Kernel: Don't explicitly seek before I/O in BlockBasedFileSystem

Use the new FileDescription APIs to avoid doing seek+read or seek+write
as two separate operations.

Kernel/FileSystem/BlockBasedFileSystem.cpp

@@ -124,10 +124,7 @@ KResult BlockBasedFileSystem::write_block(BlockIndex index, const UserOrKernelBu
  if (!allow_cache) {
  flush_specific_block_if_needed(index);
  auto base_offset = index.value() * block_size() + offset;
- auto seek_result = file_description().seek(base_offset, SEEK_SET);
- if (seek_result.is_error())
- return seek_result.error();
- auto nwritten = file_description().write(data, count);
+ auto nwritten = file_description().write(base_offset, data, count);
  if (nwritten.is_error())
  return nwritten.error();
  VERIFY(nwritten.value() == count);
@@ -153,9 +150,7 @@ bool BlockBasedFileSystem::raw_read(BlockIndex index, UserOrKernelBuffer& buffer
 {
  Locker locker(m_lock);
  auto base_offset = index.value() * m_logical_block_size;
- auto seek_result = file_description().seek(base_offset, SEEK_SET);
- VERIFY(!seek_result.is_error());
- auto nread = file_description().read(buffer, m_logical_block_size);
+ auto nread = file_description().read(buffer, base_offset, m_logical_block_size);
  VERIFY(!nread.is_error());
  VERIFY(nread.value() == m_logical_block_size);
  return true;
@@ -165,9 +160,7 @@ bool BlockBasedFileSystem::raw_write(BlockIndex index, const UserOrKernelBuffer&
 {
  Locker locker(m_lock);
  auto base_offset = index.value() * m_logical_block_size;
- auto seek_result = file_description().seek(base_offset, SEEK_SET);
- VERIFY(!seek_result.is_error());
- auto nwritten = file_description().write(buffer, m_logical_block_size);
+ auto nwritten = file_description().write(base_offset, buffer, m_logical_block_size);
  VERIFY(!nwritten.is_error());
  VERIFY(nwritten.value() == m_logical_block_size);
  return true;
@@ -220,10 +213,7 @@ KResult BlockBasedFileSystem::read_block(BlockIndex index, UserOrKernelBuffer* b
  if (!allow_cache) {
  const_cast<BlockBasedFileSystem*>(this)->flush_specific_block_if_needed(index);
  auto base_offset = index.value() * block_size() + offset;
- auto seek_result = file_description().seek(base_offset, SEEK_SET);
- if (seek_result.is_error())
- return seek_result.error();
- auto nread = file_description().read(*buffer, count);
+ auto nread = file_description().read(*buffer, base_offset, count);
  if (nread.is_error())
  return nread.error();
  VERIFY(nread.value() == count);
@@ -233,11 +223,8 @@ KResult BlockBasedFileSystem::read_block(BlockIndex index, UserOrKernelBuffer* b
  auto& entry = cache().get(index);
  if (!entry.has_data) {
  auto base_offset = index.value() * block_size();
- auto seek_result = file_description().seek(base_offset, SEEK_SET);
- if (seek_result.is_error())
- return seek_result.error();
  auto entry_data_buffer = UserOrKernelBuffer::for_kernel_buffer(entry.data);
- auto nread = file_description().read(entry_data_buffer, block_size());
+ auto nread = file_description().read(entry_data_buffer, base_offset, block_size());
  if (nread.is_error())
  return nread.error();
  VERIFY(nread.value() == block_size());
@@ -276,11 +263,8 @@ void BlockBasedFileSystem::flush_specific_block_if_needed(BlockIndex index)
  cache().for_each_dirty_entry([&](CacheEntry& entry) {
  if (entry.block_index != index) {
  size_t base_offset = entry.block_index.value() * block_size();
- auto seek_result = file_description().seek(base_offset, SEEK_SET);
- VERIFY(!seek_result.is_error());
- // FIXME: Should this error path be surfaced somehow?
  auto entry_data_buffer = UserOrKernelBuffer::for_kernel_buffer(entry.data);
- [[maybe_unused]] auto rc = file_description().write(entry_data_buffer, block_size());
+ [[maybe_unused]] auto rc = file_description().write(base_offset, entry_data_buffer, block_size());
  cleaned_entries.append(&entry);
  }
  });
@@ -298,11 +282,8 @@ void BlockBasedFileSystem::flush_writes_impl()
  u32 count = 0;
  cache().for_each_dirty_entry([&](CacheEntry& entry) {
  auto base_offset = entry.block_index.value() * block_size();
- auto seek_result = file_description().seek(base_offset, SEEK_SET);
- VERIFY(!seek_result.is_error());
- // FIXME: Should this error path be surfaced somehow?
  auto entry_data_buffer = UserOrKernelBuffer::for_kernel_buffer(entry.data);
- [[maybe_unused]] auto rc = file_description().write(entry_data_buffer, block_size());
+ [[maybe_unused]] auto rc = file_description().write(base_offset, entry_data_buffer, block_size());
  ++count;
  });
  cache().mark_all_clean();