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

Andrew Morton
2021-11-05T20:38:38Z

From: Peter Xu <peterx@redhat.com>
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/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>
---

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

--- 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;

_