From 3ecb5b9d66099e5e52ecb913f5e7cb7e77789b09 Mon Sep 17 00:00:00 2001
From: Mathieu Maret <mathieu.maret@gmail.com>
Date: Thu, 23 May 2024 00:21:41 +0200
Subject: [PATCH] VFS: design for the name cache system

---
 core/fs.c      |  13 +++++
 core/fs.h      |   7 +++
 core/fsEntry.c | 133 +++++++++++++++++++++++++++++++++++++++++++++++++
 core/fsEntry.h | 118 +++++++++++++++++++++++++++++++++++++++++++
 core/main.c    |   4 ++
 tests/test.c   | 129 +++++++++++++++++++++++++++++++++++++++++++++++
 6 files changed, 404 insertions(+)
 create mode 100644 core/fs.c
 create mode 100644 core/fs.h
 create mode 100644 core/fsEntry.c
 create mode 100644 core/fsEntry.h

diff --git a/core/fs.c b/core/fs.c
new file mode 100644
index 0000000..290b8c5
--- /dev/null
+++ b/core/fs.c
@@ -0,0 +1,13 @@
+#include "fs.h"
+
+int fsInodeUnref(struct inode *inode)
+{
+    (void)inode;
+    return 0;
+};
+
+int fsInodeRef(struct inode *inode)
+{
+    (void)inode;
+    return 0;
+};
diff --git a/core/fs.h b/core/fs.h
new file mode 100644
index 0000000..aa70ed1
--- /dev/null
+++ b/core/fs.h
@@ -0,0 +1,7 @@
+#pragma once
+
+
+struct inode {//TODO
+              };
+int fsInodeUnref(struct inode *inode);
+int fsInodeRef(struct inode *inode);
diff --git a/core/fsEntry.c b/core/fsEntry.c
new file mode 100644
index 0000000..1381652
--- /dev/null
+++ b/core/fsEntry.c
@@ -0,0 +1,133 @@
+#include "alloc.h"
+#include "assert.h"
+#include "fsEntry.h"
+#include "errno.h"
+#include "list.h"
+#include "mem.h"
+#include "stdint.h"
+
+bool_t pstringSplipPath(struct pstr *path, struct pstr *upper, struct pstr *lower)
+{
+    typeof(path->name) curPos  = path->name;
+    typeof(path->len) curLen   = path->len;
+    typeof(path->len) upperLen = 0;
+
+    // Skip leading /
+    while (curLen > 0 && curPos[0] == '/') {
+        curPos++;
+        curLen--;
+    }
+
+    upper->name = curPos;
+
+    // Find first non /
+    while (curLen > 0 && curPos[0] != '/') {
+        upperLen++;
+        curLen--;
+        curPos++;
+    }
+    upper->len = upperLen;
+
+    while (curLen > 0 && curPos[0] == '/') {
+        curPos++;
+        curLen--;
+    }
+    lower->name = curPos;
+    lower->len  = path->len - (lower->name - path->name);
+
+    return lower->len > 0;
+}
+
+bool_t pstringIsEq(struct pstr *p1, struct pstr *p2)
+{
+    return p1->len == p2->len && (memcmp(p1, p2, p1->len) == 0);
+}
+
+int fsEntryRef(struct fsEntry *entry)
+{
+    entry->ref++;
+    return 0;
+}
+
+int fsEntryUnref(struct fsEntry **entry)
+{
+    struct fsEntry *toDelete = NULL, *entryTmp;
+
+    entryTmp = *entry;
+    *entry   = NULL;
+
+    while (entryTmp) {
+        assert(entryTmp->ref > 0);
+        entryTmp->ref--;
+
+        if (entryTmp->ref > 0)
+            break;
+
+        if (entryTmp == *entry)
+            entry = NULL;
+
+        if (entryTmp->parent) {
+            struct fsEntry *parent = entryTmp->parent;
+
+            assert(entryTmp->parent->ref >= 1);
+
+            list_delete_named(parent->childs, entryTmp, prevSiblings, nextSiblings);
+            // At next iteration we will decrement parent's ref cnt
+        }
+
+        // Avoid recursivity in kernel by using a list of entry to suppress
+        list_add_tail_named(toDelete, entryTmp, prevSiblings, nextSiblings);
+
+        // now, unref parent
+        entryTmp = entryTmp->parent;
+    }
+
+    // free 0 ref entries
+    while (!list_is_empty_named(toDelete, prevSiblings, nextSiblings)) {
