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qemu/migration/block.c
Fiona Ebner 930e239d11 migration: hold the BQL during setup 
This is intended to be a semantic revert of commit 9b09503752
("migration: run setup callbacks out of big lock"). There have been so
many changes since that commit (e.g. a new setup callback
dirty_bitmap_save_setup() that also needs to be adapted now), it's
easier to do the revert manually.

For snapshots, the bdrv_writev_vmstate() function is used during setup
(in QIOChannelBlock backing the QEMUFile), but not holding the BQL
while calling it could lead to an assertion failure. To understand
how, first note the following:

1. Generated coroutine wrappers for block layer functions spawn the
coroutine and use AIO_WAIT_WHILE()/aio_poll() to wait for it.
2. If the host OS switches threads at an inconvenient time, it can
happen that a bottom half scheduled for the main thread's AioContext
is executed as part of a vCPU thread's aio_poll().

An example leading to the assertion failure is as follows:

main thread:
1. A snapshot-save QMP command gets issued.
2. snapshot_save_job_bh() is scheduled.

vCPU thread:
3. aio_poll() for the main thread's AioContext is called (e.g. when
the guest writes to a pflash device, as part of blk_pwrite which is a
generated coroutine wrapper).
4. snapshot_save_job_bh() is executed as part of aio_poll().
3. qemu_savevm_state() is called.
4. qemu_mutex_unlock_iothread() is called. Now
qemu_get_current_aio_context() returns 0x0.
5. bdrv_writev_vmstate() is executed during the usual savevm setup
via qemu_fflush(). But this function is a generated coroutine wrapper,
so it uses AIO_WAIT_WHILE. There, the assertion
assert(qemu_get_current_aio_context() == qemu_get_aio_context());
will fail.

To fix it, ensure that the BQL is held during setup. While it would
only be needed for snapshots, adapting migration too avoids additional
logic for conditional locking/unlocking in the setup callbacks.
Writing the header could (in theory) also trigger qemu_fflush() and
thus bdrv_writev_vmstate(), so the locked section also covers the
qemu_savevm_state_header() call, even for migration for consistency.

The section around multifd_send_sync_main() needs to be unlocked to
avoid a deadlock. In particular, the multifd_save_setup() function calls
socket_send_channel_create() using multifd_new_send_channel_async() as a
callback and then waits for the callback to signal via the
channels_ready semaphore. The connection happens via
qio_task_run_in_thread(), but the callback is only executed via
qio_task_thread_result() which is scheduled for the main event loop.
Without unlocking the section, the main thread would never get to
process the task result and the callback meaning there would be no
signal via the channels_ready semaphore.

The comment in ram_init_bitmaps() was introduced by 4987783400
("migration: fix incorrect memory_global_dirty_log_start outside BQL")
and is removed, because it referred to the qemu_mutex_lock_iothread()
call.

Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Message-ID: <20231013105839.415989-1-f.ebner@proxmox.com>
2023-10-17 09:25:13 +02:00

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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/osdep.h"
#include "qapi/error.h"
#include "qemu/error-report.h"
#include "qemu/main-loop.h"
#include "qemu/cutils.h"
#include "qemu/queue.h"
#include "block.h"
#include "block/dirty-bitmap.h"
#include "migration/misc.h"
#include "migration.h"
#include "migration-stats.h"
#include "migration/register.h"
#include "qemu-file.h"
#include "migration/vmstate.h"
#include "sysemu/block-backend.h"
#include "trace.h"
#include "options.h"
#define BLK_MIG_BLOCK_SIZE (1ULL << 20)
#define BDRV_SECTORS_PER_DIRTY_CHUNK (BLK_MIG_BLOCK_SIZE >> BDRV_SECTOR_BITS)
#define BLK_MIG_FLAG_DEVICE_BLOCK 0x01
#define BLK_MIG_FLAG_EOS 0x02
#define BLK_MIG_FLAG_PROGRESS 0x04
#define BLK_MIG_FLAG_ZERO_BLOCK 0x08
#define MAX_IS_ALLOCATED_SEARCH (65536 * BDRV_SECTOR_SIZE)
#define MAX_IO_BUFFERS 512
#define MAX_PARALLEL_IO 16
typedef struct BlkMigDevState {
/* Written during setup phase. Can be read without a lock. */
BlockBackend *blk;
char *blk_name;
int shared_base;
int64_t total_sectors;
QSIMPLEQ_ENTRY(BlkMigDevState) entry;
Error *blocker;
/* Only used by migration thread. Does not need a lock. */
int bulk_completed;
int64_t cur_sector;
int64_t cur_dirty;
/* Data in the aio_bitmap is protected by block migration lock.
