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Kernel: Implement O_DIRECT open() flag to bypass disk caches

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Files opened with O_DIRECT will now bypass the disk cache in read/write
operations (though metadata operations will still hit the disk cache.)

This will allow us to test actual disk performance instead of testing
disk *cache* performance, if that's what we want. :^)

There's room for improvment here, we're very aggressively flushing any
dirty cache entries for the specific block before reading/writing that
block. This is done by walking the entire cache, which may be slow.
This commit is contained in:
Andreas Kling 2019-11-05 19:35:12 +01:00
parent 3de3daf765
commit 59ed235c85
7 changed files with 59 additions and 18 deletions
Download patch file Download diff file Expand all files Collapse all files

13
Kernel/FileSystem/Ext2FileSystem.cpp
View file

@ -2,6 +2,7 @@
#include <AK/BufferStream.h>
#include <AK/StdLibExtras.h>
#include <Kernel/FileSystem/Ext2FileSystem.h>
#include <Kernel/FileSystem/FileDescription.h>
#include <Kernel/FileSystem/ext2_fs.h>
#include <Kernel/Process.h>
#include <Kernel/RTC.h>
@ -90,7 +91,6 @@ bool Ext2FS::initialize()
kprintf("ext2fs: desc size = %u\n", EXT2_DESC_SIZE(&super_block));
#endif
set_block_size(EXT2_BLOCK_SIZE(&super_block));
ASSERT(block_size() <= (int)max_block_size);
@ -610,7 +610,7 @@ RefPtr<Inode> Ext2FS::get_inode(InodeIdentifier inode) const
return new_inode;
}
ssize_t Ext2FSInode::read_bytes(off_t offset, ssize_t count, u8* buffer, FileDescription*) const
ssize_t Ext2FSInode::read_bytes(off_t offset, ssize_t count, u8* buffer, FileDescription* description) const
{
Locker inode_locker(m_lock);
ASSERT(offset >= 0);
@ -656,7 +656,7 @@ ssize_t Ext2FSInode::read_bytes(off_t offset, ssize_t count, u8* buffer, FileDes
u8 block[max_block_size];
for (int bi = first_block_logical_index; remaining_count && bi <= last_block_logical_index; ++bi) {
bool success = fs().read_block(m_block_list[bi], block);
bool success = fs().read_block(m_block_list[bi], block, description);
if (!success) {
kprintf("ext2fs: read_bytes: read_block(%u) failed (lbi: %u)\n", m_block_list[bi], bi);
return -EIO;
@ -694,7 +694,6 @@ KResult Ext2FSInode::resize(u64 new_size)
return KResult(-ENOSPC);
}
auto block_list = fs().block_list_for_inode(m_raw_inode);
if (blocks_needed_after > blocks_needed_before) {
auto new_blocks = fs().allocate_blocks(fs().group_index_from_inode(index()), blocks_needed_after - blocks_needed_before);
@ -723,7 +722,7 @@ KResult Ext2FSInode::resize(u64 new_size)
return KSuccess;
}
ssize_t Ext2FSInode::write_bytes(off_t offset, ssize_t count, const u8* data, FileDescription*)
ssize_t Ext2FSInode::write_bytes(off_t offset, ssize_t count, const u8* data, FileDescription* description)
{
ASSERT(offset >= 0);
ASSERT(count >= 0);
@ -785,7 +784,7 @@ ssize_t Ext2FSInode::write_bytes(off_t offset, ssize_t count, const u8* data, Fi
ByteBuffer block;
if (offset_into_block != 0 || num_bytes_to_copy != block_size) {
block = ByteBuffer::create_uninitialized(block_size);
bool success = fs().read_block(m_block_list[bi], block.data());
bool success = fs().read_block(m_block_list[bi], block.data(), description);
if (!success) {
kprintf("Ext2FSInode::write_bytes: read_block(%u) failed (lbi: %u)\n", m_block_list[bi], bi);
return -EIO;
@ -805,7 +804,7 @@ ssize_t Ext2FSInode::write_bytes(off_t offset, ssize_t count, const u8* data, Fi
#ifdef EXT2_DEBUG
dbgprintf("Ext2FSInode::write_bytes: writing block %u (offset_into_block: %u)\n", m_block_list[bi], offset_into_block);
#endif
bool success = fs().write_block(m_block_list[bi], block.data());
bool success = fs().write_block(m_block_list[bi], block.data(), description);
if (!success) {
kprintf("Ext2FSInode::write_bytes: write_block(%u) failed (lbi: %u)\n", m_block_list[bi], bi);
ASSERT_NOT_REACHED();