qemu/block/throttle.c
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   1/*
   2 * QEMU block throttling filter driver infrastructure
   3 *
   4 * Copyright (c) 2017 Manos Pitsidianakis
   5 *
   6 * This program is free software; you can redistribute it and/or
   7 * modify it under the terms of the GNU General Public License as
   8 * published by the Free Software Foundation; either version 2 or
   9 * (at your option) version 3 of the License.
  10 *
  11 * This program is distributed in the hope that it will be useful,
  12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 * GNU General Public License for more details.
  15 *
  16 * You should have received a copy of the GNU General Public License
  17 * along with this program; if not, see <http://www.gnu.org/licenses/>.
  18 */
  19
  20#include "qemu/osdep.h"
  21#include "block/throttle-groups.h"
  22#include "qemu/module.h"
  23#include "qemu/option.h"
  24#include "qemu/throttle-options.h"
  25#include "qapi/error.h"
  26
  27static QemuOptsList throttle_opts = {
  28    .name = "throttle",
  29    .head = QTAILQ_HEAD_INITIALIZER(throttle_opts.head),
  30    .desc = {
  31        {
  32            .name = QEMU_OPT_THROTTLE_GROUP_NAME,
  33            .type = QEMU_OPT_STRING,
  34            .help = "Name of the throttle group",
  35        },
  36        { /* end of list */ }
  37    },
  38};
  39
  40/*
  41 * If this function succeeds then the throttle group name is stored in
  42 * @group and must be freed by the caller.
  43 * If there's an error then @group remains unmodified.
  44 */
  45static int throttle_parse_options(QDict *options, char **group, Error **errp)
  46{
  47    int ret;
  48    const char *group_name;
  49    QemuOpts *opts = qemu_opts_create(&throttle_opts, NULL, 0, &error_abort);
  50
  51    if (!qemu_opts_absorb_qdict(opts, options, errp)) {
  52        ret = -EINVAL;
  53        goto fin;
  54    }
  55
  56    group_name = qemu_opt_get(opts, QEMU_OPT_THROTTLE_GROUP_NAME);
  57    if (!group_name) {
  58        error_setg(errp, "Please specify a throttle group");
  59        ret = -EINVAL;
  60        goto fin;
  61    } else if (!throttle_group_exists(group_name)) {
  62        error_setg(errp, "Throttle group '%s' does not exist", group_name);
  63        ret = -EINVAL;
  64        goto fin;
  65    }
  66
  67    *group = g_strdup(group_name);
  68    ret = 0;
  69fin:
  70    qemu_opts_del(opts);
  71    return ret;
  72}
  73
  74static int throttle_open(BlockDriverState *bs, QDict *options,
  75                         int flags, Error **errp)
  76{
  77    ThrottleGroupMember *tgm = bs->opaque;
  78    char *group;
  79    int ret;
  80
  81    ret = bdrv_open_file_child(NULL, options, "file", bs, errp);
  82    if (ret < 0) {
  83        return ret;
  84    }
  85    bs->supported_write_flags = bs->file->bs->supported_write_flags |
  86                                BDRV_REQ_WRITE_UNCHANGED;
  87    bs->supported_zero_flags = bs->file->bs->supported_zero_flags |
  88                               BDRV_REQ_WRITE_UNCHANGED;
  89
  90    ret = throttle_parse_options(options, &group, errp);
  91    if (ret == 0) {
  92        /* Register membership to group with name group_name */
  93        throttle_group_register_tgm(tgm, group, bdrv_get_aio_context(bs));
  94        g_free(group);
  95    }
  96
  97    return ret;
  98}
  99
 100static void throttle_close(BlockDriverState *bs)
 101{
 102    ThrottleGroupMember *tgm = bs->opaque;
 103    throttle_group_unregister_tgm(tgm);
 104}
 105
 106
 107static int64_t throttle_getlength(BlockDriverState *bs)
 108{
 109    return bdrv_getlength(bs->file->bs);
 110}
 111
 112static int coroutine_fn throttle_co_preadv(BlockDriverState *bs,
 113                                           int64_t offset, int64_t bytes,
 114                                           QEMUIOVector *qiov,
 115                                           BdrvRequestFlags flags)
 116{
 117
 118    ThrottleGroupMember *tgm = bs->opaque;
 119    throttle_group_co_io_limits_intercept(tgm, bytes, false);
 120
 121    return bdrv_co_preadv(bs->file, offset, bytes, qiov, flags);
 122}
 123
 124static int coroutine_fn throttle_co_pwritev(BlockDriverState *bs,
 125                                            int64_t offset, int64_t bytes,
 126                                            QEMUIOVector *qiov,
 127                                            BdrvRequestFlags flags)
 128{
 129    ThrottleGroupMember *tgm = bs->opaque;
 130    throttle_group_co_io_limits_intercept(tgm, bytes, true);
 131
 132    return bdrv_co_pwritev(bs->file, offset, bytes, qiov, flags);
 133}
 134
 135static int coroutine_fn throttle_co_pwrite_zeroes(BlockDriverState *bs,
 136                                                  int64_t offset, int64_t bytes,
 137                                                  BdrvRequestFlags flags)
 138{
 139    ThrottleGroupMember *tgm = bs->opaque;
