+
+static struct dentry *
+__dcache_find_get_entry(struct dentry *parent, u64 idx,
+ struct ceph_readdir_cache_control *cache_ctl)
+{
+ struct inode *dir = d_inode(parent);
+ struct dentry *dentry;
+ unsigned idx_mask = (PAGE_SIZE / sizeof(struct dentry *)) - 1;
+ loff_t ptr_pos = idx * sizeof(struct dentry *);
+ pgoff_t ptr_pgoff = ptr_pos >> PAGE_SHIFT;
+
+ if (ptr_pos >= i_size_read(dir))
+ return NULL;
+
+ if (!cache_ctl->page || ptr_pgoff != page_index(cache_ctl->page)) {
+ ceph_readdir_cache_release(cache_ctl);
+ cache_ctl->page = find_lock_page(&dir->i_data, ptr_pgoff);
+ if (!cache_ctl->page) {
+ dout(" page %lu not found\n", ptr_pgoff);
+ return ERR_PTR(-EAGAIN);
+ }
+ /* reading/filling the cache are serialized by
+ i_mutex, no need to use page lock */
+ unlock_page(cache_ctl->page);
+ cache_ctl->dentries = kmap(cache_ctl->page);
+ }
+
+ cache_ctl->index = idx & idx_mask;
+
+ rcu_read_lock();
+ spin_lock(&parent->d_lock);
+ /* check i_size again here, because empty directory can be
+ * marked as complete while not holding the i_mutex. */
+ if (ceph_dir_is_complete_ordered(dir) && ptr_pos < i_size_read(dir))
+ dentry = cache_ctl->dentries[cache_ctl->index];
+ else
+ dentry = NULL;
+ spin_unlock(&parent->d_lock);
+ if (dentry && !lockref_get_not_dead(&dentry->d_lockref))
+ dentry = NULL;
+ rcu_read_unlock();
+ return dentry ? : ERR_PTR(-EAGAIN);
+}
+