Hi, I encountered a qemu-nbd segfault, finally I found it was caused by NULL bs-drv, which is located in block/io.c function bdrv_co_flush line 2377:
https://git.qemu.org/?p=qemu.git;a=blob;f=block/io.c;h=4fdf93a0144fa4761a14b8cc6b2a9a6b6e5d5bec;hb=d470ad42acfc73c45d3e8ed5311a491160b4c100#l2377 It is before the patch at line 2402, so the patch needs to be updated to fix NULL bs-drv at line 2337. https://lists.gnu.org/archive/html/qemu-devel/2017-11/msg03425.html > @@ -2373,6 +2399,12 @@ int coroutine_fn bdrv_co_flush(BlockDriverState *bs) > } > > BLKDBG_EVENT(bs->file, BLKDBG_FLUSH_TO_DISK); > + if (!bs->drv) { > + /* bs->drv->bdrv_co_flush() might have ejected the BDS > + * (even in case of apparent success) */ > + ret = -ENOMEDIUM; > + goto out; > + } > if (bs->drv->bdrv_co_flush_to_disk) { > ret = bs->drv->bdrv_co_flush_to_disk(bs); > } else if (bs->drv->bdrv_aio_flush) { I have tested the latest qemu-2.11.0-rc2 and I am sure the qemu-nbd segfault is caused by NULL bs-drv in block/io.c line 2337. kernel: qemu-nbd[18768]: segfault at f8 ip 000055a24f7536a7 sp 00007f59b1137a40 error 4 in qemu-nbd[55a24f6d1000+188000] However I have no methods to reproduce the segfault manually, the qemu-nbd segfaut just occurs in my server cluster every week. Thanks -Kangjie