* Allocation and free happen during setup and cleanup respectively.
*/
unsigned long *aio_bitmap;
/* Protected by block migration lock. */
int64_t completed_sectors;
/* During migration this is protected by iothread lock / AioContext.
* Allocation and free happen during setup and cleanup respectively.
*/
BdrvDirtyBitmap *dirty_bitmap;
} BlkMigDevState;
typedef struct BlkMigBlock {
/* Only used by migration thread. */
uint8_t *buf;
BlkMigDevState *bmds;
int64_t sector;
int nr_sectors;
QEMUIOVector qiov;
BlockAIOCB *aiocb;
/* Protected by block migration lock. */
int ret;
QSIMPLEQ_ENTRY(BlkMigBlock) entry;
} BlkMigBlock;
typedef struct BlkMigState {
QSIMPLEQ_HEAD(, BlkMigDevState) bmds_list;
int64_t total_sector_sum;
bool zero_blocks;
/* Protected by lock. */
QSIMPLEQ_HEAD(, BlkMigBlock) blk_list;
int submitted;
int read_done;
/* Only used by migration thread. Does not need a lock. */
int transferred;
int prev_progress;
int bulk_completed;
/* Lock must be taken _inside_ the iothread lock and any AioContexts. */
QemuMutex lock;
} BlkMigState;
static BlkMigState block_mig_state;
static void blk_mig_lock(void)
{
qemu_mutex_lock(&block_mig_state.lock);
}
static void blk_mig_unlock(void)
{
qemu_mutex_unlock(&block_mig_state.lock);
}
/* Must run outside of the iothread lock during the bulk phase,
* or the VM will stall.
*/
static void blk_send(QEMUFile *f, BlkMigBlock * blk)
{
int len;
uint64_t flags = BLK_MIG_FLAG_DEVICE_BLOCK;
if (block_mig_state.zero_blocks &&
buffer_is_zero(blk->buf, BLK_MIG_BLOCK_SIZE)) {
flags |= BLK_MIG_FLAG_ZERO_BLOCK;
}
/* sector number and flags */
qemu_put_be64(f, (blk->sector << BDRV_SECTOR_BITS)
| flags);
/* device name */
len = strlen(blk->bmds->blk_name);
qemu_put_byte(f, len);
qemu_put_buffer(f, (uint8_t *) blk->bmds->blk_name, len);
/* if a block is zero we need to flush here since the network
* bandwidth is now a lot higher than the storage device bandwidth.
