Bug 1336649

view from code it looks if snapshot=on, qemu will get a tmpfile 
from sytem TMPDIR, TMPDIR in most linux host use tmpfs. and tmpfs not support O_DRIECT, so I guess qemu not startup with error "id=drive_image1,if=none,cache=none,aio=native,snapshot=on,format=qcow2,file=/usr/share/avocado/data/avocado-vt/images/RHEL-Server-7.3-64-virtio.qcow2: aio=native was specified, but it requires cache.direct=on, which was not specified." is expect.


int get_tmp_filename(char *filename, int size)
{
#ifdef _WIN32
    char temp_dir[MAX_PATH];
    /* GetTempFileName requires that its output buffer (4th param)
       have length MAX_PATH or greater.  */
    assert(size >= MAX_PATH);
    return (GetTempPath(MAX_PATH, temp_dir)
            && GetTempFileName(temp_dir, "qem", 0, filename)
            ? 0 : -GetLastError());
#else
    int fd;
    const char *tmpdir;
    tmpdir = getenv("TMPDIR");
    if (!tmpdir)
        tmpdir = "/tmp";
    if (snprintf(filename, size, "%s/vl.XXXXXX", tmpdir) >= size) {
        return -EOVERFLOW;
    }
    fd = mkstemp(filename);
    if (fd < 0) {
        return -errno;
    }
    if (close(fd) != 0) {
        unlink(filename);
        return -errno;
    }
    return 0;
#endif
}

mounts output on my host:

[root@xutian-dev]# (rhel7/master-1.5.3) cat /proc/mounts 
sysfs /sys sysfs rw,nosuid,nodev,noexec,relatime 0 0
proc /proc proc rw,nosuid,nodev,noexec,relatime 0 0
devtmpfs /dev devtmpfs rw,nosuid,size=6117880k,nr_inodes=1529470,mode=755 0 0
securityfs /sys/kernel/security securityfs rw,nosuid,nodev,noexec,relatime 0 0
tmpfs /dev/shm tmpfs rw,nosuid,nodev 0 0
devpts /dev/pts devpts rw,nosuid,noexec,relatime,gid=5,mode=620,ptmxmode=000 0 0
tmpfs /run tmpfs rw,nosuid,nodev,mode=755 0 0
tmpfs /sys/fs/cgroup tmpfs ro,nosuid,nodev,noexec,mode=755 0 0
cgroup /sys/fs/cgroup/systemd cgroup rw,nosuid,nodev,noexec,relatime,xattr,release_agent=/usr/lib/systemd/systemd-cgroups-agent,name=systemd 0 0
pstore /sys/fs/pstore pstore rw,nosuid,nodev,noexec,relatime 0 0
cgroup /sys/fs/cgroup/freezer cgroup rw,nosuid,nodev,noexec,relatime,freezer 0 0
cgroup /sys/fs/cgroup/memory cgroup rw,nosuid,nodev,noexec,relatime,memory 0 0
cgroup /sys/fs/cgroup/cpu,cpuacct cgroup rw,nosuid,nodev,noexec,relatime,cpu,cpuacct 0 0
cgroup /sys/fs/cgroup/blkio cgroup rw,nosuid,nodev,noexec,relatime,blkio 0 0
cgroup /sys/fs/cgroup/net_cls,net_prio cgroup rw,nosuid,nodev,noexec,relatime,net_cls,net_prio 0 0
cgroup /sys/fs/cgroup/perf_event cgroup rw,nosuid,nodev,noexec,relatime,perf_event 0 0
cgroup /sys/fs/cgroup/devices cgroup rw,nosuid,nodev,noexec,relatime,devices 0 0
cgroup /sys/fs/cgroup/pids cgroup rw,nosuid,nodev,noexec,relatime,pids 0 0
cgroup /sys/fs/cgroup/hugetlb cgroup rw,nosuid,nodev,noexec,relatime,hugetlb 0 0
cgroup /sys/fs/cgroup/cpuset cgroup rw,nosuid,nodev,noexec,relatime,cpuset 0 0
configfs /sys/kernel/config configfs rw,relatime 0 0
/dev/mapper/fedora--server_dhcp--10--17-root / xfs rw,relatime,attr2,inode64,noquota 0 0
systemd-1 /proc/sys/fs/binfmt_misc autofs rw,relatime,fd=33,pgrp=1,timeout=0,minproto=5,maxproto=5,direct 0 0
mqueue /dev/mqueue mqueue rw,relatime 0 0
hugetlbfs /dev/hugepages hugetlbfs rw,relatime 0 0
debugfs /sys/kernel/debug debugfs rw,relatime 0 0
tmpfs /tmp tmpfs rw 0 0

