feat: support fuse notify resend

Author: xujihui1985

src/abi/fuse_abi_linux.rs

@@ -197,6 +197,9 @@ const INIT_EXT: u64 = 0x4000_0000;
 // This flag indicates whether the guest kernel enable per-file dax
 const PERFILE_DAX: u64 = 0x2_0000_0000;
 
+// this flag indicates whether the guest kernel enable resend
+const HAS_RESEND: u64 = 1_u64 << 39;
+
 // This flag indicates whether to enable fd-passthrough. It was defined in the
 // Anolis kernel but not in the upstream kernel. To avoid collision, we'll set
 // it to the most significant bit.
@@ -458,6 +461,9 @@ bitflags! {
         /// If this feature is enabled, filesystem will notify guest kernel whether file
         /// enable DAX by EntryOut.Attr.flags of inode when lookup
         const PERFILE_DAX = PERFILE_DAX;
+
+        /// indicates whether the kernel support resend inflight request
+        const HAS_RESEND = HAS_RESEND;
     }
 }
 
@@ -755,7 +761,8 @@ pub enum NotifyOpcode {
     Store = 4,
     Retrieve = 5,
     Delete = 6,
-    CodeMax = 7,
+    Resend = 7,
+    CodeMax = 8,
 }
 
 #[repr(C)]

src/api/server/mod.rs

@@ -51,6 +51,7 @@ pub const MAX_REQ_PAGES: u16 = 256; // 1MB
 pub struct Server<F: FileSystem + Sync> {
     fs: F,
     vers: ArcSwap<ServerVersion>,
+    enabled: Option<FsOptions>,
 }
 
 impl<F: FileSystem + Sync> Server<F> {
@@ -62,6 +63,7 @@ impl<F: FileSystem + Sync> Server<F> {
                 major: KERNEL_VERSION,
                 minor: KERNEL_MINOR_VERSION,
             })),
+            enabled: None,
         }
     }
 }

src/api/server/sync_io.rs

@@ -57,6 +57,27 @@ impl<F: FileSystem + Sync> Server<F> {
             .map_err(Error::FailedToWrite)?;
         buffer_writer.commit(None).map_err(Error::InvalidMessage)
     }
+
+    #[cfg(feature = "fusedev")]
+    pub fn notify_resend<S: BitmapSlice>(
+        &self, 
+        mut w: FuseDevWriter<'_, S>,
+    ) -> Result<()> {
+        if !self.enabled.map_or(false,|enabled| {
+            enabled.contains(FsOptions::HAS_RESEND)
+        }) {
+            return Ok(0)
+        }
+        let mut buffer_writer = w.split_at(0).map_err(Error::FailedToSplitWriter)?;
+        let mut header = OutHeader::default();
+        header.unique = 0;
+        header.error = NotifyOpcode::Resend as i32;
+        buffer_writer
+            .write_obj(header)
+            .map_err(Error::FailedToWrite)?;
+        buffer_writer.commit(None).map_err(Error::InvalidMessage)
+    }
+
     /// Main entrance to handle requests from the transport layer.
     ///
     /// It receives Fuse requests from transport layers, parses the request according to Fuse ABI,
@@ -744,6 +765,7 @@ impl<F: FileSystem + Sync> Server<F> {
                 }
                 let vers = ServerVersion { major, minor };
                 self.vers.store(Arc::new(vers));
+                self.enabled = Some(enabled);
                 if minor < KERNEL_MINOR_VERSION_INIT_OUT_SIZE {
                     ctx.reply_ok(
                         Some(