* thus if we queue zero blocks we slow down the migration */
if (flags & BLK_MIG_FLAG_ZERO_BLOCK) {
qemu_fflush(f);
return;
}
qemu_put_buffer(f, blk->buf, BLK_MIG_BLOCK_SIZE);
}
int blk_mig_active(void)
{
return !QSIMPLEQ_EMPTY(&block_mig_state.bmds_list);
}
int blk_mig_bulk_active(void)
{
return blk_mig_active() && !block_mig_state.bulk_completed;
}
uint64_t blk_mig_bytes_transferred(void)
{
BlkMigDevState *bmds;
uint64_t sum = 0;
blk_mig_lock();
QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) {
sum += bmds->completed_sectors;
}
blk_mig_unlock();
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;
}
/* Called with migration lock held. */
static int bmds_aio_inflight(BlkMigDevState *bmds, int64_t sector)
{
int64_t chunk = sector / (int64_t)BDRV_SECTORS_PER_DIRTY_CHUNK;
if (sector < bmds->total_sectors) {
return !!(bmds->aio_bitmap[chunk / (sizeof(unsigned long) * 8)] &
(1UL << (chunk % (sizeof(unsigned long) * 8))));
} else {
return 0;
}
}
/* Called with migration lock held. */
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)
{
int64_t bitmap_size;
bitmap_size = bmds->total_sectors + BDRV_SECTORS_PER_DIRTY_CHUNK * 8 - 1;
bitmap_size /= BDRV_SECTORS_PER_DIRTY_CHUNK * 8;
bmds->aio_bitmap = g_malloc0(bitmap_size);
}
/* Never hold migration lock when yielding to the main loop! */
static void blk_mig_read_cb(void *opaque, int ret)
{
BlkMigBlock *blk = opaque;
blk_mig_lock();
blk->ret = ret;
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);
blk_mig_unlock();
}
/* Called with no lock taken. */
static int mig_save_device_bulk(QEMUFile *f, BlkMigDevState *bmds)
{
int64_t total_sectors = bmds->total_sectors;
int64_t cur_sector = bmds->cur_sector;
BlockBackend *bb = bmds->blk;
BlkMigBlock *blk;
int nr_sectors;
int64_t count;
if (bmds->shared_base) {
qemu_mutex_lock_iothread();
aio_context_acquire(blk_get_aio_context(bb));
/* Skip unallocated sectors; intentionally treats failure or
* partial sector as an allocated sector */
while (cur_sector < total_sectors &&
!bdrv_is_allocated(blk_bs(bb), cur_sector * BDRV_SECTOR_SIZE,
MAX_IS_ALLOCATED_SEARCH, &count)) {
if (count < BDRV_SECTOR_SIZE) {
break;
}
cur_sector += count >> BDRV_SECTOR_BITS;
}
aio_context_release(blk_get_aio_context(bb));
qemu_mutex_unlock_iothread();
}
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_new(BlkMigBlock, 1);
blk->buf = g_malloc(BLK_MIG_BLOCK_SIZE);
blk->bmds = bmds;
blk->sector = cur_sector;
blk->nr_sectors = nr_sectors;
qemu_iovec_init_buf(&blk->qiov, blk->buf, nr_sectors * BDRV_SECTOR_SIZE);
blk_mig_lock();
block_mig_state.submitted++;
blk_mig_unlock();
/* We do not know if bs is under the main thread (and thus does
* not acquire the AioContext when doing AIO) or rather under
* dataplane. Thus acquire both the iothread mutex and the
* AioContext.
*
* This is ugly and will disappear when we make bdrv_* thread-safe,
* without the need to acquire the AioContext.
*/
qemu_mutex_lock_iothread();
aio_context_acquire(blk_get_aio_context(bmds->blk));
bdrv_reset_dirty_bitmap(bmds->dirty_bitmap, cur_sector * BDRV_SECTOR_SIZE,
nr_sectors * BDRV_SECTOR_SIZE);
blk->aiocb = blk_aio_preadv(bb, cur_sector * BDRV_SECTOR_SIZE, &blk->qiov,
0, blk_mig_read_cb, blk);
aio_context_release(blk_get_aio_context(bmds->blk));
