From e92f0e1910f0655a0edd8d87c5a7262d36517a89 Mon Sep 17 00:00:00 2001 From: Fam Zheng Date: Mon, 10 Apr 2017 20:20:17 +0800 Subject: block: Use bdrv_coroutine_enter to start I/O coroutines BDRV_POLL_WHILE waits for the started I/O by releasing bs's ctx then polling the main context, which relies on the yielded coroutine continuing on bs->ctx before notifying qemu_aio_context with bdrv_wakeup(). Thus, using qemu_coroutine_enter to start I/O is wrong because if the coroutine is entered from main loop, co->ctx will be qemu_aio_context, as a result of the "release, poll, acquire" loop of BDRV_POLL_WHILE, race conditions happen when both main thread and the iothread access the same BDS: main loop iothread ----------------------------------------------------------------------- blockdev_snapshot aio_context_acquire(bs->ctx) virtio_scsi_data_plane_handle_cmd bdrv_drained_begin(bs->ctx) bdrv_flush(bs) bdrv_co_flush(bs) aio_context_acquire(bs->ctx).enter ... qemu_coroutine_yield(co) BDRV_POLL_WHILE() aio_context_release(bs->ctx) aio_context_acquire(bs->ctx).return ... aio_co_wake(co) aio_poll(qemu_aio_context) ... co_schedule_bh_cb() ... qemu_coroutine_enter(co) ... /* (A) bdrv_co_flush(bs) /* (B) I/O on bs */ continues... */ aio_context_release(bs->ctx) aio_context_acquire(bs->ctx) Note that in above case, bdrv_drained_begin() doesn't do the "release, poll, acquire" in BDRV_POLL_WHILE, because bs->in_flight == 0. Fix this by using bdrv_coroutine_enter and enter coroutine in the right context. iotests 109 output is updated because the coroutine reenter flow during mirror job complete is different (now through co_queue_wakeup, instead of the unconditional qemu_coroutine_switch before), making the end job len different. Signed-off-by: Fam Zheng Acked-by: Stefan Hajnoczi Reviewed-by: Kevin Wolf --- tests/qemu-iotests/109.out | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) (limited to 'tests') diff --git a/tests/qemu-iotests/109.out b/tests/qemu-iotests/109.out index e5d70d75f1..55fe536d56 100644 --- a/tests/qemu-iotests/109.out +++ b/tests/qemu-iotests/109.out @@ -10,7 +10,7 @@ Automatically detecting the format is dangerous for raw images, write operations Specify the 'raw' format explicitly to remove the restrictions. {"return": {}} {"timestamp": {"seconds": TIMESTAMP, "microseconds": TIMESTAMP}, "event": "BLOCK_JOB_ERROR", "data": {"device": "src", "operation": "write", "action": "report"}} -{"timestamp": {"seconds": TIMESTAMP, "microseconds": TIMESTAMP}, "event": "BLOCK_JOB_COMPLETED", "data": {"device": "src", "len": 1024, "offset": 0, "speed": 0, "type": "mirror", "error": "Operation not permitted"}} +{"timestamp": {"seconds": TIMESTAMP, "microseconds": TIMESTAMP}, "event": "BLOCK_JOB_COMPLETED", "data": {"device": "src", "len": 65536, "offset": 0, "speed": 0, "type": "mirror", "error": "Operation not permitted"}} {"return": []} read 65536/65536 bytes at offset 0 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec) @@ -73,7 +73,7 @@ Automatically detecting the format is dangerous for raw images, write operations Specify the 'raw' format explicitly to remove the restrictions. {"return": {}} {"timestamp": {"seconds": TIMESTAMP, "microseconds": TIMESTAMP}, "event": "BLOCK_JOB_ERROR", "data": {"device": "src", "operation": "write", "action": "report"}} -{"timestamp": {"seconds": TIMESTAMP, "microseconds": TIMESTAMP}, "event": "BLOCK_JOB_COMPLETED", "data": {"device": "src", "len": 1024, "offset": 0, "speed": 0, "type": "mirror", "error": "Operation not permitted"}} +{"timestamp": {"seconds": TIMESTAMP, "microseconds": TIMESTAMP}, "event": "BLOCK_JOB_COMPLETED", "data": {"device": "src", "len": 65536, "offset": 0, "speed": 0, "type": "mirror", "error": "Operation not permitted"}} {"return": []} read 65536/65536 bytes at offset 0 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec) @@ -115,7 +115,7 @@ Automatically detecting the format is dangerous for raw images, write operations Specify the 'raw' format explicitly to remove the restrictions. {"return": {}} {"timestamp": {"seconds": TIMESTAMP, "microseconds": TIMESTAMP}, "event": "BLOCK_JOB_ERROR", "data": {"device": "src", "operation": "write", "action": "report"}} -{"timestamp": {"seconds": TIMESTAMP, "microseconds": TIMESTAMP}, "event": "BLOCK_JOB_COMPLETED", "data": {"device": "src", "len": 2560, "offset": 0, "speed": 0, "type": "mirror", "error": "Operation not permitted"}} +{"timestamp": {"seconds": TIMESTAMP, "microseconds": TIMESTAMP}, "event": "BLOCK_JOB_COMPLETED", "data": {"device": "src", "len": 65536, "offset": 0, "speed": 0, "type": "mirror", "error": "Operation not permitted"}} {"return": []} read 65536/65536 bytes at offset 0 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec) @@ -135,7 +135,7 @@ Automatically detecting the format is dangerous for raw images, write operations Specify the 'raw' format explicitly to remove the restrictions. {"return": {}} {"timestamp": {"seconds": TIMESTAMP, "microseconds": TIMESTAMP}, "event": "BLOCK_JOB_ERROR", "data": {"device": "src", "operation": "write", "action": "report"}} -{"timestamp": {"seconds": TIMESTAMP, "microseconds": TIMESTAMP}, "event": "BLOCK_JOB_COMPLETED", "data": {"device": "src", "len": 2560, "offset": OFFSET, "speed": 0, "type": "mirror", "error": "Operation not permitted"}} +{"timestamp": {"seconds": TIMESTAMP, "microseconds": TIMESTAMP}, "event": "BLOCK_JOB_COMPLETED", "data": {"device": "src", "len": 65536, "offset": OFFSET, "speed": 0, "type": "mirror", "error": "Operation not permitted"}} {"return": []} read 65536/65536 bytes at offset 0 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec) @@ -195,7 +195,7 @@ Automatically detecting the format is dangerous for raw images, write operations Specify the 'raw' format explicitly to remove the restrictions. {"return": {}} {"timestamp": {"seconds": TIMESTAMP, "microseconds": TIMESTAMP}, "event": "BLOCK_JOB_ERROR", "data": {"device": "src", "operation": "write", "action": "report"}} -{"timestamp": {"seconds": TIMESTAMP, "microseconds": TIMESTAMP}, "event": "BLOCK_JOB_COMPLETED", "data": {"device": "src", "len": 2048, "offset": OFFSET, "speed": 0, "type": "mirror", "error": "Operation not permitted"}} +{"timestamp": {"seconds": TIMESTAMP, "microseconds": TIMESTAMP}, "event": "BLOCK_JOB_COMPLETED", "data": {"device": "src", "len": 65536, "offset": OFFSET, "speed": 0, "type": "mirror", "error": "Operation not permitted"}} {"return": []} read 65536/65536 bytes at offset 0 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec) -- cgit v1.2.3