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qemu/block/mirror.c

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/*
* Image mirroring
*
* Copyright Red Hat, Inc. 2012
*
* Authors:
* Paolo Bonzini <pbonzini@redhat.com>
*
* This work is licensed under the terms of the GNU LGPL, version 2 or later.
* See the COPYING.LIB file in the top-level directory.
*
*/
#include "trace.h"
#include "block/blockjob.h"
#include "block/block_int.h"
#include "qemu/ratelimit.h"
#include "qemu/bitmap.h"
#define SLICE_TIME 100000000ULL /* ns */
#define MAX_IN_FLIGHT 16
/* The mirroring buffer is a list of granularity-sized chunks.
* Free chunks are organized in a list.
*/
typedef struct MirrorBuffer {
QSIMPLEQ_ENTRY(MirrorBuffer) next;
} MirrorBuffer;
typedef struct MirrorBlockJob {
BlockJob common;
RateLimit limit;
BlockDriverState *target;
MirrorSyncMode mode;
BlockdevOnError on_source_error, on_target_error;
bool synced;
bool should_complete;
int64_t sector_num;
int64_t granularity;
size_t buf_size;
unsigned long *cow_bitmap;
HBitmapIter hbi;
uint8_t *buf;
QSIMPLEQ_HEAD(, MirrorBuffer) buf_free;
int buf_free_count;
unsigned long *in_flight_bitmap;
int in_flight;
int ret;
} MirrorBlockJob;
typedef struct MirrorOp {
MirrorBlockJob *s;
QEMUIOVector qiov;
int64_t sector_num;
int nb_sectors;
} MirrorOp;
static BlockErrorAction mirror_error_action(MirrorBlockJob *s, bool read,
int error)
{
s->synced = false;
if (read) {
return block_job_error_action(&s->common, s->common.bs,
s->on_source_error, true, error);
} else {
return block_job_error_action(&s->common, s->target,
s->on_target_error, false, error);
}
}
static void mirror_iteration_done(MirrorOp *op, int ret)
{
MirrorBlockJob *s = op->s;
struct iovec *iov;
int64_t chunk_num;
int i, nb_chunks, sectors_per_chunk;
trace_mirror_iteration_done(s, op->sector_num, op->nb_sectors, ret);
s->in_flight--;
iov = op->qiov.iov;
for (i = 0; i < op->qiov.niov; i++) {
MirrorBuffer *buf = (MirrorBuffer *) iov[i].iov_base;
QSIMPLEQ_INSERT_TAIL(&s->buf_free, buf, next);
s->buf_free_count++;
}
sectors_per_chunk = s->granularity >> BDRV_SECTOR_BITS;
chunk_num = op->sector_num / sectors_per_chunk;
nb_chunks = op->nb_sectors / sectors_per_chunk;
bitmap_clear(s->in_flight_bitmap, chunk_num, nb_chunks);
if (s->cow_bitmap && ret >= 0) {
bitmap_set(s->cow_bitmap, chunk_num, nb_chunks);
}
g_slice_free(MirrorOp, op);
qemu_coroutine_enter(s->common.co, NULL);
}
static void mirror_write_complete(void *opaque, int ret)
{
MirrorOp *op = opaque;
MirrorBlockJob *s = op->s;
if (ret < 0) {
BlockDriverState *source = s->common.bs;
BlockErrorAction action;
bdrv_set_dirty(source, op->sector_num, op->nb_sectors);
action = mirror_error_action(s, false, -ret);
if (action == BDRV_ACTION_REPORT && s->ret >= 0) {
s->ret = ret;
}
}
mirror_iteration_done(op, ret);
}
static void mirror_read_complete(void *opaque, int ret)
{
MirrorOp *op = opaque;
MirrorBlockJob *s = op->s;
if (ret < 0) {
BlockDriverState *source = s->common.bs;
BlockErrorAction action;
bdrv_set_dirty(source, op->sector_num, op->nb_sectors);
action = mirror_error_action(s, true, -ret);
if (action == BDRV_ACTION_REPORT && s->ret >= 0) {
s->ret = ret;
}
mirror_iteration_done(op, ret);
return;
}
bdrv_aio_writev(s->target, op->sector_num, &op->qiov, op->nb_sectors,
