82 lines
2.3 KiB
Rust
82 lines
2.3 KiB
Rust
//! Memory based communication channel between proxy & daemon for things such as cache
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//! invalidation.
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use std::os::unix::io::AsRawFd;
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use std::sync::atomic::{AtomicUsize, Ordering};
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use std::sync::Arc;
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use anyhow::Error;
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use nix::fcntl::OFlag;
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use nix::sys::mman::{MapFlags, ProtFlags};
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use nix::sys::stat::Mode;
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use once_cell::sync::OnceCell;
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use proxmox::tools::fs::CreateOptions;
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use proxmox::tools::mmap::Mmap;
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/// In-memory communication channel.
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pub struct Memcom {
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mmap: Mmap<u8>,
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}
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#[repr(C)]
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struct Head {
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// User (user.cfg) cache generation/version.
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user_cache_generation: AtomicUsize,
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}
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static INSTANCE: OnceCell<Arc<Memcom>> = OnceCell::new();
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const MEMCOM_FILE_PATH: &str = pbs_buildcfg::rundir!("/proxmox-backup-memcom");
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const EMPTY_PAGE: [u8; 4096] = [0u8; 4096];
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impl Memcom {
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/// Open the memory based communication channel singleton.
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pub fn new() -> Result<Arc<Self>, Error> {
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INSTANCE.get_or_try_init(Self::open).map(Arc::clone)
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}
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// Actual work of `new`:
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fn open() -> Result<Arc<Self>, Error> {
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let user = crate::backup_user()?;
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let options = CreateOptions::new()
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.perm(Mode::from_bits_truncate(0o660))
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.owner(user.uid)
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.group(user.gid);
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let file = proxmox::tools::fs::atomic_open_or_create_file(
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MEMCOM_FILE_PATH,
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OFlag::O_RDWR | OFlag::O_CLOEXEC,
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&EMPTY_PAGE, options)?;
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let mmap = unsafe {
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Mmap::<u8>::map_fd(
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file.as_raw_fd(),
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0,
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4096,
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ProtFlags::PROT_READ | ProtFlags::PROT_WRITE,
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MapFlags::MAP_SHARED | MapFlags::MAP_NORESERVE | MapFlags::MAP_POPULATE,
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)?
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};
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Ok(Arc::new(Self { mmap }))
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}
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// Shortcut to get the mapped `Head` as a `Head`.
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fn head(&self) -> &Head {
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unsafe { &*(self.mmap.as_ptr() as *const u8 as *const Head) }
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}
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/// Returns the user cache generation number.
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pub fn user_cache_generation(&self) -> usize {
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self.head().user_cache_generation.load(Ordering::Acquire)
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}
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/// Increase the user cache generation number.
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pub fn increase_user_cache_generation(&self) {
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self.head()
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.user_cache_generation
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.fetch_add(1, Ordering::AcqRel);
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}
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}
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