Optimize log output and print in vfs umount scenario

1. optimize the log of forget, for scenarios where forget cannot handle
when the vfs submount is dropped by umount.
2. remove the error log printed when write fuse fails, and hand it to
the caller to process and print.

Signed-off-by: zyfjeff <zyfjeff@linux.alibaba.com>

Author: zyfjeff

src/api/vfs/sync_io.rs

@@ -91,7 +91,15 @@ impl FileSystem for Vfs {
                 (Right(fs), idata) => fs.forget(ctx, idata.ino(), count),
             },
             Err(e) => {
-                error!("vfs::forget: failed to get_real_rootfs {:?}", e);
+                // When a directory is umount and invalidate entry, a forget request is triggered,
+                // which cannot be forwarded to the backend file system.
+                // this situation is reasonable, so it is changed to warn here
+                warn!(
+                    "vfs::forget: failed to get_real_rootfs {:?}, inode: {:?}, 
+                       maybe it is possible that the vfs submount was dropped by umount, 
+                       which is reasonable.",
+                    e, inode
+                );
             }
         }
     }

src/transport/fusedev/mod.rs

@@ -157,10 +157,7 @@ impl<'a, S: BitmapSlice> FuseDevWriter<'a, S> {
             }
         };
 
-        res.map_err(|e| {
-            error! {"fail to write to fuse device on commit: {}", e};
-            io::Error::from_raw_os_error(e as i32)
-        })
+        res.map_err(|e| io::Error::from_raw_os_error(e as i32))
     }
 
     /// Return number of bytes already written to the internal buffer.