mm/rmap: convert RMAP flags to a proper 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.

Link: https://lkml.kernel.org/r/20220428083441.37290-6-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Rientjes <rientjes@google.com>
Cc: Don Dutile <ddutile@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jann Horn <jannh@google.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Khalid Aziz <khalid.aziz@oracle.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Liang Zhang <zhangliang5@huawei.com>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport <rppt@linux.ibm.com>
Cc: Nadav Amit <namit@vmware.com>
Cc: Oded Gabbay <oded.gabbay@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Pedro Demarchi Gomes <pedrodemargomes@gmail.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Roman Gushchin <guro@fb.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Yang Shi <shy828301@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index 73f4154..c53a381 100644 (file)
--- 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 9f5f829..4cd8cad 100644 (file)
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3511,10 +3511,10 @@ 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;
 
@@ -3689,7 +3689,7 @@ 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))
@@ -3705,7 +3705,7 @@ 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 91a63dc..23a4113 100644 (file)
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1181,7 +1181,8 @@ 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);
 }
 
 /*
@@ -1190,7 +1191,7 @@ 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;
@@ -1229,7 +1230,7 @@ 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);