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Sync with Upstream patch: Fixes Issue # 23418: Race condition between…
… device deferred removal and resume device. Upstream PR: moby#23497 Problem Description: An example scenario that involves deferred removal 1. A new base image gets created (e.g. 'docker load -i'). The base device is activated and mounted at some point in time during image creation. 2. While image creation is in progress, a privileged container is started from another image and the host's mount name space is shared with this container ('docker run --privileged -v /:/host'). 3. Image creation completes and the base device gets unmounted. However, as the privileged container still holds a reference on the base image mount point, the base device cannot be removed right away. So it gets flagged for deferred removal. 4. Next, the privileged container terminates and thus its reference to the base image mount point gets released. The base device (which is flagged for deferred removal) may now be cleaned up by the device-mapper. This opens up an opportunity for a race between a 'kworker' thread (executing the do_deferred_remove() function) and the Docker daemon (executing the CreateSnapDevice() function). This PR cancel the deferred removal, if the device is marked for it. And reschedule the deferred removal later after the device is resumed successfully. Signed-off-by: Shishir Mahajan <[email protected]>
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Shishir Mahajan
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Sep 1, 2016
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