David Hildenbrand <da...@redhat.com> writes: > On 18.06.25 20:48, Zi Yan wrote: >> On 18 Jun 2025, at 14:39, Matthew Wilcox wrote: >> >>> On Wed, Jun 18, 2025 at 02:14:15PM -0400, Zi Yan wrote: >>>> On 18 Jun 2025, at 13:39, David Hildenbrand wrote: >>>> >>>>> ... and start moving back to per-page things that will absolutely not be >>>>> folio things in the future. Add documentation and a comment that the >>>>> remaining folio stuff (lock, refcount) will have to be reworked as well. >>>>> >>>>> While at it, convert the VM_BUG_ON() into a WARN_ON_ONCE() and handle >>>>> it gracefully (relevant with further changes), and convert a >>>>> WARN_ON_ONCE() into a VM_WARN_ON_ONCE_PAGE(). >>>> >>>> The reason is that there is no upstream code, which use movable_ops for >>>> folios? Is there any fundamental reason preventing movable_ops from >>>> being used on folios? >>> >>> folios either belong to a filesystem or they are anonymous memory, and >>> so either the filesystem knows how to migrate them (through its a_ops) >>> or the migration code knows how to handle anon folios directly. > > Right, migration of folios will be handled by migration core. > >> for device private pages, to support migrating >0 order anon or fs >> folios >> to device, how should we represent them for devices? if you think folio is >> only for anon and fs. > > I assume they are proper folios, so yes. Just like they are handled > today (-> folios) > > I was asking a related question at LSF/MM in Alistair's session: are > we sure these things will be folios even before they are assigned to a > filesystem? I recall the answer was "yes". > > So we don't (and will not) support movable_ops for folios.
Is it possible to use some device specific callbacks (DMA?) to copy from/to the device private folios (or pages) to/from the normal file/anon folios in the future? --- Best Regards, Huang, Ying
