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Kernel/FileSystem: Introduce the VFSRootContext class

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The VFSRootContext class, as its name suggests, holds a context for a
root directory with its mount table and the root custody/inode in the
same class.

The idea is derived from the Linux mount namespace mechanism.
It mimicks the concept of the ProcessList object, but it is adjusted for
a root directory tree context.
In contrast to the ProcessList concept, processes that share the default
VFSRootContext can't see other VFSRootContext related properties such as
as the mount table and root custody/inode.

To accommodate to this change progressively, we internally create 2 main
VFS root contexts for now - one for kernel processes (as they don't need
to care about VFS root contexts for the most part), and another for all
userspace programs.
This separation allows us to continue pretending for userspace that
everything is "normal" as it is used to be, until we introduce proper
interfaces in the mount-related syscalls as well as in the SysFS.

We make VFSRootContext objects being listed, as another preparation
before we could expose interfaces to userspace.
As a result, the PowerStateSwitchTask now iterates on all contexts
and tear them down one by one.
This commit is contained in:
Liav A.
2024-01-26 11:10:06 +02:00
committed by Tim Schumacher
parent 02157e3eaf
commit 01e1af732b
44 changed files with 714 additions and 380 deletions
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86
Kernel/FileSystem/VirtualFileSystem.h
View File

