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qemu/block-migration.c

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/*
* QEMU live block migration
*
* Copyright IBM, Corp. 2009
*
* Authors:
* Liran Schour <lirans@il.ibm.com>
*
* This work is licensed under the terms of the GNU GPL, version 2. See
* the COPYING file in the top-level directory.
*
* Contributions after 2012-01-13 are licensed under the terms of the
* GNU GPL, version 2 or (at your option) any later version.
*/
#include "qemu-common.h"
#include "block_int.h"
#include "hw/hw.h"
#include "qemu-queue.h"
#include "qemu-timer.h"
#include "block-migration.h"
#include "migration.h"
#include "blockdev.h"
#include <assert.h>
#define BLOCK_SIZE (BDRV_SECTORS_PER_DIRTY_CHUNK << BDRV_SECTOR_BITS)
#define BLK_MIG_FLAG_DEVICE_BLOCK 0x01
#define BLK_MIG_FLAG_EOS 0x02
#define BLK_MIG_FLAG_PROGRESS 0x04
#define MAX_IS_ALLOCATED_SEARCH 65536
//#define DEBUG_BLK_MIGRATION
#ifdef DEBUG_BLK_MIGRATION
#define DPRINTF(fmt, ...) \
do { printf("blk_migration: " fmt, ## __VA_ARGS__); } while (0)
#else
#define DPRINTF(fmt, ...) \
do { } while (0)
#endif
typedef struct BlkMigDevState {
BlockDriverState *bs;
int bulk_completed;
int shared_base;
int64_t cur_sector;
int64_t cur_dirty;
int64_t completed_sectors;
int64_t total_sectors;
int64_t dirty;
QSIMPLEQ_ENTRY(BlkMigDevState) entry;
unsigned long *aio_bitmap;
} BlkMigDevState;
typedef struct BlkMigBlock {
uint8_t *buf;
BlkMigDevState *bmds;
int64_t sector;
int nr_sectors;
struct iovec iov;
QEMUIOVector qiov;
BlockDriverAIOCB *aiocb;
int ret;
QSIMPLEQ_ENTRY(BlkMigBlock) entry;
} BlkMigBlock;
typedef struct BlkMigState {
int blk_enable;
int shared_base;
QSIMPLEQ_HEAD(bmds_list, BlkMigDevState) bmds_list;
QSIMPLEQ_HEAD(blk_list, BlkMigBlock) blk_list;
int submitted;
int read_done;
int transferred;
int64_t total_sector_sum;
int prev_progress;
int bulk_completed;
long double total_time;
long double prev_time_offset;
int reads;
} BlkMigState;
static BlkMigState block_mig_state;
static void blk_send(QEMUFile *f, BlkMigBlock * blk)
{
int len;
/* sector number and flags */
qemu_put_be64(f, (blk->sector << BDRV_SECTOR_BITS)
| BLK_MIG_FLAG_DEVICE_BLOCK);
/* device name */
len = strlen(blk->bmds->bs->device_name);
qemu_put_byte(f, len);
qemu_put_buffer(f, (uint8_t *)blk->bmds->bs->device_name, len);
qemu_put_buffer(f, blk->buf, BLOCK_SIZE);
}
int blk_mig_active(void)
{
return !QSIMPLEQ_EMPTY(&block_mig_state.bmds_list);
}
uint64_t blk_mig_bytes_transferred(void)
{
BlkMigDevState *bmds;
uint64_t sum = 0;
QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) {
sum += bmds->completed_sectors;
}
return sum << BDRV_SECTOR_BITS;
}
uint64_t blk_mig_bytes_remaining(void)
{
return blk_mig_bytes_total() - blk_mig_bytes_transferred();
}
uint64_t blk_mig_bytes_total(void)
{
BlkMigDevState *bmds;
uint64_t sum = 0;
QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) {
sum += bmds->total_sectors;
}
return sum << BDRV_SECTOR_BITS;
}
static inline long double compute_read_bwidth(void)
{
assert(block_mig_state.total_time != 0);
return (block_mig_state.reads / block_mig_state.total_time) * BLOCK_SIZE;
}
static int bmds_aio_inflight(BlkMigDevState *bmds, int64_t sector)
