@@ -104,6 +104,7 @@ void blk_get_perm(BlockBackend *blk, uint64_t *perm, uint64_t *shared_perm);
void blk_set_allow_write_beyond_eof(BlockBackend *blk, bool allow);
void blk_set_allow_aio_context_change(BlockBackend *blk, bool allow);
+void blk_set_disable_request_queuing(BlockBackend *blk, bool disable);
void blk_iostatus_enable(BlockBackend *blk);
bool blk_iostatus_is_enabled(const BlockBackend *blk);
BlockDeviceIoStatus blk_iostatus(const BlockBackend *blk);
@@ -644,6 +644,7 @@ BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs,
if (ret < 0) {
goto error;
}
+ blk_set_disable_request_queuing(job->target, true);
job->on_source_error = on_source_error;
job->on_target_error = on_target_error;
@@ -79,6 +79,9 @@ struct BlockBackend {
QLIST_HEAD(, BlockBackendAioNotifier) aio_notifiers;
int quiesce_counter;
+ CoQueue queued_requests;
+ bool disable_request_queuing;
+
VMChangeStateEntry *vmsh;
bool force_allow_inactivate;
@@ -339,6 +342,7 @@ BlockBackend *blk_new(AioContext *ctx, uint64_t perm, uint64_t shared_perm)
block_acct_init(&blk->stats);
+ qemu_co_queue_init(&blk->queued_requests);
notifier_list_init(&blk->remove_bs_notifiers);
notifier_list_init(&blk->insert_bs_notifiers);
QLIST_INIT(&blk->aio_notifiers);
@@ -1096,6 +1100,11 @@ void blk_set_allow_aio_context_change(BlockBackend *blk, bool allow)
blk->allow_aio_context_change = allow;
}
+void blk_set_disable_request_queuing(BlockBackend *blk, bool disable)
+{
+ blk->disable_request_queuing = disable;
+}
+
static int blk_check_byte_request(BlockBackend *blk, int64_t offset,
size_t size)
{
@@ -1127,13 +1136,24 @@ static int blk_check_byte_request(BlockBackend *blk, int64_t offset,
return 0;
}
+static void coroutine_fn blk_wait_while_drained(BlockBackend *blk)
+{
+ if (blk->quiesce_counter && !blk->disable_request_queuing) {
+ qemu_co_queue_wait(&blk->queued_requests, NULL);
+ }
+}
+
int coroutine_fn blk_co_preadv(BlockBackend *blk, int64_t offset,
unsigned int bytes, QEMUIOVector *qiov,
BdrvRequestFlags flags)
{
int ret;
- BlockDriverState *bs = blk_bs(blk);
+ BlockDriverState *bs;
+ blk_wait_while_drained(blk);
+
+ /* Call blk_bs() only after waiting, the graph may have changed */
+ bs = blk_bs(blk);
trace_blk_co_preadv(blk, bs, offset, bytes, flags);
ret = blk_check_byte_request(blk, offset, bytes);
@@ -1159,8 +1179,12 @@ int coroutine_fn blk_co_pwritev(BlockBackend *blk, int64_t offset,
BdrvRequestFlags flags)
{
int ret;
- BlockDriverState *bs = blk_bs(blk);
+ BlockDriverState *bs;
+ blk_wait_while_drained(blk);
+
+ /* Call blk_bs() only after waiting, the graph may have changed */
+ bs = blk_bs(blk);
trace_blk_co_pwritev(blk, bs, offset, bytes, flags);
ret = blk_check_byte_request(blk, offset, bytes);
@@ -1349,6 +1373,12 @@ static void blk_aio_read_entry(void *opaque)
BlkRwCo *rwco = &acb->rwco;
QEMUIOVector *qiov = rwco->iobuf;
+ if (rwco->blk->quiesce_counter) {
+ blk_dec_in_flight(rwco->blk);
+ blk_wait_while_drained(rwco->blk);
+ blk_inc_in_flight(rwco->blk);
+ }
+
assert(qiov->size == acb->bytes);
rwco->ret = blk_co_preadv(rwco->blk, rwco->offset, acb->bytes,
qiov, rwco->flags);
@@ -1361,6 +1391,12 @@ static void blk_aio_write_entry(void *opaque)
BlkRwCo *rwco = &acb->rwco;
QEMUIOVector *qiov = rwco->iobuf;
+ if (rwco->blk->quiesce_counter) {
+ blk_dec_in_flight(rwco->blk);
+ blk_wait_while_drained(rwco->blk);
+ blk_inc_in_flight(rwco->blk);
+ }
+
assert(!qiov || qiov->size == acb->bytes);
rwco->ret = blk_co_pwritev(rwco->blk, rwco->offset, acb->bytes,
qiov, rwco->flags);
@@ -1482,6 +1518,8 @@ void blk_aio_cancel_async(BlockAIOCB *acb)
int blk_co_ioctl(BlockBackend *blk, unsigned long int req, void *buf)
{
+ blk_wait_while_drained(blk);
+
if (!blk_is_available(blk)) {
return -ENOMEDIUM;
}
