[075/262] mm: add zap_skip_check_mapping() helper

Commit Message

Andrew Morton Nov. 5, 2021, 8:38 p.m. UTC

From: Peter Xu <[e-mail]>
Subject: 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/[e-mail]
Signed-off-by: Peter Xu <[e-mail]>
Reviewed-by: Alistair Popple <[e-mail]>
Cc: Andrea Arcangeli <[e-mail]>
Cc: Axel Rasmussen <[e-mail]>
Cc: David Hildenbrand <[e-mail]>
Cc: Hugh Dickins <[e-mail]>
Cc: Jerome Glisse <[e-mail]>
Cc: "Kirill A . Shutemov" <[e-mail]>
Cc: Liam Howlett <[e-mail]>
Cc: Matthew Wilcox <[e-mail]>
Cc: Miaohe Lin <[e-mail]>
Cc: Mike Rapoport <[e-mail]>
Cc: Yang Shi <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 include/linux/mm.h |   16 +++++++++++++++-
 mm/memory.c        |   29 ++++++-----------------------
 2 files changed, 21 insertions(+), 24 deletions(-)

Patch

--- a/include/linux/mm.h~mm-add-zap_skip_check_mapping-helper
+++ a/include/linux/mm.h
@@ -1687,10 +1687,24 @@  extern void user_shm_unlock(size_t, stru
  * 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,
--- a/mm/memory.c~mm-add-zap_skip_check_mapping-helper
+++ a/mm/memory.c
@@ -1337,16 +1337,8 @@  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);
@@ -1379,17 +1371,8 @@  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)]--;
 
@@ -3373,7 +3356,7 @@  void unmap_mapping_page(struct page *pag
 	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);
@@ -3402,7 +3385,7 @@  void unmap_mapping_pages(struct address_
 	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;