{
int64_t chunk = sector / (int64_t)BDRV_SECTORS_PER_DIRTY_CHUNK;
if ((sector << BDRV_SECTOR_BITS) < bdrv_getlength(bmds->bs)) {
return !!(bmds->aio_bitmap[chunk / (sizeof(unsigned long) * 8)] &
(1UL << (chunk % (sizeof(unsigned long) * 8))));
} else {
return 0;
}
}
static void bmds_set_aio_inflight(BlkMigDevState *bmds, int64_t sector_num,
int nb_sectors, int set)
{
int64_t start, end;
unsigned long val, idx, bit;
start = sector_num / BDRV_SECTORS_PER_DIRTY_CHUNK;
end = (sector_num + nb_sectors - 1) / BDRV_SECTORS_PER_DIRTY_CHUNK;
for (; start <= end; start++) {
idx = start / (sizeof(unsigned long) * 8);
bit = start % (sizeof(unsigned long) * 8);
val = bmds->aio_bitmap[idx];
if (set) {
val |= 1UL << bit;
} else {
val &= ~(1UL << bit);
}
bmds->aio_bitmap[idx] = val;
}
}
static void alloc_aio_bitmap(BlkMigDevState *bmds)
{
BlockDriverState *bs = bmds->bs;
int64_t bitmap_size;
bitmap_size = (bdrv_getlength(bs) >> BDRV_SECTOR_BITS) +
BDRV_SECTORS_PER_DIRTY_CHUNK * 8 - 1;
bitmap_size /= BDRV_SECTORS_PER_DIRTY_CHUNK * 8;
bmds->aio_bitmap = g_malloc0(bitmap_size);
}
static void blk_mig_read_cb(void *opaque, int ret)
{
long double curr_time = qemu_get_clock_ns(rt_clock);
BlkMigBlock *blk = opaque;
blk->ret = ret;
block_mig_state.reads++;
block_mig_state.total_time += (curr_time - block_mig_state.prev_time_offset);
block_mig_state.prev_time_offset = curr_time;
QSIMPLEQ_INSERT_TAIL(&block_mig_state.blk_list, blk, entry);
bmds_set_aio_inflight(blk->bmds, blk->sector, blk->nr_sectors, 0);
block_mig_state.submitted--;
block_mig_state.read_done++;
assert(block_mig_state.submitted >= 0);
}
static int mig_save_device_bulk(QEMUFile *f, BlkMigDevState *bmds)
{
int64_t total_sectors = bmds->total_sectors;
int64_t cur_sector = bmds->cur_sector;
BlockDriverState *bs = bmds->bs;
BlkMigBlock *blk;
int nr_sectors;
if (bmds->shared_base) {
while (cur_sector < total_sectors &&
!bdrv_is_allocated(bs, cur_sector, MAX_IS_ALLOCATED_SEARCH,
&nr_sectors)) {
cur_sector += nr_sectors;
}
}
if (cur_sector >= total_sectors) {
bmds->cur_sector = bmds->completed_sectors = total_sectors;
return 1;
}
bmds->completed_sectors = cur_sector;
cur_sector &= ~((int64_t)BDRV_SECTORS_PER_DIRTY_CHUNK - 1);
/* we are going to transfer a full block even if it is not allocated */
nr_sectors = BDRV_SECTORS_PER_DIRTY_CHUNK;
if (total_sectors - cur_sector < BDRV_SECTORS_PER_DIRTY_CHUNK) {
nr_sectors = total_sectors - cur_sector;
}
blk = g_malloc(sizeof(BlkMigBlock));
blk->buf = g_malloc(BLOCK_SIZE);
blk->bmds = bmds;
blk->sector = cur_sector;
blk->nr_sectors = nr_sectors;
blk->iov.iov_base = blk->buf;
blk->iov.iov_len = nr_sectors * BDRV_SECTOR_SIZE;
qemu_iovec_init_external(&blk->qiov, &blk->iov, 1);
if (block_mig_state.submitted == 0) {
block_mig_state.prev_time_offset = qemu_get_clock_ns(rt_clock);
}
blk->aiocb = bdrv_aio_readv(bs, cur_sector, &blk->qiov,
nr_sectors, blk_mig_read_cb, blk);
block_mig_state.submitted++;
bdrv_reset_dirty(bs, cur_sector, nr_sectors);
bmds->cur_sector = cur_sector + nr_sectors;
return (bmds->cur_sector >= total_sectors);
}
static void set_dirty_tracking(int enable)
{
BlkMigDevState *bmds;
QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) {
