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Kernel: Optimize Ext2 disk reads 

We used to read whole file until we reached the asked offset.
Now we can calculate the appropriate block and read just the asked data.
This commit is contained in:
Bananymous 2023-03-18 03:47:59 +02:00
parent 1a26a318a4
commit 8236598f9d
2 changed files with 102 additions and 128 deletions
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2
kernel/include/kernel/FS/Ext2.h
View File

@ -136,6 +136,8 @@ namespace Kernel
virtual BAN::ErrorOr<BAN::RefPtr<Inode>> directory_find(BAN::StringView) override;
private:
BAN::ErrorOr<uint32_t> data_block_index(uint32_t);
using block_callback_t = BAN::ErrorOr<bool>(*)(const BAN::Vector<uint8_t>&, void*);
BAN::ErrorOr<void> for_each_block(block_callback_t, void*);

228
kernel/kernel/FS/Ext2.cpp
View File

@ -137,92 +137,90 @@ namespace Kernel
};
}
BAN::ErrorOr<uint32_t> Ext2Inode::data_block_index(uint32_t asked_data_block)
{
uint32_t data_blocks_count = m_inode.blocks / (2 << m_fs->superblock().log_block_size);
uint32_t blocks_per_array = (1024 << m_fs->superblock().log_block_size) / sizeof(uint32_t);
if (asked_data_block >= data_blocks_count)
return BAN::Error::from_c_string("Ext2: no such block");
// Direct block
if (asked_data_block < 12)
{
uint32_t block = m_inode.block[asked_data_block];
if (block == 0)
return BAN::Error::from_errno(EIO);
return block;
}
asked_data_block -= 12;
// Singly indirect block
if (asked_data_block < blocks_per_array)
{
if (m_inode.block[12] == 0)
return BAN::Error::from_errno(EIO);
auto block_array = TRY(m_fs->read_block(m_inode.block[12]));
uint32_t block = ((uint32_t*)block_array.data())[asked_data_block];
if (block == 0)
return BAN::Error::from_errno(EIO);
return block;
}
asked_data_block -= blocks_per_array;
// Doubly indirect blocks
if (asked_data_block < blocks_per_array * blocks_per_array)
{
auto singly_indirect_array = TRY(m_fs->read_block(m_inode.block[13]));
uint32_t direct_block = ((uint32_t*)singly_indirect_array.data())[asked_data_block / blocks_per_array];
if (direct_block == 0)
return BAN::Error::from_errno(EIO);
auto block_array = TRY(m_fs->read_block(direct_block));
uint32_t block = ((uint32_t*)block_array.data())[asked_data_block % blocks_per_array];
if (block == 0)
return BAN::Error::from_errno(EIO);
return block;
}
asked_data_block -= blocks_per_array * blocks_per_array;
// Triply indirect blocks
if (asked_data_block < blocks_per_array * blocks_per_array * blocks_per_array)
{
auto doubly_indirect_array = TRY(m_fs->read_block(m_inode.block[14]));
uint32_t singly_indirect_block = ((uint32_t*)doubly_indirect_array.data())[asked_data_block / (blocks_per_array * blocks_per_array)];
if (singly_indirect_block == 0)
return BAN::Error::from_errno(EIO);
auto singly_indirect_array = TRY(m_fs->read_block(singly_indirect_block));
uint32_t direct_block = ((uint32_t*)singly_indirect_array.data())[(asked_data_block / blocks_per_array) % blocks_per_array];
if (direct_block == 0)
return BAN::Error::from_errno(EIO);
auto block_array = TRY(m_fs->read_block(direct_block));
uint32_t block = ((uint32_t*)block_array.data())[asked_data_block % blocks_per_array];
if (block == 0)
return BAN::Error::from_errno(EIO);
return block;
}
ASSERT(false);
}
BAN::ErrorOr<void> Ext2Inode::for_each_block(block_callback_t callback, void* callback_data)
{
uint32_t data_blocks_left = m_inode.blocks / (2 << m_fs->superblock().log_block_size);
uint32_t block_array_block_count = (1024 << m_fs->superblock().log_block_size) / sizeof(uint32_t);
// Direct blocks
for (uint32_t i = 0; i < 12; i++)
uint32_t data_block_count = m_inode.blocks / (2 << m_fs->superblock().log_block_size);
for (uint32_t i = 0; i < data_block_count; i++)
{
if (m_inode.block[i] == 0)
continue;
auto block_data = TRY(m_fs->read_block(m_inode.block[i]));
uint32_t data_block_index = TRY(this->data_block_index(i));
auto block_data = TRY(m_fs->read_block(data_block_index));
if (!TRY(callback(block_data, callback_data)))
return {};
if (--data_blocks_left == 0)
return {};
}
// Singly indirect block
if (m_inode.block[12])
{
auto block_array = TRY(m_fs->read_block(m_inode.block[12]));
for (uint32_t i = 0; i < block_array_block_count; i++)
{
uint32_t block = ((uint32_t*)block_array.data())[i];
if (block == 0)
continue;
auto block_data = TRY(m_fs->read_block(block));
if (!TRY(callback(block_data, callback_data)))
return {};