qemu_mutex_unlock_iothread();
bmds->cur_sector = cur_sector + nr_sectors;
return (bmds->cur_sector >= total_sectors);
}
/* Called with iothread lock taken. */
static int set_dirty_tracking(void)
{
BlkMigDevState *bmds;
int ret;
QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) {
bmds->dirty_bitmap = bdrv_create_dirty_bitmap(blk_bs(bmds->blk),
BLK_MIG_BLOCK_SIZE,
NULL, NULL);
if (!bmds->dirty_bitmap) {
ret = -errno;
goto fail;
}
}
return 0;
fail:
QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) {
if (bmds->dirty_bitmap) {
bdrv_release_dirty_bitmap(bmds->dirty_bitmap);
}
}
return ret;
}
/* Called with iothread lock taken. */
static void unset_dirty_tracking(void)
{
BlkMigDevState *bmds;
QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) {
if (bmds->dirty_bitmap) {
bdrv_release_dirty_bitmap(bmds->dirty_bitmap);
}
}
}
static int init_blk_migration(QEMUFile *f)
{
BlockDriverState *bs;
BlkMigDevState *bmds;
int64_t sectors;
BdrvNextIterator it;
int i, num_bs = 0;
struct {
BlkMigDevState *bmds;
BlockDriverState *bs;
} *bmds_bs;
Error *local_err = NULL;
int ret;
GRAPH_RDLOCK_GUARD_MAINLOOP();
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.zero_blocks = migrate_zero_blocks();
for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
num_bs++;
}
bmds_bs = g_malloc0(num_bs * sizeof(*bmds_bs));
for (i = 0, bs = bdrv_first(&it); bs; bs = bdrv_next(&it), i++) {
if (bdrv_is_read_only(bs)) {
continue;
}
sectors = bdrv_nb_sectors(bs);
if (sectors <= 0) {
ret = sectors;
bdrv_next_cleanup(&it);
goto out;
}
bmds = g_new0(BlkMigDevState, 1);
bmds->blk = blk_new(qemu_get_aio_context(),
BLK_PERM_CONSISTENT_READ, BLK_PERM_ALL);
bmds->blk_name = g_strdup(bdrv_get_device_name(bs));
bmds->bulk_completed = 0;
bmds->total_sectors = sectors;
bmds->completed_sectors = 0;
bmds->shared_base = migrate_block_incremental();
assert(i < num_bs);
bmds_bs[i].bmds = bmds;
bmds_bs[i].bs = bs;
block_mig_state.total_sector_sum += sectors;
if (bmds->shared_base) {
trace_migration_block_init_shared(bdrv_get_device_name(bs));
} else {
trace_migration_block_init_full(bdrv_get_device_name(bs));
}
QSIMPLEQ_INSERT_TAIL(&block_mig_state.bmds_list, bmds, entry);
}
/* Can only insert new BDSes now because doing so while iterating block
* devices may end up in a deadlock (iterating the new BDSes, too). */
for (i = 0; i < num_bs; i++) {
bmds = bmds_bs[i].bmds;
bs = bmds_bs[i].bs;
if (bmds) {
ret = blk_insert_bs(bmds->blk, bs, &local_err);
if (ret < 0) {
error_report_err(local_err);
goto out;
}
alloc_aio_bitmap(bmds);
error_setg(&bmds->blocker, "block device is in use by migration");
bdrv_op_block_all(bs, bmds->blocker);
}
}
ret = 0;
out:
g_free(bmds_bs);
return ret;
}
/* Called with no lock taken. */
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);
trace_migration_block_progression(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;
}
}
/* Called with iothread lock and AioContext taken. */
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;) {
blk_mig_lock();
if (bmds_aio_inflight(bmds, sector)) {
blk_mig_unlock();
blk_drain(bmds->blk);
} else {
blk_mig_unlock();
}
bdrv_dirty_bitmap_lock(bmds->dirty_bitmap);
if (bdrv_dirty_bitmap_get_locked(bmds->dirty_bitmap,
