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qemu/block/block-copy.c

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/*
* block_copy API
*
* Copyright (C) 2013 Proxmox Server Solutions
* Copyright (c) 2019 Virtuozzo International GmbH.
*
* Authors:
* Dietmar Maurer (dietmar@proxmox.com)
* Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
*
* This work is licensed under the terms of the GNU GPL, version 2 or later.
* See the COPYING file in the top-level directory.
*/
#include "qemu/osdep.h"
#include "trace.h"
#include "qapi/error.h"
#include "block/block-copy.h"
#include "sysemu/block-backend.h"
#include "qemu/units.h"
#include "qemu/coroutine.h"
#include "block/aio_task.h"
#define BLOCK_COPY_MAX_COPY_RANGE (16 * MiB)
#define BLOCK_COPY_MAX_BUFFER (1 * MiB)
#define BLOCK_COPY_MAX_MEM (128 * MiB)
#define BLOCK_COPY_MAX_WORKERS 64
#define BLOCK_COPY_SLICE_TIME 100000000ULL /* ns */
static coroutine_fn int block_copy_task_entry(AioTask *task);
typedef struct BlockCopyCallState {
/* IN parameters. Initialized in block_copy_async() and never changed. */
BlockCopyState *s;
int64_t offset;
int64_t bytes;
int max_workers;
int64_t max_chunk;
bool ignore_ratelimit;
BlockCopyAsyncCallbackFunc cb;
void *cb_opaque;
/* Coroutine where async block-copy is running */
Coroutine *co;
/* To reference all call states from BlockCopyState */
QLIST_ENTRY(BlockCopyCallState) list;
/* State */
int ret;
bool finished;
QemuCoSleepState *sleep_state;
bool cancelled;
/* OUT parameters */
bool error_is_read;
} BlockCopyCallState;
typedef struct BlockCopyTask {
AioTask task;
BlockCopyState *s;
BlockCopyCallState *call_state;
int64_t offset;
int64_t bytes;
bool zeroes;
QLIST_ENTRY(BlockCopyTask) list;
CoQueue wait_queue; /* coroutines blocked on this task */
} BlockCopyTask;
static int64_t task_end(BlockCopyTask *task)
{
return task->offset + task->bytes;
}
typedef struct BlockCopyState {
/*
* BdrvChild objects are not owned or managed by block-copy. They are
* provided by block-copy user and user is responsible for appropriate
* permissions on these children.
*/
BdrvChild *source;
BdrvChild *target;
BdrvDirtyBitmap *copy_bitmap;
int64_t in_flight_bytes;
int64_t cluster_size;
bool use_copy_range;
int64_t copy_size;
uint64_t len;
QLIST_HEAD(, BlockCopyTask) tasks; /* All tasks from all block-copy calls */
QLIST_HEAD(, BlockCopyCallState) calls;
BdrvRequestFlags write_flags;
/*
* skip_unallocated:
*
* Used by sync=top jobs, which first scan the source node for unallocated
* areas and clear them in the copy_bitmap. During this process, the bitmap
* is thus not fully initialized: It may still have bits set for areas that
* are unallocated and should actually not be copied.
*
* This is indicated by skip_unallocated.
*
* In this case, block_copy() will query the source’s allocation status,
* skip unallocated regions, clear them in the copy_bitmap, and invoke
* block_copy_reset_unallocated() every time it does.
*/
bool skip_unallocated;
ProgressMeter *progress;
SharedResource *mem;
uint64_t speed;
RateLimit rate_limit;
} BlockCopyState;
static BlockCopyTask *find_conflicting_task(BlockCopyState *s,
int64_t offset, int64_t bytes)
{
BlockCopyTask *t;
QLIST_FOREACH(t, &s->tasks, list) {
if (offset + bytes > t->offset && offset < t->offset + t->bytes) {
return t;
}
}
return NULL;
}
/*
* If there are no intersecting tasks return false. Otherwise, wait for the
* first found intersecting tasks to finish and return true.
