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Kernel: Traverse ext2 directories blockwise.

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Instead of reading in the entire contents of a directory into a large
buffer, we can iterate block by block. This only requires a small
buffer.

Because directory entries are guaranteed to never span multiple blocks
we do not have to handle any edge cases related to that.
This commit is contained in:
Mart G 2021-05-08 18:28:54 +02:00 • committed by Andreas Kling
parent 49b132a92d
commit e0deb46723
1 changed files with 23 additions and 11 deletions
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34
Kernel/FileSystem/Ext2FileSystem.cpp
View file

@ -1071,20 +1071,32 @@ KResult Ext2FSInode::traverse_as_directory(Function<bool(const FS::DirectoryEntr
Locker locker(m_lock);
VERIFY(is_directory());
auto buffer_or = read_entire();
if (buffer_or.is_error())
return buffer_or.error();
u8 buffer[max_block_size];
auto buf = UserOrKernelBuffer::for_kernel_buffer(buffer);
auto& buffer = *buffer_or.value();
auto* entry = reinterpret_cast<ext2_dir_entry_2*>(buffer.data());
auto block_size = fs().block_size();
bool allow_cache = true;
while (entry < buffer.end_pointer()) {
if (entry->inode != 0) {
dbgln_if(EXT2_DEBUG, "Ext2FSInode[{}]::traverse_as_directory(): inode {}, name_len: {}, rec_len: {}, file_type: {}, name: {}", identifier(), entry->inode, entry->name_len, entry->rec_len, entry->file_type, StringView(entry->name, entry->name_len));
if (!callback({ { entry->name, entry->name_len }, { fsid(), entry->inode }, entry->file_type }))
break;
if (m_block_list.is_empty())
m_block_list = compute_block_list();
// Directory entries are guaranteed not to span multiple blocks,
// so we can iterate over blocks separately.
for (auto& block_index : m_block_list) {
VERIFY(block_index.value() != 0);
if (auto result = fs().read_block(block_index, &buf, block_size, 0, allow_cache); result.is_error()) {
return result;
}
auto* entry = reinterpret_cast<ext2_dir_entry_2*>(buffer);
auto* entries_end = reinterpret_cast<ext2_dir_entry_2*>(buffer + block_size);
while (entry < entries_end) {
if (entry->inode != 0) {
dbgln_if(EXT2_DEBUG, "Ext2FSInode[{}]::traverse_as_directory(): inode {}, name_len: {}, rec_len: {}, file_type: {}, name: {}", identifier(), entry->inode, entry->name_len, entry->rec_len, entry->file_type, StringView(entry->name, entry->name_len));
if (!callback({ { entry->name, entry->name_len }, { fsid(), entry->inode }, entry->file_type }))
return KSuccess;
}
entry = (ext2_dir_entry_2*)((char*)entry + entry->rec_len);
}
entry = (ext2_dir_entry_2*)((char*)entry + entry->rec_len);
}
return KSuccess;