sector * BDRV_SECTOR_SIZE)) {
if (total_sectors - sector < BDRV_SECTORS_PER_DIRTY_CHUNK) {
nr_sectors = total_sectors - sector;
} else {
nr_sectors = BDRV_SECTORS_PER_DIRTY_CHUNK;
}
bdrv_reset_dirty_bitmap_locked(bmds->dirty_bitmap,
sector * BDRV_SECTOR_SIZE,
nr_sectors * BDRV_SECTOR_SIZE);
bdrv_dirty_bitmap_unlock(bmds->dirty_bitmap);
blk = g_new(BlkMigBlock, 1);
blk->buf = g_malloc(BLK_MIG_BLOCK_SIZE);
blk->bmds = bmds;
blk->sector = sector;
blk->nr_sectors = nr_sectors;
if (is_async) {
qemu_iovec_init_buf(&blk->qiov, blk->buf,
nr_sectors * BDRV_SECTOR_SIZE);
blk->aiocb = blk_aio_preadv(bmds->blk,
sector * BDRV_SECTOR_SIZE,
&blk->qiov, 0, blk_mig_read_cb,
blk);
blk_mig_lock();
block_mig_state.submitted++;
bmds_set_aio_inflight(bmds, sector, nr_sectors, 1);
blk_mig_unlock();
} else {
ret = blk_pread(bmds->blk, sector * BDRV_SECTOR_SIZE,
nr_sectors * BDRV_SECTOR_SIZE, blk->buf, 0);
if (ret < 0) {
goto error;
}
blk_send(f, blk);
g_free(blk->buf);
g_free(blk);
}
sector += nr_sectors;
bmds->cur_dirty = sector;
break;
}
bdrv_dirty_bitmap_unlock(bmds->dirty_bitmap);
sector += BDRV_SECTORS_PER_DIRTY_CHUNK;
bmds->cur_dirty = sector;
}
return (bmds->cur_dirty >= bmds->total_sectors);
error:
trace_migration_block_save_device_dirty(sector);
g_free(blk->buf);
g_free(blk);
return ret;
}
/* Called with iothread lock taken.
*
* return value:
* 0: too much data for max_downtime
* 1: few enough data for max_downtime
*/
static int blk_mig_save_dirty_block(QEMUFile *f, int is_async)
{
BlkMigDevState *bmds;
int ret = 1;
QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) {
aio_context_acquire(blk_get_aio_context(bmds->blk));
ret = mig_save_device_dirty(f, bmds, is_async);
aio_context_release(blk_get_aio_context(bmds->blk));
if (ret <= 0) {
break;
}
}
return ret;
}
/* Called with no locks taken. */
static int flush_blks(QEMUFile *f)
{
BlkMigBlock *blk;
int ret = 0;
trace_migration_block_flush_blks("Enter", block_mig_state.submitted,
block_mig_state.read_done,
block_mig_state.transferred);
blk_mig_lock();
while ((blk = QSIMPLEQ_FIRST(&block_mig_state.blk_list)) != NULL) {
if (migration_rate_exceeded(f)) {
break;
}
if (blk->ret < 0) {
ret = blk->ret;
break;
}
QSIMPLEQ_REMOVE_HEAD(&block_mig_state.blk_list, entry);
blk_mig_unlock();
blk_send(f, blk);
blk_mig_lock();
g_free(blk->buf);
g_free(blk);
block_mig_state.read_done--;
block_mig_state.transferred++;
assert(block_mig_state.read_done >= 0);
}
blk_mig_unlock();
trace_migration_block_flush_blks("Exit", block_mig_state.submitted,
block_mig_state.read_done,
block_mig_state.transferred);
return ret;
}
/* Called with iothread lock taken. */
static int64_t get_remaining_dirty(void)
{
BlkMigDevState *bmds;
int64_t dirty = 0;
QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) {
aio_context_acquire(blk_get_aio_context(bmds->blk));
dirty += bdrv_get_dirty_count(bmds->dirty_bitmap);
aio_context_release(blk_get_aio_context(bmds->blk));
}
return dirty;
}
/* Called with iothread lock taken. */
static void block_migration_cleanup_bmds(void)
{
BlkMigDevState *bmds;
BlockDriverState *bs;
AioContext *ctx;
unset_dirty_tracking();
while ((bmds = QSIMPLEQ_FIRST(&block_mig_state.bmds_list)) != NULL) {
QSIMPLEQ_REMOVE_HEAD(&block_mig_state.bmds_list, entry);