@@ -1522,7 +1560,11 @@ BlockAIOCB *blk_aio_ioctl(BlockBackend *blk, unsigned long int req, void *buf,
int blk_co_pdiscard(BlockBackend *blk, int64_t offset, int bytes)
{
- int ret = blk_check_byte_request(blk, offset, bytes);
+ int ret;
+
+ blk_wait_while_drained(blk);
+
+ ret = blk_check_byte_request(blk, offset, bytes);
if (ret < 0) {
return ret;
}
@@ -1532,6 +1574,8 @@ int blk_co_pdiscard(BlockBackend *blk, int64_t offset, int bytes)
int blk_co_flush(BlockBackend *blk)
{
+ blk_wait_while_drained(blk);
+
if (!blk_is_available(blk)) {
return -ENOMEDIUM;
}
@@ -2232,6 +2276,9 @@ static void blk_root_drained_end(BdrvChild *child, int *drained_end_counter)
if (blk->dev_ops && blk->dev_ops->drained_end) {
blk->dev_ops->drained_end(blk->dev_opaque);
}
+ while (qemu_co_enter_next(&blk->queued_requests, NULL)) {
+ /* Resume all queued requests */
+ }
}
}
@@ -350,6 +350,7 @@ void commit_start(const char *job_id, BlockDriverState *bs,
if (ret < 0) {
goto fail;
}
+ blk_set_disable_request_queuing(s->base, true);
s->base_bs = base;
/* Required permissions are already taken with block_job_add_bdrv() */
@@ -358,6 +359,7 @@ void commit_start(const char *job_id, BlockDriverState *bs,
if (ret < 0) {
goto fail;
}
+ blk_set_disable_request_queuing(s->top, true);
s->backing_file_str = g_strdup(backing_file_str);
s->on_error = on_error;
@@ -1636,6 +1636,7 @@ static BlockJob *mirror_start_job(
blk_set_force_allow_inactivate(s->target);
}
blk_set_allow_aio_context_change(s->target, true);
+ blk_set_disable_request_queuing(s->target, true);
s->replaces = g_strdup(replaces);
s->on_source_error = on_source_error;
@@ -445,6 +445,9 @@ void *block_job_create(const char *job_id, const BlockJobDriver *driver,
bdrv_op_unblock(bs, BLOCK_OP_TYPE_DATAPLANE, job->blocker);
+ /* Disable request queuing in the BlockBackend to avoid deadlocks on drain:
+ * The job reports that it's busy until it reaches a pause point. */
+ blk_set_disable_request_queuing(blk, true);
blk_set_allow_aio_context_change(blk, true);
/* Only set speed when necessary to avoid NotSupported error */
@@ -686,6 +686,7 @@ static void test_iothread_common(enum drain_type drain_type, int drain_thread)
&error_abort);
s = bs->opaque;
blk_insert_bs(blk, bs, &error_abort);
+ blk_set_disable_request_queuing(blk, true);
blk_set_aio_context(blk, ctx_a, &error_abort);
aio_context_acquire(ctx_a);
This fixes devices like IDE that can still start new requests from I/O handlers in the CPU thread while the block backend is drained. The basic assumption is that in a drain section, no new requests should be allowed through a BlockBackend (blk_drained_begin/end don't exist, we get drain sections only on the node level). However, there are two special cases where requests should not be queued: 1. Block jobs: We already make sure that block jobs are paused in a drain section, so they won't start new requests. However, if the drain_begin is called on the job's BlockBackend first, it can happen that we deadlock because the job stays busy until it reaches a pause point - which it can't if its requests aren't processed any more. The proper solution here would be to make all requests through the job's filter node instead of using a BlockBackend. For now, just disabling request queuing on the job BlockBackend is simpler. 2. In test cases where making requests through bdrv_* would be cumbersome because we'd need a BdrvChild. As we already got the functionality to disable request queuing from 1., use it in tests, too, for convenience. Signed-off-by: Kevin Wolf <kwolf@redhat.com> --- include/sysemu/block-backend.h | 1 + block/backup.c | 1 + block/block-backend.c | 53 ++++++++++++++++++++++++++++++++-- block/commit.c | 2 ++ block/mirror.c | 1 + blockjob.c | 3 ++ tests/test-bdrv-drain.c | 1 + 7 files changed, 59 insertions(+), 3 deletions(-)