*/
static bool coroutine_fn block_copy_wait_one(BlockCopyState *s, int64_t offset,
int64_t bytes)
{
BlockCopyTask *task = find_conflicting_task(s, offset, bytes);
if (!task) {
return false;
}
qemu_co_queue_wait(&task->wait_queue, NULL);
return true;
}
/*
* Search for the first dirty area in offset/bytes range and create task at
* the beginning of it.
*/
static BlockCopyTask *block_copy_task_create(BlockCopyState *s,
BlockCopyCallState *call_state,
int64_t offset, int64_t bytes)
{
BlockCopyTask *task;
int64_t max_chunk = MIN_NON_ZERO(s->copy_size, call_state->max_chunk);
if (!bdrv_dirty_bitmap_next_dirty_area(s->copy_bitmap,
offset, offset + bytes,
max_chunk, &offset, &bytes))
{
return NULL;
}
assert(QEMU_IS_ALIGNED(offset, s->cluster_size));
bytes = QEMU_ALIGN_UP(bytes, s->cluster_size);
/* region is dirty, so no existent tasks possible in it */
assert(!find_conflicting_task(s, offset, bytes));
bdrv_reset_dirty_bitmap(s->copy_bitmap, offset, bytes);
s->in_flight_bytes += bytes;
task = g_new(BlockCopyTask, 1);
*task = (BlockCopyTask) {
.task.func = block_copy_task_entry,
.s = s,
.call_state = call_state,
.offset = offset,
.bytes = bytes,
};
qemu_co_queue_init(&task->wait_queue);
QLIST_INSERT_HEAD(&s->tasks, task, list);
return task;
}
/*
* block_copy_task_shrink
*
* Drop the tail of the task to be handled later. Set dirty bits back and
* wake up all tasks waiting for us (may be some of them are not intersecting
* with shrunk task)
*/
static void coroutine_fn block_copy_task_shrink(BlockCopyTask *task,
int64_t new_bytes)
{
if (new_bytes == task->bytes) {
return;
}
assert(new_bytes > 0 && new_bytes < task->bytes);
task->s->in_flight_bytes -= task->bytes - new_bytes;
bdrv_set_dirty_bitmap(task->s->copy_bitmap,
task->offset + new_bytes, task->bytes - new_bytes);
task->bytes = new_bytes;
qemu_co_queue_restart_all(&task->wait_queue);
}
static void coroutine_fn block_copy_task_end(BlockCopyTask *task, int ret)
{
task->s->in_flight_bytes -= task->bytes;
if (ret < 0) {
bdrv_set_dirty_bitmap(task->s->copy_bitmap, task->offset, task->bytes);
}
QLIST_REMOVE(task, list);
qemu_co_queue_restart_all(&task->wait_queue);
}
void block_copy_state_free(BlockCopyState *s)
{
if (!s) {
return;
}
bdrv_release_dirty_bitmap(s->copy_bitmap);
shres_destroy(s->mem);
g_free(s);
}
static uint32_t block_copy_max_transfer(BdrvChild *source, BdrvChild *target)
{
return MIN_NON_ZERO(INT_MAX,
MIN_NON_ZERO(source->bs->bl.max_transfer,
target->bs->bl.max_transfer));
}
BlockCopyState *block_copy_state_new(BdrvChild *source, BdrvChild *target,
int64_t cluster_size, bool use_copy_range,
BdrvRequestFlags write_flags, Error **errp)
{
BlockCopyState *s;
BdrvDirtyBitmap *copy_bitmap;
copy_bitmap = bdrv_create_dirty_bitmap(source->bs, cluster_size, NULL,
errp);
if (!copy_bitmap) {
return NULL;
}
bdrv_disable_dirty_bitmap(copy_bitmap);
s = g_new(BlockCopyState, 1);
*s = (BlockCopyState) {
.source = source,
.target = target,
.copy_bitmap = copy_bitmap,
.cluster_size = cluster_size,
.len = bdrv_dirty_bitmap_size(copy_bitmap),
.write_flags = write_flags,
.mem = shres_create(BLOCK_COPY_MAX_MEM),
};
if (block_copy_max_transfer(source, target) < cluster_size) {
/*
* copy_range does not respect max_transfer. We don't want to bother
* with requests smaller than block-copy cluster size, so fallback to
* buffered copying (read and write respect max_transfer on their
* behalf).