Thanks,
Xu

Hi reporter, 

please provider your output of bash command "echo $TMPDIR; cat /proc/mounts"

thanks,
Xu

(In reply to xu from comment #2)
> Hi reporter, 
> 
> please provider your output of bash command "echo $TMPDIR; cat /proc/mounts"
> 
> thanks,
> Xu

following is :

[root@hp-z220-01 home]# echo $TMPDIR

[root@hp-z220-01 home]# cat /proc/mounts
rootfs / rootfs rw 0 0
sysfs /sys sysfs rw,nosuid,nodev,noexec,relatime 0 0
proc /proc proc rw,nosuid,nodev,noexec,relatime 0 0
devtmpfs /dev devtmpfs rw,nosuid,size=8046840k,nr_inodes=2011710,mode=755 0 0
securityfs /sys/kernel/security securityfs rw,nosuid,nodev,noexec,relatime 0 0
tmpfs /dev/shm tmpfs rw,nosuid,nodev 0 0
devpts /dev/pts devpts rw,nosuid,noexec,relatime,gid=5,mode=620,ptmxmode=000 0 0
tmpfs /run tmpfs rw,nosuid,nodev,mode=755 0 0
tmpfs /sys/fs/cgroup tmpfs ro,nosuid,nodev,noexec,mode=755 0 0
cgroup /sys/fs/cgroup/systemd cgroup rw,nosuid,nodev,noexec,relatime,xattr,release_agent=/usr/lib/systemd/systemd-cgroups-agent,name=systemd 0 0
pstore /sys/fs/pstore pstore rw,nosuid,nodev,noexec,relatime 0 0
cgroup /sys/fs/cgroup/freezer cgroup rw,nosuid,nodev,noexec,relatime,freezer 0 0
cgroup /sys/fs/cgroup/devices cgroup rw,nosuid,nodev,noexec,relatime,devices 0 0
cgroup /sys/fs/cgroup/blkio cgroup rw,nosuid,nodev,noexec,relatime,blkio 0 0
cgroup /sys/fs/cgroup/hugetlb cgroup rw,nosuid,nodev,noexec,relatime,hugetlb 0 0
cgroup /sys/fs/cgroup/net_cls,net_prio cgroup rw,nosuid,nodev,noexec,relatime,net_prio,net_cls 0 0
cgroup /sys/fs/cgroup/cpuset cgroup rw,nosuid,nodev,noexec,relatime,cpuset 0 0
cgroup /sys/fs/cgroup/cpu,cpuacct cgroup rw,nosuid,nodev,noexec,relatime,cpuacct,cpu 0 0
cgroup /sys/fs/cgroup/memory cgroup rw,nosuid,nodev,noexec,relatime,memory 0 0
cgroup /sys/fs/cgroup/perf_event cgroup rw,nosuid,nodev,noexec,relatime,perf_event 0 0
cgroup /sys/fs/cgroup/pids cgroup rw,nosuid,nodev,noexec,relatime,pids 0 0
configfs /sys/kernel/config configfs rw,relatime 0 0
/dev/mapper/rhel_hp--z220--01-root / xfs rw,relatime,attr2,inode64,noquota 0 0
rpc_pipefs /var/lib/nfs/rpc_pipefs rpc_pipefs rw,relatime 0 0
systemd-1 /proc/sys/fs/binfmt_misc autofs rw,relatime,fd=24,pgrp=1,timeout=300,minproto=5,maxproto=5,direct 0 0
mqueue /dev/mqueue mqueue rw,relatime 0 0
debugfs /sys/kernel/debug debugfs rw,relatime 0 0
hugetlbfs /dev/hugepages hugetlbfs rw,relatime 0 0
nfsd /proc/fs/nfsd nfsd rw,relatime 0 0
/dev/sda1 /boot xfs rw,relatime,attr2,inode64,noquota 0 0
/dev/mapper/rhel_hp--z220--01-home /home xfs rw,relatime,attr2,inode64,noquota 0 0
10.73.194.27:/vol/s2coredump /var/crash nfs rw,relatime,vers=3,rsize=65536,wsize=65536,namlen=255,hard,proto=tcp,timeo=600,retrans=2,sec=sys,mountaddr=10.73.194.27,mountvers=3,mountport=4046,mountproto=udp,local_lock=none,addr=10.73.194.27 0 0
10.73.194.28:/vol/S2/kvmauto/windows_img /mnt/windows nfs rw,relatime,vers=3,rsize=65536,wsize=65536,namlen=255,hard,proto=tcp,timeo=600,retrans=2,sec=sys,mountaddr=10.73.194.28,mountvers=3,mountport=4046,mountproto=udp,local_lock=none,addr=10.73.194.28 0 0
10.73.194.27:/vol/s2kvmauto/iso /home/kvm_autotest_root/iso nfs rw,relatime,vers=3,rsize=65536,wsize=65536,namlen=255,hard,proto=tcp,timeo=600,retrans=2,sec=sys,mountaddr=10.73.194.27,mountvers=3,mountport=4046,mountproto=udp,local_lock=none,addr=10.73.194.27 0 0
10.73.194.28:/vol/S2/kvmauto/linux_img /mnt/linux nfs rw,relatime,vers=3,rsize=65536,wsize=65536,namlen=255,hard,proto=tcp,timeo=600,retrans=2,sec=sys,mountaddr=10.73.194.28,mountvers=3,mountport=4046,mountproto=udp,local_lock=none,addr=10.73.194.28 0 0
tmpfs /run/user/0 tmpfs rw,nosuid,nodev,relatime,size=1614064k,mode=700 0 0