bs = blk_bs(bmds->blk);
if (bs) {
bdrv_op_unblock_all(bs, bmds->blocker);
}
error_free(bmds->blocker);
/* Save ctx, because bmds->blk can disappear during blk_unref. */
ctx = blk_get_aio_context(bmds->blk);
aio_context_acquire(ctx);
blk_unref(bmds->blk);
aio_context_release(ctx);
g_free(bmds->blk_name);
g_free(bmds->aio_bitmap);
g_free(bmds);
}
}
/* Called with iothread lock taken. */
static void block_migration_cleanup(void *opaque)
{
BlkMigBlock *blk;
bdrv_drain_all();
block_migration_cleanup_bmds();
blk_mig_lock();
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);
}
blk_mig_unlock();
}
static int block_save_setup(QEMUFile *f, void *opaque)
{
int ret;
trace_migration_block_save("setup", block_mig_state.submitted,
block_mig_state.transferred);
ret = init_blk_migration(f);
if (ret < 0) {
return ret;
}
/* start track dirty blocks */
ret = set_dirty_tracking();
if (ret) {
return ret;
}
ret = flush_blks(f);
blk_mig_reset_dirty_cursor();
qemu_put_be64(f, BLK_MIG_FLAG_EOS);
return ret;
}
static int block_save_iterate(QEMUFile *f, void *opaque)
{
int ret;
uint64_t last_bytes = qemu_file_transferred_noflush(f);
trace_migration_block_save("iterate", block_mig_state.submitted,
block_mig_state.transferred);
ret = flush_blks(f);
if (ret) {
return ret;
}
blk_mig_reset_dirty_cursor();
/* control the rate of transfer */
blk_mig_lock();
while (block_mig_state.read_done * BLK_MIG_BLOCK_SIZE <
migration_rate_get() &&
block_mig_state.submitted < MAX_PARALLEL_IO &&
(block_mig_state.submitted + block_mig_state.read_done) <
MAX_IO_BUFFERS) {
blk_mig_unlock();
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;
}
ret = 0;
} else {
/* Always called with iothread lock taken for
* simplicity, block_save_complete also calls it.
*/
qemu_mutex_lock_iothread();
ret = blk_mig_save_dirty_block(f, 1);
qemu_mutex_unlock_iothread();
}
if (ret < 0) {
return ret;
}
blk_mig_lock();
if (ret != 0) {
/* no more dirty blocks */
break;
}
}
blk_mig_unlock();
ret = flush_blks(f);
if (ret) {
return ret;
}
qemu_put_be64(f, BLK_MIG_FLAG_EOS);
uint64_t delta_bytes = qemu_file_transferred_noflush(f) - last_bytes;
return (delta_bytes > 0);
}
/* Called with iothread lock taken. */
static int block_save_complete(QEMUFile *f, void *opaque)
{
int ret;
trace_migration_block_save("complete", block_mig_state.submitted,
block_mig_state.transferred);
ret = flush_blks(f);
if (ret) {
return ret;
}
blk_mig_reset_dirty_cursor();
/* we know for sure that save bulk is completed and
all async read completed */
blk_mig_lock();
assert(block_mig_state.submitted == 0);
blk_mig_unlock();
do {
ret = blk_mig_save_dirty_block(f, 0);
if (ret < 0) {
return ret;
}
} while (ret == 0);
/* report completion */
qemu_put_be64(f, (100 << BDRV_SECTOR_BITS) | BLK_MIG_FLAG_PROGRESS);
trace_migration_block_save_complete();
qemu_put_be64(f, BLK_MIG_FLAG_EOS);
/* Make sure that our BlockBackends are gone, so that the block driver
* nodes can be inactivated. */
block_migration_cleanup_bmds();
return 0;
}
static void block_state_pending(void *opaque, uint64_t *must_precopy,
uint64_t *can_postcopy)
{
/* Estimate pending number of bytes to send */
uint64_t pending;
qemu_mutex_lock_iothread();
pending = get_remaining_dirty();
qemu_mutex_unlock_iothread();
