Kernel: Change Inode::{read/write}_bytes interface to KResultOr<ssize_t>

The error handling in all these cases was still using the old style
negative values to indicate errors. We have a nicer solution for this
now with KResultOr<T>. This change switches the interface and then all
implementers to use the new style.

Kernel/FileSystem/DevFS.cpp

@@ -80,7 +80,8 @@ DevFSInode::DevFSInode(DevFS& fs)
     : Inode(fs, fs.allocate_inode_index())
 {
 }
-ssize_t DevFSInode::read_bytes(off_t, ssize_t, UserOrKernelBuffer&, FileDescription*) const
+
+KResultOr<ssize_t> DevFSInode::read_bytes(off_t, ssize_t, UserOrKernelBuffer&, FileDescription*) const
 {
     VERIFY_NOT_REACHED();
 }
@@ -99,7 +100,7 @@ void DevFSInode::flush_metadata()
 {
 }
 
-ssize_t DevFSInode::write_bytes(off_t, ssize_t, const UserOrKernelBuffer&, FileDescription*)
+KResultOr<ssize_t> DevFSInode::write_bytes(off_t, ssize_t, const UserOrKernelBuffer&, FileDescription*)
 {
     VERIFY_NOT_REACHED();
 }
@@ -151,13 +152,13 @@ DevFSLinkInode::DevFSLinkInode(DevFS& fs, String name)
     , m_name(name)
 {
 }
-ssize_t DevFSLinkInode::read_bytes(off_t offset, ssize_t, UserOrKernelBuffer& buffer, FileDescription*) const
+KResultOr<ssize_t> DevFSLinkInode::read_bytes(off_t offset, ssize_t, UserOrKernelBuffer& buffer, FileDescription*) const
 {
     Locker locker(m_lock);
     VERIFY(offset == 0);
     VERIFY(!m_link.is_null());
     if (!buffer.write(((const u8*)m_link.substring_view(0).characters_without_null_termination()) + offset, m_link.length()))
-        return -EFAULT;
+        return EFAULT;
     return m_link.length();
 }
 InodeMetadata DevFSLinkInode::metadata() const
@@ -172,7 +173,7 @@ InodeMetadata DevFSLinkInode::metadata() const
     metadata.mtime = mepoch;
     return metadata;
 }
-ssize_t DevFSLinkInode::write_bytes(off_t offset, ssize_t count, const UserOrKernelBuffer& buffer, FileDescription*)
+KResultOr<ssize_t> DevFSLinkInode::write_bytes(off_t offset, ssize_t count, const UserOrKernelBuffer& buffer, FileDescription*)
 {
     Locker locker(m_lock);
     VERIFY(offset == 0);
@@ -345,7 +346,7 @@ String DevFSDeviceInode::name() const
     return m_cached_name;
 }
 
-ssize_t DevFSDeviceInode::read_bytes(off_t offset, ssize_t count, UserOrKernelBuffer& buffer, FileDescription* description) const
+KResultOr<ssize_t> DevFSDeviceInode::read_bytes(off_t offset, ssize_t count, UserOrKernelBuffer& buffer, FileDescription* description) const
 {
     Locker locker(m_lock);
     VERIFY(!!description);
@@ -353,7 +354,7 @@ ssize_t DevFSDeviceInode::read_bytes(off_t offset, ssize_t count, UserOrKernelBu
         return 0;
     auto nread = const_cast<Device&>(*m_attached_device).read(*description, offset, buffer, count);
     if (nread.is_error())
-        return -EIO;
+        return EIO;
     return nread.value();
 }
 
@@ -371,7 +372,7 @@ InodeMetadata DevFSDeviceInode::metadata() const
     metadata.minor_device = m_attached_device->minor();
     return metadata;
 }
-ssize_t DevFSDeviceInode::write_bytes(off_t offset, ssize_t count, const UserOrKernelBuffer& buffer, FileDescription* description)
+KResultOr<ssize_t> DevFSDeviceInode::write_bytes(off_t offset, ssize_t count, const UserOrKernelBuffer& buffer, FileDescription* description)
 {
     Locker locker(m_lock);
     VERIFY(!!description);
@@ -379,7 +380,7 @@ ssize_t DevFSDeviceInode::write_bytes(off_t offset, ssize_t count, const UserOrK
         return 0;
     auto nread = const_cast<Device&>(*m_attached_device).write(*description, offset, buffer, count);
     if (nread.is_error())
-        return -EIO;
+        return EIO;
     return nread.value();
 }
 

