[PATCH proxmox v3 03/10] shared-memory: expose msync to flush in-memory contents to filesystem

[Christian Ebner <c.ebner@proxmox.com>]

Exposes proxmox_sys::mmap::Mmap::msync() to allow flushing all
in-memory contents to the underlying mmapped file. Without this, it
is not guaranteed that contents are persisted until unmapping, which
can lead to data loss in case of host crashes or OOM situations.

Signed-off-by: Christian Ebner <c.ebner@proxmox.com>
---
 proxmox-shared-memory/src/lib.rs | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/proxmox-shared-memory/src/lib.rs b/proxmox-shared-memory/src/lib.rs
index da057366..cd67c63a 100644
--- a/proxmox-shared-memory/src/lib.rs
+++ b/proxmox-shared-memory/src/lib.rs
@@ -12,7 +12,7 @@ use std::path::Path;
 use anyhow::{bail, format_err, Error};
 use nix::errno::Errno;
 use nix::fcntl::OFlag;
-use nix::sys::mman::{MapFlags, ProtFlags};
+use nix::sys::mman::{MapFlags, MsFlags, ProtFlags};
 use nix::sys::stat::Mode;
 
 use proxmox_sys::error::SysError;
@@ -230,6 +230,11 @@ impl<T: Sized + Init> SharedMemory<T> {
     pub fn data_mut(&mut self) -> &mut T {
         &mut self.mmap[0]
     }
+
+    /// Flush all in-memory contents to the backing file.
+    pub fn msync(&self, flags: MsFlags) -> Result<(), Error> {
+        self.mmap.msync(flags).map_err(Into::into)
+    }
 }
 
 /// Helper to initialize nested data
-- 
2.47.3