[Kimchi-devel] [PATCH] [Kimchi] Bug fix #1107: Only set cache=none to disks that support direct IO

[Daniel Henrique Barboza]

Reviewed-by: Daniel Barboza <danielhb at linux.vnet.ibm.com>


On 03/06/2017 04:19 PM, Aline Manera wrote:
> ZFS volumes and GlusterFS does not support direct IO and setting
> cache=none will not allow the guest to start. So only set cache=none
> when direct IO is supported to avoid problems.
>
> Signed-off-by: Aline Manera <alinefm at linux.vnet.ibm.com>
> ---
>   xmlutils/disk.py | 24 ++++++++++++++++++------
>   1 file changed, 18 insertions(+), 6 deletions(-)
>
> diff --git a/xmlutils/disk.py b/xmlutils/disk.py
> index 02d6811..97298c5 100644
> --- a/xmlutils/disk.py
> +++ b/xmlutils/disk.py
> @@ -1,7 +1,7 @@
>   #
>   # Project Kimchi
>   #
> -# Copyright IBM Corp, 2015-2016
> +# Copyright IBM Corp, 2015-2017
>   #
>   # This library is free software; you can redistribute it and/or
>   # modify it under the terms of the GNU Lesser General Public
> @@ -17,6 +17,7 @@
>   # License along with this library; if not, write to the Free Software
>   # Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301 USA
>   
> +import errno
>   import lxml.etree as ET
>   import os
>   import socket
> @@ -28,7 +29,7 @@ from lxml.builder import E
>   
>   from wok.exception import InvalidParameter, NotFoundError
>   from wok.plugins.kimchi.utils import check_url_path
> -
> +from wok.utils import wok_log
>   
>   BUS_TO_DEV_MAP = {'ide': 'hd', 'virtio': 'vd', 'scsi': 'sd'}
>   DEV_TYPE_SRC_ATTR_MAP = {'file': 'file', 'block': 'dev'}
> @@ -51,11 +52,22 @@ def get_disk_xml(params):
>           disk_type = _get_disk_type(path) if len(path) > 0 else 'file'
>       disk = E.disk(type=disk_type, device=params['type'])
>       driver = E.driver(name='qemu', type=params['format'])
> -    if params['type'] != 'cdrom':
> -        driver.set('cache', 'none')
> +    try:
> +        fd = os.open(path, os.O_RDONLY | os.O_DIRECT)
> +        os.close(fd)
> +        wok_log.debug("Disk '%s' supports direct I/O. Setting cache=none"
> +                      "to enable live migration" % path)
> +    except OSError, e:
> +        if e.errno == errno.EINVAL:
> +            wok_log.debug("Disk '%s' does not support direct I/O: "
> +                          "'%s'. Let libvirt sets the default cache mode." %
> +                          (path, e.message))
> +    else:
> +        if params['type'] != 'cdrom':
> +            driver.set('cache', 'none')
>   
> -        if params.get('pool_type') == "netfs":
> -            driver.set("io", "native")
> +    if params.get('pool_type') == "netfs":
> +        driver.set("io", "native")
>   
>       disk.append(driver)
>