vhost_user_fs: Add support for CopyFileRange

Add support for the CopyFileRange request, introduced in FUSE 7.28.

Signed-off-by: Sergio Lopez <slp@redhat.com>

vhost_user_fs/src/passthrough.rs

@@ -4,6 +4,7 @@
 
 use std::collections::btree_map;
 use std::collections::BTreeMap;
+use std::convert::TryInto;
 use std::ffi::{CStr, CString};
 use std::fs::File;
 use std::io;
@@ -1644,4 +1645,59 @@ impl FileSystem for PassthroughFs {
             Ok(res as u64)
         }
     }
+
+    fn copyfilerange(
+        &self,
+        _ctx: Context,
+        inode_in: Inode,
+        handle_in: Handle,
+        offset_in: u64,
+        inode_out: Inode,
+        handle_out: Handle,
+        offset_out: u64,
+        len: u64,
+        flags: u64,
+    ) -> io::Result<usize> {
+        let data_in = self
+            .handles
+            .read()
+            .unwrap()
+            .get(&handle_in)
+            .filter(|hd| hd.inode == inode_in)
+            .map(Arc::clone)
+            .ok_or_else(ebadf)?;
+
+        // Take just a read lock as we're not going to alter the file descriptor offset.
+        let fd_in = data_in.file.read().unwrap().as_raw_fd();
+
+        let data_out = self
+            .handles
+            .read()
+            .unwrap()
+            .get(&handle_out)
+            .filter(|hd| hd.inode == inode_out)
+            .map(Arc::clone)
+            .ok_or_else(ebadf)?;
+
+        // Take just a read lock as we're not going to alter the file descriptor offset.
+        let fd_out = data_out.file.read().unwrap().as_raw_fd();
+
+        // Safe because this will only modify `offset_in` and `offset_out` and we check
+        // the return value.
+        let res = unsafe {
+            libc::copy_file_range(
+                fd_in,
+                &mut (offset_in as i64) as &mut _ as *mut _,
+                fd_out,
+                &mut (offset_out as i64) as &mut _ as *mut _,
+                len.try_into().unwrap(),
+                flags.try_into().unwrap(),
+            )
+        };
+        if res < 0 {
+            Err(io::Error::last_os_error())
+        } else {
+            Ok(res as usize)
+        }
+    }
 }