mirror_write_complete, op);
}
static void coroutine_fn mirror_iteration(MirrorBlockJob *s)
{
BlockDriverState *source = s->common.bs;
int nb_sectors, sectors_per_chunk, nb_chunks;
int64_t end, sector_num, next_chunk, next_sector, hbitmap_next_sector;
MirrorOp *op;
s->sector_num = hbitmap_iter_next(&s->hbi);
if (s->sector_num < 0) {
bdrv_dirty_iter_init(source, &s->hbi);
s->sector_num = hbitmap_iter_next(&s->hbi);
trace_mirror_restart_iter(s, bdrv_get_dirty_count(source));
assert(s->sector_num >= 0);
}
hbitmap_next_sector = s->sector_num;
sector_num = s->sector_num;
sectors_per_chunk = s->granularity >> BDRV_SECTOR_BITS;
end = s->common.len >> BDRV_SECTOR_BITS;
/* Extend the QEMUIOVector to include all adjacent blocks that will
* be copied in this operation.
*
* We have to do this if we have no backing file yet in the destination,
* and the cluster size is very large. Then we need to do COW ourselves.
* The first time a cluster is copied, copy it entirely. Note that,
* because both the granularity and the cluster size are powers of two,
* the number of sectors to copy cannot exceed one cluster.
*
* We also want to extend the QEMUIOVector to include more adjacent
* dirty blocks if possible, to limit the number of I/O operations and
* run efficiently even with a small granularity.
*/
nb_chunks = 0;
nb_sectors = 0;
next_sector = sector_num;
next_chunk = sector_num / sectors_per_chunk;
/* Wait for I/O to this cluster (from a previous iteration) to be done. */
while (test_bit(next_chunk, s->in_flight_bitmap)) {
trace_mirror_yield_in_flight(s, sector_num, s->in_flight);
qemu_coroutine_yield();
}
do {
int added_sectors, added_chunks;
if (!bdrv_get_dirty(source, next_sector) ||
test_bit(next_chunk, s->in_flight_bitmap)) {
assert(nb_sectors > 0);
break;
}
added_sectors = sectors_per_chunk;
if (s->cow_bitmap && !test_bit(next_chunk, s->cow_bitmap)) {
bdrv_round_to_clusters(s->target,
next_sector, added_sectors,
&next_sector, &added_sectors);
/* On the first iteration, the rounding may make us copy
* sectors before the first dirty one.
*/
if (next_sector < sector_num) {
assert(nb_sectors == 0);
sector_num = next_sector;
next_chunk = next_sector / sectors_per_chunk;
}
}
added_sectors = MIN(added_sectors, end - (sector_num + nb_sectors));
added_chunks = (added_sectors + sectors_per_chunk - 1) / sectors_per_chunk;
/* When doing COW, it may happen that there is not enough space for
* a full cluster. Wait if that is the case.
*/
while (nb_chunks == 0 && s->buf_free_count < added_chunks) {
trace_mirror_yield_buf_busy(s, nb_chunks, s->in_flight);
qemu_coroutine_yield();
}
if (s->buf_free_count < nb_chunks + added_chunks) {
trace_mirror_break_buf_busy(s, nb_chunks, s->in_flight);
break;
}
/* We have enough free space to copy these sectors. */
bitmap_set(s->in_flight_bitmap, next_chunk, added_chunks);
nb_sectors += added_sectors;
nb_chunks += added_chunks;
next_sector += added_sectors;
next_chunk += added_chunks;
} while (next_sector < end);
/* Allocate a MirrorOp that is used as an AIO callback. */
op = g_slice_new(MirrorOp);
op->s = s;
op->sector_num = sector_num;
op->nb_sectors = nb_sectors;
/* Now make a QEMUIOVector taking enough granularity-sized chunks
* from s->buf_free.
