14.06.2021 10:33, Emanuele Giuseppe Esposito wrote:
Add a CoMutex to protect concurrent access of block-copy
data structures.
This mutex also protects .copy_bitmap, because its thread-safe
API does not prevent it from assigning two tasks to the same
bitmap region.
.finished, .cancelled and reads to .ret and .error_is_read will be
protected in the following patch, because are used also outside
coroutines.
Also set block_copy_task_create as coroutine_fn because:
1) it is static and only invoked by coroutine functions
2) this patch introduces and uses a CoMutex lock there
Signed-off-by: Emanuele Giuseppe Esposito <eespo...@redhat.com>
---
block/block-copy.c | 79 +++++++++++++++++++++++++++++---------
include/block/block-copy.h | 2 +
2 files changed, 62 insertions(+), 19 deletions(-)
diff --git a/block/block-copy.c b/block/block-copy.c
index afa2f484f0..6416929abd 100644
--- a/block/block-copy.c
+++ b/block/block-copy.c
@@ -61,6 +61,7 @@ typedef struct BlockCopyCallState {
/* OUT parameters */
bool cancelled;
+ /* Fields protected by lock in BlockCopyState */
bool error_is_read;
int ret;
} BlockCopyCallState;
@@ -77,8 +78,12 @@ typedef struct BlockCopyTask {
int64_t offset;
BlockCopyMethod method;
- /* State */
+ /* State. Protected by lock in BlockCopyState */
CoQueue wait_queue; /* coroutines blocked on this task */
+ /*
+ * Only protect the case of parallel read while updating @bytes
+ * value in block_copy_task_shrink().
+ */
So, you have to add new comments and modify comment added in previous commit.
That's another sign to just merge patch 03 here.
int64_t bytes;
QLIST_ENTRY(BlockCopyTask) list;
} BlockCopyTask;
@@ -97,7 +102,8 @@ typedef struct BlockCopyState {
BdrvChild *source;
BdrvChild *target;
- /* State */
+ /* State. Protected by lock */
+ CoMutex lock;
int64_t in_flight_bytes;
BlockCopyMethod method;
QLIST_HEAD(, BlockCopyTask) tasks; /* All tasks from all block-copy calls
*/
@@ -137,6 +143,7 @@ typedef struct BlockCopyState {
bool skip_unallocated;
} BlockCopyState;
+/* Called with lock held */
static BlockCopyTask *find_conflicting_task(BlockCopyState *s,
int64_t offset, int64_t bytes)
{
@@ -154,6 +161,8 @@ static BlockCopyTask *find_conflicting_task(BlockCopyState
*s,
/*
* If there are no intersecting tasks return false. Otherwise, wait for the
* first found intersecting tasks to finish and return true.
+ *
+ * Called with lock held.
Please:
Called with lock held, may temporary release the lock. Return value of 0 proves
that lock was NOT released.
*/
static bool coroutine_fn block_copy_wait_one(BlockCopyState *s, int64_t
offset,
int64_t bytes)
@@ -164,7 +173,7 @@ static bool coroutine_fn block_copy_wait_one(BlockCopyState
*s, int64_t offset,
return false;
}
- qemu_co_queue_wait(&task->wait_queue, NULL);
+ qemu_co_queue_wait(&task->wait_queue, &s->lock);
return true;
}
@@ -191,14 +200,15 @@ static int64_t block_copy_chunk_size(BlockCopyState *s)
Hmm, you had /* Called with lock held */ comment for block_copy_chunk_size() in
a previous version.. Why dropped?
* 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)
+static coroutine_fn BlockCopyTask *block_copy_task_create(BlockCopyState *s,
+ BlockCopyCallState *call_state,
+ int64_t offset, int64_t bytes)
That breaks Qemu coding style (docs/devel/style.rst "Multiline Indent")
Function "type" becomes too long. Common practice is keep a type on a separate
line:
static coroutine_fn BlockCopyTask *
block_copy_task_create(BlockCopyState *s, BlockCopyCallState *call_state,
int64_t offset, int64_t bytes)
(and this is used in the file in one place, so it would be consistent do same
thing here)
Another way is 4-spaces indent:
static coroutine_fn BlockCopyTask *block_copy_task_create(BlockCopyState *s,
BlockCopyCallState *call_state, int64_t offset, int64_t bytes)
choose what you want.
