Fix the type conversion in statfs with TryFrom trait

deps/sefs

@@ -1 +1 @@
-Subproject commit 232823888c83c2ad3a29dee219d26252bcda37b1
+Subproject commit 10424324bc67f56f0418604202767a4fd4367d7b

src/libos/src/fs/fs_ops/statfs.rs

@@ -1,5 +1,6 @@
 use super::*;
 use rcore_fs::vfs::FsInfo;
+use std::convert::TryFrom;
 use std::ffi::CString;
 
 pub fn do_fstatfs(fd: FileDesc) -> Result<Statfs> {
@@ -8,7 +9,7 @@ pub fn do_fstatfs(fd: FileDesc) -> Result<Statfs> {
     let file_ref = current!().file(fd)?;
     let statfs = {
         let fs_info = file_ref.fs()?.info();
-        do_statfs_inner(fs_info)?
+        Statfs::try_from(fs_info)?
     };
     trace!("fstatfs result: {:?}", statfs);
     Ok(statfs)
@@ -24,25 +25,12 @@ pub fn do_statfs(path: &str) -> Result<Statfs> {
     };
     let statfs = {
         let fs_info = inode.fs().info();
-        do_statfs_inner(fs_info)?
+        Statfs::try_from(fs_info)?
     };
     trace!("statfs result: {:?}", statfs);
     Ok(statfs)
 }
 
-fn do_statfs_inner(fs_info: FsInfo) -> Result<Statfs> {
-    let statfs = if fs_info.magic == rcore_fs_unionfs::UNIONFS_MAGIC
-        || fs_info.magic == rcore_fs_sefs::SEFS_MAGIC as usize
-    {
-        let mut host_statfs = host_statfs()?;
-        host_statfs.f_type = fs_info.magic;
-        host_statfs
-    } else {
-        Statfs::from(fs_info)
-    };
-    Ok(statfs)
-}
-
 #[derive(Default, Debug)]
 #[repr(C)]
 pub struct Statfs {
@@ -87,8 +75,17 @@ impl Statfs {
     }
 }
 
-impl From<FsInfo> for Statfs {
-    fn from(info: FsInfo) -> Self {
+impl TryFrom<FsInfo> for Statfs {
+    type Error = error::Error;
+
+    fn try_from(info: FsInfo) -> Result<Self> {
+        let statfs = if info.magic == rcore_fs_unionfs::UNIONFS_MAGIC
+            || info.magic == rcore_fs_sefs::SEFS_MAGIC as usize
+        {
+            let mut host_statfs = host_statfs()?;
+            host_statfs.f_type = info.magic;
+            host_statfs
+        } else {
             Self {
                 f_type: match info.magic {
                     // The "/dev" and "/dev/shm" are tmpfs on Linux, so we transform the
@@ -111,6 +108,8 @@ impl From<FsInfo> for Statfs {
                 f_flags: 0,
                 f_spare: [0usize; 4],
             }
+        };
+        Ok(statfs)
     }
 }