Kernel/RAMFS: Add an option to control the maximum filesystem size

Kernel/FileSystem/RAMFS/FileSystem.cpp

@@ -11,12 +11,26 @@
 
 namespace Kernel {
 
-ErrorOr<NonnullRefPtr<FileSystem>> RAMFS::try_create(FileSystemSpecificOptions const&)
+static constexpr StringView MAXIMUM_SIZE_OPTION = "maximum_size"sv;
+
+ErrorOr<void> RAMFS::validate_mount_unsigned_integer_flag(StringView key, u64)
+{
+    if (key == MAXIMUM_SIZE_OPTION)
+        return {};
+    return EINVAL;
+}
+
+ErrorOr<NonnullRefPtr<FileSystem>> RAMFS::try_create(FileSystemSpecificOptions const& options)
+{
+    u64 maximum_size = parse_unsigned_filesystem_specific_option(options, MAXIMUM_SIZE_OPTION).value_or(0);
+    return TRY(adopt_nonnull_ref_or_enomem(new (nothrow) RAMFS(maximum_size)));
+}
+
+RAMFS::RAMFS(u64 maximum_size)
+    : m_maximum_size(maximum_size)
 {
-    return TRY(adopt_nonnull_ref_or_enomem(new (nothrow) RAMFS));
 }
 
-RAMFS::RAMFS() = default;
 RAMFS::~RAMFS() = default;
 
 ErrorOr<void> RAMFS::initialize()

Kernel/FileSystem/RAMFS/FileSystem.h

@@ -22,6 +22,8 @@ public:
     static ErrorOr<NonnullRefPtr<FileSystem>> try_create(FileSystemSpecificOptions const&);
     virtual ErrorOr<void> initialize() override;
 
+    static ErrorOr<void> validate_mount_unsigned_integer_flag(StringView key, u64);
+
     virtual StringView class_name() const override { return "RAMFS"sv; }
 
     virtual bool supports_watchers() const override { return true; }
@@ -37,7 +39,7 @@ public:
     virtual unsigned free_block_count() const override;
 
 private:
-    RAMFS();
+    RAMFS(u64 maximum_size);
 
     u32 total_block_count_impl() const;
 

Kernel/FileSystem/VirtualFileSystem.cpp

@@ -104,7 +104,7 @@ static constexpr FileSystemInitializer s_initializers[] = {
     { "proc"sv, "ProcFS"sv, false, false, false, {}, ProcFS::try_create, validate_mount_boolean_flag_as_invalid, validate_mount_unsigned_integer_flag_as_invalid, validate_mount_signed_integer_flag_as_invalid, validate_mount_ascii_string_flag_as_invalid },
     { "devpts"sv, "DevPtsFS"sv, false, false, false, {}, DevPtsFS::try_create, validate_mount_boolean_flag_as_invalid, validate_mount_unsigned_integer_flag_as_invalid, validate_mount_signed_integer_flag_as_invalid, validate_mount_ascii_string_flag_as_invalid },
     { "sys"sv, "SysFS"sv, false, false, false, {}, SysFS::try_create, validate_mount_boolean_flag_as_invalid, validate_mount_unsigned_integer_flag_as_invalid, validate_mount_signed_integer_flag_as_invalid, validate_mount_ascii_string_flag_as_invalid },
-    { "ram"sv, "RAMFS"sv, false, false, false, {}, RAMFS::try_create, validate_mount_boolean_flag_as_invalid, validate_mount_unsigned_integer_flag_as_invalid, validate_mount_signed_integer_flag_as_invalid, validate_mount_ascii_string_flag_as_invalid },
+    { "ram"sv, "RAMFS"sv, false, false, false, {}, RAMFS::try_create, validate_mount_boolean_flag_as_invalid, RAMFS::validate_mount_unsigned_integer_flag, validate_mount_signed_integer_flag_as_invalid, validate_mount_ascii_string_flag_as_invalid },
     { "ext2"sv, "Ext2FS"sv, true, true, true, Ext2FS::try_create, {}, validate_mount_boolean_flag_as_invalid, validate_mount_unsigned_integer_flag_as_invalid, validate_mount_signed_integer_flag_as_invalid, validate_mount_ascii_string_flag_as_invalid },
     { "9p"sv, "Plan9FS"sv, true, true, true, Plan9FS::try_create, {}, validate_mount_boolean_flag_as_invalid, validate_mount_unsigned_integer_flag_as_invalid, validate_mount_signed_integer_flag_as_invalid, validate_mount_ascii_string_flag_as_invalid },
     { "iso9660"sv, "ISO9660FS"sv, true, true, true, ISO9660FS::try_create, {}, validate_mount_boolean_flag_as_invalid, validate_mount_unsigned_integer_flag_as_invalid, validate_mount_signed_integer_flag_as_invalid, validate_mount_ascii_string_flag_as_invalid },