if (--data_blocks_left == 0)
return {};
}
}
// Doubly indirect blocks
if (m_inode.block[13])
{
auto singly_indirect_array = TRY(m_fs->read_block(m_inode.block[13]));
for (uint32_t i = 0; i < block_array_block_count; i++)
{
uint32_t singly_indirect_block = ((uint32_t*)singly_indirect_array.data())[i];
auto block_array = TRY(m_fs->read_block(singly_indirect_block));
for (uint32_t j = 0; j < block_array_block_count; j++)
{
uint32_t block = ((uint32_t*)block_array.data())[j];
if (block == 0)
continue;
auto block_data = TRY(m_fs->read_block(block));
if (!TRY(callback(block_data, callback_data)))
return {};
if (--data_blocks_left == 0)
return {};
}
}
}
// Triply indirect blocks
if (m_inode.block[14])
{
auto doubly_indirect_array = TRY(m_fs->read_block(m_inode.block[14]));
for (uint32_t i = 0; i < block_array_block_count; i++)
{
uint32_t doubly_indirect_block = ((uint32_t*)doubly_indirect_array.data())[i];
auto singly_indirect_array = TRY(m_fs->read_block(doubly_indirect_block));
for (uint32_t j = 0; j < block_array_block_count; j++)
{
uint32_t singly_indirect_block = ((uint32_t*)singly_indirect_array.data())[j];
auto block_array = TRY(m_fs->read_block(singly_indirect_block));
for (uint32_t k = 0; k < block_array_block_count; k++)
{
uint32_t block = ((uint32_t*)block_array.data())[k];
if (block == 0)
continue;
auto block_data = TRY(m_fs->read_block(block));
if (!TRY(callback(block_data, callback_data)))
return {};
if (--data_blocks_left == 0)
return {};
}
}
}
}
return BAN::Error::from_c_string("Inode did not contain enough blocks");
return {};
}
BAN::ErrorOr<size_t> Ext2Inode::read(size_t offset, void* buffer, size_t count)
@ -230,58 +228,32 @@ namespace Kernel
if (ifdir())
return BAN::Error::from_errno(EISDIR);
struct read_info
if (offset >= m_inode.size)
return 0;
if (offset + count > m_inode.size)
count = m_inode.size - offset;
const uint32_t block_size = 1024 << m_fs->superblock().log_block_size;
ASSERT(offset % block_size == 0);
const uint32_t first_block = offset / block_size;
const uint32_t last_block = BAN::Math::div_round_up<uint32_t>(offset + count, block_size);
size_t n_read = 0;
for (uint32_t block = first_block; block < last_block; block++)
{
size_t file_current_offset;
size_t file_start_offset;
size_t file_bytes_left;
uint8_t* out_byte_buffer;
size_t out_bytes_read;
size_t out_byte_buffer_size;
};
uint32_t data_block = TRY(data_block_index(block));
auto block_data = TRY(m_fs->read_block(data_block));
read_info info;
info.file_current_offset = 0;
info.file_start_offset = offset;
info.file_bytes_left = m_inode.size;
info.out_byte_buffer = (uint8_t*)buffer;
info.out_bytes_read = 0;
info.out_byte_buffer_size = count;
uint32_t to_copy = BAN::Math::min<uint32_t>(block_data.size(), count - n_read);
block_callback_t read_func =
[](const BAN::Vector<uint8_t>& block_data, void* info_) -> BAN::ErrorOr<bool>
{
read_info& info = *(read_info*)info_;
memcpy((uint8_t*)buffer + n_read, block_data.data(), to_copy);
n_read += to_copy;
}
size_t block_size = BAN::Math::min<size_t>(block_data.size(), info.file_bytes_left);
// Skip blocks before 'offset'
if (info.file_current_offset + block_size <= info.file_start_offset)
{
info.file_current_offset += block_size;
info.file_bytes_left -= block_size;
return info.file_bytes_left > 0;
}
size_t read_offset = 0;
if (info.file_current_offset < info.file_start_offset)
read_offset = info.file_start_offset - info.file_current_offset;
size_t to_read = BAN::Math::min<size_t>(block_size - read_offset, info.out_byte_buffer_size - info.out_bytes_read);
memcpy(info.out_byte_buffer + info.out_bytes_read, block_data.data() + read_offset, to_read);
info.out_bytes_read += to_read;
if (info.out_bytes_read >= info.out_byte_buffer_size)
return false;
info.file_current_offset += block_size;
info.file_bytes_left -= block_size;
return info.file_bytes_left > 0;
};
TRY(for_each_block(read_func, &info));
return info.out_bytes_read;
return count;
}
BAN::ErrorOr<BAN::RefPtr<Inode>> Ext2Inode::directory_find(BAN::StringView file_name)
@ -524,13 +496,13 @@ namespace Kernel
TRY(block_buffer.resize(block_size));
TRY(m_partition.read_sectors(block * sectors_per_block, sectors_per_block, block_buffer.data()));
return block_buffer;
}
const Ext2::Inode& Ext2FS::ext2_root_inode() const
{
return reinterpret_cast<const Ext2Inode*>(m_root_inode.operator->())->m_inode;
return reinterpret_cast<const Ext2Inode*>(m_root_inode.ptr())->m_inode;
}
}