*/
s->use_copy_range = false;
s->copy_size = cluster_size;
} else if (write_flags & BDRV_REQ_WRITE_COMPRESSED) {
/* Compression supports only cluster-size writes and no copy-range. */
s->use_copy_range = false;
s->copy_size = cluster_size;
} else {
/*
* We enable copy-range, but keep small copy_size, until first
* successful copy_range (look at block_copy_do_copy).
*/
s->use_copy_range = use_copy_range;
s->copy_size = MAX(s->cluster_size, BLOCK_COPY_MAX_BUFFER);
}
QLIST_INIT(&s->tasks);
QLIST_INIT(&s->calls);
return s;
}
void block_copy_set_progress_meter(BlockCopyState *s, ProgressMeter *pm)
{
s->progress = pm;
}
/*
* Takes ownership of @task
*
* If pool is NULL directly run the task, otherwise schedule it into the pool.
*
* Returns: task.func return code if pool is NULL
* otherwise -ECANCELED if pool status is bad
* otherwise 0 (successfully scheduled)
*/
static coroutine_fn int block_copy_task_run(AioTaskPool *pool,
BlockCopyTask *task)
{
if (!pool) {
int ret = task->task.func(&task->task);
g_free(task);
return ret;
}
aio_task_pool_wait_slot(pool);
if (aio_task_pool_status(pool) < 0) {
co_put_to_shres(task->s->mem, task->bytes);
block_copy_task_end(task, -ECANCELED);
g_free(task);
return -ECANCELED;
}
aio_task_pool_start_task(pool, &task->task);
return 0;
}
/*
* block_copy_do_copy
*
* Do copy of cluster-aligned chunk. Requested region is allowed to exceed
* s->len only to cover last cluster when s->len is not aligned to clusters.
*
* No sync here: nor bitmap neighter intersecting requests handling, only copy.
*
* Returns 0 on success.
*/
static int coroutine_fn block_copy_do_copy(BlockCopyState *s,
int64_t offset, int64_t bytes,
bool zeroes, bool *error_is_read)
{
int ret;
int64_t nbytes = MIN(offset + bytes, s->len) - offset;
void *bounce_buffer = NULL;
assert(offset >= 0 && bytes > 0 && INT64_MAX - offset >= bytes);
assert(QEMU_IS_ALIGNED(offset, s->cluster_size));
assert(QEMU_IS_ALIGNED(bytes, s->cluster_size));
assert(offset < s->len);
assert(offset + bytes <= s->len ||
offset + bytes == QEMU_ALIGN_UP(s->len, s->cluster_size));
assert(nbytes < INT_MAX);
if (zeroes) {
ret = bdrv_co_pwrite_zeroes(s->target, offset, nbytes, s->write_flags &
~BDRV_REQ_WRITE_COMPRESSED);
if (ret < 0) {
trace_block_copy_write_zeroes_fail(s, offset, ret);
*error_is_read = false;
}
return ret;
}
if (s->use_copy_range) {
ret = bdrv_co_copy_range(s->source, offset, s->target, offset, nbytes,
0, s->write_flags);
if (ret < 0) {
trace_block_copy_copy_range_fail(s, offset, ret);
s->use_copy_range = false;
s->copy_size = MAX(s->cluster_size, BLOCK_COPY_MAX_BUFFER);
/* Fallback to read+write with allocated buffer */
} else {
if (s->use_copy_range) {
/*
* Successful copy-range. Now increase copy_size. copy_range
* does not respect max_transfer (it's a TODO), so we factor
* that in here.
*
* Note: we double-check s->use_copy_range for the case when
* parallel block-copy request unsets it during previous
* bdrv_co_copy_range call.
