new: devfs设备卸载

kernel/filesystem/VFS/dcache.c

@@ -3,81 +3,127 @@
 #include <debug/bug.h>
 
 /**
- * @brief 释放dentry
+ * @brief 释放dentry，并视情况自动释放inode
  *
  * @param dentry 目标dentry
+ * 
+ * @return 错误码
+ *          注意，当dentry指向文件时，如果返回值为正数，则表示在释放了该dentry后，该dentry指向的inode的引用计数。
  */
-void vfs_dentry_put(struct vfs_dir_entry_t *dentry)
+int vfs_dentry_put(struct vfs_dir_entry_t *dentry)
 {
     int retval = 0;
     uint64_t in_value = 0;
-    // todo: 加锁、放锁
+    struct kfifo_t fifo = {0};
 
-    // 创建一个用来存放指向dentry的指针的fifo队列
-    struct kfifo_t fifo;
-    // 暂时假设队列大小为1024个元素
-    // todo: 实现队列的自动扩容功能
-    retval = kfifo_alloc(&fifo, 1024 * sizeof(uint64_t), 0);
-
-    if (retval != 0)
-        goto failed;
-
-    // 将根dentry加入队列
-    in_value = (uint64_t)dentry;
-    kfifo_in(&fifo, &in_value, sizeof(uint64_t));
-    list_del(&dentry->child_node_list); // 从父dentry中删除
-
-    while (!kfifo_empty(&fifo))
+    // 引用计数大于1时，尝试释放dentry的话，抛出错误信息
+    if (unlikely(dentry->lockref.lock_count > 1))
     {
-        // 取出队列中的下一个元素
-        kfifo_out(&fifo, &dentry, sizeof(uint64_t));
-        BUG_ON(dentry == NULL);
-        struct List *list = &dentry->subdirs_list;
-        if (!list_empty(list))
-        {
-            // 将当前dentry下的所有dentry加入队列
-            do
-            {
-                list = list_next(list);
-                in_value = (uint64_t)container_of(list, struct vfs_dir_entry_t, child_node_list);
-                if (in_value != NULL)
-                    kfifo_in(&fifo, &in_value, sizeof(uint64_t));
-
-            } while (list_next(list) != (&dentry->subdirs_list));
-        }
-
-        // 释放inode
-        vfs_free_inode(dentry->dir_inode);
-
-        // 若当前dentry是否为挂载点，则umount
-        if (is_local_mountpoint(dentry))
-            do_umount(dentry);
-
-        dentry->dir_ops->release(dentry);
-        kfree(dentry);
+        BUG_ON(1);
+        retval = -EBUSY;
+        spin_unlock(&dentry->lockref.lock);
+        goto out;
+    }
+
+    if (D_ISDIR(dentry))
+    {
+
+        // 创建一个用来存放指向dentry的指针的fifo队列
+        // 暂时假设队列大小为1024个元素
+        // todo: 实现队列的自动扩容功能
+        retval = kfifo_alloc(&fifo, 1024 * sizeof(uint64_t), 0);
+
+        if (retval != 0)
+            goto failed;
+
+        // 将根dentry加入队列
+        in_value = (uint64_t)dentry;
+        kfifo_in(&fifo, &in_value, sizeof(uint64_t));
+        list_del(&dentry->child_node_list); // 从父dentry中删除
+
+        while (!kfifo_empty(&fifo))
+        {
+            // 取出队列中的下一个元素
+            kfifo_out(&fifo, &dentry, sizeof(uint64_t));
+            BUG_ON(dentry == NULL);
+            struct List *list = &dentry->subdirs_list;
+            if (!list_empty(list))
+            {
+                // 将当前dentry下的所有dentry加入队列
+                do
+                {
+                    list = list_next(list);
+                    in_value = (uint64_t)container_of(list, struct vfs_dir_entry_t, child_node_list);
+                    if (in_value != NULL)
+                        kfifo_in(&fifo, &in_value, sizeof(uint64_t));
+
+                } while (list_next(list) != (&dentry->subdirs_list));
+            }
+            spin_lock(&dentry->lockref.lock);
+            if(dentry->lockref.count>1)
+            {
+                spin_unlock(&dentry->lockref.lock);
+                continue;
+            }
+            // 释放inode
+            spin_lock(&dentry->dir_inode->lockref.lock);
+            retval = vfs_free_inode(dentry->dir_inode);
+            if (retval > 0) // 还有其他的dentry引用着这个inode
+            {
+                spin_unlock(&dentry->dir_inode->lockref.lock);
+                retval = 0;
+            }
+
+            // 若当前dentry是否为挂载点，则umount
+            if (is_local_mountpoint(dentry))
+                do_umount(dentry);
+            if (dentry->dir_ops->release != NULL)
+                dentry->dir_ops->release(dentry);
+            kfree(dentry);
+        }
+        kfifo_free_alloc(&fifo);
+        retval = 0;
+        goto out;
+    }
+    else // 是文件或设备
+    {
+        // 释放inode
+        spin_lock(&dentry->dir_inode->lockref.lock);
+        retval = vfs_free_inode(dentry->dir_inode);
+        if (retval > 0) // 还有其他的dentry引用着这个inode
+            spin_unlock(&dentry->dir_inode->lockref.lock);
+
+        if (dentry->dir_ops->release != NULL)
+            dentry->dir_ops->release(dentry);
+        kfree(dentry);
+        goto out;
     }
-    kfifo_free_alloc(&fifo);
-    return;
 failed:;
     if (fifo.buffer != NULL)
         kfifo_free_alloc(&fifo);
     kerror("dentry_put failed.");
+out:;
+    // 在这里不用释放dentry的锁，因为dentry已经被释放掉了
+    return retval;
 }
 
 /**
- * @brief 释放inode
+ * @brief 释放inode（要求已经对inode进行加锁后调用该函数）
  *
  * @param inode 待释放的inode
  * @return int 错误码
+ *             当inode还有其他的使用者时，返回inode的使用者数量
  */
 int vfs_free_inode(struct vfs_index_node_t *inode)
 {
-    --inode->ref_count;
-    BUG_ON(inode->ref_count < 0);
-    if (inode->ref_count == 0)
+    --inode->lockref.count;
+    BUG_ON(inode->lockref.count < 0);
+    if (inode->lockref.count == 0)
     {
         kfree(inode->private_inode_info);
         kfree(inode);
+        return 0;
     }
-    return 0;
+    else // 如果inode没有被释放
+        return inode->lockref.count;
 }