bdrv_set_dirty_tracking(bmds->bs, enable);
}
}
static void init_blk_migration_it(void *opaque, BlockDriverState *bs)
{
BlkMigDevState *bmds;
int64_t sectors;
if (!bdrv_is_read_only(bs)) {
sectors = bdrv_getlength(bs) >> BDRV_SECTOR_BITS;
if (sectors <= 0) {
return;
}
bmds = g_malloc0(sizeof(BlkMigDevState));
bmds->bs = bs;
bmds->bulk_completed = 0;
bmds->total_sectors = sectors;
bmds->completed_sectors = 0;
bmds->shared_base = block_mig_state.shared_base;
alloc_aio_bitmap(bmds);
drive_get_ref(drive_get_by_blockdev(bs));
bdrv_set_in_use(bs, 1);
block_mig_state.total_sector_sum += sectors;
if (bmds->shared_base) {
DPRINTF("Start migration for %s with shared base image\n",
bs->device_name);
} else {
DPRINTF("Start full migration for %s\n", bs->device_name);
}
QSIMPLEQ_INSERT_TAIL(&block_mig_state.bmds_list, bmds, entry);
}
}
static void init_blk_migration(QEMUFile *f)
{
block_mig_state.submitted = 0;
block_mig_state.read_done = 0;
block_mig_state.transferred = 0;
block_mig_state.total_sector_sum = 0;
block_mig_state.prev_progress = -1;
block_mig_state.bulk_completed = 0;
block_mig_state.total_time = 0;
block_mig_state.reads = 0;
bdrv_iterate(init_blk_migration_it, NULL);
}
static int blk_mig_save_bulked_block(QEMUFile *f)
{
int64_t completed_sector_sum = 0;
BlkMigDevState *bmds;
int progress;
int ret = 0;
QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) {
if (bmds->bulk_completed == 0) {
if (mig_save_device_bulk(f, bmds) == 1) {
/* completed bulk section for this device */
bmds->bulk_completed = 1;
}
completed_sector_sum += bmds->completed_sectors;
ret = 1;
break;
} else {
completed_sector_sum += bmds->completed_sectors;
}
}
if (block_mig_state.total_sector_sum != 0) {
progress = completed_sector_sum * 100 /
block_mig_state.total_sector_sum;
} else {
progress = 100;
}
if (progress != block_mig_state.prev_progress) {
block_mig_state.prev_progress = progress;
qemu_put_be64(f, (progress << BDRV_SECTOR_BITS)
| BLK_MIG_FLAG_PROGRESS);
DPRINTF("Completed %d %%\r", progress);
}
return ret;
}
static void blk_mig_reset_dirty_cursor(void)
{
BlkMigDevState *bmds;
QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) {
bmds->cur_dirty = 0;
}
}
static int mig_save_device_dirty(QEMUFile *f, BlkMigDevState *bmds,
int is_async)
{
BlkMigBlock *blk;
int64_t total_sectors = bmds->total_sectors;
int64_t sector;
int nr_sectors;
int ret = -EIO;
for (sector = bmds->cur_dirty; sector < bmds->total_sectors;) {
if (bmds_aio_inflight(bmds, sector)) {
bdrv_drain_all();
}
if (bdrv_get_dirty(bmds->bs, sector)) {
if (total_sectors - sector < BDRV_SECTORS_PER_DIRTY_CHUNK) {
nr_sectors = total_sectors - sector;
} else {
nr_sectors = BDRV_SECTORS_PER_DIRTY_CHUNK;
}
blk = g_malloc(sizeof(BlkMigBlock));
blk->buf = g_malloc(BLOCK_SIZE);
blk->bmds = bmds;
blk->sector = sector;
blk->nr_sectors = nr_sectors;
if (is_async) {
blk->iov.iov_base = blk->buf;
blk->iov.iov_len = nr_sectors * BDRV_SECTOR_SIZE;
qemu_iovec_init_external(&blk->qiov, &blk->iov, 1);
if (block_mig_state.submitted == 0) {
block_mig_state.prev_time_offset = qemu_get_clock_ns(rt_clock);
}
blk->aiocb = bdrv_aio_readv(bmds->bs, sector, &blk->qiov,
nr_sectors, blk_mig_read_cb, blk);
