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Kernel: Add a mechanism for listening for changes to an inode.

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The syscall is quite simple:

    int watch_file(const char* path, int path_length);

It returns a file descriptor referring to a "InodeWatcher" object in the
kernel. It becomes readable whenever something changes about the inode.

Currently this is implemented by hooking the "metadata dirty bit" in
Inode which isn't perfect, but it's a start. :^)
This commit is contained in:
Andreas Kling 2019-07-22 20:01:11 +02:00
parent a9adf4c95b
commit c8e2bb5605
12 changed files with 200 additions and 3 deletions
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38
Kernel/FileSystem/InodeWatcher.h Normal file
View file

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#pragma once
#include <AK/Badge.h>
#include <AK/CircularQueue.h>
#include <AK/WeakPtr.h>
#include <Kernel/FileSystem/File.h>
class Inode;
class InodeWatcher final : public File {
public:
static NonnullRefPtr<InodeWatcher> create(Inode&);
virtual ~InodeWatcher() override;
struct Event {
enum class Type {
Invalid = 0,
Modified,
};
Type type { Type::Invalid };
};
virtual bool can_read(FileDescription&) const override;
virtual bool can_write(FileDescription&) const override;
virtual ssize_t read(FileDescription&, u8*, ssize_t) override;
virtual ssize_t write(FileDescription&, const u8*, ssize_t) override;
virtual String absolute_path(const FileDescription&) const override;
virtual const char* class_name() const override { return "InodeWatcher"; };
void notify_inode_event(Badge<Inode>, Event::Type);
private:
explicit InodeWatcher(Inode&);
WeakPtr<Inode> m_inode;
CircularQueue<Event, 32> m_queue;
};