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>> int rc = -EAGAIN; >> @@ -1096,6 +1114,9 @@ static int move_to_new_folio(struct folio *dst, struct folio *src, >> VM_BUG_ON_FOLIO(!folio_test_locked(src), src); >> VM_BUG_ON_FOLIO(!folio_test_locked(dst), dst); >> >> + if (already_copied) >> + dst->private = (void *)(unsigned long)PAGE_ALREADY_COPIED; >> + > > IMHO, this appears to be an unusual way to pass arguments to a function. > Why not adjust the parameters of migrate_folio()? How about turning enum > migrate_mode into a bitmask (migrate_flags)? > Using folio->private, keeps the change self-contained in migrate.c David suggested adding a dedicated unsigned long migrate_info field in the folio union. I'll switch to that, as this is cleaner and avoid hacky use of ->private. https://lore.kernel.org/linux-mm/27b1b602-129f-4bc5-a553-386e8d1f5d90@kernel.org Changing the migrate_folio() a_ops signature would touch nearly every filesystem for something that only core migration cares about, and does not look practical. We can't add to migrate_mode enum either as currently those values are mutually exclusive and ordered levels of increasing synchrony (ASYNC < SYNC_LIGHT < SYNC) And there are checks like this (cc->mode < MIGRATE_SYNC) or mode != MIGRATE_SYNC This could break it. Best regards, Shivank