*/
qemu_iovec_init(&op->qiov, nb_chunks);
next_sector = sector_num;
while (nb_chunks-- > 0) {
MirrorBuffer *buf = QSIMPLEQ_FIRST(&s->buf_free);
QSIMPLEQ_REMOVE_HEAD(&s->buf_free, next);
s->buf_free_count--;
qemu_iovec_add(&op->qiov, buf, s->granularity);
/* Advance the HBitmapIter in parallel, so that we do not examine
* the same sector twice.
*/
if (next_sector > hbitmap_next_sector && bdrv_get_dirty(source, next_sector)) {
hbitmap_next_sector = hbitmap_iter_next(&s->hbi);
}
next_sector += sectors_per_chunk;
}
bdrv_reset_dirty(source, sector_num, nb_sectors);
/* Copy the dirty cluster. */
s->in_flight++;
trace_mirror_one_iteration(s, sector_num, nb_sectors);
bdrv_aio_readv(source, sector_num, &op->qiov, nb_sectors,
mirror_read_complete, op);
}
static void mirror_free_init(MirrorBlockJob *s)
{
int granularity = s->granularity;
size_t buf_size = s->buf_size;
uint8_t *buf = s->buf;
assert(s->buf_free_count == 0);
QSIMPLEQ_INIT(&s->buf_free);
while (buf_size != 0) {
MirrorBuffer *cur = (MirrorBuffer *)buf;
QSIMPLEQ_INSERT_TAIL(&s->buf_free, cur, next);
s->buf_free_count++;
buf_size -= granularity;
buf += granularity;
}
}
static void mirror_drain(MirrorBlockJob *s)
{
while (s->in_flight > 0) {
qemu_coroutine_yield();
}
}
static void coroutine_fn mirror_run(void *opaque)
{
MirrorBlockJob *s = opaque;
BlockDriverState *bs = s->common.bs;
int64_t sector_num, end, sectors_per_chunk, length;
uint64_t last_pause_ns;
BlockDriverInfo bdi;
char backing_filename[1024];
int ret = 0;
int n;
if (block_job_is_cancelled(&s->common)) {
goto immediate_exit;
}
s->common.len = bdrv_getlength(bs);
if (s->common.len <= 0) {
block_job_completed(&s->common, s->common.len);
return;
}
length = (bdrv_getlength(bs) + s->granularity - 1) / s->granularity;
s->in_flight_bitmap = bitmap_new(length);
/* If we have no backing file yet in the destination, we cannot let
* the destination do COW. Instead, we copy sectors around the
* dirty data if needed. We need a bitmap to do that.
*/
bdrv_get_backing_filename(s->target, backing_filename,
sizeof(backing_filename));
if (backing_filename[0] && !s->target->backing_hd) {
bdrv_get_info(s->target, &bdi);
if (s->granularity < bdi.cluster_size) {
s->buf_size = MAX(s->buf_size, bdi.cluster_size);
s->cow_bitmap = bitmap_new(length);
}
}
end = s->common.len >> BDRV_SECTOR_BITS;
s->buf = qemu_blockalign(bs, s->buf_size);
sectors_per_chunk = s->granularity >> BDRV_SECTOR_BITS;
mirror_free_init(s);
if (s->mode != MIRROR_SYNC_MODE_NONE) {
/* First part, loop on the sectors and initialize the dirty bitmap. */
BlockDriverState *base;
base = s->mode == MIRROR_SYNC_MODE_FULL ? NULL : bs->backing_hd;
for (sector_num = 0; sector_num < end; ) {
int64_t next = (sector_num | (sectors_per_chunk - 1)) + 1;
ret = bdrv_co_is_allocated_above(bs, base,
sector_num, next - sector_num, &n);
if (ret < 0) {
goto immediate_exit;
}
assert(n > 0);
if (ret == 1) {
bdrv_set_dirty(bs, sector_num, n);
sector_num = next;
} else {
sector_num += n;
}
}
}
bdrv_dirty_iter_init(bs, &s->hbi);
last_pause_ns = qemu_get_clock_ns(rt_clock);
for (;;) {
uint64_t delay_ns;
int64_t cnt;
bool should_complete;
if (s->ret < 0) {
ret = s->ret;
goto immediate_exit;
}
cnt = bdrv_get_dirty_count(bs);
/* Note that even when no rate limit is applied we need to yield
* periodically with no pending I/O so that qemu_aio_flush() returns.
