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Subject[PATCH v4 4/4] mm: Add zap_skip_check_mapping() helper
Date
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.

Reviewed-by: Alistair Popple <apopple@nvidia.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
---
include/linux/mm.h | 16 +++++++++++++++-
mm/memory.c | 29 ++++++-----------------------
2 files changed, 21 insertions(+), 24 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index d1126f731221..ed44f31615d9 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1721,10 +1721,24 @@ 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 a7e427177817..8db8ce0ca6ce 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1333,16 +1333,8 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb,
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 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb,
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;

--
2.31.1
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