On 01.07.25 11:24, David Hildenbrand wrote:
On 30.06.25 19:05, Lorenzo Stoakes wrote:
On Mon, Jun 30, 2025 at 02:59:50PM +0200, David Hildenbrand wrote:
Let's factor it out, simplifying the calling code.
The assumption is that flush_dcache_page() is not required for
movable_ops pages: as documented for flush_dcache_folio(), it really
only applies when the kernel wrote to pagecache pages / pages in
highmem. movable_ops callbacks should be handling flushing
caches if ever required.
But we've enot changed this have we? The flush_dcache_folio() invocation seems
to happen the same way now as before? Did I miss something?
I think, before this change we would have called it also for movable_ops
pages
if (rc == MIGRATEPAGE_SUCCESS) {
if (__folio_test_movable(src)) {
...
}
...
if (likely(!folio_is_zone_device(dst)))
flush_dcache_folio(dst);
}
Now, we no longer do that for movable_ops pages.
For balloon pages, we're not copying anything, so we never possibly have
to flush the dcache.
For zsmalloc, we do the copy in zs_object_copy() through kmap_local.
I think we could have HIGHMEM, so I wonder if we should just do a
flush_dcache_page() in zs_object_copy().
At least, staring at highmem.h with memcpy_to_page(), it looks like that
might be the right thing to do.
So likely I'll add a patch before this one that will do the
flush_dcache_page() in there.
But reading the docs again:
"This routine need only be called for page cache pages which can
potentially ever be mapped into the address space of a user process."
So, not required IIUC. I'll clarify in the patch description.
--
Cheers,
David / dhildenb