@@ -1,5 +1,6 @@
/*
* Copyright (c) 2018-2021, Andreas Kling <kling@serenityos.org>
* Copyright (c) 2024, Liav A. <liavalb@hotmail.co.il>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
@@ -21,6 +22,7 @@
#include <Kernel/FileSystem/Mount.h>
#include <Kernel/FileSystem/MountFile.h>
#include <Kernel/FileSystem/UnveilNode.h>
#include <Kernel/FileSystem/VFSRootContext.h>
#include <Kernel/Forward.h>
#include <Kernel/Locking/MutexProtected.h>
#include <Kernel/Locking/SpinlockProtected.h>
@@ -45,6 +47,8 @@ enum class AccessFlags {
AK_ENUM_BITWISE_OPERATORS(AccessFlags);
class VirtualFileSystem {
friend class StorageManagement;
public:
// Required to be at least 8 by POSIX
// https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/limits.h.html
@@ -53,51 +57,57 @@ public:
static void initialize();
static VirtualFileSystem& the();
static bool check_matching_absolute_path_hierarchy(Custody const& first_custody, Custody const& second_custody);
static ErrorOr<FileSystemInitializer const*> find_filesystem_type_initializer(StringView fs_type);
VirtualFileSystem();
~VirtualFileSystem();
ErrorOr<void> mount_root(FileSystem&);
ErrorOr<void> mount(MountFile&, OpenFileDescription*, Custody& mount_point, int flags);
ErrorOr<void> bind_mount(Custody& source, Custody& mount_point, int flags);
ErrorOr<void> remount(Custody& mount_point, int new_flags);
ErrorOr<void> unmount(Custody& mount_point);
ErrorOr<void> unmount(Inode& guest_inode, StringView custody_path);
SpinlockProtected<IntrusiveList<&FileSystem::m_file_system_node>, LockRank::FileSystem>& all_file_systems_list(Badge<VFSRootContext>) { return m_file_systems_list; }
SpinlockProtected<IntrusiveList<&VFSRootContext::m_list_node>, LockRank::FileSystem>& all_root_contexts_list(Badge<PowerStateSwitchTask>) { return m_root_contexts; }
SpinlockProtected<IntrusiveList<&VFSRootContext::m_list_node>, LockRank::FileSystem>& all_root_contexts_list(Badge<VFSRootContext>) { return m_root_contexts; }
ErrorOr<NonnullRefPtr<OpenFileDescription>> open(Credentials const&, StringView path, int options, mode_t mode, CustodyBase const& base, Optional<UidAndGid> = {});
ErrorOr<NonnullRefPtr<OpenFileDescription>> open(Process const&, Credentials const&, StringView path, int options, mode_t mode, CustodyBase const& base, Optional<UidAndGid> = {});
ErrorOr<void> mount(VFSRootContext&, MountFile&, OpenFileDescription*, Custody& mount_point, int flags);
ErrorOr<void> pivot_root_by_copying_mounted_fs_instance(VFSRootContext&, FileSystem& fs, int root_mount_flags);
ErrorOr<void> bind_mount(VFSRootContext&, Custody& source, Custody& mount_point, int flags);
ErrorOr<void> remount(VFSRootContext&, Custody& mount_point, int new_flags);
ErrorOr<void> unmount(VFSRootContext&, Custody& mount_point);
ErrorOr<void> unmount(VFSRootContext&, Inode& guest_inode, StringView custody_path);
ErrorOr<NonnullRefPtr<OpenFileDescription>> open(VFSRootContext const&, Credentials const&, StringView path, int options, mode_t mode, CustodyBase const& base, Optional<UidAndGid> = {});
ErrorOr<NonnullRefPtr<OpenFileDescription>> open(Process const&, VFSRootContext const&, Credentials const&, StringView path, int options, mode_t mode, CustodyBase const& base, Optional<UidAndGid> = {});
ErrorOr<NonnullRefPtr<OpenFileDescription>> create(Credentials const&, StringView path, int options, mode_t mode, Custody& parent_custody, Optional<UidAndGid> = {});
ErrorOr<NonnullRefPtr<OpenFileDescription>> create(Process const&, Credentials const&, StringView path, int options, mode_t mode, Custody& parent_custody, Optional<UidAndGid> = {});
ErrorOr<void> mkdir(Credentials const&, StringView path, mode_t mode, CustodyBase const& base);
ErrorOr<void> link(Credentials const&, StringView old_path, StringView new_path, CustodyBase const& base);
ErrorOr<void> unlink(Credentials const&, StringView path, CustodyBase const& base);
ErrorOr<void> symlink(Credentials const&, StringView target, StringView linkpath, CustodyBase const& base);
ErrorOr<void> rmdir(Credentials const&, StringView path, CustodyBase const& base);
ErrorOr<void> chmod(Credentials const&, StringView path, mode_t, CustodyBase const& base, int options = 0);
ErrorOr<void> mkdir(VFSRootContext const&, Credentials const&, StringView path, mode_t mode, CustodyBase const& base);
ErrorOr<void> link(VFSRootContext const&, Credentials const&, StringView old_path, StringView new_path, CustodyBase const& base);
ErrorOr<void> unlink(VFSRootContext const&, Credentials const&, StringView path, CustodyBase const& base);
ErrorOr<void> symlink(VFSRootContext const&, Credentials const&, StringView target, StringView linkpath, CustodyBase const& base);
ErrorOr<void> rmdir(VFSRootContext const&, Credentials const&, StringView path, CustodyBase const& base);
ErrorOr<void> chmod(VFSRootContext const&, Credentials const&, StringView path, mode_t, CustodyBase const& base, int options = 0);
ErrorOr<void> chmod(Credentials const&, Custody&, mode_t);
ErrorOr<void> chown(Credentials const&, StringView path, UserID, GroupID, CustodyBase const& base, int options);
ErrorOr<void> chown(VFSRootContext const&, Credentials const&, StringView path, UserID, GroupID, CustodyBase const& base, int options);
ErrorOr<void> chown(Credentials const&, Custody&, UserID, GroupID);
ErrorOr<void> access(Credentials const&, StringView path, int mode, CustodyBase const& base, AccessFlags);
ErrorOr<InodeMetadata> lookup_metadata(Credentials const&, StringView path, CustodyBase const& base, int options = 0);
ErrorOr<void> utime(Credentials const&, StringView path, CustodyBase const& base, time_t atime, time_t mtime);
