mm/rmap: convert RMAP flags to proper a distinct rmap_t type

We want to pass the flags to more than one anon rmap function, getting rid of special "do_page_add_anon_rmap()". So let's pass around a distinct __bitwise type and refine documentation. Signed-off-by: David Hildenbrand <david@redhat.com>
davidhildenbrand · Feb 25, 2022 · 1429b19 · 1429b19
1 parent 60db3e2
commit 1429b19
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Showing 3 changed files with 24 additions and 9 deletions.
diff --git a/include/linux/rmap.h b/include/linux/rmap.h
@@ -158,9 +158,23 @@ static inline void anon_vma_merge(struct vm_area_struct *vma,
 
 struct anon_vma *page_get_anon_vma(struct page *page);
 
-/* bitflags for do_page_add_anon_rmap() */
-#define RMAP_EXCLUSIVE 0x01
-#define RMAP_COMPOUND 0x02
+/* RMAP flags, currently only relevent for some anon rmap operations. */
+typedef int __bitwise rmap_t;
+
+/*
+ * No special request: the page mapped via a small (sub)page and is possibly
+ * shared betweeen processes.
+ */
+#define RMAP_NONE		((__force rmap_t)0)
+
+/* The page is exclusive to a single process. */
+#define RMAP_EXCLUSIVE		((__force rmap_t)BIT(0))
+
+/*
+ * The page is mapped via a compound page, not via a small subpage, and
+ * should be accounted accordingly.
+ */
+#define RMAP_COMPOUND		((__force rmap_t)BIT(1))
 
 /*
  * rmap interfaces called when adding or removing pte of page
@@ -169,7 +183,7 @@ void page_move_anon_rmap(struct page *, struct vm_area_struct *);
 void page_add_anon_rmap(struct page *, struct vm_area_struct *,
 		unsigned long, bool);
 void do_page_add_anon_rmap(struct page *, struct vm_area_struct *,
-			   unsigned long, int);
+			   unsigned long, rmap_t);
 void page_add_new_anon_rmap(struct page *, struct vm_area_struct *,
 		unsigned long, bool);
 void page_add_file_rmap(struct page *, bool);

diff --git a/mm/memory.c b/mm/memory.c
@@ -3515,10 +3515,10 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
 	struct vm_area_struct *vma = vmf->vma;
 	struct page *page = NULL, *swapcache;
 	struct swap_info_struct *si = NULL;
+	rmap_t rmap_flags = RMAP_NONE;
 	swp_entry_t entry;
 	pte_t pte;
 	int locked;
-	int exclusive = 0;
 	vm_fault_t ret = 0;
 	void *shadow = NULL;
 
@@ -3693,7 +3693,7 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
 		pte = maybe_mkwrite(pte_mkdirty(pte), vma);
 		vmf->flags &= ~FAULT_FLAG_WRITE;
 		ret |= VM_FAULT_WRITE;
-		exclusive = RMAP_EXCLUSIVE;
+		rmap_flags |= RMAP_EXCLUSIVE;
 	}
 	flush_icache_page(vma, page);
 	if (pte_swp_soft_dirty(vmf->orig_pte))
@@ -3709,7 +3709,7 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
 		page_add_new_anon_rmap(page, vma, vmf->address, false);
 		lru_cache_add_inactive_or_unevictable(page, vma);
 	} else {
-		do_page_add_anon_rmap(page, vma, vmf->address, exclusive);
+		do_page_add_anon_rmap(page, vma, vmf->address, rmap_flags);
 	}
 
 	set_pte_at(vma->vm_mm, vmf->address, vmf->pte, pte);

diff --git a/mm/rmap.c b/mm/rmap.c
@@ -1139,7 +1139,8 @@ static void __page_check_anon_rmap(struct page *page,
 void page_add_anon_rmap(struct page *page,
 	struct vm_area_struct *vma, unsigned long address, bool compound)
 {
-	do_page_add_anon_rmap(page, vma, address, compound ? RMAP_COMPOUND : 0);
+	do_page_add_anon_rmap(page, vma, address,
+			      compound ? RMAP_COMPOUND : RMAP_NONE);
 }
 
 /*
@@ -1148,7 +1149,7 @@ void page_add_anon_rmap(struct page *page,
  * Everybody else should continue to use page_add_anon_rmap above.
  */
 void do_page_add_anon_rmap(struct page *page,
-	struct vm_area_struct *vma, unsigned long address, int flags)
+	struct vm_area_struct *vma, unsigned long address, rmap_t flags)
 {
 	bool compound = flags & RMAP_COMPOUND;
 	bool first;