block: Drain throttling queue with BdrvChild callback

This removes the last part of I/O throttling from block/io.c and moves
it to the BlockBackend.

Instead of having knowledge about throttling inside io.c, we can call a
BdrvChild callback .drained_begin/end, which happens to drain the
throttled requests for BlockBackend parents.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Kevin Wolf 2016-03-22 12:05:35 +01:00
parent 22aa8b246a
commit c2066af051
3 changed files with 56 additions and 31 deletions

View File

@ -91,9 +91,14 @@ static void blk_root_inherit_options(int *child_flags, QDict *child_options,
/* We're not supposed to call this function for root nodes */
abort();
}
static void blk_root_drained_begin(BdrvChild *child);
static void blk_root_drained_end(BdrvChild *child);
static const BdrvChildRole child_root = {
.inherit_options = blk_root_inherit_options,
.drained_begin = blk_root_drained_begin,
.drained_end = blk_root_drained_end,
};
/*
@ -818,9 +823,9 @@ int blk_pread_unthrottled(BlockBackend *blk, int64_t offset, uint8_t *buf,
return ret;
}
bdrv_no_throttling_begin(blk_bs(blk));
blk_root_drained_begin(blk->root);
ret = blk_pread(blk, offset, buf, count);
bdrv_no_throttling_end(blk_bs(blk));
blk_root_drained_end(blk->root);
return ret;
}
@ -1633,9 +1638,9 @@ void blk_set_io_limits(BlockBackend *blk, ThrottleConfig *cfg)
void blk_io_limits_disable(BlockBackend *blk)
{
assert(blk->public.throttle_state);
bdrv_no_throttling_begin(blk_bs(blk));
bdrv_drained_begin(blk_bs(blk));
throttle_group_unregister_blk(blk);
bdrv_no_throttling_end(blk_bs(blk));
bdrv_drained_end(blk_bs(blk));
}
/* should be called before blk_set_io_limits if a limit is set */
@ -1661,3 +1666,20 @@ void blk_io_limits_update_group(BlockBackend *blk, const char *group)
blk_io_limits_disable(blk);
blk_io_limits_enable(blk, group);
}
static void blk_root_drained_begin(BdrvChild *child)
{
BlockBackend *blk = child->opaque;
if (blk->public.io_limits_disabled++ == 0) {
throttle_group_restart_blk(blk);
}
}
static void blk_root_drained_end(BdrvChild *child)
{
BlockBackend *blk = child->opaque;
assert(blk->public.io_limits_disabled);
--blk->public.io_limits_disabled;
}

View File

@ -27,7 +27,6 @@
#include "sysemu/block-backend.h"
#include "block/blockjob.h"
#include "block/block_int.h"
#include "block/throttle-groups.h"
#include "qemu/cutils.h"
#include "qapi/error.h"
#include "qemu/error-report.h"
@ -46,28 +45,26 @@ static void coroutine_fn bdrv_co_do_rw(void *opaque);
static int coroutine_fn bdrv_co_do_write_zeroes(BlockDriverState *bs,
int64_t sector_num, int nb_sectors, BdrvRequestFlags flags);
void bdrv_no_throttling_begin(BlockDriverState *bs)
static void bdrv_parent_drained_begin(BlockDriverState *bs)
{
if (!bs->blk) {
return;
}
BdrvChild *c;
if (blk_get_public(bs->blk)->io_limits_disabled++ == 0) {
throttle_group_restart_blk(bs->blk);
QLIST_FOREACH(c, &bs->parents, next_parent) {
if (c->role->drained_begin) {
c->role->drained_begin(c);
}
}
}
void bdrv_no_throttling_end(BlockDriverState *bs)
static void bdrv_parent_drained_end(BlockDriverState *bs)
{
BlockBackendPublic *blkp;
BdrvChild *c;
if (!bs->blk) {
return;
QLIST_FOREACH(c, &bs->parents, next_parent) {
if (c->role->drained_end) {
c->role->drained_end(c);
}
}
blkp = blk_get_public(bs->blk);
assert(blkp->io_limits_disabled);
--blkp->io_limits_disabled;
}
void bdrv_refresh_limits(BlockDriverState *bs, Error **errp)
@ -248,17 +245,17 @@ static void coroutine_fn bdrv_co_yield_to_drain(BlockDriverState *bs)
*/
void coroutine_fn bdrv_co_drain(BlockDriverState *bs)
{
bdrv_no_throttling_begin(bs);
bdrv_parent_drained_begin(bs);
bdrv_io_unplugged_begin(bs);
bdrv_drain_recurse(bs);
bdrv_co_yield_to_drain(bs);
bdrv_io_unplugged_end(bs);
bdrv_no_throttling_end(bs);
bdrv_parent_drained_end(bs);
}
void bdrv_drain(BlockDriverState *bs)
{
bdrv_no_throttling_begin(bs);
bdrv_parent_drained_begin(bs);
bdrv_io_unplugged_begin(bs);
bdrv_drain_recurse(bs);
if (qemu_in_coroutine()) {
@ -267,7 +264,7 @@ void bdrv_drain(BlockDriverState *bs)
bdrv_drain_poll(bs);
}
bdrv_io_unplugged_end(bs);
bdrv_no_throttling_end(bs);
bdrv_parent_drained_end(bs);
}
/*
@ -290,7 +287,7 @@ void bdrv_drain_all(void)
if (bs->job) {
block_job_pause(bs->job);
}
bdrv_no_throttling_begin(bs);
bdrv_parent_drained_begin(bs);
bdrv_io_unplugged_begin(bs);
bdrv_drain_recurse(bs);
aio_context_release(aio_context);
@ -333,7 +330,7 @@ void bdrv_drain_all(void)
aio_context_acquire(aio_context);
bdrv_io_unplugged_end(bs);
bdrv_no_throttling_end(bs);
bdrv_parent_drained_end(bs);
if (bs->job) {
block_job_resume(bs->job);
}

View File

@ -364,6 +364,17 @@ typedef struct BdrvAioNotifier {
struct BdrvChildRole {
void (*inherit_options)(int *child_flags, QDict *child_options,
int parent_flags, QDict *parent_options);
/*
* If this pair of functions is implemented, the parent doesn't issue new
* requests after returning from .drained_begin() until .drained_end() is
* called.
*
* Note that this can be nested. If drained_begin() was called twice, new
* I/O is allowed only after drained_end() was called twice, too.
*/
void (*drained_begin)(BdrvChild *child);
void (*drained_end)(BdrvChild *child);
};
extern const BdrvChildRole child_file;
@ -526,8 +537,6 @@ int get_tmp_filename(char *filename, int size);
BlockDriver *bdrv_probe_all(const uint8_t *buf, int buf_size,
const char *filename);
bool bdrv_start_throttled_reqs(BlockDriverState *bs);
/**
* bdrv_add_before_write_notifier:
@ -710,9 +719,6 @@ BdrvChild *bdrv_root_attach_child(BlockDriverState *child_bs,
const BdrvChildRole *child_role);
void bdrv_root_unref_child(BdrvChild *child);
void bdrv_no_throttling_begin(BlockDriverState *bs);
void bdrv_no_throttling_end(BlockDriverState *bs);
void blk_dev_change_media_cb(BlockBackend *blk, bool load);
bool blk_dev_has_removable_media(BlockBackend *blk);
bool blk_dev_has_tray(BlockBackend *blk);