agent: retry mount on ENOMEM #788
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There is a race between firecracker-containerd replacing the stub drive with the actual drive and mounting this drive. When the disk is replaced the kernel will schedule asynchronous work in virtblk_config_changed. In the meantime firecracker-containerd can proceed and already send a mount command to the agent running in the guest. This mount operation will, however, fail because the guest kernel still sees the stub drive with only 512 bytes in size. The resulting error code is a ENOMEM in this case. This commit therefore adds this as an retryable error code to accommodate for this situation. The issue can be reproduced when an artificial msleep(1000) is added in virtblk_config_changed_work. This produced the following error: error="failed to get stub drive for task \"test\": failed to mount drive inside vm: failed to mount newly patched drive: rpc error: code = Unknown desc = non-retryable failure mounting drive from \"/dev/vdb\" to \"/container/test/rootfs\": cannot allocate memory" Signed-off-by: Maximilian Heyne <[email protected]>
swagatbora90
approved these changes
May 23, 2024
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There is a race between firecracker-containerd replacing the stub drive with the actual drive and mounting this drive. When the disk is replaced the kernel will schedule asynchronous work in virtblk_config_changed. In the meantime firecracker-containerd can proceed and already send a mount command to the agent running in the guest. This mount operation will, however, fail because the guest kernel still sees the stub drive with only 512 bytes in size. The resulting error code is a ENOMEM in this case. This commit therefore adds this as an retryable error code to accommodate for this situation.
The issue can be reproduced when an artificial msleep(1000) is added in virtblk_config_changed_work. This produced the following error:
error="failed to get stub drive for task "test": failed to mount
drive inside vm: failed to mount newly patched drive: rpc error: code
= Unknown desc = non-retryable failure mounting drive from
"/dev/vdb" to "/container/test/rootfs": cannot allocate memory"
By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.