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Fix incorrect checksums for small initial writes in the old store

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Details:
- Write size should be exactly csum_block_size (4k by default)
- Write should be made into a new object (unallocated space)
- In this case, the checksum of the block was calculated as if the block was
  padded with extra (2^32 - size) zero bytes due to a simple integer overflow
- As a cherry on the cake, such calculation was 'slightly' slow because it
  was processing almost 4 GB of zeroes for a small write
This commit is contained in:
Vitaliy Filippov
2026-01-16 01:07:39 +03:00
parent 819f5b7ec9
commit ddd755a0e6
2 changed files with 3 additions and 1 deletions
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src/blockstore/v1/write.cpp
+1 -1
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@@ -183,7 +183,7 @@ bool blockstore_impl_t::enqueue_write(blockstore_op_t *op)
uint32_t end = (op->offset+op->len-1) / dsk.csum_block_size;
auto fn = state & BS_ST_BIG_WRITE ? crc32c_pad : crc32c_nopad;
if (start == end)
data_csums[0] = fn(0, op->buf, op->len, op->offset - start*dsk.csum_block_size, end*dsk.csum_block_size - (op->offset+op->len));
data_csums[0] = fn(0, op->buf, op->len, op->offset - start*dsk.csum_block_size, (end+1)*dsk.csum_block_size - (op->offset+op->len));
else
{
// First block