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This special case arose for device private folio >>> migration since during migration there could be a disconnect between >>> source and destination on the folio size. >>> >>> Introduce split_unmapped_folio_to_order() to handle this special case. >>> This in turn removes the special casing introduced by the unmapped >>> parameter in __folio_split(). >> >> Such a helper would be needed in drm_pagemap_migrate_to_devmem when >> reallocating a device folio to smaller pages. >> >> Could we export it (EXPORT_SYMBOL)? drm_pagemap_migrate_to_devmem() is a function defined in tree, you just need to include huge_mm.h to use split_unmapped_folio_to_order(). Why do you need to export split_unmapped_folio_to_order()? > > As a rule we don't export things from core mm. And certainly not to non-GPL > modules. > > Unless David feels very differently or there's some enormously compelling > reason for it I'd really rather we didn't. Best Regards, Yan, Zi