copy/null-ops.c

   1 /* NBD client library in userspace.
   2  * Copyright Red Hat
   3  *
   4  * This library is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU Lesser General Public
   6  * License as published by the Free Software Foundation; either
   7  * version 2 of the License, or (at your option) any later version.
   8  *
   9  * This library is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12  * Lesser General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU Lesser General Public
  15  * License along with this library; if not, write to the Free Software
  16  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  17  */
  18
  19 #include <config.h>
  20
  21 #include <stdio.h>
  22 #include <stdlib.h>
  23 #include <stdbool.h>
  24 #include <errno.h>
  25
  26 #include "nbdcopy.h"
  27
  28 /* This sinks writes and aborts on any read-like operations.  It
  29  * should be faster than using /dev/null because it "supports" fast
  30  * zeroing.
  31  */
  32
  33 static struct rw_ops null_ops;
  34
  35 struct rw_null {
  36   struct rw rw;
  37 };
  38
  39 struct rw *
  40 null_create (const char *name)
  41 {
  42   struct rw_null *rw = calloc (1, sizeof *rw);
  43   if (rw == NULL) { perror ("calloc"); exit (EXIT_FAILURE); }
  44
  45   rw->rw.ops = &null_ops;
  46   rw->rw.name = name;
  47   rw->rw.size = INT64_MAX;
  48   rw->rw.preferred = 4096;
  49   return &rw->rw;
  50 }
  51
  52 static void
  53 null_close (struct rw *rw)
  54 {
  55   free (rw);
  56 }
  57
  58 static void
  59 null_flush (struct rw *rw)
  60 {
  61   /* nothing */
  62 }
  63
  64 static bool
  65 null_is_read_only (struct rw *rw)
  66 {
  67   return false;
  68 }
  69
  70 static bool
  71 null_can_extents (struct rw *rw)
  72 {
  73   return false;
  74 }
  75
  76 static bool
  77 null_can_multi_conn (struct rw *rw)
  78 {
  79   return true;
  80 }
  81
  82 static void
  83 null_start_multi_conn (struct rw *rw)
  84 {
  85   /* nothing */
  86 }
  87
  88 static size_t
  89 null_synch_read (struct rw *rw,
  90                  void *data, size_t len, uint64_t offset)
  91 {
  92   abort ();
  93 }
  94
  95 static void
  96 null_synch_write (struct rw *rw,
  97                   const void *data, size_t len, uint64_t offset)
  98 {
  99   /* nothing */
 100 }
 101
 102 static bool
 103 null_synch_zero (struct rw *rw, uint64_t offset, uint64_t count, bool allocate)
 104 {
 105   return true;
 106 }
 107
 108 static void
 109 null_asynch_read (struct rw *rw,
 110                   struct command *command,
 111                   nbd_completion_callback cb)
 112 {
 113   abort ();
 114 }
 115
 116 static void
 117 null_asynch_write (struct rw *rw,
 118                    struct command *command,
 119                    nbd_completion_callback cb)
 120 {
 121   int dummy = 0;
 122
 123   cb.callback (cb.user_data, &dummy);
 124 }
 125
 126 static bool
 127 null_asynch_zero (struct rw *rw, struct command *command,
 128                   nbd_completion_callback cb, bool allocate)
 129 {
 130   int dummy = 0;
 131
 132   cb.callback (cb.user_data, &dummy);
 133   return true;
 134 }
 135
 136 static unsigned
 137 null_in_flight (struct rw *rw, size_t index)
 138 {
 139   return 0;
 140 }
 141
 142 static void
 143 null_get_extents (struct rw *rw, size_t index,
 144                   uint64_t offset, uint64_t count,
 145                   extent_list *ret)
 146 {
 147   abort ();
 148 }
 149
 150 static struct rw_ops null_ops = {
 151   .ops_name = "null_ops",
 152   .close = null_close,
 153   .is_read_only = null_is_read_only,
 154   .can_extents = null_can_extents,
 155   .can_multi_conn = null_can_multi_conn,
 156   .start_multi_conn = null_start_multi_conn,
 157   .flush = null_flush,
 158   .synch_read = null_synch_read,
 159   .synch_write = null_synch_write,
 160   .synch_zero = null_synch_zero,
 161   .asynch_read = null_asynch_read,
 162   .asynch_write = null_asynch_write,
 163   .asynch_zero = null_asynch_zero,
 164   .in_flight = null_in_flight,
 165   .get_polling_fd = get_polling_fd_not_supported,
 166   .asynch_notify_read = asynch_notify_read_write_not_supported,
 167   .asynch_notify_write = asynch_notify_read_write_not_supported,
 168   .get_extents = null_get_extents,
 169 };