+        entryTmp = list_pop_head_named(toDelete, prevSiblings, nextSiblings);
+        fsInodeUnref(entryTmp->node);
+        free(entryTmp);
+    }
+
+    return 0;
+}
+
+int fsEntryNewChild(struct fsEntry *parent, const struct pstr *name, struct inode *inode,
+                    struct fsEntry **result)
+{
+    struct fsEntry *entry = malloc(sizeof(struct fsEntry));
+
+    if (!entry)
+        return -ENOMEM;
+
+    if (name && name->len > 0) {
+        char *allocName = malloc(name->len);
+
+        if (!allocName) {
+            free(entry);
+            return -ENOMEM;
+        }
+
+        memcpy(allocName, name->name, name->len);
+        entry->name.len  = name->len;
+        entry->name.name = allocName;
+    }
+
+    entry->ref    = 1;
+    entry->node   = inode;
+    entry->parent = parent;
+
+    fsInodeRef(inode);
+    if (parent) {
+        fsEntryRef(parent);
+        list_add_head_named(parent->childs, entry, prevSiblings, nextSiblings);
+    }
+
+    *result = entry;
+
+    return 0;
+}
+
+int fsEntrySetup(void){
+    return allocBookSlab(sizeof(struct fsEntry), PAGE_SIZE, 0, 0);
+}
diff --git a/core/fsEntry.h b/core/fsEntry.h
new file mode 100644
index 0000000..7d3e924
--- /dev/null
+++ b/core/fsEntry.h
@@ -0,0 +1,118 @@
+#pragma once
+
+#include "fs.h"
+#include "stdint.h"
+#include "stddef.h"
+
+/**
+ * Those structures aimes to represent VFS directory entries in memory.
+ * It's the equivalent of the Linux dentry or SimpleOs sos_fs_nscache_node.
+ */
+
+/**
+ * Path or Pascal String
+ * */
+struct pstr {
+    size_t len;
+    const char *name;
+};
+
+#define PSTR_INIT(n, l)                                                                       \
+    {                                                                                         \
+        .len = l, .name = n                                                                   \
+    }
+
+
+/**
+ * @brief Structure representing a file system entry.
+ *
+ * This structure holds information about a file system entry,
+ * including its name, associated inode, relationships within
+ * the file system hierarchy, and reference count.
+ */
+struct fsEntry {
+    struct pstr name;
+    struct inode *node;
+
+    struct fsEntry *parent;     // parent directory
+    struct fsEntry *mountpoint; // if this is a mounted fs, point to mountpoint
+    struct fsEntry *mountedFs;  // Fs possibly mounted on this fsEntry
+
+    struct fsEntry *childs;                      // point to the list of children
+    struct fsEntry *nextSiblings, *prevSiblings; // Sibling at the same level
+
+    uint ref; // reference counter
+};
+
+/**
+ * @brief Splits a pstr path into upper and lower components.
+ *
+ * This function takes a path and splits it into an upper component
+ * (the first segment of the path) and a lower component (the rest of the path).
+ *
+ * @param path Pointer to the input pstr structure representing the path.
+ * @param upper Pointer to the pstr structure to store the upper component.
+ * @param lower Pointer to the pstr structure to store the lower component.
+ * @return bool_t Returns true if there is a lower component, false otherwise.
+ */
+bool_t pstringSplipPath(struct pstr *path, struct pstr *upper, struct pstr *lower);
+
+/**
+ * @brief Compares two pstr structures to check if they are equal.
+ *
+ * This function compares the length and the content of the strings
+ * in the two provided pstr structures.
+ *
+ * @param a Pointer to the first pstr structure.
