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Subject[PATCH v2 07/24] mm: Introduce zap_details.zap_flags
Date
Instead of trying to introduce one variable for every new zap_details fields,
let's introduce a flag so that it can start to encode true/false informations.

Let's start to use this flag first to clean up the only check_mapping variable.
Firstly, the name "check_mapping" implies this is a "boolean", but actually it
stores the mapping inside, just in a way that it won't be set if we don't want
to check the mapping.

To make things clearer, introduce the 1st zap flag ZAP_FLAG_CHECK_MAPPING, so
that we only check against the mapping if this bit set. At the same time, we
can rename check_mapping into zap_mapping and set it always.

Since at it, introduce another helper zap_check_mapping_skip() and use it in
zap_pte_range() properly.

Some old comments have been removed in zap_pte_range() because they're
duplicated, and since now we're with ZAP_FLAG_CHECK_MAPPING flag, it'll be very
easy to grep this information by simply grepping the flag.

It'll also make life easier when we want to e.g. pass in zap_flags into the
callers like unmap_mapping_pages() (instead of adding new booleans besides the
even_cows parameter).

Signed-off-by: Peter Xu <peterx@redhat.com>
---
include/linux/mm.h | 19 ++++++++++++++++++-
mm/memory.c | 31 ++++++++-----------------------
2 files changed, 26 insertions(+), 24 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 9060b497f4d5c..39c944bf7ed3a 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1702,13 +1702,30 @@ static inline bool can_do_mlock(void) { return false; }
extern int user_shm_lock(size_t, struct user_struct *);
extern void user_shm_unlock(size_t, struct user_struct *);

+/* Whether to check page->mapping when zapping */
+#define ZAP_FLAG_CHECK_MAPPING BIT(0)
+
/*
* 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;
+ unsigned long zap_flags;
};

+/* Return true if skip zapping this page, false otherwise */
+static inline bool
+zap_check_mapping_skip(struct zap_details *details, struct page *page)
+{
+ if (!details || !page)
+ return false;
+
+ if (!(details->zap_flags & ZAP_FLAG_CHECK_MAPPING))
+ return false;
+
+ return 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 bcbce803e6850..94954436544f7 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1242,16 +1242,8 @@ 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_check_mapping_skip(details, page)))
+ continue;
ptent = ptep_get_and_clear_full(mm, addr, pte,
tlb->fullmm);
tlb_remove_tlb_entry(tlb, pte, addr);
@@ -1283,17 +1275,8 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb,
if (is_device_private_entry(entry)) {
struct page *page = device_private_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_check_mapping_skip(details, page)))
+ continue;
pte_clear_not_present_full(mm, addr, pte, tlb->fullmm);
rss[mm_counter(page)]--;
page_remove_rmap(page, false);
@@ -3253,9 +3236,11 @@ void unmap_mapping_pages(struct address_space *mapping, pgoff_t start,
pgoff_t nr, bool even_cows)
{
pgoff_t first_index = start, last_index = start + nr - 1;
- struct zap_details details = { };
+ struct zap_details details = { .zap_mapping = mapping };
+
+ if (!even_cows)
+ details.zap_flags |= ZAP_FLAG_CHECK_MAPPING;

- details.check_mapping = even_cows ? NULL : mapping;
if (last_index < first_index)
last_index = ULONG_MAX;

--
2.26.2
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