I agree with xu, the result is expected.  

Below info maybe can help us understand why this issue(aio=native,snapshot=on/off) in qemu2.3 work, but in qemu2.6 don't.

http://wiki.qemu.org/Features/Block/Todo#raw-posix:_Error_out_on_aio.3Dnative_with_cache.direct.3Doff_instead_of_falling_back_to_aio.3Dthreads_.5BKevin.5D

...
raw-posix: Error out on aio=native with cache.direct=off instead of falling back to aio=threads [Kevin] 
Deprecated in 2.3 (commit 9651825), intend to make it an error in 2.5 


-Pei

Commit 69bef7931e8880c709556f8444938d8bb9a16118 moves default location of snapshot images from /tmp to /var/tmp.  That is part of the qemu 2.0 release, so qemu-kvm-rhev should not be affected by this.

(In reply to Amit Shah from comment #6)
> Commit 69bef7931e8880c709556f8444938d8bb9a16118 moves default location of
> snapshot images from /tmp to /var/tmp.  That is part of the qemu 2.6
> release, so qemu-kvm-rhev should not be affected by this.

But the reporter reproduced it with QEMU-2.6, so this is probably not the case.

Anyway, looks like this is expected behavior and with libvirt this should not impact users, so I'm tempted to close this as NOTABUG. Leaving this up to Kevin to verify and decide.

(In reply to Ademar Reis from comment #7)
> (In reply to Amit Shah from comment #6)
> > Commit 69bef7931e8880c709556f8444938d8bb9a16118 moves default location of
> > snapshot images from /tmp to /var/tmp.  That is part of the qemu 2.6
> > release, so qemu-kvm-rhev should not be affected by this.
> 
> But the reporter reproduced it with QEMU-2.6, so this is probably not the
> case.
> 
> Anyway, looks like this is expected behavior and with libvirt this should
> not impact users, so I'm tempted to close this as NOTABUG. Leaving this up
> to Kevin to verify and decide.

My comment was unclear, let me try another time:

Comment 1 mentions code which was changed by commit 69bef7931e8880c709556f8444938d8bb9a16118 to use /var/tmp instead of /tmp.  So this error is most likely not due to the location of the tmpfile (or TMPDIR is defined, and is not /var/tmp).  I just wanted to point out that the code referenced in comment 1 is not what it looks like anymore in qemu-kvm-rhev.