block_mig_state.submitted++;
bmds_set_aio_inflight(bmds, sector, nr_sectors, 1);
} else {
ret = bdrv_read(bmds->bs, sector, blk->buf, nr_sectors);
if (ret < 0) {
goto error;
}
blk_send(f, blk);
g_free(blk->buf);
g_free(blk);
}
bdrv_reset_dirty(bmds->bs, sector, nr_sectors);
break;
}
sector += BDRV_SECTORS_PER_DIRTY_CHUNK;
bmds->cur_dirty = sector;
}
return (bmds->cur_dirty >= bmds->total_sectors);
error:
DPRINTF("Error reading sector %" PRId64 "\n", sector);
qemu_file_set_error(f, ret);
g_free(blk->buf);
g_free(blk);
return 0;
}
static int blk_mig_save_dirty_block(QEMUFile *f, int is_async)
{
BlkMigDevState *bmds;
int ret = 0;
QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) {
if (mig_save_device_dirty(f, bmds, is_async) == 0) {
ret = 1;
break;
}
}
return ret;
}
static void flush_blks(QEMUFile* f)
{
BlkMigBlock *blk;
DPRINTF("%s Enter submitted %d read_done %d transferred %d\n",
__FUNCTION__, block_mig_state.submitted, block_mig_state.read_done,
block_mig_state.transferred);
while ((blk = QSIMPLEQ_FIRST(&block_mig_state.blk_list)) != NULL) {
if (qemu_file_rate_limit(f)) {
break;
}
if (blk->ret < 0) {
qemu_file_set_error(f, blk->ret);
break;
}
blk_send(f, blk);
QSIMPLEQ_REMOVE_HEAD(&block_mig_state.blk_list, entry);
g_free(blk->buf);
g_free(blk);
block_mig_state.read_done--;
block_mig_state.transferred++;
assert(block_mig_state.read_done >= 0);
}
DPRINTF("%s Exit submitted %d read_done %d transferred %d\n", __FUNCTION__,
block_mig_state.submitted, block_mig_state.read_done,
block_mig_state.transferred);
}
static int64_t get_remaining_dirty(void)
{
BlkMigDevState *bmds;
int64_t dirty = 0;
QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) {
dirty += bdrv_get_dirty_count(bmds->bs);
}
return dirty * BLOCK_SIZE;
}
static int is_stage2_completed(void)
{
int64_t remaining_dirty;
long double bwidth;
if (block_mig_state.bulk_completed == 1) {
remaining_dirty = get_remaining_dirty();
if (remaining_dirty == 0) {
return 1;
}
bwidth = compute_read_bwidth();
if ((remaining_dirty / bwidth) <=
migrate_max_downtime()) {
/* finish stage2 because we think that we can finish remaining work
below max_downtime */
return 1;
}
}
return 0;
}
static void blk_mig_cleanup(void)
{
BlkMigDevState *bmds;
BlkMigBlock *blk;
set_dirty_tracking(0);
while ((bmds = QSIMPLEQ_FIRST(&block_mig_state.bmds_list)) != NULL) {
QSIMPLEQ_REMOVE_HEAD(&block_mig_state.bmds_list, entry);
bdrv_set_in_use(bmds->bs, 0);
drive_put_ref(drive_get_by_blockdev(bmds->bs));
g_free(bmds->aio_bitmap);
g_free(bmds);
}
while ((blk = QSIMPLEQ_FIRST(&block_mig_state.blk_list)) != NULL) {
QSIMPLEQ_REMOVE_HEAD(&block_mig_state.blk_list, entry);
g_free(blk->buf);
g_free(blk);
}
}
static int block_save_live(QEMUFile *f, int stage, void *opaque)
{
int ret;
DPRINTF("Enter save live stage %d submitted %d transferred %d\n",
stage, block_mig_state.submitted, block_mig_state.transferred);
if (stage < 0) {
blk_mig_cleanup();
return 0;
}
if (block_mig_state.blk_enable != 1) {
/* no need to migrate storage */
qemu_put_be64(f, BLK_MIG_FLAG_EOS);
return 1;
}
if (stage == 1) {
init_blk_migration(f);
/* start track dirty blocks */
set_dirty_tracking(1);
}
flush_blks(f);
ret = qemu_file_get_error(f);
