1 /* nbdkit
2 * Copyright (C) 2018-2020 Red Hat Inc.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions are
6 * met:
7 *
8 * * Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 *
11 * * Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
14 *
15 * * Neither the name of Red Hat nor the names of its contributors may be
16 * used to endorse or promote products derived from this software without
17 * specific prior written permission.
18 *
19 * THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND
20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
21 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
22 * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR
23 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
24 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
25 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
26 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
27 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
28 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
29 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30 * SUCH DAMAGE.
31 */
32
33 #include <config.h>
34
35 #include <stdio.h>
36 #include <stdlib.h>
37 #include <stdint.h>
38 #include <string.h>
39 #include <stdbool.h>
40 #include <assert.h>
41
42 #include <nbdkit-filter.h>
43
44 #include "minmax.h"
45
46 static enum CacheMode {
47 NONE,
48 EMULATE,
49 NOP,
50 } cachemode;
51
52 static int
nocache_config(nbdkit_next_config * next,void * nxdata,const char * key,const char * value)53 nocache_config (nbdkit_next_config *next, void *nxdata,
54 const char *key, const char *value)
55 {
56 if (strcmp (key, "cachemode") == 0) {
57 if (strcmp (value, "emulate") == 0)
58 cachemode = EMULATE;
59 else if (strcmp (value, "nop") == 0 ||
60 strcmp (value, "no-op") == 0)
61 cachemode = NOP;
62 else if (strcmp (value, "none") != 0) {
63 nbdkit_error ("unknown cachemode '%s'", value);
64 return -1;
65 }
66 return 0;
67 }
68 return next (nxdata, key, value);
69 }
70
71 #define nocache_config_help \
72 "cachemode=<MODE> Either 'none' (default), 'emulate', or 'nop'.\n" \
73
74 /* Advertise desired FLAG_SEND_CACHE mode. */
75 static int
nocache_can_cache(struct nbdkit_next_ops * next_ops,void * nxdata,void * handle)76 nocache_can_cache (struct nbdkit_next_ops *next_ops, void *nxdata,
77 void *handle)
78 {
79 switch (cachemode) {
80 case NONE:
81 return NBDKIT_CACHE_NONE;
82 case EMULATE:
83 return NBDKIT_CACHE_EMULATE;
84 case NOP:
85 return NBDKIT_CACHE_NATIVE;
86 }
87 abort ();
88 }
89
90 static int
nocache_cache(struct nbdkit_next_ops * next_ops,void * nxdata,void * handle,uint32_t count,uint64_t offs,uint32_t flags,int * err)91 nocache_cache (struct nbdkit_next_ops *next_ops, void *nxdata,
92 void *handle, uint32_t count, uint64_t offs, uint32_t flags,
93 int *err)
94 {
95 assert (cachemode == NOP);
96 assert (!flags);
97
98 return 0;
99 }
100
101 static struct nbdkit_filter filter = {
102 .name = "nocache",
103 .longname = "nbdkit nocache filter",
104 .config = nocache_config,
105 .config_help = nocache_config_help,
106 .can_cache = nocache_can_cache,
107 .cache = nocache_cache,
108 };
109
110 NBDKIT_REGISTER_FILTER(filter)
111