[PATCH v2 27/28] mm: Add isolate_lru_folio()

["Matthew Wilcox (Oracle)" <willy@infradead.org>]

Turn isolate_lru_page() into a wrapper around isolate_lru_folio().
TestClearPageLRU() would have always failed on a tail page, so
returning -EBUSY is the same behaviour.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 arch/powerpc/include/asm/mmu_context.h |  1 -
 mm/folio-compat.c                      |  8 +++++
 mm/internal.h                          |  3 +-
 mm/vmscan.c                            | 43 ++++++++++++--------------
 4 files changed, 29 insertions(+), 26 deletions(-)

diff --git a/arch/powerpc/include/asm/mmu_context.h b/arch/powerpc/include/asm/mmu_context.h
index 9ba6b585337f..b9cab0a11421 100644
--- a/arch/powerpc/include/asm/mmu_context.h
+++ b/arch/powerpc/include/asm/mmu_context.h
@@ -21,7 +21,6 @@ extern void destroy_context(struct mm_struct *mm);
 #ifdef CONFIG_SPAPR_TCE_IOMMU
 struct mm_iommu_table_group_mem_t;
 
-extern int isolate_lru_page(struct page *page);	/* from internal.h */
 extern bool mm_iommu_preregistered(struct mm_struct *mm);
 extern long mm_iommu_new(struct mm_struct *mm,
 		unsigned long ua, unsigned long entries,
diff --git a/mm/folio-compat.c b/mm/folio-compat.c
index 749555a232a8..782e766cd1ee 100644
--- a/mm/folio-compat.c
+++ b/mm/folio-compat.c
@@ -7,6 +7,7 @@
 #include <linux/migrate.h>
 #include <linux/pagemap.h>
 #include <linux/swap.h>
+#include "internal.h"
 
 struct address_space *page_mapping(struct page *page)
 {
@@ -151,3 +152,10 @@ int try_to_release_page(struct page *page, gfp_t gfp)
 	return filemap_release_folio(page_folio(page), gfp);
 }
 EXPORT_SYMBOL(try_to_release_page);
+
+int isolate_lru_page(struct page *page)
+{
+	if (WARN_RATELIMIT(PageTail(page), "trying to isolate tail page"))
+		return -EBUSY;
+	return isolate_lru_folio((struct folio *)page);
+}
diff --git a/mm/internal.h b/mm/internal.h
index 9a72d1ecdab4..8b90db90e7f2 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -157,7 +157,8 @@ extern unsigned long highest_memmap_pfn;
 /*
  * in mm/vmscan.c:
  */
-extern int isolate_lru_page(struct page *page);
+int isolate_lru_page(struct page *page);
+int isolate_lru_folio(struct folio *folio);
 extern void putback_lru_page(struct page *page);
 extern void reclaim_throttle(pg_data_t *pgdat, enum vmscan_throttle_state reason);
 
diff --git a/mm/vmscan.c b/mm/vmscan.c
index fb9584641ac7..ac2f5b76cdb2 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2168,45 +2168,40 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
 }
 
 /**
- * isolate_lru_page - tries to isolate a page from its LRU list
- * @page: page to isolate from its LRU list
+ * isolate_lru_folio - Try to isolate a folio from its LRU list.
+ * @folio: Folio to isolate from its LRU list.
  *
- * Isolates a @page from an LRU list, clears PageLRU and adjusts the
- * vmstat statistic corresponding to whatever LRU list the page was on.
+ * Isolate a @folio from an LRU list and adjust the vmstat statistic
+ * corresponding to whatever LRU list the folio was on.
  *
- * Returns 0 if the page was removed from an LRU list.
- * Returns -EBUSY if the page was not on an LRU list.
- *
- * The returned page will have PageLRU() cleared.  If it was found on
- * the active list, it will have PageActive set.  If it was found on
- * the unevictable list, it will have the PageUnevictable bit set. That flag
+ * The folio will have its LRU flag cleared.  If it was found on the
+ * active list, it will have the Active flag set.  If it was found on the
+ * unevictable list, it will have the Unevictable flag set.  These flags
  * may need to be cleared by the caller before letting the page go.
  *
- * The vmstat statistic corresponding to the list on which the page was
- * found will be decremented.
- *
- * Restrictions:
+ * Context:
  *
  * (1) Must be called with an elevated refcount on the page. This is a
- *     fundamental difference from isolate_lru_pages (which is called
+ *     fundamental difference from isolate_lru_pages() (which is called
  *     without a stable reference).
- * (2) the lru_lock must not be held.
- * (3) interrupts must be enabled.
+ * (2) The lru_lock must not be held.
+ * (3) Interrupts must be enabled.
+ *
+ * Return: 0 if the folio was removed from an LRU list.
+ * -EBUSY if the folio was not on an LRU list.
  */
-int isolate_lru_page(struct page *page)
+int isolate_lru_folio(struct folio *folio)
 {
-	struct folio *folio = page_folio(page);
 	int ret = -EBUSY;
 
-	VM_BUG_ON_PAGE(!page_count(page), page);
-	WARN_RATELIMIT(PageTail(page), "trying to isolate tail page");
+	VM_BUG_ON_FOLIO(!folio_ref_count(folio), folio);
 
-	if (TestClearPageLRU(page)) {
+	if (folio_test_clear_lru(folio)) {
 		struct lruvec *lruvec;
 
-		get_page(page);
+		folio_get(folio);
 		lruvec = folio_lruvec_lock_irq(folio);
-		del_page_from_lru_list(page, lruvec);
+		lruvec_del_folio(lruvec, folio);
 		unlock_page_lruvec_irq(lruvec);
 		ret = 0;
 	}
-- 
2.33.0