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https://github.com/RGBCube/serenity
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Kernel/Devices: Introduce the LoopDevice device
This device is a block device that allows a user to effectively treat an Inode as a block device. The static construction method is given an OpenFileDescription reference but validates that: - The description has a valid custody (so it's not some arbitrary file). Failing this requirement will yield EINVAL. - The description custody points to an Inode which is a regular file, as we only support (seekable) regular files. Failing this requirement will yield ENOTSUP. LoopDevice can be used to mount a regular file on the filesystem like other supported types of (physical) block devices.
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12 changed files with 254 additions and 4 deletions
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@ -47,6 +47,7 @@ public:
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virtual unsigned free_inode_count() const override;
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virtual bool supports_watchers() const override { return true; }
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virtual bool supports_backing_loop_devices() const override { return true; }
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virtual u8 internal_file_type_to_directory_entry_type(DirectoryEntryView const& entry) const override;
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@ -115,6 +115,7 @@ public:
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virtual bool is_socket() const { return false; }
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virtual bool is_inode_watcher() const { return false; }
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virtual bool is_mount_file() const { return false; }
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virtual bool is_loop_device() const { return false; }
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virtual bool is_regular_file() const { return false; }
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@ -34,6 +34,11 @@ public:
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virtual Inode& root_inode() = 0;
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virtual bool supports_watchers() const { return false; }
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// FIXME: We should aim to provide more concise mechanism to ensure
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// that backing Inodes from the FileSystem are kept intact so we can
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// attach them to a loop device.
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virtual bool supports_backing_loop_devices() const { return false; }
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bool is_readonly() const { return m_readonly; }
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virtual unsigned total_block_count() const { return 0; }
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@ -24,6 +24,7 @@ public:
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virtual StringView class_name() const override { return "RAMFS"sv; }
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virtual bool supports_watchers() const override { return true; }
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virtual bool supports_backing_loop_devices() const override { return true; }
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virtual Inode& root_inode() override;
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@ -5,6 +5,7 @@
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*/
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#include <AK/JsonObjectSerializer.h>
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#include <Kernel/Devices/Loop/LoopDevice.h>
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#include <Kernel/FileSystem/FileBackedFileSystem.h>
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#include <Kernel/FileSystem/SysFS/Subsystems/Kernel/DiskUsage.h>
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#include <Kernel/FileSystem/VirtualFileSystem.h>
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@ -40,8 +41,15 @@ ErrorOr<void> SysFSDiskUsage::try_generate(KBufferBuilder& builder)
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TRY(fs_object.add("mount_flags"sv, mount.flags()));
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if (fs.is_file_backed()) {
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auto pseudo_path = TRY(static_cast<const FileBackedFileSystem&>(fs).file_description().pseudo_path());
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TRY(fs_object.add("source"sv, pseudo_path->view()));
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auto& file = static_cast<const FileBackedFileSystem&>(fs).file();
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if (file.is_loop_device()) {
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auto& device = static_cast<LoopDevice const&>(file);
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auto path = TRY(device.custody().try_serialize_absolute_path());
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TRY(fs_object.add("source"sv, path->view()));
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} else {
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auto pseudo_path = TRY(static_cast<const FileBackedFileSystem&>(fs).file_description().pseudo_path());
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TRY(fs_object.add("source"sv, pseudo_path->view()));
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}
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} else {
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TRY(fs_object.add("source"sv, "none"));
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}
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@ -14,6 +14,7 @@
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#include <Kernel/Debug.h>
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#include <Kernel/Devices/BlockDevice.h>
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#include <Kernel/Devices/DeviceManagement.h>
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#include <Kernel/Devices/Loop/LoopDevice.h>
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#include <Kernel/FileSystem/Custody.h>
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#include <Kernel/FileSystem/FileBackedFileSystem.h>
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#include <Kernel/FileSystem/FileSystem.h>
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@ -213,6 +214,12 @@ ErrorOr<void> VirtualFileSystem::mount(MountFile& mount_file, OpenFileDescriptio
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}));
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TRY(fs->initialize());
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}
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if (source_description->file().is_loop_device()) {
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auto& device = static_cast<LoopDevice&>(source_description->file());
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auto path = TRY(device.custody().try_serialize_absolute_path());
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dbgln("VirtualFileSystem: mounting from loop device {}, originated from {}", device.index(), path->view());
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}
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TRY(add_file_system_to_mount_table(*fs, mount_point, flags));
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list.append(static_cast<FileBackedFileSystem&>(*fs));
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return {};
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