VFS: design for the name cache system

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;
+};

core/fs.h

@@ -0,0 +1,7 @@
+#pragma once
+
+
+struct inode {//TODO
+              };
+int fsInodeUnref(struct inode *inode);
+int fsInodeRef(struct inode *inode);

core/fsEntry.c

@@ -0,0 +1,215 @@
+#include "alloc.h"
+#include "assert.h"
+#include "fsEntry.h"
+#include "errno.h"
+#include "list.h"
+#include "mem.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(const struct pstr *p1, const struct pstr *p2)
+{
+    return p1->len == p2->len && (memcmp(p1->name, p2->name, p1->len) == 0);
+}
+
+bool_t pstringIsStr(const struct pstr *p, char *s)
+{
+    size_t slen = strlen(s);
+    return p->len == slen && (memcmp(p->name, s, slen) == 0);
+}
+
+int fsEntryRef(struct fs_entry *entry)
+{
+    entry->ref++;
+    return 0;
+}
+
+int fsEntryUnref(struct fs_entry **entry)
+{
+    struct fs_entry *toDelete = NULL, *entryTmp;
+
+    entryTmp = *entry;
+
+    while (entryTmp) {
+        assert(entryTmp->ref > 0);
+        entryTmp->ref--;
+
+        if (entryTmp->ref > 0)
+            break;
+
+        if (entryTmp == *entry)
+            *entry = NULL;
+
+        if (entryTmp->parent) {
+            struct fs_entry *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;
+}
+
+struct fs_entry *fsEntryAlloc(struct fs_entry *parent, const struct pstr *name, struct inode *inode)
+{
+    struct fs_entry *entry = zalloc(sizeof(struct fs_entry));
+
+    if (!entry)
+        return NULL;
+
+    if (name && name->len > 0) {
+        char *allocName = malloc(name->len);
+
+        if (!allocName) {
+            free(entry);
+            return NULL;
+        }
+
+        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);
+    }
+
+    return entry;
+}
+
+int fsEntryLookup(struct fs_entry *entry, const struct pstr *name, const struct fs_entry *root, struct fs_entry **result)
+{
+    if (pstringIsStr(name, ".")) {
+        *result = entry;
+    } else if (pstringIsStr(name, "..")) {
+        if (entry == root) {
+            *result = entry;
+        } else {
+            // If this entry is mounted, get the mountpoint
+            for (; entry->mountpoint; entry = entry->mountpoint) {
+                // No-op
+            }
+
+            assert(NULL != entry->parent);
+            *result = entry->parent;
+        }
+        fsEntryRef(*result);
+        return 0;
+    } else {
+        struct fs_entry *child;
+        int childIdx;
+        list_foreach_forward_named(entry->childs, child, childIdx, prevSiblings, nextSiblings)
+        {
+            if (pstringIsEq(&child->name, name)) {
+                break;
+            }
+        }
+
+        if (!list_foreach_early_break(entry->childs, child, childIdx))
+            return -ENOENT;
+
+        *result = child;
+    }
+
+    // Follow the mount chain
+    for (; (*result)->mountedFs; *result = (*result)->mountedFs)
+        ;
+
+    fsEntryRef(*result);
+
+    return 0;
+}
+
+int fsEntrySetup(void)
+{
+    return allocBookSlab(sizeof(struct fs_entry), PAGE_SIZE, 0, 0);
+}
+
+int fsEntryMount(struct fs_entry *mountpoint, struct fs_entry *mounted)
+{
+    if (mountpoint->mountedFs != NULL || mounted->mountpoint != NULL) {
+        return -EBUSY;
+    }
+
+    mountpoint->mountedFs = mounted;
+    mounted->mountpoint = mountpoint;
+
+    fsEntryRef(mounted);
+    fsEntryRef(mountpoint);
+
+    return 0;
+}
+
+int fsEntryUmount(struct fs_entry *mounted)
+{
+    if (!mounted->mountpoint || !mounted->mountpoint->mountedFs || mounted->mountpoint->mountedFs != mounted)
+        return -ENOENT;
+
+    if (mounted->mountedFs)
+        return -EBUSY;
+
+    // self + mounted
+    if (mounted->ref != 2)
+        return -EBUSY;
+
+
+    mounted->mountpoint->mountedFs = NULL;
+    fsEntryUnref(&mounted->mountpoint);
+    mounted->mountpoint = NULL;
+    fsEntryUnref(&mounted);
+
+    return 0;
+}

