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Kernel/Ext2FS: Simplify read/write loops

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This removes removes the need to know the last block in advance, and
makes the loops slightly easier to reason about by depending on fewer
conditions.
This commit is contained in:
implicitfield 2024-04-23 22:02:21 +04:00 committed by Tim Schumacher
parent 7337ad43b5
commit ba96a0e4f8
1 changed files with 14 additions and 15 deletions
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29
Kernel/FileSystem/Ext2FS/Inode.cpp
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@ -560,20 +560,18 @@ ErrorOr<size_t> Ext2FSInode::read_bytes_locked(off_t offset, size_t count, UserO
int const block_size = fs().logical_block_size();
BlockBasedFileSystem::BlockIndex first_block_logical_index = offset / block_size;
BlockBasedFileSystem::BlockIndex last_block_logical_index = (offset + count) / block_size;
if (last_block_logical_index >= m_block_list.size())
last_block_logical_index = m_block_list.size() - 1;
int offset_into_first_block = offset % block_size;
size_t nread = 0;
auto remaining_count = min((off_t)count, (off_t)size() - offset);
auto current_block_logical_index = first_block_logical_index;
dbgln_if(EXT2_VERY_DEBUG, "Ext2FSInode[{}]::read_bytes(): Reading up to {} bytes, {} bytes into inode to {}", identifier(), count, offset, buffer.user_or_kernel_ptr());
for (auto bi = first_block_logical_index; remaining_count && bi <= last_block_logical_index; bi = bi.value() + 1) {
auto block_index = m_block_list[bi.value()];
size_t offset_into_block = (bi == first_block_logical_index) ? offset_into_first_block : 0;
while (remaining_count) {
auto block_index = m_block_list[current_block_logical_index.value()];
size_t offset_into_block = (current_block_logical_index == first_block_logical_index) ? offset_into_first_block : 0;
size_t num_bytes_to_copy = min((size_t)block_size - offset_into_block, (size_t)remaining_count);
auto buffer_offset = buffer.offset(nread);
if (block_index.value() == 0) {
@ -581,10 +579,11 @@ ErrorOr<size_t> Ext2FSInode::read_bytes_locked(off_t offset, size_t count, UserO
TRY(buffer_offset.memset(0, num_bytes_to_copy));
} 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);
dmesgln("Ext2FSInode[{}]::read_bytes(): Failed to read block {} (index {})", identifier(), block_index.value(), current_block_logical_index);
return result.release_error();
}
}
current_block_logical_index = current_block_logical_index.value() + 1;
remaining_count -= num_bytes_to_copy;
nread += num_bytes_to_copy;
}
@ -702,25 +701,25 @@ ErrorOr<size_t> Ext2FSInode::write_bytes_locked(off_t offset, size_t count, User
}
BlockBasedFileSystem::BlockIndex first_block_logical_index = offset / block_size;
BlockBasedFileSystem::BlockIndex last_block_logical_index = (offset + count) / block_size;
if (last_block_logical_index >= m_block_list.size())
last_block_logical_index = m_block_list.size() - 1;
size_t offset_into_first_block = offset % block_size;
size_t nwritten = 0;
auto remaining_count = min((off_t)count, (off_t)new_size - offset);
auto current_block_logical_index = first_block_logical_index;
dbgln_if(EXT2_VERY_DEBUG, "Ext2FSInode[{}]::write_bytes_locked(): Writing {} bytes, {} bytes into inode from {}", identifier(), count, offset, data.user_or_kernel_ptr());
for (auto bi = first_block_logical_index; remaining_count && bi <= last_block_logical_index; bi = bi.value() + 1) {
size_t offset_into_block = (bi == first_block_logical_index) ? offset_into_first_block : 0;
while (remaining_count) {
auto block_index = m_block_list[current_block_logical_index.value()];
size_t offset_into_block = (current_block_logical_index == first_block_logical_index) ? offset_into_first_block : 0;
size_t num_bytes_to_copy = min((size_t)block_size - offset_into_block, (size_t)remaining_count);
dbgln_if(EXT2_DEBUG, "Ext2FSInode[{}]::write_bytes_locked(): Writing block {} (offset_into_block: {})", identifier(), m_block_list[bi.value()], offset_into_block);
if (auto result = fs().write_block(m_block_list[bi.value()], data.offset(nwritten), num_bytes_to_copy, offset_into_block, allow_cache); result.is_error()) {
dbgln("Ext2FSInode[{}]::write_bytes_locked(): Failed to write block {} (index {})", identifier(), m_block_list[bi.value()], bi);
dbgln_if(EXT2_DEBUG, "Ext2FSInode[{}]::write_bytes_locked(): Writing block {} (offset_into_block: {})", identifier(), block_index, offset_into_block);
if (auto result = fs().write_block(block_index, data.offset(nwritten), num_bytes_to_copy, offset_into_block, allow_cache); result.is_error()) {
dbgln("Ext2FSInode[{}]::write_bytes_locked(): Failed to write block {} (index {})", identifier(), block_index, current_block_logical_index);
return result.release_error();
}
current_block_logical_index = current_block_logical_index.value() + 1;
remaining_count -= num_bytes_to_copy;
nwritten += num_bytes_to_copy;
}