Kernel/FileSystem/DevFS.h

@@ -57,11 +57,11 @@ public:
 
 protected:
     DevFSInode(DevFS&);
-    virtual ssize_t read_bytes(off_t, ssize_t, UserOrKernelBuffer& buffer, FileDescription*) const override;
+    virtual KResultOr<ssize_t> read_bytes(off_t, ssize_t, UserOrKernelBuffer& buffer, FileDescription*) const override;
     virtual KResult traverse_as_directory(Function<bool(const FS::DirectoryEntryView&)>) const override;
     virtual RefPtr<Inode> lookup(StringView name) override;
     virtual void flush_metadata() override;
-    virtual ssize_t write_bytes(off_t, ssize_t, const UserOrKernelBuffer& buffer, FileDescription*) override;
+    virtual KResultOr<ssize_t> write_bytes(off_t, ssize_t, const UserOrKernelBuffer& buffer, FileDescription*) override;
     virtual KResultOr<NonnullRefPtr<Inode>> create_child(const String& name, mode_t, dev_t, uid_t, gid_t) override;
     virtual KResult add_child(Inode&, const StringView& name, mode_t) override;
     virtual KResult remove_child(const StringView& name) override;
@@ -83,9 +83,9 @@ private:
     String determine_name() const;
     DevFSDeviceInode(DevFS&, const Device&);
     // ^Inode
-    virtual ssize_t read_bytes(off_t, ssize_t, UserOrKernelBuffer& buffer, FileDescription*) const override;
+    virtual KResultOr<ssize_t> read_bytes(off_t, ssize_t, UserOrKernelBuffer& buffer, FileDescription*) const override;
     virtual InodeMetadata metadata() const override;
-    virtual ssize_t write_bytes(off_t, ssize_t, const UserOrKernelBuffer& buffer, FileDescription*) override;
+    virtual KResultOr<ssize_t> write_bytes(off_t, ssize_t, const UserOrKernelBuffer& buffer, FileDescription*) override;
     virtual KResult chown(uid_t, gid_t) override;
 
     NonnullRefPtr<Device> m_attached_device;
@@ -106,9 +106,9 @@ public:
 protected:
     DevFSLinkInode(DevFS&, String);
     // ^Inode
-    virtual ssize_t read_bytes(off_t, ssize_t, UserOrKernelBuffer& buffer, FileDescription*) const override;
+    virtual KResultOr<ssize_t> read_bytes(off_t, ssize_t, UserOrKernelBuffer& buffer, FileDescription*) const override;
     virtual InodeMetadata metadata() const override;
-    virtual ssize_t write_bytes(off_t, ssize_t, const UserOrKernelBuffer& buffer, FileDescription*) override;
+    virtual KResultOr<ssize_t> write_bytes(off_t, ssize_t, const UserOrKernelBuffer& buffer, FileDescription*) override;
 
     const String m_name;
     String m_link;

Kernel/FileSystem/DevPtsFS.cpp

@@ -100,12 +100,12 @@ DevPtsFSInode::~DevPtsFSInode()
 {
 }
 
-ssize_t DevPtsFSInode::read_bytes(off_t, ssize_t, UserOrKernelBuffer&, FileDescription*) const
+KResultOr<ssize_t> DevPtsFSInode::read_bytes(off_t, ssize_t, UserOrKernelBuffer&, FileDescription*) const
 {
     VERIFY_NOT_REACHED();
 }
 
-ssize_t DevPtsFSInode::write_bytes(off_t, ssize_t, const UserOrKernelBuffer&, FileDescription*)
+KResultOr<ssize_t> DevPtsFSInode::write_bytes(off_t, ssize_t, const UserOrKernelBuffer&, FileDescription*)
 {
     VERIFY_NOT_REACHED();
 }

Kernel/FileSystem/DevPtsFS.h

@@ -47,12 +47,12 @@ private:
     DevPtsFSInode(DevPtsFS&, InodeIndex, SlavePTY*);
 
