eb5e0ae65a
pbs-datastore now ended up depending on tokio after all, but that's fine for now for the fuse code I added pbs-fuse-loop (has the old fuse_loop and its 'loopdev' module) ultimately only binaries should depend on this to avoid the library link the only thins remaining to move out the client binary are the api method return types, those will need to be moved to pbs-api-types... Signed-off-by: Wolfgang Bumiller <w.bumiller@proxmox.com>
97 lines
3.2 KiB
Rust
97 lines
3.2 KiB
Rust
//! Helpers to work with /dev/loop* devices
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use std::fs::{File, OpenOptions};
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use std::path::Path;
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use std::os::unix::io::{RawFd, AsRawFd};
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use anyhow::Error;
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const LOOP_CONTROL: &str = "/dev/loop-control";
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const LOOP_NAME: &str = "/dev/loop";
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/// Implements a subset of loop device ioctls necessary to assign and release
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/// a single file from a free loopdev.
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mod loop_ioctl {
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use nix::{ioctl_none, ioctl_write_int_bad, ioctl_write_ptr_bad};
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const LOOP_IOCTL: u16 = 0x4C; // 'L'
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const LOOP_SET_FD: u16 = 0x00;
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const LOOP_CLR_FD: u16 = 0x01;
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const LOOP_SET_STATUS64: u16 = 0x04;
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const LOOP_CTRL_GET_FREE: u16 = 0x82;
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ioctl_write_int_bad!(ioctl_set_fd, (LOOP_IOCTL << 8) | LOOP_SET_FD);
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ioctl_none!(ioctl_clr_fd, LOOP_IOCTL, LOOP_CLR_FD);
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ioctl_none!(ioctl_ctrl_get_free, LOOP_IOCTL, LOOP_CTRL_GET_FREE);
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ioctl_write_ptr_bad!(ioctl_set_status64, (LOOP_IOCTL << 8) | LOOP_SET_STATUS64, LoopInfo64);
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pub const LO_FLAGS_READ_ONLY: u32 = 1;
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pub const LO_FLAGS_PARTSCAN: u32 = 8;
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const LO_NAME_SIZE: usize = 64;
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const LO_KEY_SIZE: usize = 32;
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#[repr(C)]
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pub struct LoopInfo64 {
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pub lo_device: u64,
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pub lo_inode: u64,
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pub lo_rdevice: u64,
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pub lo_offset: u64,
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pub lo_sizelimit: u64,
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pub lo_number: u32,
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pub lo_encrypt_type: u32,
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pub lo_encrypt_key_size: u32,
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pub lo_flags: u32,
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pub lo_file_name: [u8; LO_NAME_SIZE],
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pub lo_crypt_name: [u8; LO_NAME_SIZE],
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pub lo_encrypt_key: [u8; LO_KEY_SIZE],
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pub lo_init: [u64; 2],
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}
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}
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// ioctl helpers create public fns, do not export them outside the module
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// users should use the wrapper functions below
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use loop_ioctl::*;
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/// Use the GET_FREE ioctl to get or add a free loop device, of which the
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/// /dev/loopN path will be returned. This is inherently racy because of the
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/// delay between this and calling assign, but since assigning is atomic it
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/// does not matter much and will simply cause assign to fail.
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pub fn get_or_create_free_dev() -> Result<String, Error> {
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let ctrl_file = File::open(LOOP_CONTROL)?;
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let free_num = unsafe { ioctl_ctrl_get_free(ctrl_file.as_raw_fd())? };
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let loop_file_path = format!("{}{}", LOOP_NAME, free_num);
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Ok(loop_file_path)
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}
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fn assign_dev(fd: RawFd, backing_fd: RawFd) -> Result<(), Error> {
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unsafe { ioctl_set_fd(fd, backing_fd)?; }
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// set required read-only flag and partscan for convenience
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let mut info: LoopInfo64 = unsafe { std::mem::zeroed() };
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info.lo_flags = LO_FLAGS_READ_ONLY | LO_FLAGS_PARTSCAN;
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unsafe { ioctl_set_status64(fd, &info)?; }
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Ok(())
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}
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/// Open the next available /dev/loopN file and assign the given path to
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/// it as it's backing file in read-only mode.
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pub fn assign<P: AsRef<Path>>(loop_dev: P, backing: P) -> Result<(), Error> {
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let loop_file = File::open(loop_dev)?;
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let backing_file = OpenOptions::new()
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.read(true)
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.open(backing)?;
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assign_dev(loop_file.as_raw_fd(), backing_file.as_raw_fd())?;
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Ok(())
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}
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/// Unassign any file descriptors currently attached to the given
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/// /dev/loopN device.
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pub fn unassign<P: AsRef<Path>>(path: P) -> Result<(), Error> {
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let loop_file = File::open(path)?;
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unsafe { ioctl_clr_fd(loop_file.as_raw_fd())?; }
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Ok(())
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}
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