Enable retry and recover for tarfs

[jiangliu]

Enhance tarfs implementation by:

• retry downloading from registry if the background downloading task fails
• recover snapshot information related to tarfs on startup
• remount EROFS associated with tarfs when restart
• avoid redundant merge operation if the image has only one layer
• auto detach loop devices when they are not used anymore

[codecov[bot]]

Codecov Report

Merging #538 (e0124e7) into main (5009c52) will increase coverage by 0.33%. Report is 4 commits behind head on main. The diff coverage is 14.16%.

Additional details and impacted files

[](https://app.codecov.io/gh/containerd/nydus-snapshotter/pull/538?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=containerd) ```diff @@ Coverage Diff @@ ## main #538 +/- ## ========================================== + Coverage 33.63% 33.97% +0.33% ========================================== Files 65 68 +3 Lines 8259 9352 +1093 ========================================== + Hits 2778 3177 +399 - Misses 5166 5817 +651 - Partials 315 358 +43 ``` | [Files](https://app.codecov.io/gh/containerd/nydus-snapshotter/pull/538?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=containerd) | Coverage Δ | | |---|---|---| | [snapshot/process.go](https://app.codecov.io/gh/containerd/nydus-snapshotter/pull/538?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=containerd#diff-c25hcHNob3QvcHJvY2Vzcy5nbw==) | `0.00% <0.00%> (ø)` | | | [pkg/manager/manager.go](https://app.codecov.io/gh/containerd/nydus-snapshotter/pull/538?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=containerd#diff-cGtnL21hbmFnZXIvbWFuYWdlci5nbw==) | `0.00% <0.00%> (ø)` | | | [snapshot/snapshot.go](https://app.codecov.io/gh/containerd/nydus-snapshotter/pull/538?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=containerd#diff-c25hcHNob3Qvc25hcHNob3QuZ28=) | `0.00% <0.00%> (ø)` | | | [pkg/tarfs/losetup\_linux.go](https://app.codecov.io/gh/containerd/nydus-snapshotter/pull/538?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=containerd#diff-cGtnL3RhcmZzL2xvc2V0dXBfbGludXguZ28=) | `0.00% <0.00%> (ø)` | | | [pkg/tarfs/tarfs.go](https://app.codecov.io/gh/containerd/nydus-snapshotter/pull/538?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=containerd#diff-cGtnL3RhcmZzL3RhcmZzLmdv) | `28.23% <20.97%> (ø)` | | ... and [5 files with indirect coverage changes](https://app.codecov.io/gh/containerd/nydus-snapshotter/pull/538/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=containerd)

[imeoer]

Can we add some e2e test cases for tarfs in https://github.com/containerd/nydus-snapshotter/blob/main/integration/entrypoint.sh?