     // ^Inode
-    virtual ssize_t read_bytes(off_t, ssize_t, UserOrKernelBuffer& buffer, FileDescription*) const override;
+    virtual KResultOr<ssize_t> read_bytes(off_t, ssize_t, UserOrKernelBuffer& buffer, FileDescription*) const override;
     virtual InodeMetadata metadata() const override;
     virtual KResult traverse_as_directory(Function<bool(const FS::DirectoryEntryView&)>) const override;
     virtual RefPtr<Inode> lookup(StringView name) override;
     virtual void flush_metadata() override;
-    virtual ssize_t write_bytes(off_t, ssize_t, const UserOrKernelBuffer& buffer, FileDescription*) override;
+    virtual KResultOr<ssize_t> write_bytes(off_t, ssize_t, const UserOrKernelBuffer& buffer, FileDescription*) override;
     virtual KResultOr<NonnullRefPtr<Inode>> create_child(const String& name, mode_t, dev_t, uid_t, gid_t) override;
     virtual KResult add_child(Inode&, const StringView& name, mode_t) override;
     virtual KResult remove_child(const StringView& name) override;

Kernel/FileSystem/Ext2FileSystem.cpp

@@ -807,7 +807,7 @@ RefPtr<Inode> Ext2FS::get_inode(InodeIdentifier inode) const
     return new_inode;
 }
 
-ssize_t Ext2FSInode::read_bytes(off_t offset, ssize_t count, UserOrKernelBuffer& buffer, FileDescription* description) const
+KResultOr<ssize_t> Ext2FSInode::read_bytes(off_t offset, ssize_t count, UserOrKernelBuffer& buffer, FileDescription* description) const
 {
     Locker inode_locker(m_lock);
     VERIFY(offset >= 0);
@@ -823,7 +823,7 @@ ssize_t Ext2FSInode::read_bytes(off_t offset, ssize_t count, UserOrKernelBuffer&
         VERIFY(offset == 0);
         ssize_t nread = min((off_t)size() - offset, static_cast<off_t>(count));
         if (!buffer.write(((const u8*)m_raw_inode.i_block) + offset, (size_t)nread))
-            return -EFAULT;
+            return EFAULT;
         return nread;
     }
 
@@ -832,7 +832,7 @@ ssize_t Ext2FSInode::read_bytes(off_t offset, ssize_t count, UserOrKernelBuffer&
 
     if (m_block_list.is_empty()) {
         dmesgln("Ext2FSInode[{}]::read_bytes(): Empty block list", identifier());
-        return -EIO;
+        return EIO;
     }
 
     bool allow_cache = !description || !description->is_direct();
@@ -859,7 +859,7 @@ ssize_t Ext2FSInode::read_bytes(off_t offset, ssize_t count, UserOrKernelBuffer&
         if (block_index.value() == 0) {
             // This is a hole, act as if it's filled with zeroes.
             if (!buffer_offset.memset(0, num_bytes_to_copy))
-                return -EFAULT;
+                return EFAULT;
         } else {
             if (auto result = fs().read_block(block_index, &buffer_offset, num_bytes_to_copy, offset_into_block, allow_cache); result.is_error()) {
                 dmesgln("Ext2FSInode[{}]::read_bytes(): Failed to read block {} (index {})", identifier(), block_index.value(), bi);
@@ -940,19 +940,19 @@ KResult Ext2FSInode::resize(u64 new_size)
         auto clear_from = old_size;
         u8 zero_buffer[PAGE_SIZE] {};
         while (bytes_to_clear) {
-            auto nwritten = write_bytes(clear_from, min(static_cast<u64>(sizeof(zero_buffer)), bytes_to_clear), UserOrKernelBuffer::for_kernel_buffer(zero_buffer), nullptr);
+            auto result = write_bytes(clear_from, min(static_cast<u64>(sizeof(zero_buffer)), bytes_to_clear), UserOrKernelBuffer::for_kernel_buffer(zero_buffer), nullptr);
-            if (nwritten < 0)
+            if (result.is_error())
-                return KResult((ErrnoCode)-nwritten);
+                return result.error();
-            VERIFY(nwritten != 0);
+            VERIFY(result.value() != 0);
-            bytes_to_clear -= nwritten;
+            bytes_to_clear -= result.value();
-            clear_from += nwritten;
+            clear_from += result.value();
         }
     }
 
