[PATCH v14 045/138] mm/memcg: Add folio_memcg_lock() and folio_memcg_unlock()

Matthew Wilcox (Oracle)
2021-07-15T04:14:00Z

These are the folio equivalents of lock_page_memcg() and
unlock_page_memcg().

lock_page_memcg() and unlock_page_memcg() have too many callers to be
easily replaced in a single patch, so reimplement them as wrappers for
now to be cleaned up later when enough callers have been converted to
use folios.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
include/linux/memcontrol.h | 10 +++++++++
mm/memcontrol.c | 45 ++++++++++++++++++++++++--------------
2 files changed, 39 insertions(+), 16 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 20084c47d2ca..4b79dd6b3a9c 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -950,6 +950,8 @@ void mem_cgroup_print_oom_group(struct mem_cgroup *memcg);
extern bool cgroup_memory_noswap;
#endif

+void folio_memcg_lock(struct folio *folio);
+void folio_memcg_unlock(struct folio *folio);
void lock_page_memcg(struct page *page);
void unlock_page_memcg(struct page *page);

@@ -1367,6 +1369,14 @@ static inline void unlock_page_memcg(struct page *page)
{
}

+static inline void folio_memcg_lock(struct folio *folio)
+{
+}
+
+static inline void folio_memcg_unlock(struct folio *folio)
+{
+}
+
static inline void mem_cgroup_handle_over_high(void)
{
}
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 96c34357fbca..0dd40ea67a90 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1965,18 +1965,17 @@ void mem_cgroup_print_oom_group(struct mem_cgroup *memcg)
}

/**
- * lock_page_memcg - lock a page and memcg binding
- * @page: the page
+ * folio_memcg_lock - Bind a folio to its memcg.
+ * @folio: The folio.
*
- * This function protects unlocked LRU pages from being moved to
+ * This function prevents unlocked LRU folios from being moved to
* another cgroup.
*
- * It ensures lifetime of the locked memcg. Caller is responsible
- * for the lifetime of the page.
+ * It ensures lifetime of the bound memcg. The caller is responsible
+ * for the lifetime of the folio.
*/
-void lock_page_memcg(struct page *page)
+void folio_memcg_lock(struct folio *folio)
{
- struct page *head = compound_head(page); /* rmap on tail pages */
struct mem_cgroup *memcg;
unsigned long flags;

@@ -1990,7 +1989,7 @@ void lock_page_memcg(struct page *page)
if (mem_cgroup_disabled())
return;
again:
- memcg = page_memcg(head);
+ memcg = folio_memcg(folio);
if (unlikely(!memcg))
return;

@@ -2004,7 +2003,7 @@ void lock_page_memcg(struct page *page)
return;

spin_lock_irqsave(&memcg->move_lock, flags);
- if (memcg != page_memcg(head)) {
+ if (memcg != folio_memcg(folio)) {
spin_unlock_irqrestore(&memcg->move_lock, flags);
goto again;
}
@@ -2018,9 +2017,15 @@ void lock_page_memcg(struct page *page)
memcg->move_lock_task = current;
memcg->move_lock_flags = flags;
}
+EXPORT_SYMBOL(folio_memcg_lock);
+
+void lock_page_memcg(struct page *page)
+{
+ folio_memcg_lock(page_folio(page));
+}
EXPORT_SYMBOL(lock_page_memcg);

-static void __unlock_page_memcg(struct mem_cgroup *memcg)
+static void __folio_memcg_unlock(struct mem_cgroup *memcg)
{
if (memcg && memcg->move_lock_task == current) {
unsigned long flags = memcg->move_lock_flags;
@@ -2035,14 +2040,22 @@ static void __unlock_page_memcg(struct mem_cgroup *memcg)
}

/**
- * unlock_page_memcg - unlock a page and memcg binding
- * @page: the page
+ * folio_memcg_unlock - Release the binding between a folio and its memcg.
+ * @folio: The folio.
+ *
+ * This releases the binding created by folio_memcg_lock(). This does
+ * not change the accounting of this folio to its memcg, but it does
+ * permit others to change it.
*/
-void unlock_page_memcg(struct page *page)
+void folio_memcg_unlock(struct folio *folio)
{
- struct page *head = compound_head(page);
+ __folio_memcg_unlock(folio_memcg(folio));
+}
+EXPORT_SYMBOL(folio_memcg_unlock);

- __unlock_page_memcg(page_memcg(head));
+void unlock_page_memcg(struct page *page)
+{
+ folio_memcg_unlock(page_folio(page));
}
EXPORT_SYMBOL(unlock_page_memcg);

@@ -5666,7 +5679,7 @@ static int mem_cgroup_move_account(struct page *page,

page->memcg_data = (unsigned long)to;

- __unlock_page_memcg(from);
+ __folio_memcg_unlock(from);

ret = 0;
nid = page_to_nid(page);
--
2.30.2