pbs-config: use new SharedMemory helpers from proxmox-shared-memory crate

depend on proxmox-shared-memory crate.

Signed-off-by: Dietmar Maurer <dietmar@proxmox.com>

pbs-config/src/config_version_cache.rs

@@ -0,0 +1,121 @@
+use std::path::Path;
+use std::sync::Arc;
+use std::sync::atomic::{AtomicUsize, Ordering};
+use std::mem::MaybeUninit;
+
+use anyhow::{bail, Error};
+use once_cell::sync::OnceCell;
+use nix::sys::stat::Mode;
+
+use proxmox::tools::fs::{create_path, CreateOptions};
+
+// openssl::sha::sha256(b"Proxmox Backup ConfigVersionCache v1.0")[0..8];
+pub const PROXMOX_BACKUP_CONFIG_VERSION_CACHE_MAGIC_1_0: [u8; 8] = [25, 198, 168, 230, 154, 132, 143, 131];
+
+const FILE_PATH: &str = pbs_buildcfg::rundir!("/shmem/config-versions");
+
+use proxmox_shared_memory::*;
+
+#[derive(Debug)]
+#[repr(C)]
+struct ConfigVersionCacheData {
+    magic: [u8; 8],
+    // User (user.cfg) cache generation/version.
+    user_cache_generation: AtomicUsize,
+    // Traffic control (traffic-control.cfg) generation/version.
+    traffic_control_generation: AtomicUsize,
+
+    // Add further atomics here (and reduce padding size)
+
+    padding: [u8; 4096 - 3*8],
+}
+
+
+impl Init for ConfigVersionCacheData {
+    fn initialize(this: &mut MaybeUninit<Self>) {
+        unsafe {
+            let me = &mut *this.as_mut_ptr();
+            me.magic = PROXMOX_BACKUP_CONFIG_VERSION_CACHE_MAGIC_1_0;
+        }
+    }
+
+    fn check_type_magic(this: &MaybeUninit<Self>) -> Result<(), Error> {
+        unsafe {
+            let me = &*this.as_ptr();
+            if me.magic != PROXMOX_BACKUP_CONFIG_VERSION_CACHE_MAGIC_1_0 {
+                bail!("ConfigVersionCache: wrong magic number");
+            }
+            Ok(())
+        }
+    }
+}
+
+
+pub struct ConfigVersionCache {
+    shmem: SharedMemory<ConfigVersionCacheData>
+}
+
+static INSTANCE: OnceCell<Arc< ConfigVersionCache>> = OnceCell::new();
+
+impl ConfigVersionCache {
+
+    /// Open the memory based communication channel singleton.
+    pub fn new() -> Result<Arc<Self>, Error> {
+        INSTANCE.get_or_try_init(Self::open).map(Arc::clone)
+    }
+
+    // Actual work of `new`:
+    fn open() -> Result<Arc<Self>, Error> {
+        let user = crate::backup_user()?;
+
+        let dir_opts = CreateOptions::new()
+            .perm(Mode::from_bits_truncate(0o770))
+            .owner(user.uid)
+            .group(user.gid);
+
+        let file_path = Path::new(FILE_PATH);
+        let dir_path = file_path.parent().unwrap();
+        
+        create_path(
+            dir_path,
+            Some(dir_opts.clone()),
+            Some(dir_opts))?;
+
+        let file_opts = CreateOptions::new()
+            .perm(Mode::from_bits_truncate(0o660))
+            .owner(user.uid)
+            .group(user.gid);
+
+        let shmem: SharedMemory<ConfigVersionCacheData> =
+            SharedMemory::open(file_path, file_opts)?;
+
+        Ok(Arc::new(Self { shmem }))
+    }
+
+    /// Returns the user cache generation number.
+    pub fn user_cache_generation(&self) -> usize {
+        self.shmem.data()
+            .user_cache_generation.load(Ordering::Acquire)
+    }
+
+    /// Increase the user cache generation number.
+    pub fn increase_user_cache_generation(&self) {
+        self.shmem.data()
+            .user_cache_generation
+            .fetch_add(1, Ordering::AcqRel);
+    }
+
+    /// Returns the traffic control generation number.
+    pub fn traffic_control_generation(&self) -> usize {
+        self.shmem.data()
+            .traffic_control_generation.load(Ordering::Acquire)
+    }
+
+    /// Increase the traffic control generation number.
+    pub fn increase_traffic_control_generation(&self) {
+        self.shmem.data()
+            .traffic_control_generation
+            .fetch_add(1, Ordering::AcqRel);
+    }
+
+}