call nbd_aio_command_completed(3).
26       Or supply the optional "completion_callback" which will be invoked as
27       described in "Completion callbacks" in libnbd(3).
28
29       Other parameters behave as documented in nbd_cache(3).
30
31       By default, libnbd will reject attempts to use this function with
32       parameters that are likely to result in server failure, such as
33       requesting an unknown command flag.  The nbd_set_strict_mode(3)
34       function can be used to alter which scenarios should await a server
35       reply rather than failing fast.
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RETURN VALUE

38       This call returns the 64 bit cookie of the command.  The cookie is ≥ 1.
39       Cookies are unique (per libnbd handle, not globally).
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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.
46
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.
56
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_AIO_CACHE 1
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SEE ALSO

63       nbd_aio_command_completed(3), nbd_cache(3), nbd_can_cache(3),
64       nbd_create(3), nbd_set_strict_mode(3), "Issuing asynchronous commands"
65       in libnbd(3), libnbd(3).
66

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_aio_cache(3)
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