blk_mig_lock();
pending += block_mig_state.submitted * BLK_MIG_BLOCK_SIZE +
block_mig_state.read_done * BLK_MIG_BLOCK_SIZE;
blk_mig_unlock();
/* Report at least one block pending during bulk phase */
if (!pending && !block_mig_state.bulk_completed) {
pending = BLK_MIG_BLOCK_SIZE;
}
trace_migration_block_state_pending(pending);
/* We don't do postcopy */
*must_precopy += pending;
}
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;
BlockBackend *blk, *blk_prev = NULL;
Error *local_err = NULL;
uint8_t *buf;
int64_t total_sectors = 0;
int nr_sectors;
int ret;
BlockDriverInfo bdi;
int cluster_size = BLK_MIG_BLOCK_SIZE;
do {
addr = qemu_get_be64(f);
flags = addr & (BDRV_SECTOR_SIZE - 1);
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';
blk = blk_by_name(device_name);
if (!blk) {
fprintf(stderr, "Error unknown block device %s\n",
device_name);
return -EINVAL;
}
if (blk != blk_prev) {
blk_prev = blk;
total_sectors = blk_nb_sectors(blk);
if (total_sectors <= 0) {
error_report("Error getting length of block device %s",
device_name);
return -EINVAL;
}
blk_activate(blk, &local_err);
if (local_err) {
error_report_err(local_err);
return -EINVAL;
}
ret = bdrv_get_info(blk_bs(blk), &bdi);
if (ret == 0 && bdi.cluster_size > 0 &&
bdi.cluster_size <= BLK_MIG_BLOCK_SIZE &&
BLK_MIG_BLOCK_SIZE % bdi.cluster_size == 0) {
cluster_size = bdi.cluster_size;
} else {
cluster_size = BLK_MIG_BLOCK_SIZE;
}
}
if (total_sectors - addr < BDRV_SECTORS_PER_DIRTY_CHUNK) {
nr_sectors = total_sectors - addr;
} else {
nr_sectors = BDRV_SECTORS_PER_DIRTY_CHUNK;
}
if (flags & BLK_MIG_FLAG_ZERO_BLOCK) {
ret = blk_pwrite_zeroes(blk, addr * BDRV_SECTOR_SIZE,
nr_sectors * BDRV_SECTOR_SIZE,
BDRV_REQ_MAY_UNMAP);
} else {
int i;
int64_t cur_addr;
uint8_t *cur_buf;
buf = g_malloc(BLK_MIG_BLOCK_SIZE);
qemu_get_buffer(f, buf, BLK_MIG_BLOCK_SIZE);
for (i = 0; i < BLK_MIG_BLOCK_SIZE / cluster_size; i++) {
cur_addr = addr * BDRV_SECTOR_SIZE + i * cluster_size;
cur_buf = buf + i * cluster_size;
if ((!block_mig_state.zero_blocks ||
cluster_size < BLK_MIG_BLOCK_SIZE) &&
buffer_is_zero(cur_buf, cluster_size)) {
ret = blk_pwrite_zeroes(blk, cur_addr,
cluster_size,
BDRV_REQ_MAY_UNMAP);
} else {
ret = blk_pwrite(blk, cur_addr, cluster_size, cur_buf,
0);
}
if (ret < 0) {
break;
}
}
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 block migration flags: 0x%x\n", flags);
return -EINVAL;
}
ret = qemu_file_get_error(f);
if (ret != 0) {
return ret;
}
} while (!(flags & BLK_MIG_FLAG_EOS));
return 0;
}
static bool block_is_active(void *opaque)
{
return migrate_block();
}
static SaveVMHandlers savevm_block_handlers = {
.save_setup = block_save_setup,
.save_live_iterate = block_save_iterate,
.save_live_complete_precopy = block_save_complete,
.state_pending_exact = block_state_pending,
.state_pending_estimate = block_state_pending,
.load_state = block_load,
.save_cleanup = block_migration_cleanup,
.is_active = block_is_active,
};
void blk_mig_init(void)
{
QSIMPLEQ_INIT(&block_mig_state.bmds_list);
QSIMPLEQ_INIT(&block_mig_state.blk_list);
qemu_mutex_init(&block_mig_state.lock);
register_savevm_live("block", 0, 1, &savevm_block_handlers,
&block_mig_state);
}
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