# K1626–K1630: atomic one-to-three extent growth

The file starts with one allocated, nonmetadata block. Growth reserves two
additional free blocks in a private bitmap copy. The file's extent list and
the public bitmap change only after both reservations succeed. If the second
reservation reports no space, the old first block, extent count, and bitmap
remain unchanged. The positive fixture grows from block 10 to three separate
blocks 10, 20, and 30; the negative fixture has only block 20 free.

This model validates ownership metadata. It does not copy or read file bytes;
old data preservation, real disk rollback, and six guest profiles require
separate K1630 evidence.