if (ret) {
blk_mig_cleanup();
return ret;
}
blk_mig_reset_dirty_cursor();
if (stage == 2) {
/* control the rate of transfer */
while ((block_mig_state.submitted +
block_mig_state.read_done) * BLOCK_SIZE <
qemu_file_get_rate_limit(f)) {
if (block_mig_state.bulk_completed == 0) {
/* first finish the bulk phase */
if (blk_mig_save_bulked_block(f) == 0) {
/* finished saving bulk on all devices */
block_mig_state.bulk_completed = 1;
}
} else {
if (blk_mig_save_dirty_block(f, 1) == 0) {
/* no more dirty blocks */
break;
}
}
}
flush_blks(f);
ret = qemu_file_get_error(f);
if (ret) {
blk_mig_cleanup();
return ret;
}
}
if (stage == 3) {
/* we know for sure that save bulk is completed and
all async read completed */
assert(block_mig_state.submitted == 0);
while (blk_mig_save_dirty_block(f, 0) != 0);
blk_mig_cleanup();
/* report completion */
qemu_put_be64(f, (100 << BDRV_SECTOR_BITS) | BLK_MIG_FLAG_PROGRESS);
ret = qemu_file_get_error(f);
if (ret) {
return ret;
}
DPRINTF("Block migration completed\n");
}
qemu_put_be64(f, BLK_MIG_FLAG_EOS);
return ((stage == 2) && is_stage2_completed());
}
static int block_load(QEMUFile *f, void *opaque, int version_id)
{
static int banner_printed;
int len, flags;
char device_name[256];
int64_t addr;
BlockDriverState *bs, *bs_prev = NULL;
uint8_t *buf;
int64_t total_sectors = 0;
int nr_sectors;
int ret;
do {
addr = qemu_get_be64(f);
flags = addr & ~BDRV_SECTOR_MASK;
addr >>= BDRV_SECTOR_BITS;
if (flags & BLK_MIG_FLAG_DEVICE_BLOCK) {
/* get device name */
len = qemu_get_byte(f);
qemu_get_buffer(f, (uint8_t *)device_name, len);
device_name[len] = '\0';
bs = bdrv_find(device_name);
if (!bs) {
fprintf(stderr, "Error unknown block device %s\n",
device_name);
return -EINVAL;
}
if (bs != bs_prev) {
bs_prev = bs;
total_sectors = bdrv_getlength(bs) >> BDRV_SECTOR_BITS;
if (total_sectors <= 0) {
error_report("Error getting length of block device %s",
device_name);
return -EINVAL;
}
}
if (total_sectors - addr < BDRV_SECTORS_PER_DIRTY_CHUNK) {
nr_sectors = total_sectors - addr;
} else {
nr_sectors = BDRV_SECTORS_PER_DIRTY_CHUNK;
}
buf = g_malloc(BLOCK_SIZE);
qemu_get_buffer(f, buf, BLOCK_SIZE);
ret = bdrv_write(bs, addr, buf, nr_sectors);
g_free(buf);
if (ret < 0) {
return ret;
}
} else if (flags & BLK_MIG_FLAG_PROGRESS) {
if (!banner_printed) {
printf("Receiving block device images\n");
banner_printed = 1;
}
printf("Completed %d %%%c", (int)addr,
(addr == 100) ? '\n' : '\r');
fflush(stdout);
} else if (!(flags & BLK_MIG_FLAG_EOS)) {
fprintf(stderr, "Unknown flags\n");
return -EINVAL;
}
ret = qemu_file_get_error(f);
if (ret != 0) {
return ret;
}
} while (!(flags & BLK_MIG_FLAG_EOS));
return 0;
}
static void block_set_params(const MigrationParams *params, void *opaque)
{
block_mig_state.blk_enable = params->blk;
block_mig_state.shared_base = params->shared;
/* shared base means that blk_enable = 1 */
block_mig_state.blk_enable |= params->shared;
}
void blk_mig_init(void)
{
QSIMPLEQ_INIT(&block_mig_state.bmds_list);
QSIMPLEQ_INIT(&block_mig_state.blk_list);
register_savevm_live(NULL, "block", 0, 1, block_set_params,
block_save_live, NULL, block_load, &block_mig_state);
}
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