ErrorOr<void> utimensat(Credentials const&, StringView path, CustodyBase const& base, timespec const& atime, timespec const& mtime, int options = 0);
ErrorOr<void> do_utimens(Credentials const& credentials, Custody& custody, timespec const& atime, timespec const& mtime);
ErrorOr<void> rename(Credentials const&, CustodyBase const& old_base, StringView oldpath, CustodyBase const& new_base, StringView newpath);
ErrorOr<void> mknod(Credentials const&, StringView path, mode_t, dev_t, CustodyBase const& base);
ErrorOr<NonnullRefPtr<Custody>> open_directory(Credentials const&, StringView path, CustodyBase const& base);
ErrorOr<void> access(VFSRootContext const&, Credentials const&, StringView path, int mode, CustodyBase const& base, AccessFlags);
ErrorOr<InodeMetadata> lookup_metadata(VFSRootContext const&, Credentials const&, StringView path, CustodyBase const& base, int options = 0);
ErrorOr<void> utime(VFSRootContext const&, Credentials const&, StringView path, CustodyBase const& base, time_t atime, time_t mtime);
ErrorOr<void> utimensat(VFSRootContext const&, Credentials const&, StringView path, CustodyBase const& base, timespec const& atime, timespec const& mtime, int options = 0);
ErrorOr<void> do_utimens(Credentials const&, Custody& custody, timespec const& atime, timespec const& mtime);
ErrorOr<void> rename(VFSRootContext const&, Credentials const&, CustodyBase const& old_base, StringView oldpath, CustodyBase const& new_base, StringView newpath);
ErrorOr<void> mknod(VFSRootContext const&, Credentials const&, StringView path, mode_t, dev_t, CustodyBase const& base);
ErrorOr<NonnullRefPtr<Custody>> open_directory(VFSRootContext const&, Credentials const&, StringView path, CustodyBase const& base);
ErrorOr<void> for_each_mount(Function<ErrorOr<void>(Mount const&)>) const;
ErrorOr<void> for_each_mount(VFSRootContext& context, Function<ErrorOr<void>(Mount const&)>) const;
void sync_filesystems();
void lock_all_filesystems();
static void sync();
NonnullRefPtr<Custody> root_custody();
ErrorOr<NonnullRefPtr<Custody>> resolve_path(Credentials const&, StringView path, CustodyBase const& base, RefPtr<Custody>* out_parent = nullptr, int options = 0, int symlink_recursion_level = 0);
ErrorOr<NonnullRefPtr<Custody>> resolve_path(Process const&, Credentials const&, StringView path, CustodyBase const& base, RefPtr<Custody>* out_parent = nullptr, int options = 0, int symlink_recursion_level = 0);
ErrorOr<NonnullRefPtr<Custody>> resolve_path_without_veil(Credentials const&, StringView path, NonnullRefPtr<Custody> base, RefPtr<Custody>* out_parent = nullptr, int options = 0, int symlink_recursion_level = 0);
ErrorOr<NonnullRefPtr<Custody>> resolve_path(VFSRootContext const&, Credentials const&, StringView path, CustodyBase const& base, RefPtr<Custody>* out_parent = nullptr, int options = 0, int symlink_recursion_level = 0);
ErrorOr<NonnullRefPtr<Custody>> resolve_path(Process const&, VFSRootContext const&, Credentials const&, StringView path, CustodyBase const& base, RefPtr<Custody>* out_parent = nullptr, int options = 0, int symlink_recursion_level = 0);
ErrorOr<NonnullRefPtr<Custody>> resolve_path_without_veil(VFSRootContext const&, Credentials const&, StringView path, NonnullRefPtr<Custody> base, RefPtr<Custody>* out_parent = nullptr, int options = 0, int symlink_recursion_level = 0);
private:
friend class OpenFileDescription;
@@ -108,20 +118,16 @@ private:
ErrorOr<void> validate_path_against_process_veil(Custody const& path, int options);
ErrorOr<void> validate_path_against_process_veil(StringView path, int options);
ErrorOr<void> add_file_system_to_mount_table(FileSystem& file_system, Custody& mount_point, int flags);
static void delete_mount_from_list(Mount& mount);
ErrorOr<void> remove_mount(Mount& mount, IntrusiveList<&FileBackedFileSystem::m_file_backed_file_system_node>& file_backed_fs_list);
static ErrorOr<NonnullRefPtr<FileSystem>> create_and_initialize_filesystem_from_mount_file(MountFile& mount_file);
static ErrorOr<NonnullRefPtr<FileSystem>> create_and_initialize_filesystem_from_mount_file_and_description(IntrusiveList<&FileBackedFileSystem::m_file_backed_file_system_node>& file_backed_fs_list, MountFile& mount_file, OpenFileDescription& source_description);
static ErrorOr<void> verify_mount_file_and_description_requirements(MountFile& mount_file, OpenFileDescription& source_description);
ErrorOr<void> traverse_directory_inode(Inode&, Function<ErrorOr<void>(FileSystem::DirectoryEntryView const&)>);
static bool check_matching_absolute_path_hierarchy(Custody const& first_custody, Custody const& second_custody);
bool mount_point_exists_at_custody(Custody& mount_point);
ErrorOr<void> apply_to_mount_for_host_custody(Custody const& current_custody, Function<void(Mount&)>);
RefPtr<Inode> m_root_inode;
SpinlockProtected<RefPtr<Custody>, LockRank::None> m_root_custody {};
SpinlockProtected<IntrusiveList<&Mount::m_vfs_list_node>, LockRank::None> m_mounts {};
ErrorOr<void> apply_to_mount_for_host_custody(VFSRootContext&, Custody const& current_custody, Function<void(Mount&)>);
// NOTE: The FileBackedFileSystem list is protected by a mutex because we need to scan it
// to search for existing filesystems for already used block devices and therefore when doing
@@ -131,6 +137,8 @@ private:
MutexProtected<IntrusiveList<&FileBackedFileSystem::m_file_backed_file_system_node>> m_file_backed_file_systems_list {};
SpinlockProtected<IntrusiveList<&FileSystem::m_file_system_node>, LockRank::FileSystem> m_file_systems_list {};
SpinlockProtected<IntrusiveList<&VFSRootContext::m_list_node>, LockRank::FileSystem> m_root_contexts {};
};
}