start pageblock-aligned. Since commit c89511ab2f8f ("mm: compaction: Restart compaction from near where it left off"), the free scanner has the same problem. This patch makes sure that the pfn range passed to isolate_freepages_block() is within the same block so that pfn_valid() checks are unnecessary. In answer to Henrik's wondering why others have not reported this: reproducing this requires a large enough hole with the right aligment to have compaction walk into a PFN range with no memmap. Size and alignment depends in the memory model - 4M for FLATMEM and 128M for SPARSEMEM on x86. It needs a "lucky" machine. Reported-by: Henrik Rydberg Signed-off-by: Mel Gorman Signed-off-by: Linus Torvalds µÃe’Fx