     return KSuccess;
 }
 
-ssize_t Ext2FSInode::write_bytes(off_t offset, ssize_t count, const UserOrKernelBuffer& data, FileDescription* description)
+KResultOr<ssize_t> Ext2FSInode::write_bytes(off_t offset, ssize_t count, const UserOrKernelBuffer& data, FileDescription* description)
 {
     VERIFY(offset >= 0);
     VERIFY(count >= 0);
@@ -967,7 +967,7 @@ ssize_t Ext2FSInode::write_bytes(off_t offset, ssize_t count, const UserOrKernel
         if (max((size_t)(offset + count), (size_t)m_raw_inode.i_size) < max_inline_symlink_length) {
             dbgln_if(EXT2_DEBUG, "Ext2FSInode[{}]::write_bytes(): Poking into i_block array for inline symlink '{}' ({} bytes)", identifier(), data.copy_into_string(count), count);
             if (!data.read(((u8*)m_raw_inode.i_block) + offset, (size_t)count))
-                return -EFAULT;
+                return EFAULT;
             if ((size_t)(offset + count) > (size_t)m_raw_inode.i_size)
                 m_raw_inode.i_size = offset + count;
             set_metadata_dirty(true);
@@ -988,7 +988,7 @@ ssize_t Ext2FSInode::write_bytes(off_t offset, ssize_t count, const UserOrKernel
 
     if (m_block_list.is_empty()) {
         dbgln("Ext2FSInode[{}]::write_bytes(): Empty block list", identifier());
-        return -EIO;
+        return EIO;
     }
 
     BlockBasedFS::BlockIndex first_block_logical_index = offset / block_size;
@@ -1113,11 +1113,11 @@ KResult Ext2FSInode::write_directory(const Vector<Ext2FSDirectoryEntry>& entries
     stream.fill_to_end(0);
 
     auto buffer = UserOrKernelBuffer::for_kernel_buffer(stream.data());
-    ssize_t nwritten = write_bytes(0, stream.size(), buffer, nullptr);
+    auto result = write_bytes(0, stream.size(), buffer, nullptr);
-    if (nwritten < 0)
+    if (result.is_error())
-        return KResult((ErrnoCode)-nwritten);
+        return result.error();
     set_metadata_dirty(true);
-    if (static_cast<size_t>(nwritten) != directory_data.size())
+    if (static_cast<size_t>(result.value()) != directory_data.size())
         return EIO;
     return KSuccess;
 }

Kernel/FileSystem/Ext2FileSystem.h

@@ -38,12 +38,12 @@ public:
 
 private:
     // ^Inode
-    virtual ssize_t read_bytes(off_t, ssize_t, UserOrKernelBuffer& buffer, FileDescription*) const override;
+    virtual KResultOr<ssize_t> read_bytes(off_t, ssize_t, UserOrKernelBuffer& buffer, FileDescription*) const override;
     virtual InodeMetadata metadata() const override;
     virtual KResult traverse_as_directory(Function<bool(const FS::DirectoryEntryView&)>) const override;
     virtual RefPtr<Inode> lookup(StringView name) override;
     virtual void flush_metadata() override;
-    virtual ssize_t write_bytes(off_t, ssize_t, const UserOrKernelBuffer& data, FileDescription*) override;
+    virtual KResultOr<ssize_t> write_bytes(off_t, ssize_t, const UserOrKernelBuffer& data, FileDescription*) override;
     virtual KResultOr<NonnullRefPtr<Inode>> create_child(const String& name, mode_t, dev_t, uid_t, gid_t) override;
     virtual KResult add_child(Inode& child, const StringView& name, mode_t) override;
     virtual KResult remove_child(const StringView& name) override;

Kernel/FileSystem/Inode.cpp

@@ -60,9 +60,10 @@ KResultOr<NonnullOwnPtr<KBuffer>> Inode::read_entire(FileDescription* descriptio
     off_t offset = 0;
     for (;;) {
         auto buf = UserOrKernelBuffer::for_kernel_buffer(buffer);
-        nread = read_bytes(offset, sizeof(buffer), buf, description);
+        auto result = read_bytes(offset, sizeof(buffer), buf, description);
-        if (nread < 0)
+        if (result.is_error())
-            return KResult((ErrnoCode)-nread);
+            return result.error();
+        nread = result.value();
         VERIFY(nread <= (ssize_t)sizeof(buffer));
         if (nread <= 0)
             break;

