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Kernel: Don't hog file system lock when doing BlockBasedFileSystem I/O

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The file system lock is meant to protect the file system metadata
(super blocks, bitmaps, etc.) Not protect processes from reading
independent parts of the disk at once.

This patch introduces a new lock to protect the *block cache* instead,
which is the real thing that needs synchronization.
This commit is contained in:
Andreas Kling 2021-07-16 01:08:00 +02:00
parent abf0249f35
commit a7d193951f
Notes: sideshowbarker 2024-07-18 08:59:31 +09:00 
Author: https://github.com/awesomekling
Commit: https://github.com/SerenityOS/serenity/commit/a7d193951f9
2 changed files with 7 additions and 10 deletions
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16
Kernel/FileSystem/BlockBasedFileSystem.cpp
View File

@ -116,11 +116,12 @@ BlockBasedFileSystem::~BlockBasedFileSystem()
KResult BlockBasedFileSystem::write_block(BlockIndex index, const UserOrKernelBuffer& data, size_t count, size_t offset, bool allow_cache)
{
Locker locker(m_lock);
VERIFY(m_logical_block_size);
VERIFY(offset + count <= block_size());
dbgln_if(BBFS_DEBUG, "BlockBasedFileSystem::write_block {}, size={}", index, count);
Locker locker(m_cache_lock);
if (!allow_cache) {
flush_specific_block_if_needed(index);
auto base_offset = index.value() * block_size() + offset;
@ -148,7 +149,6 @@ KResult BlockBasedFileSystem::write_block(BlockIndex index, const UserOrKernelBu
bool BlockBasedFileSystem::raw_read(BlockIndex index, UserOrKernelBuffer& buffer)
{
Locker locker(m_lock);
auto base_offset = index.value() * m_logical_block_size;
auto nread = file_description().read(buffer, base_offset, m_logical_block_size);
VERIFY(!nread.is_error());
@ -158,7 +158,6 @@ bool BlockBasedFileSystem::raw_read(BlockIndex index, UserOrKernelBuffer& buffer
bool BlockBasedFileSystem::raw_write(BlockIndex index, const UserOrKernelBuffer& buffer)
{
Locker locker(m_lock);
auto base_offset = index.value() * m_logical_block_size;
auto nwritten = file_description().write(base_offset, buffer, m_logical_block_size);
VERIFY(!nwritten.is_error());
@ -168,7 +167,6 @@ bool BlockBasedFileSystem::raw_write(BlockIndex index, const UserOrKernelBuffer&
bool BlockBasedFileSystem::raw_read_blocks(BlockIndex index, size_t count, UserOrKernelBuffer& buffer)
{
Locker locker(m_lock);
auto current = buffer;
for (auto block = index.value(); block < (index.value() + count); block++) {
if (!raw_read(BlockIndex { block }, current))
@ -180,7 +178,6 @@ bool BlockBasedFileSystem::raw_read_blocks(BlockIndex index, size_t count, UserO
bool BlockBasedFileSystem::raw_write_blocks(BlockIndex index, size_t count, const UserOrKernelBuffer& buffer)
{
Locker locker(m_lock);
auto current = buffer;
for (auto block = index.value(); block < (index.value() + count); block++) {
if (!raw_write(block, current))
@ -192,7 +189,6 @@ bool BlockBasedFileSystem::raw_write_blocks(BlockIndex index, size_t count, cons
KResult BlockBasedFileSystem::write_blocks(BlockIndex index, unsigned count, const UserOrKernelBuffer& data, bool allow_cache)
{
Locker locker(m_lock);
VERIFY(m_logical_block_size);
dbgln_if(BBFS_DEBUG, "BlockBasedFileSystem::write_blocks {}, count={}", index, count);
for (unsigned i = 0; i < count; ++i) {
@ -205,11 +201,12 @@ KResult BlockBasedFileSystem::write_blocks(BlockIndex index, unsigned count, con
KResult BlockBasedFileSystem::read_block(BlockIndex index, UserOrKernelBuffer* buffer, size_t count, size_t offset, bool allow_cache) const
{
Locker locker(m_lock);
VERIFY(m_logical_block_size);
VERIFY(offset + count <= block_size());
dbgln_if(BBFS_DEBUG, "BlockBasedFileSystem::read_block {}", index);
Locker locker(m_cache_lock);
if (!allow_cache) {
const_cast<BlockBasedFileSystem*>(this)->flush_specific_block_if_needed(index);
auto base_offset = index.value() * block_size() + offset;
@ -237,7 +234,6 @@ KResult BlockBasedFileSystem::read_block(BlockIndex index, UserOrKernelBuffer* b
KResult BlockBasedFileSystem::read_blocks(BlockIndex index, unsigned count, UserOrKernelBuffer& buffer, bool allow_cache) const
{
Locker locker(m_lock);
VERIFY(m_logical_block_size);
if (!count)
return EINVAL;
@ -256,7 +252,7 @@ KResult BlockBasedFileSystem::read_blocks(BlockIndex index, unsigned count, User
void BlockBasedFileSystem::flush_specific_block_if_needed(BlockIndex index)
{
Locker locker(m_lock);
Locker locker(m_cache_lock);
if (!cache().is_dirty())
return;
Vector<CacheEntry*, 32> cleaned_entries;
@ -276,7 +272,7 @@ void BlockBasedFileSystem::flush_specific_block_if_needed(BlockIndex index)
void BlockBasedFileSystem::flush_writes_impl()
{
Locker locker(m_lock);
Locker locker(m_cache_lock);
if (!cache().is_dirty())
return;
u32 count = 0;

1
Kernel/FileSystem/BlockBasedFileSystem.h
View File

@ -42,6 +42,7 @@ private:
DiskCache& cache() const;
void flush_specific_block_if_needed(BlockIndex index);
mutable Lock m_cache_lock;
mutable OwnPtr<DiskCache> m_cache;
};