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Kernel: Place ext2 dir entries so they don't span multiple blocks

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Ext2 dir entries spanning multiple blocks are not allowed.
If they do occur they are flagged as corrupt by e2fsck for example.
This commit is contained in:
Mart G 2021-05-07 14:47:38 +02:00 • committed by Andreas Kling
parent 293a5c2b49
commit 25a5e59f79
2 changed files with 31 additions and 23 deletions
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52
Kernel/FileSystem/Ext2FileSystem.cpp
View file

@ -27,6 +27,7 @@ struct Ext2FSDirectoryEntry {
String name;
InodeIndex inode_index { 0 };
u8 file_type { 0 };
u16 record_length { 0 };
};
static u8 to_ext2_file_type(mode_t mode)
@ -1089,45 +1090,52 @@ KResult Ext2FSInode::traverse_as_directory(Function<bool(const FS::DirectoryEntr
return KSuccess;
}
KResult Ext2FSInode::write_directory(const Vector<Ext2FSDirectoryEntry>& entries)
KResult Ext2FSInode::write_directory(Vector<Ext2FSDirectoryEntry>& entries)
{
Locker locker(m_lock);
int directory_size = 0;
for (auto& entry : entries)
directory_size += EXT2_DIR_REC_LEN(entry.name.length());
auto block_size = fs().block_size();
int blocks_needed = ceil_div(static_cast<size_t>(directory_size), block_size);
int occupied_size = blocks_needed * block_size;
dbgln_if(EXT2_DEBUG, "Ext2FSInode[{}]::write_directory(): New directory contents to write (size {}, occupied {}):", identifier(), directory_size, occupied_size);
auto directory_data = ByteBuffer::create_uninitialized(occupied_size);
OutputMemoryStream stream { directory_data };
// Calculate directory size and record length of entries so that
// the following constraints are met:
// - All used blocks must be entirely filled.
// - Entries are aligned on a 4-byte boundary.
// - No entry may span multiple blocks.
size_t directory_size = 0;
size_t space_in_block = block_size;
for (size_t i = 0; i < entries.size(); ++i) {
auto& entry = entries[i];
entry.record_length = EXT2_DIR_REC_LEN(entry.name.length());
space_in_block -= entry.record_length;
if (i + 1 < entries.size()) {
if (EXT2_DIR_REC_LEN(entries[i + 1].name.length()) > space_in_block) {
entry.record_length += space_in_block;
space_in_block = block_size;
}
} else {
entry.record_length += space_in_block;
}
directory_size += entry.record_length;
}
int record_length = EXT2_DIR_REC_LEN(entry.name.length());
if (i == entries.size() - 1)
record_length += occupied_size - directory_size;
dbgln_if(EXT2_DEBUG, "Ext2FSInode[{}]::write_directory(): New directory contents to write (size {}):", identifier(), directory_size);
dbgln_if(EXT2_DEBUG, "Ext2FSInode[{}]::write_directory(): Writing inode: {}, name_len: {}, rec_len: {}, file_type: {}, name: {}", identifier(), entry.inode_index, u16(entry.name.length()), u16(record_length), u8(entry.file_type), entry.name);
auto directory_data = ByteBuffer::create_uninitialized(directory_size);
OutputMemoryStream stream { directory_data };
for (auto& entry : entries) {
dbgln_if(EXT2_DEBUG, "Ext2FSInode[{}]::write_directory(): Writing inode: {}, name_len: {}, rec_len: {}, file_type: {}, name: {}", identifier(), entry.inode_index, u16(entry.name.length()), u16(entry.record_length), u8(entry.file_type), entry.name);
stream << u32(entry.inode_index.value());
stream << u16(record_length);
stream << u16(entry.record_length);
stream << u8(entry.name.length());
stream << u8(entry.file_type);
stream << entry.name.bytes();
int padding = record_length - entry.name.length() - 8;
int padding = entry.record_length - entry.name.length() - 8;
for (int j = 0; j < padding; ++j)
stream << u8(0);
}
stream.fill_to_end(0);
VERIFY(stream.is_end());
if (auto result = resize(stream.size()); result.is_error())
return result;

2
Kernel/FileSystem/Ext2FileSystem.h
View file

@ -58,7 +58,7 @@ private:
virtual KResult truncate(u64) override;
virtual KResultOr<int> get_block_address(int) override;
KResult write_directory(const Vector<Ext2FSDirectoryEntry>&);
KResult write_directory(Vector<Ext2FSDirectoryEntry>&);
bool populate_lookup_cache() const;
KResult resize(u64);
KResult write_indirect_block(BlockBasedFS::BlockIndex, Span<BlockBasedFS::BlockIndex>);