mm: add zap_skip_check_mapping() helper

Use the helper for the checks.  Rename "check_mapping" into
"zap_mapping" because "check_mapping" looks like a bool but in fact it
stores the mapping itself.  When it's set, we check the mapping (it must
be non-NULL).  When it's cleared we skip the check, which works like the
old way.

Move the duplicated comments to the helper too.

Link: https://lkml.kernel.org/r/20210915181538.11288-1-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Alistair Popple <apopple@nvidia.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: "Kirill A . Shutemov" <kirill@shutemov.name>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Yang Shi <shy828301@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/include/linux/mm.h b/include/linux/mm.h
index c5b600d..6e29deb 100644 (file)
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1687,10 +1687,24 @@ extern void user_shm_unlock(size_t, struct ucounts *);
  * Parameter block passed down to zap_pte_range in exceptional cases.
  */
 struct zap_details {
-       struct address_space *check_mapping;    /* Check page->mapping if set */
+       struct address_space *zap_mapping;      /* Check page->mapping if set */
        struct page *single_page;               /* Locked page to be unmapped */
 };
 
+/*
+ * We set details->zap_mappings when we want to unmap shared but keep private
+ * pages. Return true if skip zapping this page, false otherwise.
+ */
+static inline bool
+zap_skip_check_mapping(struct zap_details *details, struct page *page)
+{
+       if (!details || !page)
+               return false;
+
+       return details->zap_mapping &&
+           (details->zap_mapping != page_rmapping(page));
+}
+
 struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
                             pte_t pte);
 struct page *vm_normal_page_pmd(struct vm_area_struct *vma, unsigned long addr,

diff --git a/mm/memory.c b/mm/memory.c
index d4ed701..48b2e04 100644 (file)
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1333,16 +1333,8 @@ again:
                        struct page *page;
 
                        page = vm_normal_page(vma, addr, ptent);
-                       if (unlikely(details) && page) {
-                               /*
-                                * unmap_shared_mapping_pages() wants to
-                                * invalidate cache without truncating:
-                                * unmap shared but keep private pages.
-                                */
-                               if (details->check_mapping &&
-                                   details->check_mapping != page_rmapping(page))
-                                       continue;
-                       }
+                       if (unlikely(zap_skip_check_mapping(details, page)))
+                               continue;
                        ptent = ptep_get_and_clear_full(mm, addr, pte,
                                                        tlb->fullmm);
                        tlb_remove_tlb_entry(tlb, pte, addr);
@@ -1375,17 +1367,8 @@ again:
                    is_device_exclusive_entry(entry)) {
                        struct page *page = pfn_swap_entry_to_page(entry);
 
-                       if (unlikely(details && details->check_mapping)) {
-                               /*
-                                * unmap_shared_mapping_pages() wants to
-                                * invalidate cache without truncating:
-                                * unmap shared but keep private pages.
-                                */
-                               if (details->check_mapping !=
-                                   page_rmapping(page))
-                                       continue;
-                       }
-
+                       if (unlikely(zap_skip_check_mapping(details, page)))
+                               continue;
                        pte_clear_not_present_full(mm, addr, pte, tlb->fullmm);
                        rss[mm_counter(page)]--;
 
@@ -3369,7 +3352,7 @@ void unmap_mapping_page(struct page *page)
        first_index = page->index;
        last_index = page->index + thp_nr_pages(page) - 1;
 
-       details.check_mapping = mapping;
+       details.zap_mapping = mapping;
        details.single_page = page;
 
        i_mmap_lock_write(mapping);
@@ -3398,7 +3381,7 @@ void unmap_mapping_pages(struct address_space *mapping, pgoff_t start,
        pgoff_t first_index = start;
        pgoff_t last_index = start + nr - 1;
 
-       details.check_mapping = even_cows ? NULL : mapping;
+       details.zap_mapping = even_cows ? NULL : mapping;
        if (last_index < first_index)
                last_index = ULONG_MAX;