mmap'd anon pages fail in io_uring IOSQE_BUFFER_SELECT usage about memmap2-rs

[rrichardson]

It's rather embarrassing really. buf goes out of scope at the end of the else clause. There is a drop impld for MmapInner which munmap's the region that was just mmap'd . RIAA for the loss.

It makes sense that something should control the lifetime of the mmap'd region, but it was a tiny bit of a surprise because I looked for a drop impl'd on MmapMut, and there was none. It is impl'd on the private type MmapInner that is owned by MmapMut. It's a bit of a sharp edge, but I should have known.

[adamreichold]

Could you share what the issue was? Maybe other people will run into it as well and could then quickly find the solution here.