67 lines
No EOL
2.1 KiB
Rust
67 lines
No EOL
2.1 KiB
Rust
use alloc::sync::Arc;
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use super::BlockDevice;
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use super::Dirty;
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use super::BLOCK_SZ;
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type BitmapBlock = [u64; 64];
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const BLOCK_BITS: usize = BLOCK_SZ * 8;
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pub struct Bitmap {
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start_block_id: usize,
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blocks: usize,
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}
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/// Return (block_pos, bits64_pos, inner_pos)
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fn decomposition(mut bit: usize) -> (usize, usize, usize) {
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let block_pos = bit / BLOCK_BITS;
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bit = bit % BLOCK_BITS;
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(block_pos, bit / 64, bit % 64)
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}
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impl Bitmap {
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pub fn new(start_block_id: usize, blocks: usize) -> Self {
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Self {
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start_block_id,
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blocks,
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}
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}
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pub fn alloc(&self, block_device: &Arc<dyn BlockDevice>) -> Option<usize> {
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for block_id in 0..self.blocks {
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let mut dirty_bitmap_block: Dirty<BitmapBlock> = Dirty::new(
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block_id + self.start_block_id as usize,
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0,
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block_device.clone()
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);
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let bitmap_block = dirty_bitmap_block.get_mut();
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if let Some((bits64_pos, inner_pos)) = bitmap_block
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.iter()
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.enumerate()
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.find(|(_, bits64)| **bits64 != u64::MAX)
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.map(|(bits64_pos, bits64)| {
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(bits64_pos, bits64.trailing_ones() as usize)
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}) {
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// modify cache
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bitmap_block[bits64_pos] |= 1u64 << inner_pos;
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return Some(block_id * BLOCK_BITS + bits64_pos * 64 + inner_pos as usize);
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// after dirty is dropped, data will be written back automatically
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}
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}
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None
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}
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pub fn dealloc(&self, block_device: &Arc<dyn BlockDevice>, bit: usize) {
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let (block_pos, bits64_pos, inner_pos) = decomposition(bit);
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let mut dirty_bitmap_block: Dirty<BitmapBlock> = Dirty::new(
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block_pos + self.start_block_id,
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0,
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block_device.clone(),
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);
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dirty_bitmap_block.modify(|bitmap_block| {
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assert!(bitmap_block[bits64_pos] & (1u64 << inner_pos) > 0);
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bitmap_block[bits64_pos] -= 1u64 << inner_pos;
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});
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}
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pub fn maximum(&self) -> usize {
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self.blocks * BLOCK_BITS
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}
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} |