aboutsummaryrefslogtreecommitdiff
path: root/block
diff options
context:
space:
mode:
authorStefan Hajnoczi <stefanha@redhat.com>2018-02-16 16:50:13 +0000
committerKevin Wolf <kwolf@redhat.com>2018-03-02 18:39:07 +0100
commit33f2a7577787910bda161f428c904ac6a14b2454 (patch)
treedb049b4cacc288b6f3c5b7314baac4ea0ab25ffe /block
parent7719f3c968c59e1bcda7e177679dc765b59e578f (diff)
block: add BlockBackend->in_flight counter
BlockBackend currently relies on BlockDriverState->in_flight to track requests for blk_drain(). There is a corner case where BlockDriverState->in_flight cannot be used though: blk->root can be NULL when there is no medium. This results in a segfault when the NULL pointer is dereferenced. Introduce a BlockBackend->in_flight counter for aio requests so it works even when blk->root == NULL. Based on a patch by Kevin Wolf <kwolf@redhat.com>. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Diffstat (limited to 'block')
-rw-r--r--block/block-backend.c60
1 files changed, 53 insertions, 7 deletions
diff --git a/block/block-backend.c b/block/block-backend.c
index 0266ac990b..a775a3dd2f 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -73,6 +73,14 @@ struct BlockBackend {
int quiesce_counter;
VMChangeStateEntry *vmsh;
bool force_allow_inactivate;
+
+ /* Number of in-flight aio requests. BlockDriverState also counts
+ * in-flight requests but aio requests can exist even when blk->root is
+ * NULL, so we cannot rely on its counter for that case.
+ * Accessed with atomic ops.
+ */
+ unsigned int in_flight;
+ AioWait wait;
};
typedef struct BlockBackendAIOCB {
@@ -1225,11 +1233,22 @@ int blk_make_zero(BlockBackend *blk, BdrvRequestFlags flags)
return bdrv_make_zero(blk->root, flags);
}
+static void blk_inc_in_flight(BlockBackend *blk)
+{
+ atomic_inc(&blk->in_flight);
+}
+
+static void blk_dec_in_flight(BlockBackend *blk)
+{
+ atomic_dec(&blk->in_flight);
+ aio_wait_kick(&blk->wait);
+}
+
static void error_callback_bh(void *opaque)
{
struct BlockBackendAIOCB *acb = opaque;
- bdrv_dec_in_flight(acb->common.bs);
+ blk_dec_in_flight(acb->blk);
acb->common.cb(acb->common.opaque, acb->ret);
qemu_aio_unref(acb);
}
@@ -1240,7 +1259,7 @@ BlockAIOCB *blk_abort_aio_request(BlockBackend *blk,
{
struct BlockBackendAIOCB *acb;
- bdrv_inc_in_flight(blk_bs(blk));
+ blk_inc_in_flight(blk);
acb = blk_aio_get(&block_backend_aiocb_info, blk, cb, opaque);
acb->blk = blk;
acb->ret = ret;
@@ -1263,7 +1282,7 @@ static const AIOCBInfo blk_aio_em_aiocb_info = {
static void blk_aio_complete(BlkAioEmAIOCB *acb)
{
if (acb->has_returned) {
- bdrv_dec_in_flight(acb->common.bs);
+ blk_dec_in_flight(acb->rwco.blk);
acb->common.cb(acb->common.opaque, acb->rwco.ret);
qemu_aio_unref(acb);
}
@@ -1284,7 +1303,7 @@ static BlockAIOCB *blk_aio_prwv(BlockBackend *blk, int64_t offset, int bytes,
BlkAioEmAIOCB *acb;
Coroutine *co;
- bdrv_inc_in_flight(blk_bs(blk));
+ blk_inc_in_flight(blk);
acb = blk_aio_get(&blk_aio_em_aiocb_info, blk, cb, opaque);
acb->rwco = (BlkRwCo) {
.blk = blk,
@@ -1521,14 +1540,41 @@ int blk_flush(BlockBackend *blk)
void blk_drain(BlockBackend *blk)
{
- if (blk_bs(blk)) {
- bdrv_drain(blk_bs(blk));
+ BlockDriverState *bs = blk_bs(blk);
+
+ if (bs) {
+ bdrv_drained_begin(bs);
+ }
+
+ /* We may have -ENOMEDIUM completions in flight */
+ AIO_WAIT_WHILE(&blk->wait,
+ blk_get_aio_context(blk),
+ atomic_mb_read(&blk->in_flight) > 0);
+
+ if (bs) {
+ bdrv_drained_end(bs);
}
}
void blk_drain_all(void)
{
- bdrv_drain_all();
+ BlockBackend *blk = NULL;
+
+ bdrv_drain_all_begin();
+
+ while ((blk = blk_all_next(blk)) != NULL) {
+ AioContext *ctx = blk_get_aio_context(blk);
+
+ aio_context_acquire(ctx);
+
+ /* We may have -ENOMEDIUM completions in flight */
+ AIO_WAIT_WHILE(&blk->wait, ctx,
+ atomic_mb_read(&blk->in_flight) > 0);
+
+ aio_context_release(ctx);
+ }
+
+ bdrv_drain_all_end();
}
void blk_set_on_error(BlockBackend *blk, BlockdevOnError on_read_error,