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Date: Wed, 1 Sep 2021 16:57:22 -0400
From: Peter Xu <peterx@...hat.com>
To: linux-kernel@...r.kernel.org, linux-mm@...ck.org
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Matthew Wilcox <willy@...radead.org>,
Yang Shi <shy828301@...il.com>,
Miaohe Lin <linmiaohe@...wei.com>,
Hugh Dickins <hughd@...gle.com>,
David Hildenbrand <david@...hat.com>, peterx@...hat.com,
Mike Rapoport <rppt@...ux.vnet.ibm.com>,
Andrea Arcangeli <aarcange@...hat.com>,
"Kirill A . Shutemov" <kirill@...temov.name>,
Jerome Glisse <jglisse@...hat.com>,
Alistair Popple <apopple@...dia.com>
Subject: [PATCH 4/5] mm: Introduce zap_details.zap_flags
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@...hat.com>
---
include/linux/mm.h | 19 ++++++++++++++++++-
mm/memory.c | 34 ++++++++++------------------------
2 files changed, 28 insertions(+), 25 deletions(-)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 69259229f090..fcbc1c4f8e8e 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1716,14 +1716,31 @@ static inline bool can_do_mlock(void) { return false; }
extern int user_shm_lock(size_t, struct ucounts *);
extern void user_shm_unlock(size_t, struct ucounts *);
+/* 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;
struct page *single_page; /* Locked page to be unmapped */
+ unsigned long zap_flags;
};
+/* 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;
+
+ 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 3b860f6a51ac..05ccacda4fe9 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)]--;
@@ -3369,8 +3352,9 @@ 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;
+ details.zap_flags = ZAP_FLAG_CHECK_MAPPING;
i_mmap_lock_write(mapping);
if (unlikely(!RB_EMPTY_ROOT(&mapping->i_mmap.rb_root)))
@@ -3395,9 +3379,11 @@ 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;
--
2.31.1
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