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
7

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 (
18                  struct nbd_handle *h, uint64_t count,
19                  uint64_t offset,
20                  nbd_completion_callback completion_callback,
21                  uint32_t flags
22                );
23

DESCRIPTION

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

40       This call returns the 64 bit cookie of the command.  The cookie is ≥ 1.
41       Cookies are unique (per libnbd handle, not globally).
42

ERRORS

44       On error -1 is returned.
45
46       Refer to "ERROR HANDLING" in libnbd(3) for how to get further details
47       of the error.
48
49       The following parameters must not be NULL: "h".  For more information
50       see "Non-NULL parameters" in libnbd(3).
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HANDLE STATE

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

57       This function first appeared in libnbd 1.0.
58
59       If you need to test if this function is available at compile time check
60       if the following macro is defined:
61
62        #define LIBNBD_HAVE_NBD_AIO_CACHE 1
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SEE ALSO

65       nbd_aio_command_completed(3), nbd_cache(3), nbd_can_cache(3),
66       nbd_create(3), nbd_set_strict_mode(3), "Issuing asynchronous commands"
67       in libnbd(3), libnbd(3).
68

AUTHORS

70       Eric Blake
71
72       Richard W.M. Jones
73

75       Copyright Red Hat
76

LICENSE

78       This library is free software; you can redistribute it and/or modify it
79       under the terms of the GNU Lesser General Public License as published
80       by the Free Software Foundation; either version 2 of the License, or
81       (at your option) any later version.
82
83       This library is distributed in the hope that it will be useful, but
84       WITHOUT ANY WARRANTY; without even the implied warranty of
85       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
86       Lesser General Public License for more details.
87
88       You should have received a copy of the GNU Lesser General Public
89       License along with this library; if not, write to the Free Software
90       Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
91       02110-1301 USA
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95libnbd-1.18.1                     2023-10-31                  nbd_aio_cache(3)
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