Wentao Zhang 52c11cb152 Fix delete a image while saving it, delete successfully but failed to save it ...

Issue Description:
 * 1. Saving more than one images, `docker save -o a.tar aaa bbb`
 * 2. Delete the last image which in saving progress.  `docker rmi bbb`

Espected:
 Saving images operation shouldn't be disturbed. But the real result is that failed to
save image and get an error as below:
  `Error response from daemon: open
/var/lib/docker/image/devicemapper/imagedb/content/sha256/7c24e4d533a76e801662ad1b7e6e06bc1204f80110b5623e96ba2877c51479a1:
no such file or directory`

Analysis:
  1. While saving more than one images, it will get all the image info from reference/imagestore,
     and then using the `cached data` to save the images to a tar file.
  2. But this process doesn't have a resource lock, if a deletion operation comes, the image will be deleted,
     so saving operation will fail.

Solution:
 When begin to save an image, `Get` all the layers first. then the
deletion operation won't delete the layers.

Signed-off-by: Wentao Zhang <zhangwentao234@huawei.com>
Upstream-commit: 4a014e6b0d7e2d310ee1ba442128a6802559a63a
Component: engine

2017-06-01 18:13:20 +08:00

components/engine

Fix delete a image while saving it, delete successfully but failed to save it

2017-06-01 18:13:20 +08:00

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