[PATCH v5 09/26] mm: Introduce ZAP_FLAG_SKIP_SWAP
From: Peter Xu <peterx@redhat.com>
Date: 2021-07-15 20:15:23
Also in:
lkml
Subsystem:
memory management, memory management - core, the rest · Maintainers:
Andrew Morton, David Hildenbrand, Linus Torvalds
Firstly, the comment in zap_pte_range() is misleading because it checks against
details rather than check_mappings, so it's against what the code did.
Meanwhile, it's confusing too on not explaining why passing in the details
pointer would mean to skip all swap entries. New user of zap_details could
very possibly miss this fact if they don't read deep until zap_pte_range()
because there's no comment at zap_details talking about it at all, so swap
entries could be errornously skipped without being noticed.
This partly reverts 3e8715fdc03e ("mm: drop zap_details::check_swap_entries"),
but introduce ZAP_FLAG_SKIP_SWAP flag, which means the opposite of previous
"details" parameter: the caller should explicitly set this to skip swap
entries, otherwise swap entries will always be considered (which is still the
major case here).
Cc: Kirill A. Shutemov <redacted>
Reviewed-by: Alistair Popple <apopple@nvidia.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
---
include/linux/mm.h | 12 ++++++++++++
mm/memory.c | 8 +++++---
2 files changed, 17 insertions(+), 3 deletions(-)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 26088174daab..62a75e4414e3 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h@@ -1717,6 +1717,8 @@ extern void user_shm_unlock(size_t, struct ucounts *); /* Whether to check page->mapping when zapping */ #define ZAP_FLAG_CHECK_MAPPING BIT(0) +/* Whether to skip zapping swap entries */ +#define ZAP_FLAG_SKIP_SWAP BIT(1) /* * Parameter block passed down to zap_pte_range in exceptional cases.
@@ -1740,6 +1742,16 @@ zap_skip_check_mapping(struct zap_details *details, struct page *page) return details->zap_mapping != page_rmapping(page); } +/* Return true if skip swap entries, false otherwise */ +static inline bool +zap_skip_swap(struct zap_details *details) +{ + if (!details) + return false; + + return details->zap_flags & ZAP_FLAG_SKIP_SWAP; +} + 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 2a5a6650f069..d6b1adbf29e4 100644
--- a/mm/memory.c
+++ b/mm/memory.c@@ -1379,8 +1379,7 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb, continue; } - /* If details->check_mapping, we leave swap entries. */ - if (unlikely(details)) + if (unlikely(zap_skip_swap(details))) continue; if (!non_swap_entry(entry))
@@ -3379,7 +3378,10 @@ 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 = { .zap_mapping = mapping }; + struct zap_details details = { + .zap_mapping = mapping, + .zap_flags = ZAP_FLAG_SKIP_SWAP, + }; if (!even_cows) details.zap_flags |= ZAP_FLAG_CHECK_MAPPING;
--
2.31.1