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docker: Unmount -init layer root before taking a snapshot

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When we are creating a container, first we call into graph driver to take
snapshot of image and create root for container-init. Then we write some
files to it and call into graph driver again to create container root
from container-init as base.

Once we have written files to container-init root, we don't unmount it
before taking a snapshot of it. Looks like with XFS it leaves it in such
a state that when we mount the container root, it goes into log recovery
path.

Jul 22 10:24:54 vm2-f22 kernel: XFS (dm-6): Mounting V4 Filesystem
Jul 22 10:24:54 vm2-f22 kernel: XFS (dm-6): Starting recovery (logdev: internal)
Jul 22 10:24:54 vm2-f22 kernel: XFS (dm-6): Ending recovery (logdev: internal)

This should not be required. So let us unmount container-init before use
it  as a base for container root and then XFS does not go into this
internal recovery path.

Somebody had raised this issue for ext4 sometime back and proposed the same
change. I had shot it down at that point of time. I think now time has
come for this change.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
This commit is contained in:
Vivek Goyal 2015-07-22 10:32:53 -04:00
parent f0d0a52d80
commit fe26669205
1 changed files with 5 additions and 1 deletions
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6
daemon/daemon_unix.go
View file

@ -81,12 +81,16 @@ func (daemon *Daemon) createRootfs(container *Container) error {
if err != nil { if err != nil {
return err return err
} }
defer daemon.driver.Put(initID)
if err := setupInitLayer(initPath); err != nil { if err := setupInitLayer(initPath); err != nil {
daemon.driver.Put(initID)
return err return err
} }
// We want to unmount init layer before we take snapshot of it
// for the actual container.
daemon.driver.Put(initID)
if err := daemon.driver.Create(container.ID, initID); err != nil { if err := daemon.driver.Create(container.ID, initID); err != nil {
return err return err
} }