Kernel/FileSystem/Inode.h

@@ -52,10 +52,10 @@ public:
     virtual KResult attach(FileDescription&) { return KSuccess; }
     virtual void detach(FileDescription&) { }
     virtual void did_seek(FileDescription&, off_t) { }
-    virtual ssize_t read_bytes(off_t, ssize_t, UserOrKernelBuffer& buffer, FileDescription*) const = 0;
+    virtual KResultOr<ssize_t> read_bytes(off_t, ssize_t, UserOrKernelBuffer& buffer, FileDescription*) const = 0;
     virtual KResult traverse_as_directory(Function<bool(const FS::DirectoryEntryView&)>) const = 0;
     virtual RefPtr<Inode> lookup(StringView name) = 0;
-    virtual ssize_t write_bytes(off_t, ssize_t, const UserOrKernelBuffer& data, FileDescription*) = 0;
+    virtual KResultOr<ssize_t> write_bytes(off_t, ssize_t, const UserOrKernelBuffer& data, FileDescription*) = 0;
     virtual KResultOr<NonnullRefPtr<Inode>> create_child(const String& name, mode_t, dev_t, uid_t, gid_t) = 0;
     virtual KResult add_child(Inode&, const StringView& name, mode_t) = 0;
     virtual KResult remove_child(const StringView& name) = 0;

Kernel/FileSystem/InodeFile.cpp

@@ -31,13 +31,14 @@ KResultOr<size_t> InodeFile::read(FileDescription& description, u64 offset, User
     if (Checked<off_t>::addition_would_overflow(offset, count))
         return EOVERFLOW;
 
-    ssize_t nread = m_inode->read_bytes(offset, count, buffer, &description);
+    auto result = m_inode->read_bytes(offset, count, buffer, &description);
+    if (result.is_error())
+        return result.error();
+    auto nread = result.value();
     if (nread > 0) {
         Thread::current()->did_file_read(nread);
         evaluate_block_conditions();
     }
-    if (nread < 0)
-        return KResult((ErrnoCode)-nread);
     return nread;
 }
 
@@ -46,7 +47,11 @@ KResultOr<size_t> InodeFile::write(FileDescription& description, u64 offset, con
     if (Checked<off_t>::addition_would_overflow(offset, count))
         return EOVERFLOW;
 
-    ssize_t nwritten = m_inode->write_bytes(offset, count, data, &description);
+    auto result = m_inode->write_bytes(offset, count, data, &description);
+    if (result.is_error())
+        return result.error();
+
+    auto nwritten = result.value();
     if (nwritten > 0) {
         auto mtime_result = m_inode->set_mtime(kgettimeofday().to_truncated_seconds());
         Thread::current()->did_file_write(nwritten);
@@ -54,8 +59,6 @@ KResultOr<size_t> InodeFile::write(FileDescription& description, u64 offset, con
         if (mtime_result.is_error())
             return mtime_result;
     }
-    if (nwritten < 0)
-        return KResult((ErrnoCode)-nwritten);
     return nwritten;
 }
 

Kernel/FileSystem/Plan9FileSystem.cpp

@@ -728,7 +728,7 @@ KResult Plan9FSInode::ensure_open_for_mode(int mode)
     }
 }
 
-ssize_t Plan9FSInode::read_bytes(off_t offset, ssize_t size, UserOrKernelBuffer& buffer, FileDescription*) const
+KResultOr<ssize_t> Plan9FSInode::read_bytes(off_t offset, ssize_t size, UserOrKernelBuffer& buffer, FileDescription*) const
 {
     auto result = const_cast<Plan9FSInode&>(*this).ensure_open_for_mode(O_RDONLY);
     if (result.is_error())
@@ -762,22 +762,22 @@ ssize_t Plan9FSInode::read_bytes(off_t offset, ssize_t size, UserOrKernelBuffer&
     // Guard against the server returning more data than requested.
     size_t nread = min(data.length(), (size_t)size);
     if (!buffer.write(data.characters_without_null_termination(), nread))
-        return -EFAULT;
+        return EFAULT;
 
     return nread;
 }
 
-ssize_t Plan9FSInode::write_bytes(off_t offset, ssize_t size, const UserOrKernelBuffer& data, FileDescription*)
+KResultOr<ssize_t> Plan9FSInode::write_bytes(off_t offset, ssize_t size, const UserOrKernelBuffer& data, FileDescription*)
 {
     auto result = ensure_open_for_mode(O_WRONLY);
     if (result.is_error())
-        return result;
+        return result.error();
 
     size = fs().adjust_buffer_size(size);
 
     auto data_copy = data.copy_into_string(size); // FIXME: this seems ugly
     if (data_copy.is_null())
-        return -EFAULT;
+        return EFAULT;
 
