DragonOS/kernel/src/filesystem/vfs/mount.c

#include "mount.h"
#include "VFS.h"
#include <common/glib.h>
#include <common/string.h>

static struct List mnt_list_head; // 挂载点链表头

/**
 * @brief 初始化mount机制
 *
 * @return int 错误码
 */
int mount_init()
{
    list_init(&mnt_list_head);
    return 0;
}

/**
 * @brief 将new_dentry挂载
 *
 * @param old_dentry 挂载点的dentry
 * @param new_dentry 待挂载的新的dentry(需使用vfs_alloc_dentry来分配)
 * @return int 错误码
 */
int do_mount(struct vfs_dir_entry_t *old_dentry, struct vfs_dir_entry_t *new_dentry)
{
    struct mountpoint *mp = (struct mountpoint *)kzalloc(sizeof(struct mountpoint), 0);
    list_init(&mp->mnt_list);
    mp->dentry = old_dentry;
    mp->parent_dentry = old_dentry->parent;

    // 拷贝名称
    strncpy(new_dentry->name, old_dentry->name, old_dentry->name_length);
    kdebug("new_dentry->name=%s, old_dentry->name=%s, old_dentry->name_length=%d", new_dentry->name, old_dentry->name, old_dentry->name_length);

    new_dentry->d_flags |= VFS_DF_MOUNTED; // 标记新的dentry是一个挂载点

    list_init(&new_dentry->child_node_list);
    list_init(&new_dentry->subdirs_list);
    new_dentry->parent = old_dentry->parent;

    // 将新的dentry的list结点替换掉父dentry的列表中的old_dentry的list结点
    list_replace(&old_dentry->child_node_list, &new_dentry->child_node_list);

    // 后挂载的dentry在链表的末尾（umount恢复的时候需要依赖这个性质）
    list_append(&mnt_list_head, &mp->mnt_list);

    return 0;
}

/**
 * @brief 取消某个文件系统的挂载
 *
 * @param dentry 对应文件系统的根dentry
 * @return int 错误码
 */
int do_umount(struct vfs_dir_entry_t *dentry)
{
    // todo: 实现umount（主要是结点的恢复问题）

    return 0;
}

/**
 * @brief 根据mountpoint的父目录dentry查找第一个符合条件的mountpoint结构体
 *
 * @param dentry 父dentry
 * @return struct mountpoint* 第一个符合条件的mountpoint结构体的指针
 */
struct mountpoint *mount_find_mnt_list_by_parent(struct vfs_dir_entry_t *dentry)
{
    struct List *list = &mnt_list_head;
    struct mountpoint *ret = NULL;
    if (list_empty(list))
        return NULL;

    while (list_next(list) != &mnt_list_head)
    {
        list = list_next(list);
        struct mountpoint *tmp = container_of(list, struct mountpoint, mnt_list);
        if (dentry == tmp->parent_dentry)
            return tmp;
    }

    return NULL;
}

/**
 * @brief 将挂载点结构体从链表中删除并释放
 *
 * @param mp mountpoint结构体
 * @return int 错误码
 */
int mount_release_mountpoint(struct mountpoint *mp)
{
    list_del(&mp->mnt_list);
    return kfree(mp);
}