+ * @param b Pointer to the second pstr structure.
+ * @return int Returns 1 if the structures are equal, 0 otherwise.
+ */
+bool_t pstringIsEq(struct pstr *p1, struct pstr *p2);
+
+/**
+ * @brief Increments the reference count of a file system entry.
+ *
+ * This function increments the reference count of the given file system
+ * entry. It is typically used to manage the lifecycle of file system
+ * entries, ensuring that they are not prematurely deallocated.
+ *
+ * @param entry Pointer to the fsEntry structure whose reference count will be incremented.
+ * @return int Returns 0 on success.
+ */
+int fsEntryRef(struct fsEntry *entry);
+
+/**
+ * @brief Decrements the reference count of a file system entry.
+ *
+ * This function decrements the reference count of the given file system
+ * entry. It is typically used to manage the lifecycle of file system
+ * entries, ensuring that they are not prematurely deallocated.
+ *
+ * @param entry Pointer to the fsEntry structure whose reference count will be incremented.
+ * @return int Returns 0 on success.
+ */
+int fsEntryUnref(struct fsEntry **entry);
+
+/**
+ * @brief Creates a new child fsEntry under the specified parent.
+ *
+ * This function allocates and initializes a new fsEntry structure
+ * representing a file system entry. The new entry is added as a child
+ * of the specified parent. It also handles reference counting for
+ * the parent entry and the associated inode.
+ *
+ * @param parent Pointer to the parent fsEntry. Can be NULL if the new entry has no parent.
+ * @param name Pointer to the pstr structure representing the name of the new entry. Can be NULL.
+ * @param inode Pointer to the inode associated with the new entry.
+ * @param result Pointer to a location where the pointer to the newly created fsEntry will be stored.
+ * @return int Returns 0 on success, or a negative error code on failure.
+ *         -ENOMEM if memory allocation fails.
+ */
+int fsEntryNewChild(struct fsEntry *parent, const struct pstr *name, struct inode *inode,
+                    struct fsEntry **result);
+
+/**
+ * @brief Setup the fsEntry subsystem
+ *
+ */
+int fsEntrySetup(void);
diff --git a/core/main.c b/core/main.c
index c3a188f..24312a5 100644
--- a/core/main.c
+++ b/core/main.c
@@ -3,6 +3,7 @@
 #include "ata.h"
 #include "elf.h"
 #include "exception.h"
+#include "fsEntry.h"
 #include "gdt.h"
 #include "idt.h"
 #include "interrupt.h"
@@ -259,6 +260,9 @@ void kmain(unsigned long magic, unsigned long addr)
     irqSetRoutine(IRQ_TIMER, pit_handler);
 
     ATAInit();
+
+    // VFS name caching
+    fsEntrySetup();
 #ifdef RUN_TEST
     run_test();
 #endif
diff --git a/tests/test.c b/tests/test.c
index 4f7d964..1f1a70f 100644
--- a/tests/test.c
+++ b/tests/test.c
@@ -3,8 +3,11 @@
 #include "ata.h"
 #include "assert.h"
 #include "cpu_context.h"
+#include "fsEntry.h"
 #include "kernel.h"
 #include "klibc.h"
+#include "stddef.h"
+#include "stdint.h"
 #include "thread.h"
 #include "list.h"
 #include "mem.h"
@@ -493,8 +496,134 @@ void testRingBuffer()
     ringbufferDestroy(inst);
 }
 
+void printPstr(struct pstr *str){
+    for(uint i = 0; i < str->len; i++){
+        putc(str->name[i]);
+    }
+}
+void printPstrln(struct pstr *str){
+     printPstr(str);
+     putc('\n');
+}
+
+void testFsPstring()
+{
+    bool_t result;
+    struct pstr path, upper, lower, lower2, lower3;
+
+    // Test 1