     Plan9FS::Message message { fs(), Plan9FS::Message::Type::Twrite };
     message << fid() << (u64)offset;

Kernel/FileSystem/Plan9FileSystem.h

@@ -156,8 +156,8 @@ public:
     // ^Inode
     virtual InodeMetadata metadata() const override;
     virtual void flush_metadata() override;
-    virtual ssize_t read_bytes(off_t, ssize_t, UserOrKernelBuffer& buffer, FileDescription*) const override;
+    virtual KResultOr<ssize_t> read_bytes(off_t, ssize_t, UserOrKernelBuffer& buffer, FileDescription*) const override;
-    virtual ssize_t write_bytes(off_t, ssize_t, const UserOrKernelBuffer& data, FileDescription*) override;
+    virtual KResultOr<ssize_t> write_bytes(off_t, ssize_t, const UserOrKernelBuffer& data, FileDescription*) override;
     virtual KResult traverse_as_directory(Function<bool(const FS::DirectoryEntryView&)>) const override;
     virtual RefPtr<Inode> lookup(StringView name) override;
     virtual KResultOr<NonnullRefPtr<Inode>> create_child(const String& name, mode_t, dev_t, uid_t, gid_t) override;

Kernel/FileSystem/ProcFS.cpp

@@ -1222,17 +1222,17 @@ InodeMetadata ProcFSInode::metadata() const
     return metadata;
 }
 
-ssize_t ProcFSInode::read_bytes(off_t offset, ssize_t count, UserOrKernelBuffer& buffer, FileDescription* description) const
+KResultOr<ssize_t> ProcFSInode::read_bytes(off_t offset, ssize_t count, UserOrKernelBuffer& buffer, FileDescription* description) const
 {
     dbgln_if(PROCFS_DEBUG, "ProcFS: read_bytes offset: {} count: {}", offset, count);
     VERIFY(offset >= 0);
     VERIFY(buffer.user_or_kernel_ptr());
 
     if (!description)
-        return -EIO;
+        return EIO;
     if (!description->data()) {
         dbgln_if(PROCFS_DEBUG, "ProcFS: Do not have cached data!");
-        return -EIO;
+        return EIO;
     }
 
     // Be sure to keep a reference to data_buffer while we use it!
@@ -1243,7 +1243,7 @@ ssize_t ProcFSInode::read_bytes(off_t offset, ssize_t count, UserOrKernelBuffer&
 
     ssize_t nread = min(static_cast<off_t>(data_buffer->size() - offset), static_cast<off_t>(count));
     if (!buffer.write(data_buffer->data() + offset, nread))
-        return -EFAULT;
+        return EFAULT;
 
     return nread;
 }
@@ -1454,7 +1454,7 @@ void ProcFSInode::flush_metadata()
 {
 }
 
-ssize_t ProcFSInode::write_bytes(off_t offset, ssize_t size, const UserOrKernelBuffer& buffer, FileDescription*)
+KResultOr<ssize_t> ProcFSInode::write_bytes(off_t offset, ssize_t size, const UserOrKernelBuffer& buffer, FileDescription*)
 {
     // For process-specific inodes, hold the process's ptrace lock across the write
     // and refuse to write at all data if the process is not dumpable.
@@ -1493,10 +1493,10 @@ ssize_t ProcFSInode::write_bytes(off_t offset, ssize_t size, const UserOrKernelB
                 break;
             }
         } else
-            return -EPERM;
+            return EPERM;
     } else {
         if (!directory_entry->write_callback)
-            return -EPERM;
+            return EPERM;
         write_callback = directory_entry->write_callback;
     }
 

