erofs-freebsd-out-tree/docs/pre13-low-a1.md

Pre13 L-A1

This batch aligns the remaining low-risk helper vocabulary with Linux:

• compress.h now uses the Linux include guard name.
• erofs_inode_is_data_compressed() replaces four equivalent FULL/COMPACT tests that do not need to distinguish the two layouts.
• erofs_addrmask() directly uses the existing 48-bit feature helper.

Static proof:

• For every value from zero through EROFS_INODE_DATALAYOUT_MAX, the new compressed-layout helper equals the replaced boolean expression.
• The helper was not substituted in zmap.c, where FULL and COMPACT remain distinct cases.
• erofs_is_48bit() and erofs_sb_has_48bit() tested the same incompat bit; address-mask values and control flow are unchanged.
• The old include guard and duplicate 48-bit helper have no remaining source consumers.

No build, QEMU, smoke, or feature test was run for this batch.