core/fsEntry.h

@@ -0,0 +1,183 @@
+#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                                                                   \
+    }
+
+#define PSTR_STATIC_INIT(n)                                                                   \
+    {                                                                                         \
+        .len = sizeof(n) - 1, .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 fs_entry {
+    struct pstr name;
+    struct inode *node;
+
+    struct fs_entry *parent;     // parent directory
+    struct fs_entry *mountpoint; // if this is a mounted fs, point to mountpoint
+    struct fs_entry *mountedFs;  // Fs possibly mounted on this fsEntry
+
+    struct fs_entry *childs;                      // point to the list of children
+    struct fs_entry *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(const struct pstr *p1, const struct pstr *p2);
+
+/**
+ * @brief Checks if a pstr structure matches a given C string.
+ *
+ * @param s Pointer to the null-terminated C string to compare.
+ * @return bool_t Returns true if the pstr matches the C string, false otherwise.
+ */
+bool_t pstringIsStr(const struct pstr *p, char *s);
+
+/**
+ * @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 fs_entry *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 decremented.
+ * @return int Returns 0 on success.
+ */
+int fsEntryUnref(struct fs_entry **entry);
+
+/**
+ * @brief Allocates and initializes a new fsEntry.
+ *
+ * This function allocates memory for a new `fsEntry` structure, initializes
+ * it with the provided name and inode, and adds it to the parent's list of children.
+ *
+ * @param parent Pointer to the parent `fsEntry` structure. 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` structure associated with the new entry.
+ *
+ * @return struct fsEntry* Pointer to the newly allocated `fsEntry` structure, or NULL if allocation fails.
+ *
+ * @note The reference count of the new entry is set to 1.
+ * @note If a parent is provided, the new entry is added to the parent's list of children and the parent's reference count is incremented.
+ * @note The inode's reference count is incremented.
+ */
+struct fs_entry *fsEntryAlloc(struct fs_entry *parent, const struct pstr *name, struct inode *inode);
+
+/**
+ * @brief Looks up an entry in the file system.
+ *
+ * This function searches for a specified entry within the children
+ * of a given directory entry. The search is limited to the entries
+ * that are already in memory. If the entry is not found, it indicates
+ * that the entry must be resolved using disk accesses.
+ *
+ * @param entry The node in which we are looking for the entry.
+ * @param name The name of the entry we are looking for.
+ * @param root The base node beyond which lookup must not go (to
+ * support chroot): a kind of "barrier".
+ * @param result The fsEntry for the given entry (set only when
+ * the return value is 0).
+ *
+ * @return int Returns 0 if the entry is found, otherwise returns a non-zero error code.
+ *         -ENOENT if the entry could not be found in the entry directory.
+ *
+ * @note The mountpoints are followed.
+ * @note result is a NEW reference to the node. It should be unreferenced when unused.
+ */
+int fsEntryLookup(struct fs_entry *entry, const struct pstr *name,
+                          const struct fs_entry *root, struct fs_entry **result);
+/**
+ * @brief Setup the fsEntry subsystem
+ *
+ */
+int fsEntrySetup(void);
+
+/**
+ * @brief Mounts a file system entry at a specified mount point.
+ *
+ * This function mounts a file system entry (`mounted`) at a specified mount point (`mountpoint`).
+ * It updates the `mountedFs` field of the mount point and the `mountpoint` field of the mounted entry.
+ *
+ * @param mountpoint Pointer to the `fsEntry` structure representing the mount point.
+ * @param mounted Pointer to the `fsEntry` structure representing the file system entry to be mounted.
+ *
+ * @return int Returns 0 on success, or -EBUSY if either the mount point is already occupied or the mounted entry is already mounted.
+ *
+ * @note The reference counts of both the mount point and the mounted entry are incremented.
+ */
+int fsEntryMount(struct fs_entry *mountpoint, struct fs_entry *mounted);
+
+/**
+ * @brief Unmounts a file system entry.
+ *
+ * This function unmounts a file system entry (`mounted`) from its mount point.
+ * It updates the `mountedFs` field of the mount point and the `mountpoint` field of the mounted entry.
+ *
+ * @param mounted Pointer to the `fsEntry` structure representing the file system entry to be unmounted.
+ *
+ * @return int Returns 0 on success, -ENOENT if the entry is not mounted, or -EBUSY if the entry is busy.
+ *
+ * @note The unmount operation fails if the mounted entry has children or other references.
+ * @note The reference counts of both the mount point and the mounted entry are decremented.
+ */
+int fsEntryUmount(struct fs_entry *mounted);

core/klibc.c

@@ -171,7 +171,7 @@ void reverse(char s[])
 }
 
 /* K&R */
-int strlen(const char s[])
+size_t strlen(const char s[])
 {
     int i = 0;
     while (s[i] != '\0')