Kernel/FileSystem/ProcFS.h

@@ -78,12 +78,12 @@ private:
     // ^Inode
     virtual KResult attach(FileDescription&) override;
     virtual void did_seek(FileDescription&, off_t) override;
-    virtual ssize_t read_bytes(off_t, ssize_t, UserOrKernelBuffer& buffer, FileDescription*) const override;
+    virtual KResultOr<ssize_t> read_bytes(off_t, ssize_t, UserOrKernelBuffer& buffer, FileDescription*) const override;
     virtual InodeMetadata metadata() const override;
     virtual KResult traverse_as_directory(Function<bool(const FS::DirectoryEntryView&)>) const override;
     virtual RefPtr<Inode> lookup(StringView name) override;
     virtual void flush_metadata() override;
-    virtual ssize_t write_bytes(off_t, ssize_t, const UserOrKernelBuffer& buffer, FileDescription*) override;
+    virtual KResultOr<ssize_t> write_bytes(off_t, ssize_t, const UserOrKernelBuffer& buffer, FileDescription*) override;
     virtual KResultOr<NonnullRefPtr<Inode>> create_child(const String& name, mode_t, dev_t, uid_t, gid_t) override;
     virtual KResult add_child(Inode&, const StringView& name, mode_t) override;
     virtual KResult remove_child(const StringView& name) override;
@@ -111,12 +111,12 @@ private:
     // ^Inode
     virtual KResult attach(FileDescription&) override;
     virtual void did_seek(FileDescription&, off_t) override;
-    virtual ssize_t read_bytes(off_t, ssize_t, UserOrKernelBuffer&, FileDescription*) const override { VERIFY_NOT_REACHED(); }
+    virtual KResultOr<ssize_t> read_bytes(off_t, ssize_t, UserOrKernelBuffer&, FileDescription*) const override { VERIFY_NOT_REACHED(); }
     virtual InodeMetadata metadata() const override;
     virtual KResult traverse_as_directory(Function<bool(const FS::DirectoryEntryView&)>) const override { VERIFY_NOT_REACHED(); }
     virtual RefPtr<Inode> lookup(StringView name) override;
     virtual void flush_metadata() override {};
-    virtual ssize_t write_bytes(off_t, ssize_t, const UserOrKernelBuffer&, FileDescription*) override { VERIFY_NOT_REACHED(); }
+    virtual KResultOr<ssize_t> write_bytes(off_t, ssize_t, const UserOrKernelBuffer&, FileDescription*) override { VERIFY_NOT_REACHED(); }
     virtual KResultOr<NonnullRefPtr<Inode>> create_child(const String& name, mode_t, dev_t, uid_t, gid_t) override;
     virtual KResult add_child(Inode&, const StringView& name, mode_t) override;
     virtual KResult remove_child(const StringView& name) override;

Kernel/FileSystem/TmpFS.cpp

@@ -126,7 +126,7 @@ KResult TmpFSInode::traverse_as_directory(Function<bool(const FS::DirectoryEntry
     return KSuccess;
 }
 
-ssize_t TmpFSInode::read_bytes(off_t offset, ssize_t size, UserOrKernelBuffer& buffer, FileDescription*) const
+KResultOr<ssize_t> TmpFSInode::read_bytes(off_t offset, ssize_t size, UserOrKernelBuffer& buffer, FileDescription*) const
 {
     Locker locker(m_lock, Lock::Mode::Shared);
     VERIFY(!is_directory());
@@ -143,11 +143,11 @@ ssize_t TmpFSInode::read_bytes(off_t offset, ssize_t size, UserOrKernelBuffer& b
         size = m_metadata.size - offset;
 
     if (!buffer.write(m_content->data() + offset, size))
-        return -EFAULT;
+        return EFAULT;
     return size;
 }
 
-ssize_t TmpFSInode::write_bytes(off_t offset, ssize_t size, const UserOrKernelBuffer& buffer, FileDescription*)
+KResultOr<ssize_t> TmpFSInode::write_bytes(off_t offset, ssize_t size, const UserOrKernelBuffer& buffer, FileDescription*)
 {
     Locker locker(m_lock);
     VERIFY(!is_directory());
@@ -175,7 +175,7 @@ ssize_t TmpFSInode::write_bytes(off_t offset, ssize_t size, const UserOrKernelBu
             //        existing ones.
             auto tmp = KBuffer::try_create_with_size(new_size * 2);
             if (!tmp)
-                return -ENOMEM;
+                return ENOMEM;
             tmp->set_size(new_size);
             if (m_content)
                 memcpy(tmp->data(), m_content->data(), old_size);
@@ -187,7 +187,7 @@ ssize_t TmpFSInode::write_bytes(off_t offset, ssize_t size, const UserOrKernelBu
     }
 
     if (!buffer.read(m_content->data() + offset, size)) // TODO: partial reads?
-        return -EFAULT;
+        return EFAULT;
     return size;
 }
 