The problem is that bdrv_temp_snapshot_options() automatically sets
cache.direct=off for the temporary file, but it doesn't change the aio=native
setting, so we end up with a somewhat confusing error message.

The expected behaviour isn't completely clear, but I think I'm leaning towards
the position that on the command line, you configure the image file layer and
not the temporary snapshot layer. So aio=native shouldn't be set for the
snapshot layer and bdrv_temp_snapshot_options() must filter out the
corresponding flag.

After implementing this fix, you will get a temporary snapshot with
cache=unsafe,aio=threads on top of the real image with cache=none,aio=native.

Fix included in qemu-kvm-rhev-2.6.0-9.el7

According to #comment 9, Verified on:
qemu: qemu-kvm-rhev-2.6.0-9.el7.x86_64
kernel: kernel-3.10.0-453.el7.x86_64

steps:

1. boot up guest with commandline:

cat testme.sh

/usr/libexec/qemu-kvm \
    -name 'avocado-vt-vm1'  \
    -sandbox off  \
    -machine pc  \
    -nodefaults  \
    -vga cirrus  \
    -chardev socket,id=qmp_id_qmpmonitor1,path=/var/tmp/monitor-qmpmonitor1-20160516-052527-XpOtv1yH,server,nowait \
    -mon chardev=qmp_id_qmpmonitor1,mode=control  \
    -chardev socket,id=qmp_id_catch_monitor,path=/var/tmp/monitor-catch_monitor-20160516-052527-XpOtv1yH,server,nowait \
    -mon chardev=qmp_id_catch_monitor,mode=control \
    -device pvpanic,ioport=0x505,id=id76oG5J  \
    -chardev socket,id=serial_id_serial0,path=/var/tmp/serial-serial0-20160516-052527-XpOtv1yH,server,nowait \
    -device isa-serial,chardev=serial_id_serial0  \
    -chardev socket,id=seabioslog_id_20160516-052527-XpOtv1yH,path=/var/tmp/seabios-20160516-052527-XpOtv1yH,server,nowait \
    -device isa-debugcon,chardev=seabioslog_id_20160516-052527-XpOtv1yH,iobase=0x402 \
    -device ich9-usb-ehci1,id=usb1,addr=1d.7,multifunction=on,bus=pci.0 \
    -device ich9-usb-uhci1,id=usb1.0,multifunction=on,masterbus=usb1.0,addr=1d.0,firstport=0,bus=pci.0 \
    -device ich9-usb-uhci2,id=usb1.1,multifunction=on,masterbus=usb1.0,addr=1d.2,firstport=2,bus=pci.0 \
    -device ich9-usb-uhci3,id=usb1.2,multifunction=on,masterbus=usb1.0,addr=1d.4,firstport=4,bus=pci.0 \
    -drive id=drive_image1,if=none,cache=none,aio=native,snapshot=on,format=qcow2,file=/usr/share/avocado/data/avocado-vt/images/RHEL-Server-7.3-64-virtio.qcow2 \
    -device virtio-blk-pci,id=image1,drive=drive_image1,bootindex=0,bus=pci.0,addr=03,disable-legacy=off,disable-modern=on \
    -device virtio-net-pci,mac=9a:17:18:19:1a:1b,id=idFlFOIk,vectors=4,netdev=idRnJbnY,bus=pci.0,addr=04,disable-legacy=off,disable-modern=on  \
    -netdev tap,id=idRnJbnY,vhost=on \
    -m 8192  \
    -smp 4,maxcpus=4,cores=2,threads=1,sockets=2  \
    -cpu 'Opteron_G3',+kvm_pv_unhalt \
    -device usb-tablet,id=usb-tablet1,bus=usb1.0,port=1  \
    -vnc :0  \
    -rtc base=utc,clock=host,driftfix=slew  \
    -boot order=cdn,once=c,menu=off,strict=off \
    -enable-kvm \
    -monitor stdio \

2.boot up with no errors

[root@hp-dl385g7-04 home]# sh testme.sh 
QEMU 2.6.0 monitor - type 'help' for more information
(qemu) info status
VM status: running

3.also tried when specify the option "cache=unsafe,aio=threads",also works fine.

so will mark this bug as verified,thanks.

Continued with comment #12, set the bug to be correct status as verified.

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://rhn.redhat.com/errata/RHBA-2016-2673.html