core/klibc.h

@@ -26,7 +26,7 @@ __attribute__ ((access (write_only, 1, 3))) void *memset(void *s, int c, size_t
 char *itoa(long long int value, char *str, int base);
 int atoi(const char *str);
 void reverse(char s[]);
-int strlen(const char s[]);
+size_t strlen(const char s[]);
 __attribute__ ((access (read_only, 1, 2))) unsigned int strnlen(const char *s, size_t count);
 int strcmp(const char s1[], const char s2[]);
 __attribute__ ((access (read_only, 2), access (write_only, 1, 3))) char *strzcpy(char *dst, const char *src, int len);

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

tests/test.c

@@ -3,8 +3,12 @@
 #include "ata.h"
 #include "assert.h"
 #include "cpu_context.h"
+#include "errno.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 +497,194 @@ 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///";
+    path.name = tmp;
+    path.len = strlen(tmp);
+    struct pstr test  = PSTR_STATIC_INIT("test");
+    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 inode;
+    struct pstr rootname    = PSTR_STATIC_INIT("/");
+    struct pstr homename    = PSTR_STATIC_INIT("home");
+    struct pstr usrname     = PSTR_STATIC_INIT("usr");
+    struct pstr file1name   = PSTR_STATIC_INIT("file1");
+    struct pstr mntname     = PSTR_STATIC_INIT("mnt");
+    struct pstr mntfilename = PSTR_STATIC_INIT("file2");
+    struct pstr dot         = PSTR_STATIC_INIT(".");
+    struct pstr dot2        = PSTR_STATIC_INIT("..");
+
+    // create fs with /home, /mnt, /usr/file1
+    struct fs_entry *root    = fsEntryAlloc(NULL, &rootname, &inode);
+    struct fs_entry *home    = fsEntryAlloc(root, &homename, &inode);
+    struct fs_entry *usr     = fsEntryAlloc(root, &usrname, &inode);
+    struct fs_entry *mnt     = fsEntryAlloc(root, &mntname, &inode);
+    struct fs_entry *file1   = fsEntryAlloc(home, &file1name, &inode);
+
+    // /file2
+    struct fs_entry *rootExt = fsEntryAlloc(NULL, &rootname, &inode);
+    struct fs_entry *mntfile = fsEntryAlloc(rootExt, &mntfilename, &inode);
+    struct fs_entry *res, *res2;
+
+    assert(root && home && usr);
+
+    printf("Test fsEntry: Lookup\n");
+    // find a child
+    assert(fsEntryLookup(root, &homename, NULL, &res) == 0);
+    assert(home == res);
+    fsEntryUnref(&res);
+
+    // cd .
+    assert(fsEntryLookup(home, &dot, NULL, &res) == 0);
+    assert(home == res);
+    fsEntryUnref(&res);
+
+    // cd ..
+    assert(fsEntryLookup(home, &dot2, NULL, &res) == 0);
+    assert(root == res);
+    fsEntryUnref(&res);
+
+    // find a non-child fail
+    assert(fsEntryLookup(home, &usrname, NULL, &res) == -ENOENT);
+
+    // find mnt and mount rootExt
+    assert(fsEntryLookup(root, &mntname, NULL, &res) == 0);
+    assert(res == mnt);
+    assert(fsEntryMount(res, rootExt)==0);
+    fsEntryUnref(&res); //lookup increase ref
+
+    // find on mounted
+    assert(fsEntryLookup(root, &mntname, NULL, &res) == 0);
+    fsEntryUnref(&res); //lookup increase ref
+    assert(fsEntryLookup(res, &mntfilename, NULL, &res2) == 0);
+    fsEntryUnref(&res2); //lookup increase ref
+
+    // Clen rootExt
+    fsEntryUnref(&mntfile);
+
+    // unmount rootExt
+    assert(fsEntryUmount(rootExt) == 0);
+
+
+    printf("Test fsEntry: free tree\n");
+    fsEntryUnref(&usr);
+    assert(root->ref > 0);
+    assert(usr == NULL);
+    fsEntryUnref(&home);
+    assert(home != NULL);
+    fsEntryUnref(&file1);
+    assert(file1 == NULL);
+    fsEntryUnref(&mnt);
+    assert(mnt == NULL);
+
+    fsEntryUnref(&mntfile);
+    fsEntryUnref(&rootExt);
+}
+
 void run_test(void)
 {
+    testFsPstring();
+    testFsEntry();
     // Example of checking thx to access attributs
     //int a[4] = {0};
     //int b[3] = {0};