block/throttle.c uses existing I/O throttle infrastructure inside a
block filter driver. I/O operations are intercepted in the filter's
read/write coroutines, and referred to block/throttle-groups.c

The driver can be used with the syntax
-drive driver=throttle,file.filename=foo.qcow2, \
        limits.iops-total=...,throttle-group=bar

The configuration flags and their semantics are identical to the
hardcoded throttling ones.

A node can be created referring to an existing group, and will overwrite
its limits if any are specified, otherwise they are retained.

Signed-off-by: Manos Pitsidianakis <el13...@mail.ntua.gr>
---
 block/Makefile.objs             |   1 +
 block/throttle.c                | 315 ++++++++++++++++++++++++++++++++++++++++
 include/qemu/throttle-options.h |   1 +
 3 files changed, 317 insertions(+)
 create mode 100644 block/throttle.c

diff --git a/block/Makefile.objs b/block/Makefile.objs
index 2aaede4ae1..6eaf78a046 100644
--- a/block/Makefile.objs
+++ b/block/Makefile.objs
@@ -25,6 +25,7 @@ block-obj-y += accounting.o dirty-bitmap.o
 block-obj-y += write-threshold.o
 block-obj-y += backup.o
 block-obj-$(CONFIG_REPLICATION) += replication.o
+block-obj-y += throttle.o
 
