dcache.c中的d_hash函数和dentry操作中的d_hash之间的调用路径展示一下

1. 在dcache.c中定义了d_hash函数，该函数用于计算给定dentry的哈希值：

unsigned int d_hash(const struct dentry *dentry, const struct qstr *name)
{
    return full_name_hash(name->name, name->len);
}

2. 在dentry操作中，需要将dentry插入到dentry缓存中，因此需要调用d_hash函数来计算dentry的哈希值。这个过程发生在d_alloc和d_instantiate函数中。

struct dentry *d_alloc(struct dentry *parent, const struct qstr *name)
{
    struct dentry *dentry;
    unsigned int len = name->len;
    unsigned int hash = d_hash(parent, name); // 调用d_hash计算哈希值

    // 分配dentry对象并初始化
    dentry = __d_alloc(parent->d_sb, len);
    dentry->d_name = *name;
    dentry->d_parent = parent;
    dentry->d_flags |= DCACHE_UNHASHED;

    return dentry;
}

void d_instantiate(struct dentry *entry, struct inode *inode)
{
    spin_lock(&dcache_lock);

    // 设置dentry的inode和哈希值
    entry->d_inode = inode;
    entry->d_flags &= ~DCACHE_UNHASHED;
    entry->d_hash = inode->i_ino; // inode的编号作为哈希值

    // 将dentry插入到哈希表中
    d_hash_and_lookup(entry, NULL);

    spin_unlock(&dcache_lock);
}

3. 在d_instantiate函数中，还调用了d_hash_and_lookup函数来将dentry插入到哈希表中。

static inline void d_hash_and_lookup(struct dentry *entry, struct qstr *str)
{
    struct hlist_head *head = dentry_hash(entry->d_sb, entry->d_hash);

    spin_lock(&dcache_lock);

    // 将dentry插入到哈希表中
    hlist_add_head(&entry->d_hash, head);

    spin_unlock(&dcache_lock);
}

4. d_hash_and_lookup函数中调用了dentry_hash函数来获取哈希表中对应哈希值的链表头。

static inline struct hlist_head *dentry_hash(const struct super_block *sb, unsigned long hashval)
{
    return &sb->s_dentry_hashtable[hashval & (sb->s_dentry_hashtable_size - 1)];
}

5. 在dentry缓存中查找dentry时，也需要调用d_hash函数来计算dentry的哈希值。这个过程发生在d_lookup函数中。

struct dentry *d_lookup(const struct dentry * parent, const struct qstr * name)
{
    struct dentry *dentry;
    unsigned int len = name->len;
    unsigned int hash = d_hash(parent, name); // 调用d_hash计算哈希值

    spin_lock(&dcache_lock);

    // 在哈希表中查找dentry
    dentry = __d_lookup(parent, name, hash);

    spin_unlock(&dcache_lock);

    return dentry;
}

6. 在__d_lookup函数中，也需要调用dentry_hash函数来获取哈希表中对应哈希值的链表头。

static struct dentry *__d_lookup(const struct dentry * parent, const struct qstr * name, unsigned int hash)
{
    struct dentry *dentry;
    struct hlist_head *head = dentry_hash(parent->d_sb, hash); // 调用dentry_hash获取哈希表中对应的链表头

    // 遍历链表查找dentry
    hlist_for_each_entry(dentry, head, d_hash)
    {
        if (dentry->d_parent == parent && dentry->d_name.hash == hash && dentry_cmp(dentry, name) == 0)
            return dentry;
    }

    return NULL;
}