[RFC PATCH 10/32] mm/slub: Convert kfree() to use a struct slab

[Vlastimil Babka <vbabka@xxxxxxx>]

From: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>

Convert kfree(), kmem_cache_free() and ___cache_free() to resolve object
addresses to struct slab, using folio as intermediate step where needed. Keep
passing the result as struct page for now in preparation for mass conversion of
internal functions.

[ vbabka@xxxxxxx: Use folio as intermediate step when checking for
  large kmalloc pages ]

Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>
---
 mm/slub.c | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index d3e7c776227f..641e6fe2dbc0 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -3517,7 +3517,7 @@ static __always_inline void slab_free(struct kmem_cache *s, struct page *page,
 #ifdef CONFIG_KASAN_GENERIC
 void ___cache_free(struct kmem_cache *cache, void *x, unsigned long addr)
 {
-	do_slab_free(cache, virt_to_head_page(x), x, NULL, 1, addr);
+	do_slab_free(cache, slab_page(virt_to_slab(x)), x, NULL, 1, addr);
 }
 #endif
 
@@ -3526,7 +3526,7 @@ void kmem_cache_free(struct kmem_cache *s, void *x)
 	s = cache_from_obj(s, x);
 	if (!s)
 		return;
-	slab_free(s, virt_to_head_page(x), x, NULL, 1, _RET_IP_);
+	slab_free(s, slab_page(virt_to_slab(x)), x, NULL, 1, _RET_IP_);
 	trace_kmem_cache_free(_RET_IP_, x, s->name);
 }
 EXPORT_SYMBOL(kmem_cache_free);
@@ -4546,7 +4546,8 @@ EXPORT_SYMBOL(__ksize);
 
 void kfree(const void *x)
 {
-	struct page *page;
+	struct folio *folio;
+	struct slab *slab;
 	void *object = (void *)x;
 
 	trace_kfree(_RET_IP_, x);
@@ -4554,12 +4555,13 @@ void kfree(const void *x)
 	if (unlikely(ZERO_OR_NULL_PTR(x)))
 		return;
 
-	page = virt_to_head_page(x);
-	if (unlikely(!PageSlab(page))) {
-		free_nonslab_page(page, object);
+	folio = page_folio(virt_to_page(x));
+	if (unlikely(!folio_test_slab(folio))) {
+		free_nonslab_page(folio_page(folio, 0), object);
 		return;
 	}
-	slab_free(page->slab_cache, page, object, NULL, 1, _RET_IP_);
+	slab = folio_slab(folio);
+	slab_free(slab->slab_cache, slab_page(slab), object, NULL, 1, _RET_IP_);
 }
 EXPORT_SYMBOL(kfree);
 
-- 
2.33.1