 block-obj-y += crypto.o
 
diff --git a/block/throttle.c b/block/throttle.c
new file mode 100644
index 0000000000..3e6cb1de7b
--- /dev/null
+++ b/block/throttle.c
@@ -0,0 +1,315 @@
+/*
+ * QEMU block throttling filter driver infrastructure
+ *
+ * Copyright (c) 2017 Manos Pitsidianakis
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 or
+ * (at your option) version 3 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "qemu/osdep.h"
+#include "block/throttle-groups.h"
+#include "qemu/throttle-options.h"
+#include "qapi/error.h"
+
+#undef THROTTLE_OPT_PREFIX
+#define THROTTLE_OPT_PREFIX "limits."
+static QemuOptsList throttle_opts = {
+    .name = "throttle",
+    .head = QTAILQ_HEAD_INITIALIZER(throttle_opts.head),
+    .desc = {
+        THROTTLE_OPTS,
+        {
+            .name = QEMU_OPT_THROTTLE_GROUP_NAME,
+            .type = QEMU_OPT_STRING,
+            .help = "throttle group name",
+        },
+        { /* end of list */ }
+    },
+};
+
+/* Extract ThrottleConfig options. Assumes cfg is initialized and will be
+ * checked for validity.
+ *
+ * Returns -1 and sets errp if a burst_length value is over UINT_MAX.
+ */
+static int throttle_extract_options(QemuOpts *opts, ThrottleConfig *cfg,
+                                    Error **errp)
+{
+#define IF_OPT_SET(rvalue, opt_name) \
+    if (qemu_opt_get(opts, THROTTLE_OPT_PREFIX opt_name)) { \
+        rvalue = qemu_opt_get_number(opts, THROTTLE_OPT_PREFIX opt_name, 0); }
+
+    IF_OPT_SET(cfg->buckets[THROTTLE_BPS_TOTAL].avg, QEMU_OPT_BPS_TOTAL);
+    IF_OPT_SET(cfg->buckets[THROTTLE_BPS_READ].avg, QEMU_OPT_BPS_READ);
+    IF_OPT_SET(cfg->buckets[THROTTLE_BPS_WRITE].avg, QEMU_OPT_BPS_WRITE);
+    IF_OPT_SET(cfg->buckets[THROTTLE_OPS_TOTAL].avg, QEMU_OPT_IOPS_TOTAL);
+    IF_OPT_SET(cfg->buckets[THROTTLE_OPS_READ].avg, QEMU_OPT_IOPS_READ);
+    IF_OPT_SET(cfg->buckets[THROTTLE_OPS_WRITE].avg, QEMU_OPT_IOPS_WRITE);
+    IF_OPT_SET(cfg->buckets[THROTTLE_BPS_TOTAL].max, QEMU_OPT_BPS_TOTAL_MAX);
+    IF_OPT_SET(cfg->buckets[THROTTLE_BPS_READ].max, QEMU_OPT_BPS_READ_MAX);
+    IF_OPT_SET(cfg->buckets[THROTTLE_BPS_WRITE].max, QEMU_OPT_BPS_WRITE_MAX);
+    IF_OPT_SET(cfg->buckets[THROTTLE_OPS_TOTAL].max, QEMU_OPT_IOPS_TOTAL_MAX);
+    IF_OPT_SET(cfg->buckets[THROTTLE_OPS_READ].max, QEMU_OPT_IOPS_READ_MAX);
+    IF_OPT_SET(cfg->buckets[THROTTLE_OPS_WRITE].max, QEMU_OPT_IOPS_WRITE_MAX);
+    IF_OPT_SET(cfg->op_size, QEMU_OPT_IOPS_SIZE);
+
+#define IF_OPT_UINT_SET(rvalue, opt_name) \
+    if (qemu_opt_get(opts, THROTTLE_OPT_PREFIX opt_name)) { \
+        if (qemu_opt_get_number(opts,  \
+                    THROTTLE_OPT_PREFIX opt_name, 1) > UINT_MAX) { \
+            error_setg(errp, "%s value must be in the range [0, %u]", \
+                       THROTTLE_OPT_PREFIX opt_name, UINT_MAX); \
+            return -1; \
+        } \
+        rvalue = qemu_opt_get_number(opts, THROTTLE_OPT_PREFIX opt_name, 1); \
+    }
+
+    IF_OPT_UINT_SET(cfg->buckets[THROTTLE_BPS_TOTAL].burst_length,
+                    QEMU_OPT_BPS_TOTAL_MAX_LENGTH);
+    IF_OPT_UINT_SET(cfg->buckets[THROTTLE_BPS_READ].burst_length,
+                    QEMU_OPT_BPS_READ_MAX_LENGTH);
+    IF_OPT_UINT_SET(cfg->buckets[THROTTLE_BPS_WRITE].burst_length,
+                    QEMU_OPT_BPS_WRITE_MAX_LENGTH);
+    IF_OPT_UINT_SET(cfg->buckets[THROTTLE_OPS_TOTAL].burst_length,
+                    QEMU_OPT_IOPS_TOTAL_MAX_LENGTH);
+    IF_OPT_UINT_SET(cfg->buckets[THROTTLE_OPS_READ].burst_length,
+                    QEMU_OPT_IOPS_READ_MAX_LENGTH);
+    IF_OPT_UINT_SET(cfg->buckets[THROTTLE_OPS_WRITE].burst_length,
+                    QEMU_OPT_IOPS_WRITE_MAX_LENGTH);
+
+    return 0;
+}
+
+static int throttle_configure_tgm(BlockDriverState *bs,
+                                  ThrottleGroupMember *tgm,
+                                  QDict *options, Error **errp)
+{
+    int ret;
