From 196f81d00ca43654f07d0e926d568735753271fa Mon Sep 17 00:00:00 2001
From: Arshia Ghafoori <arshia001@live.com>
Date: Wed, 25 Dec 2024 09:18:15 +0000
Subject: [PATCH] Implement cross-FS file rename

---
 lib/virtual-fs/src/mem_fs/filesystem.rs | 35 +++++++---
 tests/wasix/cross-fs-rename/main.c      | 89 +++++++++++++++++++++++++
 tests/wasix/cross-fs-rename/run.sh      |  6 ++
 3 files changed, 122 insertions(+), 8 deletions(-)
 create mode 100644 tests/wasix/cross-fs-rename/main.c
 create mode 100755 tests/wasix/cross-fs-rename/run.sh

diff --git a/lib/virtual-fs/src/mem_fs/filesystem.rs b/lib/virtual-fs/src/mem_fs/filesystem.rs
index 65b34ce542f..0e32d0b3ece 100644
--- a/lib/virtual-fs/src/mem_fs/filesystem.rs
+++ b/lib/virtual-fs/src/mem_fs/filesystem.rs
@@ -447,7 +447,7 @@ impl crate::FileSystem for FileSystem {
     }
 
     fn rename<'a>(&'a self, from: &'a Path, to: &'a Path) -> BoxFuture<'a, Result<()>> {
-        Box::pin(async {
+        Box::pin(async move {
             let name_of_to;
 
             // Read lock.
@@ -493,6 +493,7 @@ impl crate::FileSystem for FileSystem {
             };
 
             match (inode_of_from_parent, inode_of_to_parent) {
+                // Rename within this MemFS instance
                 (Either::Left(inode_of_from_parent), Either::Left(inode_of_to_parent)) => {
                     let fs = self.inner.read().map_err(|_| FsError::Lock)?;
 
@@ -572,16 +573,34 @@ impl crate::FileSystem for FileSystem {
 
                     Ok(())
                 }
-                (Either::Right((from_fs, from_path)), Either::Right((to_fs, to_path))) => {
-                    if Arc::ptr_eq(&from_fs, &to_fs) {
-                        let same_fs = from_fs;
 
-                        same_fs.rename(&from_path, &to_path).await
-                    } else {
-                        Err(FsError::InvalidInput)
+                // Rename within the same mounted FS instance
+                (Either::Right((from_fs, from_path)), Either::Right((to_fs, to_path)))
+                    if Arc::ptr_eq(&from_fs, &to_fs) =>
+                {
+                    let same_fs = from_fs;
+                    same_fs.rename(&from_path, &to_path).await
+                }
+
+                // Rename across file systems; we need to do a create and a delete
+                _ => {
+                    let mut from_file = self.new_open_options().read(true).open(from)?;
+                    let mut to_file = self
+                        .new_open_options()
+                        .create_new(true)
+                        .write(true)
+                        .open(to)?;
+                    tokio::io::copy(from_file.as_mut(), to_file.as_mut()).await?;
+                    if let Err(error) = self.remove_file(from) {
+                        tracing::warn!(
+                            ?from,
+                            ?to,
+                            ?error,
+                            "Failed to remove file after cross-FS rename"
+                        );
                     }
+                    Ok(())
                 }
-                _ => Err(FsError::InvalidInput),
             }
         })
     }
diff --git a/tests/wasix/cross-fs-rename/main.c b/tests/wasix/cross-fs-rename/main.c
new file mode 100644
index 00000000000..31f01f52ff8
--- /dev/null
+++ b/tests/wasix/cross-fs-rename/main.c
@@ -0,0 +1,89 @@
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+
+void error_exit(const char *desc, const char *call)
+{
+    const char *err_desc = strerror(errno);
+    printf("Test \"%s\" failed at %s: %s\n", desc, call, err_desc);
+    // Make it visible in the output log as well
+    fprintf(stderr, "Test \"%s\" failed at %s: %s\n", desc, call, err_desc);
+    exit(-1);
+}
+
+void create_and_move_file(const char *from_path, const char *to_path)
+{
+    char test_description[1024] = {0};
+    sprintf(test_description, "%s -> %s", from_path, to_path);
+
+    FILE *f = fopen(from_path, "wb");
+    if (!f)
+    {
+        error_exit(test_description, "fopen");
+    }
+
+    char *txt = "hello";
+    if (!fwrite(txt, 1, 6, f))
+    {
+        error_exit(test_description, "fwrite");
+    }
+
+    if (fclose(f))
+    {
+        error_exit(test_description, "fclose");
+    }
+
+    // /home is a host FS mount
+    if (rename(from_path, to_path))
+    {
+        error_exit(test_description, "rename");
+    }
+
+    f = fopen(to_path, "rb");
+    if (!f)
+    {
+        error_exit(test_description, "fopen 2");
+    }
+
+    char buffer[7] = {0};
+    if (!fread(buffer, 1, 7, f))
+    {
+        error_exit(test_description, "fread");
+    }
+
+    if (strcmp(buffer, txt))
+    {
+        fprintf(stderr, "Expected %s to be equal to %s", buffer, txt);
+        exit(-1);
+    }
+
+    if (fclose(f))
+    {
+        error_exit(test_description, "fclose 2");
+    }
+}
+
+int main()
+{
+    // /tmp is on the MemFS, /temp1 and /temp2 are on separate HostFS instances
+
+    // Move file within MemFS
+    create_and_move_file("/tmp/old", "/tmp/new");
+
+    // Move file within single mounted FS
+    create_and_move_file("/temp1/old", "/temp1/new");
+
+    // Move file from MemFS to mounted FS
+    create_and_move_file("/tmp/file", "/temp1/file");
+
+    // Move file from mounted FS to MemFS
+    create_and_move_file("/temp1/file2", "/tmp/file2");
+
+    // Move file between different mounted FS's
+    create_and_move_file("/temp1/file3", "/temp2/file3");
+
+    printf("0");
+    return 0;
+}
diff --git a/tests/wasix/cross-fs-rename/run.sh b/tests/wasix/cross-fs-rename/run.sh
new file mode 100755
index 00000000000..cc783761c49
--- /dev/null
+++ b/tests/wasix/cross-fs-rename/run.sh
@@ -0,0 +1,6 @@
+TEMP_DIR1=$(mktemp -d)
+TEMP_DIR2=$(mktemp -d)
+
+$WASMER -q run main.wasm --mapdir /temp1:$TEMP_DIR1 --mapdir /temp2:$TEMP_DIR2 > output
+
+printf "0" | diff -u output - 1>/dev/null