bug: block device capacity defaults to amount of free space in `/dev`

[lukenels]

When using a block device with FileDeviceBuilder, the capacity defaults to the amount of free space in the parent directory of the device (typically /dev) rather than the capacity of the device itself.

For example, I have a 950GB block device at /dev/nvme3n1:

$ blockdev --getsize64 /dev/nvme3n1
950000000000

But because of the logic to query the free space in the parent directory, the capacity defaults to ~3.3MB (the amount of free space in devtmpfs on this host):

let device = FileDeviceBuilder::new("/dev/nvme3n1").build().unwrap();
// Prints "capacity = 3354624"
println!("capacity = {}", device.capacity());

For block devices, the default device capacity could be computed instead via the file size (or, on Linux, using the BLKGETSIZE64 ioctl).

---

rustc 1.89.0
foyer 0.19.2

[MrCroxx]

Hi, Luke. Thank you for reporting, and nice catch. 🙌

I'll put this issue in planning. I'll it when I have bandwidth. Or if you're interested, feel free to help fix it as well. Either way, thank you very much.