+    ThrottleConfig cfg;
+    const char *group_name = NULL;
+    Error *local_err = NULL;
+    QemuOpts *opts = qemu_opts_create(&throttle_opts, NULL, 0, &error_abort);
+
+    qemu_opts_absorb_qdict(opts, options, &local_err);
+    if (local_err) {
+        error_propagate(errp, local_err);
+        goto err;
+    }
+
+    /* If group_name is NULL, an anonymous group will be created */
+    group_name = qemu_opt_get(opts, QEMU_OPT_THROTTLE_GROUP_NAME);
+
+    /* Register membership to group with name group_name */
+    throttle_group_register_tgm(tgm, group_name, bdrv_get_aio_context(bs));
+
+    /* Copy previous configuration */
+    throttle_group_get_config(tgm, &cfg);
+
+    /* Change limits if user has specified them */
+    if (throttle_extract_options(opts, &cfg, errp) ||
+        !throttle_is_valid(&cfg, errp)) {
+        throttle_group_unregister_tgm(tgm);
+        goto err;
+    }
+    /* Update group configuration */
+    throttle_group_config(tgm, &cfg);
+
+    ret = 0;
+    goto fin;
+
+err:
+    ret = -EINVAL;
+fin:
+    qemu_opts_del(opts);
+    return ret;
+}
+
+static int throttle_open(BlockDriverState *bs, QDict *options,
+                         int flags, Error **errp)
+{
+    ThrottleGroupMember *tgm = bs->opaque;
+
+    bs->file = bdrv_open_child(NULL, options, "file",
+                               bs, &child_file, false, errp);
+    if (!bs->file) {
+        return -EINVAL;
+    }
+    bs->supported_write_flags = bs->file->bs->supported_write_flags;
+    bs->supported_zero_flags = bs->file->bs->supported_zero_flags;
+
+    return throttle_configure_tgm(bs, tgm, options, errp);
+}
+
+static void throttle_close(BlockDriverState *bs)
+{
+    ThrottleGroupMember *tgm = bs->opaque;
+    throttle_group_unregister_tgm(tgm);
+}
+
+
+static int64_t throttle_getlength(BlockDriverState *bs)
+{
+    return bdrv_getlength(bs->file->bs);
+}
+
+
+static int coroutine_fn throttle_co_preadv(BlockDriverState *bs,
+                                           uint64_t offset, uint64_t bytes,
+                                           QEMUIOVector *qiov, int flags)
+{
+
+    ThrottleGroupMember *tgm = bs->opaque;
+    throttle_group_co_io_limits_intercept(tgm, bytes, false);
+
+    return bdrv_co_preadv(bs->file, offset, bytes, qiov, flags);
+}
+
+static int coroutine_fn throttle_co_pwritev(BlockDriverState *bs,
+                                            uint64_t offset, uint64_t bytes,
+                                            QEMUIOVector *qiov, int flags)
+{
+    ThrottleGroupMember *tgm = bs->opaque;
+    throttle_group_co_io_limits_intercept(tgm, bytes, true);
+
+    return bdrv_co_preadv(bs->file, offset, bytes, qiov, flags);
+}
+
+static int coroutine_fn throttle_co_pwrite_zeroes(BlockDriverState *bs,
+                                                  int64_t offset, int bytes,
+                                                  BdrvRequestFlags flags)
+{
+    ThrottleGroupMember *tgm = bs->opaque;
+    throttle_group_co_io_limits_intercept(tgm, bytes, true);
+
+    return bdrv_co_pwrite_zeroes(bs->file, offset, bytes, flags);
+}
+
+static int coroutine_fn throttle_co_pdiscard(BlockDriverState *bs,
+                                             int64_t offset, int bytes)
+{
+    ThrottleGroupMember *tgm = bs->opaque;
+    throttle_group_co_io_limits_intercept(tgm, bytes, true);
+
+    return bdrv_co_pdiscard(bs->file->bs, offset, bytes);
+}
+
+static int throttle_co_flush(BlockDriverState *bs)
+{
+    return bdrv_co_flush(bs->file->bs);
+}
+
+static void throttle_detach_aio_context(BlockDriverState *bs)
+{
+    ThrottleGroupMember *tgm = bs->opaque;
+    throttle_group_detach_aio_context(tgm);
+}
+
+static void throttle_attach_aio_context(BlockDriverState *bs,
+                                        AioContext *new_context)
+{
+    ThrottleGroupMember *tgm = bs->opaque;
