The patch titled
Subject: ksm: convert cmp_and_merge_page() to use a folio
has been added to the -mm mm-unstable branch. Its filename is
ksm-convert-cmp_and_merge_page-to-use-a-folio.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/ksm-convert-cmp_and_merge_page-to-use-a-folio.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>
Subject: ksm: convert cmp_and_merge_page() to use a folio
Date: Wed, 2 Oct 2024 16:25:28 +0100
By making try_to_merge_two_pages() and stable_tree_search() return a
folio, we can replace kpage with kfolio. This replaces 7 calls to
compound_head() with one.
Link: https://lkml.kernel.org/r/20241002152533.1350629-3-willy@xxxxxxxxxxxxx
Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Cc: Alex Shi <alexs@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/ksm.c | 48 ++++++++++++++++++++++++------------------------
1 file changed, 24 insertions(+), 24 deletions(-)
--- a/mm/ksm.c~ksm-convert-cmp_and_merge_page-to-use-a-folio
+++ a/mm/ksm.c
@@ -1582,7 +1582,7 @@ out:
* Note that this function upgrades page to ksm page: if one of the pages
* is already a ksm page, try_to_merge_with_ksm_page should be used.
*/
-static struct page *try_to_merge_two_pages(struct ksm_rmap_item *rmap_item,
+static struct folio *try_to_merge_two_pages(struct ksm_rmap_item *rmap_item,
struct page *page,
struct ksm_rmap_item *tree_rmap_item,
struct page *tree_page)
@@ -1600,7 +1600,7 @@ static struct page *try_to_merge_two_pag
if (err)
break_cow(rmap_item);
}
- return err ? NULL : page;
+ return err ? NULL : page_folio(page);
}
static __always_inline
@@ -1789,7 +1789,7 @@ static __always_inline struct folio *cha
* This function returns the stable tree node of identical content if found,
* NULL otherwise.
*/
-static struct page *stable_tree_search(struct page *page)
+static struct folio *stable_tree_search(struct page *page)
{
int nid;
struct rb_root *root;
@@ -1804,7 +1804,7 @@ static struct page *stable_tree_search(s
if (page_node && page_node->head != &migrate_nodes) {
/* ksm page forked */
folio_get(folio);
- return &folio->page;
+ return folio;
}
nid = get_kpfn_nid(folio_pfn(folio));
@@ -1899,7 +1899,7 @@ again:
folio_put(tree_folio);
goto replace;
}
- return &tree_folio->page;
+ return tree_folio;
}
}
@@ -1913,7 +1913,7 @@ again:
out:
if (is_page_sharing_candidate(page_node)) {
folio_get(folio);
- return &folio->page;
+ return folio;
} else
return NULL;
@@ -1963,7 +1963,7 @@ replace:
}
stable_node_dup->head = &migrate_nodes;
list_add(&stable_node_dup->list, stable_node_dup->head);
- return &folio->page;
+ return folio;
chain_append:
/*
@@ -2217,7 +2217,7 @@ static void cmp_and_merge_page(struct pa
struct ksm_rmap_item *tree_rmap_item;
struct page *tree_page = NULL;
struct ksm_stable_node *stable_node;
- struct page *kpage;
+ struct folio *kfolio;
unsigned int checksum;
int err;
bool max_page_sharing_bypass = false;
@@ -2259,31 +2259,31 @@ static void cmp_and_merge_page(struct pa
return;
}
- /* We first start with searching the page inside the stable tree */
- kpage = stable_tree_search(page);
- if (kpage == page && rmap_item->head == stable_node) {
- put_page(kpage);
+ /* Start by searching for the folio in the stable tree */
+ kfolio = stable_tree_search(page);
+ if (&kfolio->page == page && rmap_item->head == stable_node) {
+ folio_put(kfolio);
return;
}
remove_rmap_item_from_tree(rmap_item);
- if (kpage) {
- if (PTR_ERR(kpage) == -EBUSY)
+ if (kfolio) {
+ if (kfolio == ERR_PTR(-EBUSY))
return;
- err = try_to_merge_with_ksm_page(rmap_item, page, kpage);
+ err = try_to_merge_with_ksm_page(rmap_item, page, &kfolio->page);
if (!err) {
/*
* The page was successfully merged:
* add its rmap_item to the stable tree.
*/
- lock_page(kpage);
- stable_tree_append(rmap_item, page_stable_node(kpage),
+ folio_lock(kfolio);
+ stable_tree_append(rmap_item, folio_stable_node(kfolio),
max_page_sharing_bypass);
- unlock_page(kpage);
+ folio_unlock(kfolio);
}
- put_page(kpage);
+ folio_put(kfolio);
return;
}
@@ -2292,7 +2292,7 @@ static void cmp_and_merge_page(struct pa
if (tree_rmap_item) {
bool split;
- kpage = try_to_merge_two_pages(rmap_item, page,
+ kfolio = try_to_merge_two_pages(rmap_item, page,
tree_rmap_item, tree_page);
/*
* If both pages we tried to merge belong to the same compound
@@ -2307,20 +2307,20 @@ static void cmp_and_merge_page(struct pa
split = PageTransCompound(page)
&& compound_head(page) == compound_head(tree_page);
put_page(tree_page);
- if (kpage) {
+ if (kfolio) {
/*
* The pages were successfully merged: insert new
* node in the stable tree and add both rmap_items.
*/
- lock_page(kpage);
- stable_node = stable_tree_insert(page_folio(kpage));
+ folio_lock(kfolio);
+ stable_node = stable_tree_insert(kfolio);
if (stable_node) {
stable_tree_append(tree_rmap_item, stable_node,
false);
stable_tree_append(rmap_item, stable_node,
false);
}
- unlock_page(kpage);
+ folio_unlock(kfolio);
/*
* If we fail to insert the page into the stable tree,
_
Patches currently in -mm which might be from willy@xxxxxxxxxxxxx are
ksm-use-a-folio-in-try_to_merge_one_page.patch
ksm-convert-cmp_and_merge_page-to-use-a-folio.patch
ksm-convert-should_skip_rmap_item-to-take-a-folio.patch
mm-add-pageanonnotksm.patch
mm-remove-pageksm.patch