* We do so every SLICE_TIME nanoseconds, or when there is an error,
* or when the source is clean, whichever comes first.
*/
if (qemu_get_clock_ns(rt_clock) - last_pause_ns < SLICE_TIME &&
s->common.iostatus == BLOCK_DEVICE_IO_STATUS_OK) {
if (s->in_flight == MAX_IN_FLIGHT || s->buf_free_count == 0 ||
(cnt == 0 && s->in_flight > 0)) {
trace_mirror_yield(s, s->in_flight, s->buf_free_count, cnt);
qemu_coroutine_yield();
continue;
} else if (cnt != 0) {
mirror_iteration(s);
continue;
}
}
should_complete = false;
if (s->in_flight == 0 && cnt == 0) {
trace_mirror_before_flush(s);
ret = bdrv_flush(s->target);
if (ret < 0) {
if (mirror_error_action(s, false, -ret) == BDRV_ACTION_REPORT) {
goto immediate_exit;
}
} else {
/* We're out of the streaming phase. From now on, if the job
* is cancelled we will actually complete all pending I/O and
* report completion. This way, block-job-cancel will leave
* the target in a consistent state.
*/
s->common.offset = end * BDRV_SECTOR_SIZE;
if (!s->synced) {
block_job_ready(&s->common);
s->synced = true;
}
should_complete = s->should_complete ||
block_job_is_cancelled(&s->common);
cnt = bdrv_get_dirty_count(bs);
}
}
if (cnt == 0 && should_complete) {
/* The dirty bitmap is not updated while operations are pending.
* If we're about to exit, wait for pending operations before
* calling bdrv_get_dirty_count(bs), or we may exit while the
* source has dirty data to copy!
*
* Note that I/O can be submitted by the guest while
* mirror_populate runs.
*/
trace_mirror_before_drain(s, cnt);
bdrv_drain_all();
cnt = bdrv_get_dirty_count(bs);
}
ret = 0;
trace_mirror_before_sleep(s, cnt, s->synced);
if (!s->synced) {
/* Publish progress */
s->common.offset = (end - cnt) * BDRV_SECTOR_SIZE;
if (s->common.speed) {
delay_ns = ratelimit_calculate_delay(&s->limit, sectors_per_chunk);
} else {
delay_ns = 0;
}
block_job_sleep_ns(&s->common, rt_clock, delay_ns);
if (block_job_is_cancelled(&s->common)) {
break;
}
} else if (!should_complete) {
delay_ns = (s->in_flight == 0 && cnt == 0 ? SLICE_TIME : 0);
block_job_sleep_ns(&s->common, rt_clock, delay_ns);
} else if (cnt == 0) {
/* The two disks are in sync. Exit and report successful
* completion.
*/
assert(QLIST_EMPTY(&bs->tracked_requests));
s->common.cancelled = false;
break;
}
last_pause_ns = qemu_get_clock_ns(rt_clock);
}
immediate_exit:
if (s->in_flight > 0) {
/* We get here only if something went wrong. Either the job failed,
* or it was cancelled prematurely so that we do not guarantee that
* the target is a copy of the source.
