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blockjobs: add state transition table

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The state transition table has mostly been implied. We're about to make
it a bit more complex, so let's make the STM explicit instead.

Perform state transitions with a function that for now just asserts the
transition is appropriate.

Transitions:
Undefined -> Created: During job initialization.
Created   -> Running: Once the job is started.
                      Jobs cannot transition from "Created" to "Paused"
                      directly, but will instead synchronously transition
                      to running to paused immediately.
Running   -> Paused:  Normal workflow for pauses.
Running   -> Ready:   Normal workflow for jobs reaching their sync point.
                      (e.g. mirror)
Ready     -> Standby: Normal workflow for pausing ready jobs.
Paused    -> Running: Normal resume.
Standby   -> Ready:   Resume of a Standby job.

+---------+
|UNDEFINED|
+--+------+
   |
+--v----+
|CREATED|
+--+----+
   |
+--v----+     +------+
|RUNNING<----->PAUSED|
+--+----+     +------+
   |
+--v--+       +-------+
|READY<------->STANDBY|
+-----+       +-------+

Notably, there is no state presently defined as of this commit that
deals with a job after the "running" or "ready" states, so this table
will be adjusted alongside the commits that introduce those states.

Signed-off-by: John Snow <jsnow@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
John Snow 2018-03-10 03:27:30 -05:00 committed by Kevin Wolf
parent 58b295ba52
commit c9de40505f
2 changed files with 36 additions and 7 deletions
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3
block/trace-events
View File

@ -4,6 +4,9 @@
bdrv_open_common(void *bs, const char *filename, int flags, const char *format_name) "bs %p filename \"%s\" flags 0x%x format_name \"%s\""
bdrv_lock_medium(void *bs, bool locked) "bs %p locked %d"
# blockjob.c
block_job_state_transition(void *job, int ret, const char *legal, const char *s0, const char *s1) "job %p (ret: %d) attempting %s transition (%s-->%s)"
# block/block-backend.c
blk_co_preadv(void *blk, void *bs, int64_t offset, unsigned int bytes, int flags) "blk %p bs %p offset %"PRId64" bytes %u flags 0x%x"
blk_co_pwritev(void *blk, void *bs, int64_t offset, unsigned int bytes, int flags) "blk %p bs %p offset %"PRId64" bytes %u flags 0x%x"

40
blockjob.c
View File

@ -28,6 +28,7 @@
#include "block/block.h"
#include "block/blockjob_int.h"
#include "block/block_int.h"
#include "block/trace.h"
#include "sysemu/block-backend.h"
#include "qapi/error.h"
#include "qapi/qapi-events-block-core.h"
@ -41,6 +42,31 @@
* block_job_enter. */
static QemuMutex block_job_mutex;
/* BlockJob State Transition Table */
bool BlockJobSTT[BLOCK_JOB_STATUS__MAX][BLOCK_JOB_STATUS__MAX] = {
/* U, C, R, P, Y, S */
/* U: */ [BLOCK_JOB_STATUS_UNDEFINED] = {0, 1, 0, 0, 0, 0},
/* C: */ [BLOCK_JOB_STATUS_CREATED] = {0, 0, 1, 0, 0, 0},
/* R: */ [BLOCK_JOB_STATUS_RUNNING] = {0, 0, 0, 1, 1, 0},
/* P: */ [BLOCK_JOB_STATUS_PAUSED] = {0, 0, 1, 0, 0, 0},
/* Y: */ [BLOCK_JOB_STATUS_READY] = {0, 0, 0, 0, 0, 1},
/* S: */ [BLOCK_JOB_STATUS_STANDBY] = {0, 0, 0, 0, 1, 0},
};
static void block_job_state_transition(BlockJob *job, BlockJobStatus s1)
{
BlockJobStatus s0 = job->status;
assert(s1 >= 0 && s1 <= BLOCK_JOB_STATUS__MAX);
trace_block_job_state_transition(job, job->ret, BlockJobSTT[s0][s1] ?
"allowed" : "disallowed",
qapi_enum_lookup(&BlockJobStatus_lookup,
s0),
qapi_enum_lookup(&BlockJobStatus_lookup,
s1));
assert(BlockJobSTT[s0][s1]);
job->status = s1;
}
static void block_job_lock(void)
{
qemu_mutex_lock(&block_job_mutex);
@ -320,7 +346,7 @@ void block_job_start(BlockJob *job)
job->pause_count--;
job->busy = true;
job->paused = false;
job->status = BLOCK_JOB_STATUS_RUNNING;
block_job_state_transition(job, BLOCK_JOB_STATUS_RUNNING);
bdrv_coroutine_enter(blk_bs(job->blk), job->co);
}
@ -702,7 +728,7 @@ void *block_job_create(const char *job_id, const BlockJobDriver *driver,
job->paused = true;
job->pause_count = 1;
job->refcnt = 1;
job->status = BLOCK_JOB_STATUS_CREATED;
block_job_state_transition(job, BLOCK_JOB_STATUS_CREATED);
aio_timer_init(qemu_get_aio_context(), &job->sleep_timer,
QEMU_CLOCK_REALTIME, SCALE_NS,
block_job_sleep_timer_cb, job);
@ -817,13 +843,13 @@ void coroutine_fn block_job_pause_point(BlockJob *job)
if (block_job_should_pause(job) && !block_job_is_cancelled(job)) {
BlockJobStatus status = job->status;
job->status = status == BLOCK_JOB_STATUS_READY ? \
BLOCK_JOB_STATUS_STANDBY : \
BLOCK_JOB_STATUS_PAUSED;
block_job_state_transition(job, status == BLOCK_JOB_STATUS_READY ? \
BLOCK_JOB_STATUS_STANDBY : \
BLOCK_JOB_STATUS_PAUSED);
job->paused = true;
block_job_do_yield(job, -1);
job->paused = false;
job->status = status;
block_job_state_transition(job, status);
}
if (job->driver->resume) {
@ -929,7 +955,7 @@ void block_job_iostatus_reset(BlockJob *job)
void block_job_event_ready(BlockJob *job)
{
job->status = BLOCK_JOB_STATUS_READY;
block_job_state_transition(job, BLOCK_JOB_STATUS_READY);
job->ready = true;
if (block_job_is_internal(job)) {