+    path.name = "/usr/local/bin";
+    path.len = 14;
+    result = pstringSplipPath(&path, &upper, &lower);
+    printf("Test 1:\n");
+    printPstrln(&path);
+    printPstrln(&upper);
+    printPstrln(&lower);
+    printf("Result: %s\n\n", result ? "true" : "false");
+
+    // Test 2
+    path.name = "/home/user";
+    path.len = 10;
+    result = pstringSplipPath(&path, &upper, &lower);
+    printf("Test 2:\n");
+    printPstrln(&path);
+    printPstrln(&upper);
+    printPstrln(&lower);
+    printf("Result: %s\n\n", result ? "true" : "false");
+
+    // Test 3
+    path.name = "/tmp";
+    path.len = 4;
+    result = pstringSplipPath(&path, &upper, &lower);
+    printf("Test 3:\n");
+    printPstrln(&path);
+    printPstrln(&upper);
+    printPstrln(&lower);
+    printf("Result: %s\n\n", result ? "true" : "false");
+
+    // Test 4
+    path.name = "/var/log/";
+    path.len = 9;
+    result = pstringSplipPath(&path, &upper, &lower);
+    printf("Test 4:\n");
+    printPstrln(&path);
+    printPstrln(&upper);
+    printPstrln(&lower);
+    printf("Result: %s\n\n", result ? "true" : "false");
+
+    // Test 5
+    path.name = "/";
+    path.len = 1;
+    result = pstringSplipPath(&path, &upper, &lower);
+    printf("Test 5:\n");
+    printPstrln(&path);
+    printPstrln(&upper);
+    printPstrln(&lower);
+    printf("Result: %s\n\n", result ? "true" : "false");
+
+    // Test 6
+    const char *tmp   = "///home///file/test///";
+    const char *testS = "test";
+    path.name = tmp;
+    path.len = strlen(tmp);
+    struct pstr test  = PSTR_INIT(testS, strlen(testS));
+    struct pstr empty = PSTR_INIT("", 0);
+    struct pstr slash = PSTR_INIT("/", 1);
+    struct pstr dot = PSTR_INIT("..", 2);
+
+    printf("Test 6:\n");
+    printPstr(&path);
+    assert(pstringSplipPath(&path, &upper, &lower));
+    printf("\nUpper: ");
+    printPstr(&upper);
+    printf("\nLower: ");
+    printPstr(&lower);
+    printf("\n");
+    assert(pstringSplipPath(&lower, &upper, &lower2));
+    printf("\nUpper: ");
+    printPstr(&upper);
+    printf("\nLower: ");
+    printPstr(&lower2);
+    printf("\n");
+    assert(pstringSplipPath(&lower2, &upper, &lower3) == 0);
+    printf("\nUpper: ");
+    printPstr(&upper);
+    printf("\nLower: ");
+    printPstr(&lower3);
+    printf("\n");
+    assert(pstringIsEq(&upper, &test));
+    assert(pstringSplipPath(&empty, &upper, &lower) == FALSE);
+    assert(pstringSplipPath(&slash, &upper, &lower) == FALSE);
+    assert(pstringIsEq(&empty, &test) == FALSE);
+    assert(pstringIsEq(&dot, &test) == FALSE);
+
+
+}
+
+void testFsEntry()
+{
+    printf("Test fsEntry: create tree\n");
+    struct inode node;
+    struct fsEntry *root, *home, *usr;
+    struct pstr rootname = PSTR_INIT("root", 4);
+    struct pstr homename = PSTR_INIT("home", 4);
+    struct pstr usrname  = PSTR_INIT("usr", 3);
+    assert(fsEntryNewChild(NULL, &rootname, &node, &root) == 0);
+    assert(fsEntryNewChild(root, &homename, &node, &home) == 0);
+    assert(fsEntryNewChild(root, &usrname, &node, &usr) == 0);
+
+    printf("Test fsEntry: free tree\n");
+    fsEntryUnref(&usr);
+    assert(root->ref > 0);
+    assert(usr == NULL);
+    fsEntryUnref(&home);
+    assert(usr == NULL);
+}
+
 void run_test(void)
 {
+    testFsPstring();
+    testFsEntry();
     // Example of checking thx to access attributs
     //int a[4] = {0};
     //int b[3] = {0};