Message ID | 20170321052602.GA2785@lemon |
---|---|
State | New |
Headers | show |
On Mon, Mar 20, 2017 at 10:26 PM, Fam Zheng <famz@redhat.com> wrote: > On Fri, 03/17 09:55, Ed Swierk wrote: >> I'm running into the same problem taking an external snapshot with a >> virtio-blk drive with iothread, so it's not specific to virtio-scsi. >> Run a Linux guest on qemu master >> >> qemu-system-x86_64 -nographic -enable-kvm -monitor >> telnet:0.0.0.0:1234,server,nowait -m 1024 -object >> iothread,id=iothread1 -drive file=/x/drive.qcow2,if=none,id=drive0 >> -device virtio-blk-pci,iothread=iothread1,drive=drive0 >> >> Then in the monitor >> >> snapshot_blkdev drive0 /x/snap1.qcow2 >> >> qemu bombs with >> >> qemu-system-x86_64: /x/qemu/include/block/aio.h:457: >> aio_enable_external: Assertion `ctx->external_disable_cnt > 0' failed. >> >> whereas without the iothread the assertion failure does not occur. > > > Can you test this one? > > --- > > > diff --git a/blockdev.c b/blockdev.c > index c5b2c2c..4c217d5 100644 > --- a/blockdev.c > +++ b/blockdev.c > @@ -1772,6 +1772,8 @@ static void external_snapshot_prepare(BlkActionState *common, > return; > } > > + bdrv_set_aio_context(state->new_bs, state->aio_context); > + > /* This removes our old bs and adds the new bs. This is an operation that > * can fail, so we need to do it in .prepare; undoing it for abort is > * always possible. */ > @@ -1789,8 +1791,6 @@ static void external_snapshot_commit(BlkActionState *common) > ExternalSnapshotState *state = > DO_UPCAST(ExternalSnapshotState, common, common); > > - bdrv_set_aio_context(state->new_bs, state->aio_context); > - > /* We don't need (or want) to use the transactional > * bdrv_reopen_multiple() across all the entries at once, because we > * don't want to abort all of them if one of them fails the reopen */ With this change, a different assertion fails on running snapshot_blkdev: qemu-system-x86_64: /x/qemu/block/io.c:164: bdrv_drain_recurse: Assertion `qemu_get_current_aio_context() == qemu_get_aio_context()' failed. --Ed
On Tue, 03/21 05:20, Ed Swierk wrote: > On Mon, Mar 20, 2017 at 10:26 PM, Fam Zheng <famz@redhat.com> wrote: > > On Fri, 03/17 09:55, Ed Swierk wrote: > >> I'm running into the same problem taking an external snapshot with a > >> virtio-blk drive with iothread, so it's not specific to virtio-scsi. > >> Run a Linux guest on qemu master > >> > >> qemu-system-x86_64 -nographic -enable-kvm -monitor > >> telnet:0.0.0.0:1234,server,nowait -m 1024 -object > >> iothread,id=iothread1 -drive file=/x/drive.qcow2,if=none,id=drive0 > >> -device virtio-blk-pci,iothread=iothread1,drive=drive0 > >> > >> Then in the monitor > >> > >> snapshot_blkdev drive0 /x/snap1.qcow2 > >> > >> qemu bombs with > >> > >> qemu-system-x86_64: /x/qemu/include/block/aio.h:457: > >> aio_enable_external: Assertion `ctx->external_disable_cnt > 0' failed. > >> > >> whereas without the iothread the assertion failure does not occur. > > > > > > Can you test this one? > > > > --- > > > > > > diff --git a/blockdev.c b/blockdev.c > > index c5b2c2c..4c217d5 100644 > > --- a/blockdev.c > > +++ b/blockdev.c > > @@ -1772,6 +1772,8 @@ static void external_snapshot_prepare(BlkActionState *common, > > return; > > } > > > > + bdrv_set_aio_context(state->new_bs, state->aio_context); > > + > > /* This removes our old bs and adds the new bs. This is an operation that > > * can fail, so we need to do it in .prepare; undoing it for abort is > > * always possible. */ > > @@ -1789,8 +1791,6 @@ static void external_snapshot_commit(BlkActionState *common) > > ExternalSnapshotState *state = > > DO_UPCAST(ExternalSnapshotState, common, common); > > > > - bdrv_set_aio_context(state->new_bs, state->aio_context); > > - > > /* We don't need (or want) to use the transactional > > * bdrv_reopen_multiple() across all the entries at once, because we > > * don't want to abort all of them if one of them fails the reopen */ > > With this change, a different assertion fails on running snapshot_blkdev: > > qemu-system-x86_64: /x/qemu/block/io.c:164: bdrv_drain_recurse: > Assertion `qemu_get_current_aio_context() == qemu_get_aio_context()' > failed. Is there a backtrace?
