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Kernel: Implement multi-watch InodeWatcher :^)

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This patch modifies InodeWatcher to switch to a one watcher, multiple
watches architecture.  The following changes have been made:

- The watch_file syscall is removed, and in its place the
  create_iwatcher, iwatcher_add_watch and iwatcher_remove_watch calls
  have been added.
- InodeWatcher now holds multiple WatchDescriptions for each file that
  is being watched.
- The InodeWatcher file descriptor can be read from to receive events on
  all watched files.

Co-authored-by: Gunnar Beutner <gunnar@beutner.name>
This commit is contained in:
sin-ack 2021-05-12 19:17:51 +00:00 • committed by Andreas Kling
parent 2de11b0dc8
commit fe5ca6ca27
16 changed files with 521 additions and 262 deletions
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63
Kernel/FileSystem/InodeWatcher.h
View file

@ -1,5 +1,6 @@
/*
* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
* Copyright (c) 2021, sin-ack <sin-ack@protonmail.com>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
@ -7,38 +8,76 @@
#pragma once
#include <AK/Badge.h>
#include <AK/Checked.h>
#include <AK/CircularQueue.h>
#include <AK/WeakPtr.h>
#include <AK/HashMap.h>
#include <AK/NonnullOwnPtr.h>
#include <Kernel/API/InodeWatcherEvent.h>
#include <Kernel/FileSystem/File.h>
#include <Kernel/Lock.h>
namespace Kernel {
class Inode;
// A specific description of a watch.
struct WatchDescription {
int wd;
Inode& inode;
unsigned event_mask;
static NonnullOwnPtr<WatchDescription> create(int wd, Inode& inode, unsigned event_mask)
{
return adopt_own(*new WatchDescription(wd, inode, event_mask));
}
private:
WatchDescription(int wd, Inode& inode, unsigned event_mask)
: wd(wd)
, inode(inode)
, event_mask(event_mask)
{
}
};
class InodeWatcher final : public File {
public:
static NonnullRefPtr<InodeWatcher> create(Inode&);
static NonnullRefPtr<InodeWatcher> create();
virtual ~InodeWatcher() override;
virtual bool can_read(const FileDescription&, size_t) const override;
virtual bool can_write(const FileDescription&, size_t) const override;
virtual KResultOr<size_t> read(FileDescription&, u64, UserOrKernelBuffer&, size_t) override;
virtual KResultOr<size_t> write(FileDescription&, u64, const UserOrKernelBuffer&, size_t) override;
// Can't write to an inode watcher.
virtual bool can_write(const FileDescription&, size_t) const override { return true; }
virtual KResultOr<size_t> write(FileDescription&, u64, const UserOrKernelBuffer&, size_t) override { return EIO; }
virtual KResult close() override;
virtual String absolute_path(const FileDescription&) const override;
virtual const char* class_name() const override { return "InodeWatcher"; };
virtual bool is_inode_watcher() const override { return true; }
void notify_inode_event(Badge<Inode>, InodeWatcherEvent::Type);
void notify_child_added(Badge<Inode>, const InodeIdentifier& child_id);
void notify_child_removed(Badge<Inode>, const InodeIdentifier& child_id);
void notify_inode_event(Badge<Inode>, InodeIdentifier, InodeWatcherEvent::Type, String const& name = {});
KResultOr<int> register_inode(Inode&, unsigned event_mask);
KResult unregister_by_wd(int);
void unregister_by_inode(Badge<Inode>, InodeIdentifier);
private:
explicit InodeWatcher(Inode&);
explicit InodeWatcher() { }
Lock m_lock;
WeakPtr<Inode> m_inode;
CircularQueue<InodeWatcherEvent, 32> m_queue;
mutable Lock m_lock;
struct Event {
int wd { 0 };
InodeWatcherEvent::Type type { InodeWatcherEvent::Type::Invalid };
String path;
};
CircularQueue<Event, 32> m_queue;
Checked<int> m_wd_counter { 1 };
// NOTE: These two hashmaps provide two different ways of reaching the same
// watch description, so they will overlap.
HashMap<int, NonnullOwnPtr<WatchDescription>> m_wd_to_watches;
HashMap<InodeIdentifier, WatchDescription*> m_inode_to_watches;
};
}