[PATCH v4 05/17] mm/rmap: convert RMAP flags to a proper distinct rmap_t type

David Hildenbrand
2022-04-28T08:38:39Z

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.

Acked-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
include/linux/rmap.h | 22 ++++++++++++++++++----
mm/memory.c | 6 +++---
mm/rmap.c | 7 ++++---
3 files changed, 25 insertions(+), 10 deletions(-)

diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index 9d602fc34063..2d0f12119a13 100644
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -160,9 +160,23 @@ 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 relevant for some anon rmap operations. */
+typedef int __bitwise rmap_t;
+
+/*
+ * No special request: if the page is a subpage of a compound page, it is
+ * mapped via a PTE. The mapped (sub)page is possibly shared between processes.
+ */
+#define RMAP_NONE ((__force rmap_t)0)
+
+/* The (sub)page is exclusive to a single process. */
+#define RMAP_EXCLUSIVE ((__force rmap_t)BIT(0))
+
+/*
+ * The compound page is not mapped via PTEs, but instead via a single PMD and
+ * should be accounted accordingly.
+ */
+#define RMAP_COMPOUND ((__force rmap_t)BIT(1))

/*
* rmap interfaces called when adding or removing pte of page
@@ -171,7 +185,7 @@ void page_move_anon_rmap(struct page *, struct vm_area_struct *);
void page_add_anon_rmap(struct page *, struct vm_area_struct *,
unsigned long address, bool compound);
void do_page_add_anon_rmap(struct page *, struct vm_area_struct *,
- unsigned long address, int flags);
+ unsigned long address, rmap_t flags);
void page_add_new_anon_rmap(struct page *, struct vm_area_struct *,
unsigned long address, bool compound);
void page_add_file_rmap(struct page *, struct vm_area_struct *,
diff --git a/mm/memory.c b/mm/memory.c
index 2112484682a9..414f4cf4fcf1 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3507,10 +3507,10 @@ 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;

@@ -3685,7 +3685,7 @@ 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))
@@ -3701,7 +3701,7 @@ 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
index eb246fc8b089..8359aed9255e 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1137,7 +1137,8 @@ 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);
}

/*
@@ -1146,7 +1147,7 @@ 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;
@@ -1185,7 +1186,7 @@ void do_page_add_anon_rmap(struct page *page,
/* address might be in next vma when migration races vma_adjust */
else if (first)
__page_set_anon_rmap(page, vma, address,
- flags & RMAP_EXCLUSIVE);
+ !!(flags & RMAP_EXCLUSIVE));
else
__page_check_anon_rmap(page, vma, address);

--
2.35.1