 140    throttle_group_co_io_limits_intercept(tgm, bytes, true);
 141
 142    return bdrv_co_pwrite_zeroes(bs->file, offset, bytes, flags);
 143}
 144
 145static int coroutine_fn throttle_co_pdiscard(BlockDriverState *bs,
 146                                             int64_t offset, int64_t bytes)
 147{
 148    ThrottleGroupMember *tgm = bs->opaque;
 149    throttle_group_co_io_limits_intercept(tgm, bytes, true);
 150
 151    return bdrv_co_pdiscard(bs->file, offset, bytes);
 152}
 153
 154static int coroutine_fn throttle_co_pwritev_compressed(BlockDriverState *bs,
 155                                                       int64_t offset,
 156                                                       int64_t bytes,
 157                                                       QEMUIOVector *qiov)
 158{
 159    return throttle_co_pwritev(bs, offset, bytes, qiov,
 160                               BDRV_REQ_WRITE_COMPRESSED);
 161}
 162
 163static int coroutine_fn throttle_co_flush(BlockDriverState *bs)
 164{
 165    return bdrv_co_flush(bs->file->bs);
 166}
 167
 168static void throttle_detach_aio_context(BlockDriverState *bs)
 169{
 170    ThrottleGroupMember *tgm = bs->opaque;
 171    throttle_group_detach_aio_context(tgm);
 172}
 173
 174static void throttle_attach_aio_context(BlockDriverState *bs,
 175                                        AioContext *new_context)
 176{
 177    ThrottleGroupMember *tgm = bs->opaque;
 178    throttle_group_attach_aio_context(tgm, new_context);
 179}
 180
 181static int throttle_reopen_prepare(BDRVReopenState *reopen_state,
 182                                   BlockReopenQueue *queue, Error **errp)
 183{
 184    int ret;
 185    char *group = NULL;
 186
 187    assert(reopen_state != NULL);
 188    assert(reopen_state->bs != NULL);
 189
 190    ret = throttle_parse_options(reopen_state->options, &group, errp);
 191    reopen_state->opaque = group;
 192    return ret;
 193}
 194
 195static void throttle_reopen_commit(BDRVReopenState *reopen_state)
 196{
 197    BlockDriverState *bs = reopen_state->bs;
 198    ThrottleGroupMember *tgm = bs->opaque;
 199    char *group = reopen_state->opaque;
 200
 201    assert(group);
 202
 203    if (strcmp(group, throttle_group_get_name(tgm))) {
 204        throttle_group_unregister_tgm(tgm);
 205        throttle_group_register_tgm(tgm, group, bdrv_get_aio_context(bs));
 206    }
 207    g_free(reopen_state->opaque);
 208    reopen_state->opaque = NULL;
 209}
 210
 211static void throttle_reopen_abort(BDRVReopenState *reopen_state)
 212{
 213    g_free(reopen_state->opaque);
 214    reopen_state->opaque = NULL;
 215}
 216
 217static void coroutine_fn throttle_co_drain_begin(BlockDriverState *bs)
 218{
 219    ThrottleGroupMember *tgm = bs->opaque;
 220    if (qatomic_fetch_inc(&tgm->io_limits_disabled) == 0) {
 221        throttle_group_restart_tgm(tgm);
 222    }
 223}
 224
 225static void coroutine_fn throttle_co_drain_end(BlockDriverState *bs)
 226{
 227    ThrottleGroupMember *tgm = bs->opaque;
 228    assert(tgm->io_limits_disabled);
 229    qatomic_dec(&tgm->io_limits_disabled);
 230}
 231
 232static const char *const throttle_strong_runtime_opts[] = {
 233    QEMU_OPT_THROTTLE_GROUP_NAME,
 234
 235    NULL
 236};
 237
 238static BlockDriver bdrv_throttle = {
 239    .format_name                        =   "throttle",
 240    .instance_size                      =   sizeof(ThrottleGroupMember),
 241
 242    .bdrv_open                          =   throttle_open,
 243    .bdrv_close                         =   throttle_close,
 244    .bdrv_co_flush                      =   throttle_co_flush,
 245
 246    .bdrv_child_perm                    =   bdrv_default_perms,
 247
 248    .bdrv_getlength                     =   throttle_getlength,
 249
 250    .bdrv_co_preadv                     =   throttle_co_preadv,
 251    .bdrv_co_pwritev                    =   throttle_co_pwritev,
 252
 253    .bdrv_co_pwrite_zeroes              =   throttle_co_pwrite_zeroes,
 254    .bdrv_co_pdiscard                   =   throttle_co_pdiscard,
 255    .bdrv_co_pwritev_compressed         =   throttle_co_pwritev_compressed,
 256
 257    .bdrv_attach_aio_context            =   throttle_attach_aio_context,
 258    .bdrv_detach_aio_context            =   throttle_detach_aio_context,
 259
 260    .bdrv_reopen_prepare                =   throttle_reopen_prepare,
 261    .bdrv_reopen_commit                 =   throttle_reopen_commit,
 262    .bdrv_reopen_abort                  =   throttle_reopen_abort,
 263
 264    .bdrv_co_drain_begin                =   throttle_co_drain_begin,
 265    .bdrv_co_drain_end                  =   throttle_co_drain_end,
 266
 267    .is_filter                          =   true,
 268    .strong_runtime_opts                =   throttle_strong_runtime_opts,
 269};
 270
 271static void bdrv_throttle_init(void)
 272{
 273    bdrv_register(&bdrv_throttle);
 274}
 275
 276block_init(bdrv_throttle_init);
 277