*/
assert(ret < 0 || (!s->synced && block_job_is_cancelled(&s->common)));
mirror_drain(s);
}
assert(s->in_flight == 0);
qemu_vfree(s->buf);
g_free(s->cow_bitmap);
g_free(s->in_flight_bitmap);
bdrv_set_dirty_tracking(bs, 0);
bdrv_iostatus_disable(s->target);
if (s->should_complete && ret == 0) {
if (bdrv_get_flags(s->target) != bdrv_get_flags(s->common.bs)) {
bdrv_reopen(s->target, bdrv_get_flags(s->common.bs), NULL);
}
bdrv_swap(s->target, s->common.bs);
}
bdrv_close(s->target);
bdrv_delete(s->target);
block_job_completed(&s->common, ret);
}
static void mirror_set_speed(BlockJob *job, int64_t speed, Error **errp)
{
MirrorBlockJob *s = container_of(job, MirrorBlockJob, common);
if (speed < 0) {
error_set(errp, QERR_INVALID_PARAMETER, "speed");
return;
}
ratelimit_set_speed(&s->limit, speed / BDRV_SECTOR_SIZE, SLICE_TIME);
}
static void mirror_iostatus_reset(BlockJob *job)
{
MirrorBlockJob *s = container_of(job, MirrorBlockJob, common);
bdrv_iostatus_reset(s->target);
}
static void mirror_complete(BlockJob *job, Error **errp)
{
MirrorBlockJob *s = container_of(job, MirrorBlockJob, common);
int ret;
ret = bdrv_open_backing_file(s->target, NULL);
if (ret < 0) {
char backing_filename[PATH_MAX];
bdrv_get_full_backing_filename(s->target, backing_filename,
sizeof(backing_filename));
error_set(errp, QERR_OPEN_FILE_FAILED, backing_filename);
return;
}
if (!s->synced) {
error_set(errp, QERR_BLOCK_JOB_NOT_READY, job->bs->device_name);
return;
}
s->should_complete = true;
block_job_resume(job);
}
static BlockJobType mirror_job_type = {
.instance_size = sizeof(MirrorBlockJob),
.job_type = "mirror",
.set_speed = mirror_set_speed,
.iostatus_reset= mirror_iostatus_reset,
.complete = mirror_complete,
};
void mirror_start(BlockDriverState *bs, BlockDriverState *target,
int64_t speed, int64_t granularity, int64_t buf_size,
MirrorSyncMode mode, BlockdevOnError on_source_error,
BlockdevOnError on_target_error,
BlockDriverCompletionFunc *cb,
void *opaque, Error **errp)
{
MirrorBlockJob *s;
if (granularity == 0) {
/* Choose the default granularity based on the target file's cluster
* size, clamped between 4k and 64k. */
BlockDriverInfo bdi;
if (bdrv_get_info(target, &bdi) >= 0 && bdi.cluster_size != 0) {
granularity = MAX(4096, bdi.cluster_size);
granularity = MIN(65536, granularity);
} else {
granularity = 65536;
}
}
assert ((granularity & (granularity - 1)) == 0);
if ((on_source_error == BLOCKDEV_ON_ERROR_STOP ||
on_source_error == BLOCKDEV_ON_ERROR_ENOSPC) &&
!bdrv_iostatus_is_enabled(bs)) {
error_set(errp, QERR_INVALID_PARAMETER, "on-source-error");
return;
}
s = block_job_create(&mirror_job_type, bs, speed, cb, opaque, errp);
if (!s) {
return;
}
s->on_source_error = on_source_error;
s->on_target_error = on_target_error;
s->target = target;
s->mode = mode;
s->granularity = granularity;
s->buf_size = MAX(buf_size, granularity);
bdrv_set_dirty_tracking(bs, granularity);
bdrv_set_enable_write_cache(s->target, true);
bdrv_set_on_error(s->target, on_target_error, on_target_error);
bdrv_iostatus_enable(s->target);
s->common.co = qemu_coroutine_create(mirror_run);
trace_mirror_start(bs, s, s->common.co, opaque);
qemu_coroutine_enter(s->common.co, s);
}
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