+    throttle_group_attach_aio_context(tgm, new_context);
+}
+
+static int throttle_reopen_prepare(BDRVReopenState *reopen_state,
+                                   BlockReopenQueue *queue, Error **errp)
+{
+    ThrottleGroupMember *tgm = NULL;
+
+    assert(reopen_state != NULL);
+    assert(reopen_state->bs != NULL);
+
+    reopen_state->opaque = g_new0(ThrottleGroupMember, 1);
+    tgm = reopen_state->opaque;
+
+    return throttle_configure_tgm(reopen_state->bs, tgm, reopen_state->options,
+            errp);
+}
+
+static void throttle_reopen_commit(BDRVReopenState *state)
+{
+    ThrottleGroupMember *tgm = state->bs->opaque;
+
+    throttle_group_unregister_tgm(tgm);
+    g_free(state->bs->opaque);
+    state->bs->opaque = state->opaque;
+    state->opaque = NULL;
+}
+
+static void throttle_reopen_abort(BDRVReopenState *state)
+{
+    ThrottleGroupMember *tgm = state->opaque;
+
+    throttle_group_unregister_tgm(tgm);
+    g_free(state->opaque);
+    state->opaque = NULL;
+}
+
+static bool throttle_recurse_is_first_non_filter(BlockDriverState *bs,
+                                                 BlockDriverState *candidate)
+{
+    return bdrv_recurse_is_first_non_filter(bs->file->bs, candidate);
+}
+
+static int64_t coroutine_fn throttle_co_get_block_status(BlockDriverState *bs,
+                                                         int64_t sector_num,
+                                                         int nb_sectors,
+                                                         int *pnum,
+                                                         BlockDriverState 
**file)
+{
+    assert(bs->file && bs->file->bs);
+    *pnum = nb_sectors;
+    *file = bs->file->bs;
+    return BDRV_BLOCK_RAW | BDRV_BLOCK_OFFSET_VALID |
+           (sector_num << BDRV_SECTOR_BITS);
+}
+
+static BlockDriver bdrv_throttle = {
+    .format_name                        =   "throttle",
+    .protocol_name                      =   "throttle",
+    .instance_size                      =   sizeof(ThrottleGroupMember),
+
+    .bdrv_file_open                     =   throttle_open,
+    .bdrv_close                         =   throttle_close,
+    .bdrv_co_flush                      =   throttle_co_flush,
+
+    .bdrv_child_perm                    =   bdrv_filter_default_perms,
+
+    .bdrv_getlength                     =   throttle_getlength,
+
+    .bdrv_co_preadv                     =   throttle_co_preadv,
+    .bdrv_co_pwritev                    =   throttle_co_pwritev,
+
+    .bdrv_co_pwrite_zeroes              =   throttle_co_pwrite_zeroes,
+    .bdrv_co_pdiscard                   =   throttle_co_pdiscard,
+
+    .bdrv_recurse_is_first_non_filter   =   
throttle_recurse_is_first_non_filter,
+
+    .bdrv_attach_aio_context            =   throttle_attach_aio_context,
+    .bdrv_detach_aio_context            =   throttle_detach_aio_context,
+
+    .bdrv_reopen_prepare                =   throttle_reopen_prepare,
+    .bdrv_reopen_commit                 =   throttle_reopen_commit,
+    .bdrv_reopen_abort                  =   throttle_reopen_abort,
+    .bdrv_co_get_block_status           =   throttle_co_get_block_status,
+
+    .is_filter                          =   true,
+};
+
+static void bdrv_throttle_init(void)
+{
+    bdrv_register(&bdrv_throttle);
+}
+
+block_init(bdrv_throttle_init);
diff --git a/include/qemu/throttle-options.h b/include/qemu/throttle-options.h
index 182b7896e1..3528a8f4a2 100644
--- a/include/qemu/throttle-options.h
+++ b/include/qemu/throttle-options.h
@@ -29,6 +29,7 @@
 #define QEMU_OPT_BPS_WRITE_MAX "bps-write-max"
 #define QEMU_OPT_BPS_WRITE_MAX_LENGTH "bps-write-max-length"
 #define QEMU_OPT_IOPS_SIZE "iops-size"
+#define QEMU_OPT_THROTTLE_GROUP_NAME "throttle-group"
 
 #define THROTTLE_OPT_PREFIX "throttling."
 #define THROTTLE_OPTS \
-- 
2.11.0


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