Kernel/FileSystem/TmpFS.h

@@ -54,12 +54,12 @@ public:
     const TmpFS& fs() const { return static_cast<const TmpFS&>(Inode::fs()); }
 
     // ^Inode
-    virtual ssize_t read_bytes(off_t, ssize_t, UserOrKernelBuffer& buffer, FileDescription*) const override;
+    virtual KResultOr<ssize_t> read_bytes(off_t, ssize_t, UserOrKernelBuffer& buffer, FileDescription*) const override;
     virtual InodeMetadata metadata() const override;
     virtual KResult traverse_as_directory(Function<bool(const FS::DirectoryEntryView&)>) const override;
     virtual RefPtr<Inode> lookup(StringView name) override;
     virtual void flush_metadata() override;
-    virtual ssize_t write_bytes(off_t, ssize_t, const UserOrKernelBuffer& buffer, FileDescription*) override;
+    virtual KResultOr<ssize_t> write_bytes(off_t, ssize_t, const UserOrKernelBuffer& buffer, FileDescription*) override;
     virtual KResultOr<NonnullRefPtr<Inode>> create_child(const String& name, mode_t, dev_t, uid_t, gid_t) override;
     virtual KResult add_child(Inode&, const StringView& name, mode_t) override;
     virtual KResult remove_child(const StringView& name) override;

Kernel/FileSystem/VirtualFileSystem.cpp

@@ -710,9 +710,9 @@ KResult VFS::symlink(StringView target, StringView linkpath, Custody& base)
         return inode_or_error.error();
     auto& inode = inode_or_error.value();
     auto target_buffer = UserOrKernelBuffer::for_kernel_buffer(const_cast<u8*>((const u8*)target.characters_without_null_termination()));
-    ssize_t nwritten = inode->write_bytes(0, target.length(), target_buffer, nullptr);
+    auto result = inode->write_bytes(0, target.length(), target_buffer, nullptr);
-    if (nwritten < 0)
+    if (result.is_error())
-        return KResult((ErrnoCode)-nwritten);
+        return result.error();
     return KSuccess;
 }
 

Kernel/Syscalls/mmap.cpp

@@ -50,8 +50,8 @@ static bool should_make_executable_exception_for_dynamic_loader(bool make_readab
 
     Elf32_Ehdr header;
     auto buffer = UserOrKernelBuffer::for_kernel_buffer((u8*)&header);
-    auto nread = inode.read_bytes(0, sizeof(header), buffer, nullptr);
+    auto result = inode.read_bytes(0, sizeof(header), buffer, nullptr);
-    if (nread != sizeof(header))
+    if (result.is_error() || result.value() != sizeof(header))
         return false;
 
     // The file is a valid ELF binary

Kernel/VM/Region.cpp

@@ -540,13 +540,14 @@ PageFaultResponse Region::handle_inode_fault(size_t page_index_in_region, Scoped
     // Reading the page may block, so release the MM lock temporarily
     mm_lock.unlock();
     auto buffer = UserOrKernelBuffer::for_kernel_buffer(page_buffer);
-    auto nread = inode.read_bytes(page_index_in_vmobject * PAGE_SIZE, PAGE_SIZE, buffer, nullptr);
+    auto result = inode.read_bytes(page_index_in_vmobject * PAGE_SIZE, PAGE_SIZE, buffer, nullptr);
     mm_lock.lock();
 
-    if (nread < 0) {
+    if (result.is_error()) {
-        dmesgln("MM: handle_inode_fault had error ({}) while reading!", nread);
+        dmesgln("MM: handle_inode_fault had error ({}) while reading!", result.error());
         return PageFaultResponse::ShouldCrash;
     }
+    auto nread = result.value();
     if (nread < PAGE_SIZE) {
         // If we read less than a page, zero out the rest to avoid leaking uninitialized data.
         memset(page_buffer + nread, 0, PAGE_SIZE - nread);