*/
s->copy_size =
MIN(MAX(s->cluster_size, BLOCK_COPY_MAX_COPY_RANGE),
QEMU_ALIGN_DOWN(block_copy_max_transfer(s->source,
s->target),
s->cluster_size));
}
goto out;
}
}
/*
* In case of failed copy_range request above, we may proceed with buffered
* request larger than BLOCK_COPY_MAX_BUFFER. Still, further requests will
* be properly limited, so don't care too much. Moreover the most likely
* case (copy_range is unsupported for the configuration, so the very first
* copy_range request fails) is handled by setting large copy_size only
* after first successful copy_range.
*/
bounce_buffer = qemu_blockalign(s->source->bs, nbytes);
ret = bdrv_co_pread(s->source, offset, nbytes, bounce_buffer, 0);
if (ret < 0) {
trace_block_copy_read_fail(s, offset, ret);
*error_is_read = true;
goto out;
}
ret = bdrv_co_pwrite(s->target, offset, nbytes, bounce_buffer,
s->write_flags);
if (ret < 0) {
trace_block_copy_write_fail(s, offset, ret);
*error_is_read = false;
goto out;
}
out:
qemu_vfree(bounce_buffer);
return ret;
}
static coroutine_fn int block_copy_task_entry(AioTask *task)
{
BlockCopyTask *t = container_of(task, BlockCopyTask, task);
bool error_is_read = false;
int ret;
ret = block_copy_do_copy(t->s, t->offset, t->bytes, t->zeroes,
&error_is_read);
if (ret < 0 && !t->call_state->ret) {
t->call_state->ret = ret;
t->call_state->error_is_read = error_is_read;
} else {
progress_work_done(t->s->progress, t->bytes);
}
co_put_to_shres(t->s->mem, t->bytes);
block_copy_task_end(t, ret);
return ret;
}
static int block_copy_block_status(BlockCopyState *s, int64_t offset,
int64_t bytes, int64_t *pnum)
{
int64_t num;
BlockDriverState *base;
int ret;
if (s->skip_unallocated) {
base = bdrv_backing_chain_next(s->source->bs);
} else {
base = NULL;
}
ret = bdrv_block_status_above(s->source->bs, base, offset, bytes, &num,
NULL, NULL);
if (ret < 0 || num < s->cluster_size) {
/*
* On error or if failed to obtain large enough chunk just fallback to
* copy one cluster.
*/
num = s->cluster_size;
ret = BDRV_BLOCK_ALLOCATED | BDRV_BLOCK_DATA;
} else if (offset + num == s->len) {
num = QEMU_ALIGN_UP(num, s->cluster_size);
} else {
num = QEMU_ALIGN_DOWN(num, s->cluster_size);
}
*pnum = num;
return ret;
}
/*
* Check if the cluster starting at offset is allocated or not.
* return via pnum the number of contiguous clusters sharing this allocation.
*/
static int block_copy_is_cluster_allocated(BlockCopyState *s, int64_t offset,
int64_t *pnum)
{
BlockDriverState *bs = s->source->bs;
int64_t count, total_count = 0;
int64_t bytes = s->len - offset;
int ret;
assert(QEMU_IS_ALIGNED(offset, s->cluster_size));
while (true) {
ret = bdrv_is_allocated(bs, offset, bytes, &count);
if (ret < 0) {
return ret;
}
total_count += count;
if (ret || count == 0) {
/*
* ret: partial segment(s) are considered allocated.
* otherwise: unallocated tail is treated as an entire segment.
*/
*pnum = DIV_ROUND_UP(total_count, s->cluster_size);
return ret;
}
/* Unallocated segment(s) with uncertain following segment(s) */
if (total_count >= s->cluster_size) {
*pnum = total_count / s->cluster_size;
return 0;
}
offset += count;
bytes -= count;
}
}
/*
* Reset bits in copy_bitmap starting at offset if they represent unallocated
* data in the image. May reset subsequent contiguous bits.
* @return 0 when the cluster at @offset was unallocated,
* 1 otherwise, and -ret on error.