{
BlockCopyTask *task;
- int64_t max_chunk = block_copy_chunk_size(s);
+ int64_t max_chunk;
- max_chunk = MIN_NON_ZERO(max_chunk, call_state->max_chunk);
+ QEMU_LOCK_GUARD(&s->lock);
+ max_chunk = MIN_NON_ZERO(block_copy_chunk_size(s), call_state->max_chunk);
if (!bdrv_dirty_bitmap_next_dirty_area(s->copy_bitmap,
offset, offset + bytes,
max_chunk, &offset, &bytes))
@@ -240,6 +250,7 @@ static BlockCopyTask *block_copy_task_create(BlockCopyState
*s,
static void coroutine_fn block_copy_task_shrink(BlockCopyTask *task,
int64_t new_bytes)
{
+ QEMU_LOCK_GUARD(&task->s->lock);
if (new_bytes == task->bytes) {
return;
}
@@ -256,6 +267,7 @@ static void coroutine_fn
block_copy_task_shrink(BlockCopyTask *task,
static void coroutine_fn block_copy_task_end(BlockCopyTask *task, int ret)
{
+ QEMU_LOCK_GUARD(&task->s->lock);
task->s->in_flight_bytes -= task->bytes;
if (ret < 0) {
bdrv_set_dirty_bitmap(task->s->copy_bitmap, task->offset,
task->bytes);
@@ -334,12 +346,14 @@ BlockCopyState *block_copy_state_new(BdrvChild *source,
BdrvChild *target,
}
ratelimit_init(&s->rate_limit);
+ qemu_co_mutex_init(&s->lock);
QLIST_INIT(&s->tasks);
QLIST_INIT(&s->calls);
return s;
}
+/* Only set before running the job, so it is thread safe to call. */
It's not thread-safe to call, it's just not used so that we don't have to care
abot thread-safety.. So, maybe:
Only set before running the job, no need for locking.
void block_copy_set_progress_meter(BlockCopyState *s, ProgressMeter *pm)
{
s->progress = pm;
@@ -480,16 +494,20 @@ static coroutine_fn int block_copy_task_entry(AioTask
*task)
int ret;
ret = block_copy_do_copy(s, t->offset, t->bytes, &method, &error_is_read);
- if (s->method == t->method) {
- s->method = method;
- }
- if (ret < 0) {
- if (!t->call_state->ret) {
- t->call_state->ret = ret;
- t->call_state->error_is_read = error_is_read;
+
+ WITH_QEMU_LOCK_GUARD(&s->lock) {
+ if (s->method == t->method) {
+ s->method = method;
+ }
+
+ if (ret < 0) {
+ if (!t->call_state->ret) {
+ t->call_state->ret = ret;
+ t->call_state->error_is_read = error_is_read;
+ }
+ } else {
+ progress_work_done(s->progress, t->bytes);
}
- } else {
- progress_work_done(s->progress, t->bytes);
}
co_put_to_shres(s->mem, t->bytes);
block_copy_task_end(t, ret);
@@ -591,10 +609,12 @@ int64_t block_copy_reset_unallocated(BlockCopyState *s,
bytes = clusters * s->cluster_size;
if (!ret) {
+ qemu_co_mutex_lock(&s->lock);
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);
+ qemu_co_mutex_unlock(&s->lock);
}
*count = bytes;
@@ -734,14 +754,33 @@ static int coroutine_fn
block_copy_common(BlockCopyCallState *call_state)
int ret;
BlockCopyState *s = call_state->s;
+ qemu_co_mutex_lock(&s->lock);
QLIST_INSERT_HEAD(&s->calls, call_state, list);
+ qemu_co_mutex_unlock(&s->lock);
do {
ret = block_copy_dirty_clusters(call_state);
if (ret == 0 && !call_state->cancelled) {
- ret = block_copy_wait_one(s, call_state->offset,
- call_state->bytes);
+ WITH_QEMU_LOCK_GUARD(&s->lock) {
+ /*
+ * Check that there is no task we still need to
+ * wait to complete
+ */
+ ret = block_copy_wait_one(s, call_state->offset,
+ call_state->bytes);
+ if (ret == 0) {
+ /*
Please add: block_copy_wait_one return value 0 also means that it didn't relase
the lock. So, we are still in the same critical section, not interrupted by any
concurrent access to state.
(actually, I started to write a comment that critical section is broken here,
but understood that all is OK)
+ * No pending tasks, but check again the bitmap in this
+ * same critical section, since a task might have failed
+ * between this and the critical section in
+ * block_copy_dirty_clusters().
+ */
+ ret = bdrv_dirty_bitmap_next_dirty(s->copy_bitmap,
+ call_state->offset,
+ call_state->bytes) > 0;
It should be s/> 0/>= 0/. bdrv_dirty_bitmap_next_dirty() returns -1 if not
found. And 0 is valid offset.
+ }
+ }
}
k>
/*
@@ -761,7 +800,9 @@ static int coroutine_fn
block_copy_common(BlockCopyCallState *call_state)
call_state->cb(call_state->cb_opaque);
}
+ qemu_co_mutex_lock(&s->lock);
QLIST_REMOVE(call_state, list);
+ qemu_co_mutex_unlock(&s->lock);
return ret;
}
diff --git a/include/block/block-copy.h b/include/block/block-copy.h
index 338f2ea7fd..bf8f0c679f 100644
--- a/include/block/block-copy.h
+++ b/include/block/block-copy.h
Please, add
[diff]
orderFile = /path/to/qemu/scripts/git.orderfile
to your .git/config file, for good ordering of files inside a patch. For
example, headers would be at the top of the patch.
@@ -18,6 +18,8 @@
#include "block/block.h"
#include "qemu/co-shared-resource.h"
+/* All APIs are thread-safe*/
To be honest, you can add this comment only in the following commit.
Also, whitespace missed.
+
typedef void (*BlockCopyAsyncCallbackFunc)(void *opaque);
typedef struct BlockCopyState BlockCopyState;
typedef struct BlockCopyCallState BlockCopyCallState;
Overall, looks close :)
--
Best regards,
Vladimir