On Tue, Mar 21, 2017 at 5:50 AM, Fam Zheng <famz@redhat.com> wrote: > On Tue, 03/21 05:20, Ed Swierk wrote: >> On Mon, Mar 20, 2017 at 10:26 PM, Fam Zheng <famz@redhat.com> wrote: >> > On Fri, 03/17 09:55, Ed Swierk wrote: >> >> I'm running into the same problem taking an external snapshot with a >> >> virtio-blk drive with iothread, so it's not specific to virtio-scsi. >> >> Run a Linux guest on qemu master >> >> >> >> qemu-system-x86_64 -nographic -enable-kvm -monitor >> >> telnet:0.0.0.0:1234,server,nowait -m 1024 -object >> >> iothread,id=iothread1 -drive file=/x/drive.qcow2,if=none,id=drive0 >> >> -device virtio-blk-pci,iothread=iothread1,drive=drive0 >> >> >> >> Then in the monitor >> >> >> >> snapshot_blkdev drive0 /x/snap1.qcow2 >> >> >> >> qemu bombs with >> >> >> >> qemu-system-x86_64: /x/qemu/include/block/aio.h:457: >> >> aio_enable_external: Assertion `ctx->external_disable_cnt > 0' failed. >> >> >> >> whereas without the iothread the assertion failure does not occur. >> > >> > >> > Can you test this one? >> > >> > --- >> > >> > >> > diff --git a/blockdev.c b/blockdev.c >> > index c5b2c2c..4c217d5 100644 >> > --- a/blockdev.c >> > +++ b/blockdev.c >> > @@ -1772,6 +1772,8 @@ static void external_snapshot_prepare(BlkActionState *common, >> > return; >> > } >> > >> > + bdrv_set_aio_context(state->new_bs, state->aio_context); >> > + >> > /* This removes our old bs and adds the new bs. This is an operation that >> > * can fail, so we need to do it in .prepare; undoing it for abort is >> > * always possible. */ >> > @@ -1789,8 +1791,6 @@ static void external_snapshot_commit(BlkActionState *common) >> > ExternalSnapshotState *state = >> > DO_UPCAST(ExternalSnapshotState, common, common); >> > >> > - bdrv_set_aio_context(state->new_bs, state->aio_context); >> > - >> > /* We don't need (or want) to use the transactional >> > * bdrv_reopen_multiple() across all the entries at once, because we >> > * don't want to abort all of them if one of them fails the reopen */ >> >> With this change, a different assertion fails on running snapshot_blkdev: >> >> qemu-system-x86_64: /x/qemu/block/io.c:164: bdrv_drain_recurse: >> Assertion `qemu_get_current_aio_context() == qemu_get_aio_context()' >> failed. Actually running snapshot_blkdev command in the text monitor doesn't trigger this assertion (I mixed up my notes). Instead it's triggered by the following sequence in qmp-shell: (QEMU) blockdev-snapshot-sync device=drive0 format=qcow2 snapshot-file=/x/snap1.qcow2 {"return": {}} (QEMU) block-commit device=drive0 {"return": {}} (QEMU) block-job-complete device=drive0 {"return": {}} > Is there a backtrace? #0 0x00007ffff3757067 in raise () from /lib/x86_64-linux-gnu/libc.so.6 #1 0x00007ffff3758448 in abort () from /lib/x86_64-linux-gnu/libc.so.6 #2 0x00007ffff3750266 in ?? () from /lib/x86_64-linux-gnu/libc.so.6 #3 0x00007ffff3750312 in __assert_fail () from /lib/x86_64-linux-gnu/libc.so.6 #4 0x0000555555b4b0bb in bdrv_drain_recurse (bs=bs@entry=0x555557bd6010) at /x/qemu/block/io.c:164 #5 0x0000555555b4b7ad in bdrv_drained_begin (bs=0x555557bd6010) at /x/qemu/block/io.c:231 #6 0x0000555555b4b802 in bdrv_parent_drained_begin (bs=0x5555568c1a00) at /x/qemu/block/io.c:53 #7 bdrv_drained_begin (bs=bs@entry=0x5555568c1a00) at /x/qemu/block/io.c:228 #8 0x0000555555b4be1e in bdrv_co_drain_bh_cb (opaque=0x7fff9aaece40) at /x/qemu/block/io.c:190 #9 0x0000555555bb431e in aio_bh_call (bh=0x55555750e5f0) at /x/qemu/util/async.c:90 #10 aio_bh_poll (ctx=ctx@entry=0x555556718090) at /x/qemu/util/async.c:118 #11 0x0000555555bb72eb in aio_poll (ctx=0x555556718090, blocking=blocking@entry=true) at /x/qemu/util/aio-posix.c:682 #12 0x00005555559443ce in iothread_run (opaque=0x555556717b80) at /x/qemu/iothread.c:59 #13 0x00007ffff3ad50a4 in start_thread () from /lib/x86_64-linux-gnu/libpthread.so.0 #14 0x00007ffff380a87d in clone () from /lib/x86_64-linux-gnu/libc.so.6 --Ed
diff --git a/blockdev.c b/blockdev.c index c5b2c2c..4c217d5 100644 --- a/blockdev.c +++ b/blockdev.c @@ -1772,6 +1772,8 @@ static void external_snapshot_prepare(BlkActionState *common, return; } + bdrv_set_aio_context(state->new_bs, state->aio_context); + /* This removes our old bs and adds the new bs. This is an operation that * can fail, so we need to do it in .prepare; undoing it for abort is * always possible. */ @@ -1789,8 +1791,6 @@ static void external_snapshot_commit(BlkActionState *common) ExternalSnapshotState *state = DO_UPCAST(ExternalSnapshotState, common, common); - bdrv_set_aio_context(state->new_bs, state->aio_context); - /* We don't need (or want) to use the transactional * bdrv_reopen_multiple() across all the entries at once, because we * don't want to abort all of them if one of them fails the reopen */