*/
int64_t block_copy_reset_unallocated(BlockCopyState *s,
int64_t offset, int64_t *count)
{
int ret;
int64_t clusters, bytes;
ret = block_copy_is_cluster_allocated(s, offset, &clusters);
if (ret < 0) {
return ret;
}
bytes = clusters * s->cluster_size;
if (!ret) {
bdrv_reset_dirty_bitmap(s->copy_bitmap, offset, bytes);
progress_set_remaining(s->progress,
bdrv_get_dirty_count(s->copy_bitmap) +
s->in_flight_bytes);
}
*count = bytes;
return ret;
}
/*
* block_copy_dirty_clusters
*
* Copy dirty clusters in @offset/@bytes range.
* Returns 1 if dirty clusters found and successfully copied, 0 if no dirty
* clusters found and -errno on failure.
*/
static int coroutine_fn
block_copy_dirty_clusters(BlockCopyCallState *call_state)
{
BlockCopyState *s = call_state->s;
int64_t offset = call_state->offset;
int64_t bytes = call_state->bytes;
int ret = 0;
bool found_dirty = false;
int64_t end = offset + bytes;
AioTaskPool *aio = NULL;
/*
* block_copy() user is responsible for keeping source and target in same
* aio context
*/
assert(bdrv_get_aio_context(s->source->bs) ==
bdrv_get_aio_context(s->target->bs));
assert(QEMU_IS_ALIGNED(offset, s->cluster_size));
assert(QEMU_IS_ALIGNED(bytes, s->cluster_size));
while (bytes && aio_task_pool_status(aio) == 0 && !call_state->cancelled) {
BlockCopyTask *task;
int64_t status_bytes;
task = block_copy_task_create(s, call_state, offset, bytes);
if (!task) {
/* No more dirty bits in the bitmap */
trace_block_copy_skip_range(s, offset, bytes);
break;
}
if (task->offset > offset) {
trace_block_copy_skip_range(s, offset, task->offset - offset);
}
found_dirty = true;
ret = block_copy_block_status(s, task->offset, task->bytes,
&status_bytes);
assert(ret >= 0); /* never fail */
if (status_bytes < task->bytes) {
block_copy_task_shrink(task, status_bytes);
}
if (s->skip_unallocated && !(ret & BDRV_BLOCK_ALLOCATED)) {
block_copy_task_end(task, 0);
progress_set_remaining(s->progress,
bdrv_get_dirty_count(s->copy_bitmap) +
s->in_flight_bytes);
trace_block_copy_skip_range(s, task->offset, task->bytes);
offset = task_end(task);
bytes = end - offset;
g_free(task);
continue;
}
task->zeroes = ret & BDRV_BLOCK_ZERO;
if (s->speed) {
if (!call_state->ignore_ratelimit) {
uint64_t ns = ratelimit_calculate_delay(&s->rate_limit, 0);
if (ns > 0) {
block_copy_task_end(task, -EAGAIN);
g_free(task);
qemu_co_sleep_ns_wakeable(QEMU_CLOCK_REALTIME, ns,
&call_state->sleep_state);
continue;
}
}
ratelimit_calculate_delay(&s->rate_limit, task->bytes);
}
trace_block_copy_process(s, task->offset);
co_get_from_shres(s->mem, task->bytes);
offset = task_end(task);
bytes = end - offset;
if (!aio && bytes) {
aio = aio_task_pool_new(call_state->max_workers);
}
ret = block_copy_task_run(aio, task);
if (ret < 0) {
goto out;
}
}
out:
if (aio) {
aio_task_pool_wait_all(aio);
/*
* We are not really interested in -ECANCELED returned from
* block_copy_task_run. If it fails, it means some task already failed
* for real reason, let's return first failure.
* Still, assert that we don't rewrite failure by success.
*
* Note: ret may be positive here because of block-status result.
*/
assert(ret >= 0 || aio_task_pool_status(aio) < 0);
ret = aio_task_pool_status(aio);
aio_task_pool_free(aio);
}
return ret < 0 ? ret : found_dirty;
}
void block_copy_kick(BlockCopyCallState *call_state)
{
if (call_state->sleep_state) {
qemu_co_sleep_wake(call_state->sleep_state);
}
}
/*
* block_copy_common
*
* Copy requested region, accordingly to dirty bitmap.
