On 3/3/21 10:16 PM, Alistair Popple wrote:
Migration is currently implemented as a mode of operation for try_to_unmap_one() generally specified by passing the TTU_MIGRATION flag or in the case of splitting a huge anonymous page TTU_SPLIT_FREEZE. However it does not have much in common with the rest of the unmap functionality of try_to_unmap_one() and thus splitting it into a separate function reduces the complexity of try_to_unmap_one() making it more readable. Several simplifications can also be made in try_to_migrate_one() based on the following observations: - All users of TTU_MIGRATION also set TTU_IGNORE_MLOCK. - No users of TTU_MIGRATION ever set TTU_IGNORE_HWPOISON. - No users of TTU_MIGRATION ever set TTU_BATCH_FLUSH. TTU_SPLIT_FREEZE is a special case of migration used when splitting an anonymous page. This is most easily dealt with by calling the correct function from unmap_page() in mm/huge_memory.c - either try_to_migrate() for PageAnon or try_to_unmap(). Signed-off-by: Alistair Popple <apopple@xxxxxxxxxx> Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Looks reasonable to me. I do worry a bit about code duplication. At some point in the future, it might be discovered that other combinations of TTU_XXX flags are needed in which case a careful check of try_to_migrate() and try_to_unmap() will be needed. Reviewed-by: Ralph Campbell <rcampbell@xxxxxxxxxx>
