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// Copyright 2018 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef SRC_STORAGE_BLOBFS_CACHE_NODE_H_
#define SRC_STORAGE_BLOBFS_CACHE_NODE_H_
#ifndef __Fuchsia__
#error Fuchsia-only Header
#endif
#include <lib/fit/function.h>
#include <fbl/intrusive_wavl_tree.h>
#include <fbl/mutex.h>
#include <fbl/ref_ptr.h>
#include "src/lib/digest/digest.h"
#include "src/lib/storage/vfs/cpp/paged_vnode.h"
#include "src/storage/blobfs/cache_policy.h"
namespace blobfs {
using digest::Digest;
// Forward declared because CacheNode needs a mechanism for accessing the class when it runs out of
// strong references.
class BlobCache;
// An abstract blob-backed Vnode, which is managed by the BlobCache.
class CacheNode : public fs::PagedVnode,
private fbl::Recyclable<CacheNode>,
public fbl::WAVLTreeContainable<CacheNode*> {
public:
explicit CacheNode(fs::PagedVfs* vfs, const Digest& digest,
std::optional<CachePolicy> override_cache_policy = std::nullopt);
virtual ~CacheNode() = default;
const Digest& digest() const { return digest_; }
// Required for memory management, see the class comment above Vnode for more.
void fbl_recycle() { RecycleNode(); }
// Returns a reference to the BlobCache.
//
// The BlobCache must outlive all CacheNodes; this method is invoked from the recycler of a
// CacheNode.
//
// The implementation of this method must not invoke any other CacheNode methods. The
// implementation of this method must not attempt to acquire a reference to |this|.
virtual BlobCache& GetCache() = 0;
// Identifies if the node should be recycled when it is terminated, keeping it cached (although
// possibly in a reduced state).
//
// This should be true as long as the blob exists on persistent storage, and would be visible
// again on reboot.
//
// The implementation of this method must not invoke any other CacheNode methods. The
// implementation of this method must not attempt to acquire a reference to |this|.
virtual bool ShouldCache() const = 0;
// Places the Vnode into a low-memory state. This function may be invoked when migrating the node
// from a "live cache" to a "closed cache".
//
// The implementation of this method must not invoke any other CacheNode methods. The
// implementation of this method must not attempt to acquire a reference to |this|.
virtual void ActivateLowMemory() = 0;
// If the node should have a specific cache discipline, this method returns it. Otherwise, the
// system-wide policy is applied.
std::optional<CachePolicy> overriden_cache_policy() const { return overriden_cache_policy_; }
void set_overridden_cache_policy(CachePolicy policy) { overriden_cache_policy_ = policy; }
protected:
// Vnode memory management function called when the reference count reaches 0.
void RecycleNode() override;
private:
digest::Digest digest_;
std::optional<CachePolicy> overriden_cache_policy_;
};
} // namespace blobfs
#endif // SRC_STORAGE_BLOBFS_CACHE_NODE_H_