* Collaborate with parallel block_copy requests: if they succeed it will help
* us. If they fail, we will retry not-copied regions. So, if we return error,
* it means that some I/O operation failed in context of _this_ block_copy call,
* not some parallel operation.
*/
static int coroutine_fn block_copy_common(BlockCopyCallState *call_state)
{
int ret;
QLIST_INSERT_HEAD(&call_state->s->calls, call_state, list);
do {
ret = block_copy_dirty_clusters(call_state);
if (ret == 0 && !call_state->cancelled) {
ret = block_copy_wait_one(call_state->s, call_state->offset,
call_state->bytes);
}
/*
* We retry in two cases:
* 1. Some progress done
* Something was copied, which means that there were yield points
* and some new dirty bits may have appeared (due to failed parallel
* block-copy requests).
* 2. We have waited for some intersecting block-copy request
* It may have failed and produced new dirty bits.
*/
} while (ret > 0 && !call_state->cancelled);
call_state->finished = true;
if (call_state->cb) {
call_state->cb(call_state->cb_opaque);
}
QLIST_REMOVE(call_state, list);
return ret;
}
int coroutine_fn block_copy(BlockCopyState *s, int64_t start, int64_t bytes,
bool ignore_ratelimit)
{
BlockCopyCallState call_state = {
.s = s,
.offset = start,
.bytes = bytes,
.ignore_ratelimit = ignore_ratelimit,
.max_workers = BLOCK_COPY_MAX_WORKERS,
};
return block_copy_common(&call_state);
}
static void coroutine_fn block_copy_async_co_entry(void *opaque)
{
block_copy_common(opaque);
}
BlockCopyCallState *block_copy_async(BlockCopyState *s,
int64_t offset, int64_t bytes,
int max_workers, int64_t max_chunk,
BlockCopyAsyncCallbackFunc cb,
void *cb_opaque)
{
BlockCopyCallState *call_state = g_new(BlockCopyCallState, 1);
*call_state = (BlockCopyCallState) {
.s = s,
.offset = offset,
.bytes = bytes,
.max_workers = max_workers,
.max_chunk = max_chunk,
.cb = cb,
.cb_opaque = cb_opaque,
.co = qemu_coroutine_create(block_copy_async_co_entry, call_state),
};
qemu_coroutine_enter(call_state->co);
return call_state;
}
void block_copy_call_free(BlockCopyCallState *call_state)
{
if (!call_state) {
return;
}
assert(call_state->finished);
g_free(call_state);
}
bool block_copy_call_finished(BlockCopyCallState *call_state)
{
return call_state->finished;
}
bool block_copy_call_succeeded(BlockCopyCallState *call_state)
{
return call_state->finished && !call_state->cancelled &&
call_state->ret == 0;
}
bool block_copy_call_failed(BlockCopyCallState *call_state)
{
return call_state->finished && !call_state->cancelled &&
call_state->ret < 0;
}
bool block_copy_call_cancelled(BlockCopyCallState *call_state)
{
return call_state->cancelled;
}
int block_copy_call_status(BlockCopyCallState *call_state, bool *error_is_read)
{
assert(call_state->finished);
if (error_is_read) {
*error_is_read = call_state->error_is_read;
}
return call_state->ret;
}
void block_copy_call_cancel(BlockCopyCallState *call_state)
{
call_state->cancelled = true;
block_copy_kick(call_state);
}
BdrvDirtyBitmap *block_copy_dirty_bitmap(BlockCopyState *s)
{
return s->copy_bitmap;
}
void block_copy_set_skip_unallocated(BlockCopyState *s, bool skip)
{
s->skip_unallocated = skip;
}
void block_copy_set_speed(BlockCopyState *s, uint64_t speed)
{
s->speed = speed;
if (speed > 0) {
ratelimit_set_speed(&s->rate_limit, speed, BLOCK_COPY_SLICE_TIME);
}
/*
* Note: it's good to kick all call states from here, but it should be done
* only from a coroutine, to not crash if s->calls list changed while
* entering one call. So for now, the only user of this function kicks its
* only one call_state by hand.
*/
}
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