aec7a80c6f
Some snapshotters (like overlayfs or zfs) can't mount the same
directories twice. For example if the same directroy is used as an upper
directory in two mounts the kernel will output this warning:
overlayfs: upperdir is in-use as upperdir/workdir of another mount, accessing files from both mounts will result in undefined behavior.
And indeed accessing the files from both mounts will result in an "No
such file or directory" error.
This change introduces reference counts for the mounts, if a directory
is already mounted the mount interface will only increment the mount
counter and return the mount target effectively making sure that the
filesystem doesn't end up in an undefined behavior.
Signed-off-by: Djordje Lukic <djordje.lukic@docker.com>
(cherry picked from commit 32d58144fd)
Signed-off-by: Bjorn Neergaard <bjorn.neergaard@docker.com>
41 lines
1.2 KiB
Go
41 lines
1.2 KiB
Go
package containerd
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import (
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"context"
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"fmt"
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"github.com/docker/docker/container"
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"github.com/sirupsen/logrus"
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)
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// Mount mounts the container filesystem in a temporary location, use defer imageService.Unmount
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// to unmount the filesystem when calling this
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func (i *ImageService) Mount(ctx context.Context, container *container.Container) error {
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snapshotter := i.client.SnapshotService(container.Driver)
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mounts, err := snapshotter.Mounts(ctx, container.ID)
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if err != nil {
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return err
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}
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var root string
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if root, err = i.refCountMounter.Mount(mounts, container.ID); err != nil {
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return fmt.Errorf("failed to mount %s: %w", root, err)
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}
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logrus.WithField("container", container.ID).Debugf("container mounted via snapshotter: %v", root)
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container.BaseFS = root
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return nil
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}
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// Unmount unmounts the container base filesystem
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func (i *ImageService) Unmount(ctx context.Context, container *container.Container) error {
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root := container.BaseFS
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if err := i.refCountMounter.Unmount(root); err != nil {
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logrus.WithField("container", container.ID).WithError(err).Error("error unmounting container")
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return fmt.Errorf("failed to unmount %s: %w", root, err)
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}
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return nil
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}
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