cache: fix null pointer access when cachemanager.Disable is true

[jiangliu]

Filesystem.cacheMgr is null when cacheManager.Disable is configured to be true, thus cause null pointer access. Fix it by always create the cacheMgr object no matter cacheManager.Disable is true or false.

[codecov[bot]]

Codecov Report

Merging #536 (fd4be45) into main (0da2966) will decrease coverage by 0.01%. Report is 1 commits behind head on main. The diff coverage is 0.00%.

Additional details and impacted files

[](https://app.codecov.io/gh/containerd/nydus-snapshotter/pull/536?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=containerd) ```diff @@ Coverage Diff @@ ## main #536 +/- ## ========================================== - Coverage 33.56% 33.56% -0.01% ========================================== Files 65 65 Lines 8175 8176 +1 ========================================== Hits 2744 2744 - Misses 5116 5117 +1 Partials 315 315 ``` | [Files Changed](https://app.codecov.io/gh/containerd/nydus-snapshotter/pull/536?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=containerd) | Coverage Δ | | |---|---|---| | [snapshot/snapshot.go](https://app.codecov.io/gh/containerd/nydus-snapshotter/pull/536?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)` | |

[sctb512]

Why not check if the cacheMgr is nil? It seems stargzResolver and referrerMgr also have the same problem.

[jiangliu]

Why not check if the cacheMgr is nil? It seems stargzResolver and referrerMgr also have the same problem.

With the evolution of nydus-snapshotter, cache manager becomes mandatory instead optional now. On the other hand, stargzResolver and referrerMgr are optional.