nydus-image: optimize the way to generate tarfs

Optimize the way to generate tarfs from tar file, to reduce memory
and time consumption.

Signed-off-by: Jiang Liu <gerry@linux.alibaba.com>

rafs/src/builder/core/bootstrap.rs

@@ -159,8 +159,7 @@ impl Bootstrap {
         if parent.is_dir() {
             // Sort children list by name, so that we can improve performance in fs read_dir using
             // binary search.
-            tree.children
-                .sort_by_key(|child| child.node.name().to_os_string());
+            tree.children.sort_by_key(|child| child.name.clone());
             parent.inode.set_child_count(tree.children.len() as u32);
             if ctx.fs_version.is_v5() {
                 parent.inode.set_child_index(index);

rafs/src/builder/core/tree.rs

@@ -16,7 +16,7 @@
 //!   lower tree (MetadataTree).
 //! - Traverse the merged tree (OverlayTree) to dump bootstrap and data blobs.
 
-use std::ffi::OsStr;
+use std::ffi::{OsStr, OsString};
 use std::path::{Path, PathBuf};
 use std::sync::Arc;
 
@@ -36,15 +36,18 @@ use crate::metadata::{Inode, RafsInodeExt, RafsSuper};
 pub struct Tree {
     /// Filesystem node.
     pub node: Node,
+    pub name: OsString,
     /// Children tree nodes.
     pub children: Vec<Tree>,
 }
 
 impl Tree {
     /// Create a new instance of `Tree` from a filesystem node.
     pub fn new(node: Node) -> Self {
+        let name = node.name().to_owned();
         Tree {
             node,
+            name,
             children: Vec::new(),
         }
     }
@@ -86,6 +89,17 @@ impl Tree {
         Ok(())
     }
 
+    /// Get index of child node with specified `name`.
+    #[allow(clippy::manual_find)]
+    pub fn get_child_idx(&self, name: &OsStr) -> Option<usize> {
+        for idx in 0..self.children.len() {
+            if self.children[idx].name == name {
+                return Some(idx);
+            }
+        }
+        None
+    }
+
     /// Apply new node (upper layer) to node tree (lower layer).
     ///
     /// Support overlay defined in OCI image layer spec
@@ -133,7 +147,7 @@ impl Tree {
             for idx in 0..self.children.len() {
                 let child = &mut self.children[idx];
                 // Skip if path component name not match
-                if target_paths[depth] != child.node.name() {
+                if target_paths[depth] != child.name {
                     continue;
                 }
                 // Modifications: Replace the node
@@ -154,13 +168,10 @@ impl Tree {
         }
 
         // Additions: Add new node to children
-        if depth == target_paths_len - 1 && target_paths[depth - 1] == self.node.name() {
+        if depth == target_paths_len - 1 && target_paths[depth - 1] == self.name {
             let mut node = target.clone();
             node.overlay = Overlay::UpperAddition;
-            self.children.push(Tree {
-                node,
-                children: Vec::new(),
-            });
+            self.children.push(Tree::new(node));
             return Ok(true);
         }
 
@@ -202,7 +213,7 @@ impl Tree {
             // Handle Removals
             if depth == target_paths_len - 1
                 && whiteout_type.is_removal()
-                && origin_name == Some(child.node.name())
+                && origin_name == Some(&child.name)
             {
                 // Remove the whole lower node
                 self.children.remove(idx);
@@ -215,7 +226,7 @@ impl Tree {
                 && depth == target_paths_len - 2
             {
                 if let Some(parent_name) = parent_name {
-                    if parent_name == child.node.name() {
+                    if parent_name == child.name {
                         child.node.overlay = Overlay::UpperOpaque;
                         // Remove children of the lower node
                         child.children.clear();
@@ -224,7 +235,7 @@ impl Tree {
                 }
             } else if whiteout_type == WhiteoutType::OverlayFsOpaque
                 && depth == target_paths_len - 1
-                && target.name() == child.node.name()
+                && target.name() == child.name
             {
                 // Remove all children under the opaque directory
                 child.node.overlay = Overlay::UpperOpaque;

rafs/src/builder/core/v6.rs

@@ -159,14 +159,14 @@ impl Node {
         let mut d_size = 0;
 
         // Sort all children if "." and ".." are not at the head after sorting.
-        if !tree.children.is_empty() && tree.children[0].node.name() < ".." {
+        if !tree.children.is_empty() && tree.children[0].name < *".." {
             let mut children = Vec::with_capacity(tree.children.len() + 2);
             let dot = OsString::from(".");
             let dotdot = OsString::from("..");
             children.push(dot.as_os_str());
             children.push(dotdot.as_os_str());
             for child in tree.children.iter() {
-                children.push(child.node.name());
+                children.push(&child.name);
             }
             children.sort_unstable();
 
@@ -187,7 +187,7 @@ impl Node {
                 + "..".as_bytes().len()
                 + size_of::<RafsV6Dirent>()) as u64;
             for child in tree.children.iter() {
-                let len = child.node.name().as_bytes().len() + size_of::<RafsV6Dirent>();
+                let len = child.name.as_bytes().len() + size_of::<RafsV6Dirent>();
                 // erofs disk format requires dirent to be aligned to block size.
                 if (d_size % block_size) + len as u64 > block_size {
                     d_size = round_up(d_size as u64, block_size);
@@ -604,13 +604,13 @@ impl Bootstrap {
             trace!(
                 "{:?} child {:?} offset {}, mode {}",
                 node.name(),
-                child.node.name(),
+                child.name,
                 child.node.v6_offset,
                 child.node.inode.mode()
             );
             node.v6_dirents.push((
                 child.node.v6_offset,
-                child.node.name().to_os_string(),
+                child.name.to_os_string(),
                 child.node.inode.mode(),
             ));
             if child.node.is_dir() {