✨ 089 文件系统 namei

docs/11 文件系统/089 文件系统 namei.md

@@ -0,0 +1,11 @@
+# 文件系统 namei
+
+主要完成以下函数：
+
+```c++
+// 获取 pathname 对应的父目录 inode
+static inode_t *named(char *pathname, char **next);
+
+// 获取 pathname 对应的 inode
+static inode_t *namei(char *pathname);
+```

src/fs/namei.c

@@ -3,11 +3,73 @@
 #include <onix/stat.h>
 #include <onix/syscall.h>
 #include <onix/string.h>
+#include <onix/task.h>
 #include <onix/assert.h>
 #include <onix/debug.h>
+#include <onix/stat.h>
 
 #define LOGK(fmt, args...) DEBUGK(fmt, ##args)
 
+#define P_EXEC IXOTH
+#define P_READ IROTH
+#define P_WRITE IWOTH
+
+static bool permission(inode_t *inode, u16 mask)
+{
+    u16 mode = inode->desc->mode;
+
+    if (!inode->desc->nlinks)
+        return false;
+
+    task_t *task = running_task();
+    if (task->uid == KERNEL_USER)
+        return true;
+
+    if (task->uid == inode->desc->uid)
+        mode >>= 6;
+    else if (task->gid == inode->desc->gid)
+        mode >>= 3;
+
+    if ((mode & mask & 0b111) == mask)
+        return true;
+    return false;
+}
+
+// 获取第一个分隔符
+char *strsep(const char *str)
+{
+    char *ptr = (char *)str;
+    while (true)
+    {
+        if (IS_SEPARATOR(*ptr))
+        {
+            return ptr;
+        }
+        if (*ptr++ == EOS)
+        {
+            return NULL;
+        }
+    }
+}
+
+// 获取最后一个分隔符
+char *strrsep(const char *str)
+{
+    char *last = NULL;
+    char *ptr = (char *)str;
+    while (true)
+    {
+        if (IS_SEPARATOR(*ptr))
+        {
+            last = ptr;
+        }
+        if (*ptr++ == EOS)
+        {
+            return last;
+        }
+    }
+}
+
 // 判断文件名是否相等
 static bool match_name(const char *name, const char *entry_name, char **next)
 {
@@ -121,58 +183,103 @@ static buffer_t *add_entry(inode_t *dir, const char *name, dentry_t **result)
     };
 }
 
-#include <onix/task.h>
-
-void dir_test()
+// 获取 pathname 对应的父目录 inode
+inode_t *named(char *pathname, char **next)
 {
+    inode_t *inode = NULL;
     task_t *task = running_task();
-    inode_t *inode = task->iroot;
+    char *left = pathname;
+    if (IS_SEPARATOR(left[0]))
+    {
+        inode = task->iroot;
+        left++;
+    }
+    else if (left[0])
+        inode = task->ipwd;
+    else
+        return NULL;
+
     inode->count++;
-    char *next = NULL;
+    *next = left;
+
+    if (!*left)
+    {
+        return inode;
+    }
+
+    char *right = strrsep(left);
+    if (!right || right < left)
+    {
+        return inode;
+    }
+
+    right++;
+
+    *next = left;
     dentry_t *entry = NULL;
     buffer_t *buf = NULL;
+    while (true)
+    {
+        buf = find_entry(&inode, left, next, &entry);
+        if (!buf)
+            goto failure;
 
-    buf = find_entry(&inode, "hello.txt", &next, &entry);
-    idx_t nr = entry->nr;
-    brelse(buf);
+        dev_t dev = inode->dev;
+        iput(inode);
+        inode = iget(dev, entry->nr);
+        if (!ISDIR(inode->desc->mode) || !permission(inode, P_EXEC))
+            goto failure;
 
-    buf = add_entry(inode, "world.txt", &entry);
-    entry->nr = nr;
+        if (right == *next)
+            goto success;
 
-    inode_t *hello = iget(inode->dev, nr);
-    hello->desc->nlinks++;
-    hello->buf->dirty = true;
+        left = *next;
+    }
 
-    iput(inode);
-    iput(hello);
+success:
     brelse(buf);
+    return inode;
 
-    // char pathname[] = "d1/d2/d3/d4";
-
-    // dev_t dev = inode->dev;
-    // char *name = pathname;
-    // buf = find_entry(&inode, name, &next, &entry);
-    // brelse(buf);
+failure:
+    brelse(buf);
+    iput(inode);
+    return NULL;
+}
 
-    // iput(inode);
-    // inode = iget(dev, entry->nr);
+// 获取 pathname 对应的 inode
+inode_t *namei(char *pathname)
+{
+    char *next = NULL;
+    inode_t *dir = named(pathname, &next);
+    if (!dir)
+        return NULL;
+    if (!(*next))
+        return dir;
 
-    // name = next;
-    // buf = find_entry(&inode, name, &next, &entry);
-    // brelse(buf);
+    char *name = next;
+    dentry_t *entry = NULL;
+    buffer_t *buf = find_entry(&dir, name, &next, &entry);
+    if (!buf)
+    {
+        iput(dir);
+        return NULL;
+    }
 
-    // iput(inode);
-    // inode = iget(dev, entry->nr);
+    inode_t *inode = iget(dir->dev, entry->nr);
 
-    // name = next;
-    // buf = find_entry(&inode, name, &next, &entry);
-    // brelse(buf);
+    iput(dir);
+    brelse(buf);
+    return inode;
+}
 
-    // iput(inode);
-    // inode = iget(dev, entry->nr);
+void dir_test()
+{
+    char pathname[] = "/";
+    char *name = NULL;
+    inode_t *inode = named(pathname, &name);
+    iput(inode);
 
-    // name = next;
-    // buf = find_entry(&inode, name, &next, &entry);
-    // brelse(buf);
-    // iput(inode);
+    inode = namei("/home/hello.txt");
+    LOGK("get inode %d\n", inode->nr);
+    iput(inode);
 }

src/include/onix/fs.h

@@ -98,4 +98,7 @@ inode_t *get_root_inode();          // 获取根目录 inode
 inode_t *iget(dev_t dev, idx_t nr); // 获得设备 dev 的 nr inode
 void iput(inode_t *inode);          // 释放 inode
 
+inode_t *named(char *pathname, char **next); // 获取 pathname 对应的父目录 inode
+inode_t *namei(char *pathname);              // 获取 pathname 对应的 inode
+
 #endif