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Kernel/Devices: Introduce the LoopDevice device

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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.
This commit is contained in:
Liav A 2024-02-23 17:11:48 +02:00 • committed by Andrew Kaster
parent a9d240c647
commit 5dcf03ad9a
12 changed files with 254 additions and 4 deletions
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12
Kernel/FileSystem/SysFS/Subsystems/Kernel/DiskUsage.cpp
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@ -5,6 +5,7 @@
*/
#include <AK/JsonObjectSerializer.h>
#include <Kernel/Devices/Loop/LoopDevice.h>
#include <Kernel/FileSystem/FileBackedFileSystem.h>
#include <Kernel/FileSystem/SysFS/Subsystems/Kernel/DiskUsage.h>
#include <Kernel/FileSystem/VirtualFileSystem.h>
@ -40,8 +41,15 @@ ErrorOr<void> SysFSDiskUsage::try_generate(KBufferBuilder& builder)
TRY(fs_object.add("mount_flags"sv, mount.flags()));
if (fs.is_file_backed()) {
auto pseudo_path = TRY(static_cast<const FileBackedFileSystem&>(fs).file_description().pseudo_path());
TRY(fs_object.add("source"sv, pseudo_path->view()));
auto& file = static_cast<const FileBackedFileSystem&>(fs).file();
if (file.is_loop_device()) {
auto& device = static_cast<LoopDevice const&>(file);
auto path = TRY(device.custody().try_serialize_absolute_path());
TRY(fs_object.add("source"sv, path->view()));
} else {
auto pseudo_path = TRY(static_cast<const FileBackedFileSystem&>(fs).file_description().pseudo_path());
TRY(fs_object.add("source"sv, pseudo_path->view()));
}
} else {
TRY(fs_object.add("source"sv, "none"));
}