Kernel: Tidy up SysFS construction

- Use KResultOr and TRY() to propagate errors
- Check for OOM errors
- Move allocation out of constructors

There's still a lot more to do here, as SysFS is still quite brittle
in the face of memory pressure.

Kernel/FileSystem/SysFS.cpp

@@ -61,13 +61,12 @@ SysFSRootDirectory::SysFSRootDirectory()
     m_buses_directory = buses_directory;
 }
 
-NonnullRefPtr<SysFS> SysFS::create()
+KResultOr<NonnullRefPtr<SysFS>> SysFS::try_create()
 {
-    return adopt_ref(*new (nothrow) SysFS);
+    return adopt_nonnull_ref_or_enomem(new (nothrow) SysFS);
 }
 
 SysFS::SysFS()
-    : m_root_inode(SysFSComponentRegistry::the().root_directory().to_inode(*this))
 {
 }
 
@@ -77,6 +76,7 @@ SysFS::~SysFS()
 
 KResult SysFS::initialize()
 {
+    m_root_inode = TRY(SysFSComponentRegistry::the().root_directory().to_inode(*this));
     return KSuccess;
 }
 
@@ -85,9 +85,9 @@ Inode& SysFS::root_inode()
     return *m_root_inode;
 }
 
-NonnullRefPtr<SysFSInode> SysFSInode::create(SysFS const& fs, SysFSComponent const& component)
+KResultOr<NonnullRefPtr<SysFSInode>> SysFSInode::try_create(SysFS const& fs, SysFSComponent const& component)
 {
-    return adopt_ref(*new (nothrow) SysFSInode(fs, component));
+    return adopt_nonnull_ref_or_enomem(new (nothrow) SysFSInode(fs, component));
 }
 
 SysFSInode::SysFSInode(SysFS const& fs, SysFSComponent const& component)
@@ -179,9 +179,9 @@ KResult SysFSInode::truncate(u64)
     return EPERM;
 }
 
-NonnullRefPtr<SysFSDirectoryInode> SysFSDirectoryInode::create(SysFS const& sysfs, SysFSComponent const& component)
+KResultOr<NonnullRefPtr<SysFSDirectoryInode>> SysFSDirectoryInode::try_create(SysFS const& sysfs, SysFSComponent const& component)
 {
-    return adopt_ref(*new (nothrow) SysFSDirectoryInode(sysfs, component));
+    return adopt_nonnull_ref_or_enomem(new (nothrow) SysFSDirectoryInode(sysfs, component));
 }
 
 SysFSDirectoryInode::SysFSDirectoryInode(SysFS const& fs, SysFSComponent const& component)
@@ -217,7 +217,7 @@ KResultOr<NonnullRefPtr<Inode>> SysFSDirectoryInode::lookup(StringView name)
     auto component = m_associated_component->lookup(name);
     if (!component)
         return ENOENT;
-    return component->to_inode(fs());
+    return TRY(component->to_inode(fs()));
 }
 
 SysFSBusDirectory& SysFSComponentRegistry::buses_directory()

Kernel/FileSystem/SysFS.h

@@ -60,7 +60,7 @@ class SysFS final : public FileSystem {
 
 public:
     virtual ~SysFS() override;
-    static NonnullRefPtr<SysFS> create();
+    static KResultOr<NonnullRefPtr<SysFS>> try_create();
 
     virtual KResult initialize() override;
     virtual StringView class_name() const override { return "SysFS"sv; }
@@ -70,7 +70,7 @@ public:
 private:
     SysFS();
 
-    NonnullRefPtr<SysFSInode> m_root_inode;
+    RefPtr<SysFSInode> m_root_inode;
 };
 
 class SysFSInode : public Inode {
@@ -78,7 +78,7 @@ class SysFSInode : public Inode {
     friend class SysFSDirectoryInode;
 
 public:
-    static NonnullRefPtr<SysFSInode> create(SysFS const&, SysFSComponent const&);
+    static KResultOr<NonnullRefPtr<SysFSInode>> try_create(SysFS const&, SysFSComponent const&);
     StringView name() const { return m_associated_component->name(); }
 
 protected:
@@ -106,7 +106,7 @@ class SysFSDirectoryInode : public SysFSInode {
     friend class SysFS;
 
 public:
-    static NonnullRefPtr<SysFSDirectoryInode> create(SysFS const&, SysFSComponent const&);
+    static KResultOr<NonnullRefPtr<SysFSDirectoryInode>> try_create(SysFS const&, SysFSComponent const&);
     virtual ~SysFSDirectoryInode() override;
 
     SysFS& fs() { return static_cast<SysFS&>(Inode::fs()); }

Kernel/FileSystem/SysFSComponent.cpp

@@ -61,14 +61,14 @@ SysFSDirectory::SysFSDirectory(StringView name, SysFSDirectory const& parent_dir
 {
 }
 
-NonnullRefPtr<SysFSInode> SysFSDirectory::to_inode(SysFS const& sysfs_instance) const
+KResultOr<NonnullRefPtr<SysFSInode>> SysFSDirectory::to_inode(SysFS const& sysfs_instance) const
 {
-    return SysFSDirectoryInode::create(sysfs_instance, *this);
+    return TRY(SysFSDirectoryInode::try_create(sysfs_instance, *this));
 }
 
-NonnullRefPtr<SysFSInode> SysFSComponent::to_inode(SysFS const& sysfs_instance) const
+KResultOr<NonnullRefPtr<SysFSInode>> SysFSComponent::to_inode(SysFS const& sysfs_instance) const
 {
-    return SysFSInode::create(sysfs_instance, *this);
+    return SysFSInode::try_create(sysfs_instance, *this);
 }
 
 }

Kernel/FileSystem/SysFSComponent.h

@@ -32,7 +32,7 @@ public:
     virtual KResultOr<size_t> write_bytes(off_t, size_t, UserOrKernelBuffer const&, FileDescription*) { return EROFS; }
     virtual KResult refresh_data(FileDescription&) const { return KSuccess; }
 
-    virtual NonnullRefPtr<SysFSInode> to_inode(SysFS const&) const;
+    virtual KResultOr<NonnullRefPtr<SysFSInode>> to_inode(SysFS const&) const;
 
     InodeIndex component_index() const { return m_component_index; };
 
@@ -51,7 +51,7 @@ public:
     virtual KResult traverse_as_directory(unsigned, Function<bool(FileSystem::DirectoryEntryView const&)>) const override;
     virtual RefPtr<SysFSComponent> lookup(StringView name) override;
 
-    virtual NonnullRefPtr<SysFSInode> to_inode(SysFS const& sysfs_instance) const override final;
+    virtual KResultOr<NonnullRefPtr<SysFSInode>> to_inode(SysFS const& sysfs_instance) const override final;
 
 protected:
     explicit SysFSDirectory(StringView name);

Kernel/Syscalls/mount.cpp

@@ -85,7 +85,7 @@ KResultOr<FlatPtr> Process::sys$mount(Userspace<const Syscall::SC_mount_params*>
     } else if (fs_type == "dev"sv || fs_type == "DevFS"sv) {
         fs = TRY(DevFS::try_create());
     } else if (fs_type == "sys"sv || fs_type == "SysFS"sv) {
-        fs = SysFS::create();
+        fs = TRY(SysFS::try_create());
     } else if (fs_type == "tmp"sv || fs_type == "TmpFS"sv) {
         fs = TRY(TmpFS::try_create());
     } else if (fs_type == "iso9660"sv || fs_type == "ISO9660FS"sv) {