Virtualised gix fails with No such device because of MAP_SHARED mmap. about gitoxide

[gl-yziquel]

The test is conclusive: the fix you proposed works on such a virtualised setting. You should feel free to commit it to the main branch.

All clear.

[gl-yziquel]

Just wait for the test for some 24 to 48 hours.

[Byron]

Thanks a lot for letting me know!

gitoxide crates use the mmap2 crate which hides these details entirely. That's great as it means there is no deeper reason behind the MAP_SHARED mode, and it shouldn't be a problem to switch to MAP_PRIVATE.

Since I probably won't be able to reproduce the issue I wonder if you'd be willing to validate a version from a PR that I could create rather swiftly?

Thanks for your help.

[gl-yziquel]

Thanks a lot for letting me know!

gitoxide crates use the mmap2 crate which hides these details entirely. That's great as it means there is no deeper reason behind the MAP_SHARED mode, and it shouldn't be a problem to switch to MAP_PRIVATE.

Since I probably won't be able to reproduce the issue I wonder if you'd be willing to validate a version from a PR that I could create rather swiftly?

Thanks for your help.

I'll have to build the PR myself on that guest. Which will be a problem since I cannot run "cargo build" (for likely the same reason, which indeed led me down here first with gix). So it will take some amount of tweaking to get it right. Moreover, I have to go get some food. So I won't reply in a quick feedback loop. Do not expect a reply before sunday or monday...

[Byron]

Thanks for the quick response and for your help.

I am sorry to hear cargo also bails out in that setup. In case, for some reason, it's not due to memmap but to C toolchains or such, you should be able to build gix with cargo build --bin gix --no-default-features --features max-pure, which requires only a Rust compiler and a linker and Cargo.

[gl-yziquel]

Just looked at the proposed fix. Yes, the memmap2 crate has a way to enforce MAP_PRIVATE. I hope this will fix it (as it will allow me to narrow down the behaviour of virtiofs). Going to get some food. Then I'll try it out.

Thank you for being so unbelievably responsive.

[Byron]

Bugs get the priority lane :).