Fix for qemu-nbd hang

NBD device once used seem to run into intermittent trouble when
used with mount repeatedly. Adding code to explicitly flush the
device buffers using 'blockdev --flushbufs'.

Closes-Bug: #973413
Partial-Bug: #1254890
Change-Id: I2b7053b9a069d6e82f6f6baf9ad480efa4388d91
This commit is contained in:
Davanum Srinivas 2013-12-29 19:18:04 -05:00
parent beca18af16
commit dd3f96e915
4 changed files with 18 additions and 0 deletions

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@ -27,6 +27,9 @@ umount: CommandFilter, umount, root
# nova/virt/disk/mount/nbd.py: 'qemu-nbd', '-d', device
qemu-nbd: CommandFilter, qemu-nbd, root
# nova/virt/disk/mount/nbd.py: 'blockdev', '--flushbufs', device
blockdev: CommandFilter, blockdev, root
# nova/virt/disk/mount/loop.py: 'losetup', '--find', '--show', image
# nova/virt/disk/mount/loop.py: 'losetup', '--detach', device
losetup: CommandFilter, losetup, root

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@ -227,12 +227,14 @@ class TestVirtDisk(test.NoDBTestCase):
disk_api.teardown_container('/mnt/nbd/nopart')
expected_commands += [
('blockdev', '--flushbufs', '/dev/nbd15'),
('umount', '/dev/nbd15'),
('qemu-nbd', '-d', '/dev/nbd15'),
]
disk_api.teardown_container('/mnt/nbd/part')
expected_commands += [
('blockdev', '--flushbufs', '/dev/nbd15'),
('umount', '/dev/mapper/nbd15p1'),
('kpartx', '-d', '/dev/nbd15'),
('qemu-nbd', '-d', '/dev/nbd15'),

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@ -205,10 +205,14 @@ class Mount(object):
"""Unmount the device from the file system."""
if not self.mounted:
return
self.flush_dev()
LOG.debug(_("Umount %s") % self.mapped_device)
utils.execute('umount', self.mapped_device, run_as_root=True)
self.mounted = False
def flush_dev(self):
pass
def do_mount(self):
"""Call the get, map and mnt operations."""
status = False

View File

@ -129,3 +129,12 @@ class NbdMount(api.Mount):
utils.execute('qemu-nbd', '-d', self.device, run_as_root=True)
self.linked = False
self.device = None
def flush_dev(self):
"""flush NBD block device buffer."""
# Perform an explicit BLKFLSBUF to support older qemu-nbd(s).
# Without this flush, when a nbd device gets re-used the
# qemu-nbd intermittently hangs.
if self.device:
utils.execute('blockdev', '--flushbufs',
self.device, run_as_root=True)