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Ext2FS: Avoid a lot of redundant writes to inode block arrays.

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This commit is contained in:
Andreas Kling 2019-03-27 14:24:37 +01:00
parent 750d79dcaf
commit d5508e5116
1 changed files with 27 additions and 8 deletions
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35
Kernel/Ext2FileSystem.cpp
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@ -191,9 +191,10 @@ bool Ext2FS::write_block_list_for_inode(InodeIndex inode_index, ext2_inode& e2in
{
LOCKER(m_lock);
dbgprintf("Ext2FS: writing %u block(s) to i_block array\n", min(EXT2_NDIR_BLOCKS, blocks.size()));
// NOTE: There is a mismatch between i_blocks and blocks.size() since i_blocks includes meta blocks and blocks.size() does not.
auto old_block_count = ceil_div(e2inode.i_size, block_size());
auto old_shape = compute_block_list_shape(e2inode.i_blocks / (2 << super_block().s_log_block_size));
auto old_shape = compute_block_list_shape(old_block_count);
auto new_shape = compute_block_list_shape(blocks.size());
Vector<BlockIndex> new_meta_blocks;
@ -205,24 +206,42 @@ bool Ext2FS::write_block_list_for_inode(InodeIndex inode_index, ext2_inode& e2in
e2inode.i_blocks = (blocks.size() + new_shape.meta_blocks) * (block_size() / 512);
bool inode_dirty = false;
unsigned output_block_index = 0;
unsigned remaining_blocks = blocks.size();
for (unsigned i = 0; i < new_shape.direct_blocks; ++i) {
e2inode.i_block[i] = blocks[output_block_index++];
if (e2inode.i_block[i] != blocks[output_block_index])
inode_dirty = true;
e2inode.i_block[i] = blocks[output_block_index];
++output_block_index;
--remaining_blocks;
}
write_ext2_inode(inode_index, e2inode);
if (inode_dirty) {
dbgprintf("Ext2FS: Writing %u direct block(s) to i_block array of inode %u\n", min(EXT2_NDIR_BLOCKS, blocks.size()), inode_index);
write_ext2_inode(inode_index, e2inode);
inode_dirty = false;
}
if (!remaining_blocks)
return true;
if (!e2inode.i_block[EXT2_IND_BLOCK]) {
e2inode.i_block[EXT2_IND_BLOCK] = new_meta_blocks.take_last();
write_ext2_inode(inode_index, e2inode);
BlockIndex new_indirect_block = new_meta_blocks.take_last();
if (e2inode.i_block[EXT2_IND_BLOCK] != new_indirect_block)
inode_dirty = true;
e2inode.i_block[EXT2_IND_BLOCK] = new_indirect_block;
if (inode_dirty) {
dbgprintf("Ext2FS: Adding the indirect block to i_block array of inode %u\n", inode_index);
write_ext2_inode(inode_index, e2inode);
inode_dirty = false;
}
}
{
dbgprintf("Ext2FS: Writing out indirect blockptr block for inode %u\n", inode_index);
if (old_shape.indirect_blocks == new_shape.indirect_blocks) {
// No need to update the singly indirect block array.
remaining_blocks -= new_shape.indirect_blocks;
} else {
auto block_contents = ByteBuffer::create_uninitialized(block_size());
BufferStream stream(block_contents);
ASSERT(new_shape.indirect_blocks <= EXT2_ADDR_PER_BLOCK(&super_block()));