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>
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7719f3c968
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33f2a75777
2
block.c
2
block.c
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@ -4713,7 +4713,7 @@ out:
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AioContext *bdrv_get_aio_context(BlockDriverState *bs)
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AioContext *bdrv_get_aio_context(BlockDriverState *bs)
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{
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{
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return bs->aio_context;
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return bs ? bs->aio_context : qemu_get_aio_context();
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}
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}
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AioWait *bdrv_get_aio_wait(BlockDriverState *bs)
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AioWait *bdrv_get_aio_wait(BlockDriverState *bs)
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@ -73,6 +73,14 @@ struct BlockBackend {
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int quiesce_counter;
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int quiesce_counter;
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VMChangeStateEntry *vmsh;
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VMChangeStateEntry *vmsh;
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bool force_allow_inactivate;
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bool force_allow_inactivate;
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/* Number of in-flight aio requests. BlockDriverState also counts
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* in-flight requests but aio requests can exist even when blk->root is
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* NULL, so we cannot rely on its counter for that case.
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* Accessed with atomic ops.
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*/
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unsigned int in_flight;
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AioWait wait;
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};
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};
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typedef struct BlockBackendAIOCB {
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typedef struct BlockBackendAIOCB {
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@ -1225,11 +1233,22 @@ int blk_make_zero(BlockBackend *blk, BdrvRequestFlags flags)
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return bdrv_make_zero(blk->root, flags);
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return bdrv_make_zero(blk->root, flags);
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}
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}
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static void blk_inc_in_flight(BlockBackend *blk)
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{
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atomic_inc(&blk->in_flight);
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}
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static void blk_dec_in_flight(BlockBackend *blk)
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{
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atomic_dec(&blk->in_flight);
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aio_wait_kick(&blk->wait);
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}
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static void error_callback_bh(void *opaque)
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static void error_callback_bh(void *opaque)
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{
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{
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struct BlockBackendAIOCB *acb = opaque;
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struct BlockBackendAIOCB *acb = opaque;
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bdrv_dec_in_flight(acb->common.bs);
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blk_dec_in_flight(acb->blk);
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acb->common.cb(acb->common.opaque, acb->ret);
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acb->common.cb(acb->common.opaque, acb->ret);
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qemu_aio_unref(acb);
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qemu_aio_unref(acb);
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}
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}
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@ -1240,7 +1259,7 @@ BlockAIOCB *blk_abort_aio_request(BlockBackend *blk,
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{
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{
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struct BlockBackendAIOCB *acb;
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struct BlockBackendAIOCB *acb;
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bdrv_inc_in_flight(blk_bs(blk));
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blk_inc_in_flight(blk);
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acb = blk_aio_get(&block_backend_aiocb_info, blk, cb, opaque);
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acb = blk_aio_get(&block_backend_aiocb_info, blk, cb, opaque);
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acb->blk = blk;
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acb->blk = blk;
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acb->ret = ret;
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acb->ret = ret;
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@ -1263,7 +1282,7 @@ static const AIOCBInfo blk_aio_em_aiocb_info = {
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static void blk_aio_complete(BlkAioEmAIOCB *acb)
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static void blk_aio_complete(BlkAioEmAIOCB *acb)
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{
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{
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if (acb->has_returned) {
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if (acb->has_returned) {
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bdrv_dec_in_flight(acb->common.bs);
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blk_dec_in_flight(acb->rwco.blk);
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acb->common.cb(acb->common.opaque, acb->rwco.ret);
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acb->common.cb(acb->common.opaque, acb->rwco.ret);
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qemu_aio_unref(acb);
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qemu_aio_unref(acb);
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}
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}
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@ -1284,7 +1303,7 @@ static BlockAIOCB *blk_aio_prwv(BlockBackend *blk, int64_t offset, int bytes,
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BlkAioEmAIOCB *acb;
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BlkAioEmAIOCB *acb;
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Coroutine *co;
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Coroutine *co;
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bdrv_inc_in_flight(blk_bs(blk));
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blk_inc_in_flight(blk);
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acb = blk_aio_get(&blk_aio_em_aiocb_info, blk, cb, opaque);
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acb = blk_aio_get(&blk_aio_em_aiocb_info, blk, cb, opaque);
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acb->rwco = (BlkRwCo) {
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acb->rwco = (BlkRwCo) {
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.blk = blk,
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.blk = blk,
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@ -1521,14 +1540,41 @@ int blk_flush(BlockBackend *blk)
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void blk_drain(BlockBackend *blk)
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void blk_drain(BlockBackend *blk)
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{
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{
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if (blk_bs(blk)) {
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BlockDriverState *bs = blk_bs(blk);
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bdrv_drain(blk_bs(blk));
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if (bs) {
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bdrv_drained_begin(bs);
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}
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/* We may have -ENOMEDIUM completions in flight */
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AIO_WAIT_WHILE(&blk->wait,
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blk_get_aio_context(blk),
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atomic_mb_read(&blk->in_flight) > 0);
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if (bs) {
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bdrv_drained_end(bs);
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}
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}
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}
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}
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void blk_drain_all(void)
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void blk_drain_all(void)
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{
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{
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bdrv_drain_all();
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BlockBackend *blk = NULL;
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bdrv_drain_all_begin();
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while ((blk = blk_all_next(blk)) != NULL) {
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AioContext *ctx = blk_get_aio_context(blk);
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aio_context_acquire(ctx);
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/* We may have -ENOMEDIUM completions in flight */
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AIO_WAIT_WHILE(&blk->wait, ctx,
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atomic_mb_read(&blk->in_flight) > 0);
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aio_context_release(ctx);
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}
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bdrv_drain_all_end();
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}
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}
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void blk_set_on_error(BlockBackend *blk, BlockdevOnError on_read_error,
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void blk_set_on_error(BlockBackend *blk, BlockdevOnError on_read_error,
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