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SubjectRe: [PATCH] mm: shmem: enable thp migration (Re: [PATCH v1] mm: consider non-anonymous thp as unmovable page)
On Fri, Apr 06, 2018 at 03:07:11AM +0000, Naoya Horiguchi wrote:
> Subject: [PATCH] mm: enable thp migration for shmem thp

This patch is buggy, but not in a significant way:

> @@ -524,13 +524,26 @@ int migrate_page_move_mapping(struct address_space *mapping,
> }
>
> radix_tree_replace_slot(&mapping->i_pages, pslot, newpage);

^^^ this line should have been deleted

> + if (PageTransHuge(page)) {
> + int i;
> + int index = page_index(page);
> +
> + for (i = 0; i < HPAGE_PMD_NR; i++) {
^^^ or this iteration should start at 1
> + pslot = radix_tree_lookup_slot(&mapping->i_pages,
> + index + i);
> + radix_tree_replace_slot(&mapping->i_pages, pslot,
> + newpage + i);
> + }
> + } else {
> + radix_tree_replace_slot(&mapping->i_pages, pslot, newpage);
^^^ and if the second option, then we don't need this line
> + }

So either this:

- radix_tree_replace_slot(&mapping->i_pages, pslot, newpage);
+ if (PageTransHuge(page)) {
+ int i;
+ int index = page_index(page);
+
+ for (i = 0; i < HPAGE_PMD_NR; i++) {
+ pslot = radix_tree_lookup_slot(&mapping->i_pages,
+ index + i);
+ radix_tree_replace_slot(&mapping->i_pages, pslot,
+ newpage + i);
+ }
+ } else {
+ radix_tree_replace_slot(&mapping->i_pages, pslot, newpage);
+ }

Or this:

radix_tree_replace_slot(&mapping->i_pages, pslot, newpage);
+ if (PageTransHuge(page)) {
+ int i;
+ int index = page_index(page);
+
+ for (i = 1; i < HPAGE_PMD_NR; i++) {
+ pslot = radix_tree_lookup_slot(&mapping->i_pages,
+ index + i);
+ radix_tree_replace_slot(&mapping->i_pages, pslot,
+ newpage + i);
+ }
+ }

The second one is shorter and involves fewer lookups ...

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