From bd5120f8d0e6f5f1e2a944a779a08c2839516999 Mon Sep 17 00:00:00 2001
From: "S.J.R. van Schaik" <stephan@whiteboxsystems.nl>
Date: Mon, 12 Jun 2017 13:15:28 +0200
Subject: [PATCH] mufs: use a buffer to operate on data in-place to reduce the
 amount of I/O in read_dirent()/write_dirent()

---
 source/fs/mufs/dir.c | 56 +++++++++++++++++++++++++---------------------------
 1 file changed, 27 insertions(+), 29 deletions(-)

diff --git a/source/fs/mufs/dir.c b/source/fs/mufs/dir.c
index dab058a..ceada1c 100644
--- a/source/fs/mufs/dir.c
+++ b/source/fs/mufs/dir.c
@@ -178,55 +178,53 @@ size_t read_dirent(struct mufs *fs, struct mufs_tree *tree,
 	struct mufs_dirent *dirent, uint32_t va)
 {
 	struct flash_dev *dev = fs->dev;
-	struct mufs_dentry entry;
-	size_t ret = 0;
-	size_t len;
-	uint32_t base, offset;
+	char data[1 << dev->log2_block_size];
+	struct mufs_dentry *entry;
+	uint32_t offset;
 
 	offset = va & ((UINT32_C(1) << dev->log2_block_size) - 1);
-	base = align(va, dev->log2_block_size);
+	va = align(va, dev->log2_block_size);
 
-	if (va + sizeof(entry) > tree->file_size)
+	if (mufs_tree_read(tree, data, va, 1 << dev->log2_block_size) == 0)
 		return 0;
 
-	if (mufs_tree_read(tree, &entry, va, sizeof entry) == 0)
+	if (offset + sizeof entry > (UINT32_C(1) << dev->log2_block_size))
 		return 0;
 
-	if (!entry.type)
+	entry = (struct mufs_dentry *)(data + offset);
+
+	if (!entry->type)
 		return 0;
 
-	ret += sizeof entry;
-	va += sizeof entry;
-	len = min(entry.path_len, sizeof(dirent->path - 1));
-
-	if (va + len > tree->file_size)
+	if (offset + sizeof *entry + entry->path_len >
+		(UINT32_C(1) << dev->log2_block_size))
 		return 0;
 
-	if (mufs_tree_read(tree, dirent->path, va, len) == 0)
-		return 0;
+	memcpy(dirent->path, data + offset + sizeof *entry, entry->path_len);
+	dirent->path[entry->path_len] = '\0';
+	dirent->type = entry->type;
 
-	dirent->path[len] = '\0';
-	ret += len;
-
-	dirent->type = entry.type;
-
-	if (mufs_lookup_page(tree, &dirent->tree.va, base) < 0)
+	if (mufs_lookup_page(tree, &dirent->tree.va, va) < 0)
 		return 0;
 
 	dirent->tree.fs = fs;
 	dirent->tree.va = (dirent->tree.va << dev->log2_block_size) + offset +
 		offsetof(struct mufs_dentry, tree);
-	dirent->tree.file_size = entry.tree.file_size;
-	dirent->tree.root = entry.tree.root;
-	dirent->tree.depth = entry.tree.depth;
+	dirent->tree.file_size = entry->tree.file_size;
+	dirent->tree.root = entry->tree.root;
+	dirent->tree.depth = entry->tree.depth;
 
-	return ret;
+	return sizeof *entry + entry->path_len;
 }
 
 size_t write_dirent(struct mufs_tree *tree,
 	uint32_t va, struct mufs_dirent *dirent)
 {
+	struct mufs *fs = tree->fs;
+	struct flash_dev *dev = fs->dev;
+	char data[1 << dev->log2_block_size];
 	struct mufs_dentry entry;
+	size_t size;
 
 	entry.type = dirent->type;
 	entry.tree.file_size = dirent->tree.file_size;
@@ -234,11 +232,11 @@ size_t write_dirent(struct mufs_tree *tree,
 	entry.tree.depth = dirent->tree.depth;
 	entry.path_len = strlen(dirent->path);
 
-	if (mufs_tree_write(tree, dirent->path, va + sizeof entry,
-		entry.path_len) == 0)
-		return 0;
+	memcpy(data, &entry, sizeof entry);
+	memcpy(data + sizeof entry, dirent->path, entry.path_len);
+	size = sizeof entry + entry.path_len;
 
-	if (mufs_tree_write(tree, &entry, va, sizeof entry) == 0)
+	if (mufs_tree_write(tree, data, va, size) == 0)
 		return 0;
 
 	va += sizeof entry + entry.path_len;