From: Peter Xu <peterx@redhat.com>
To: linux-kernel@vger.kernel.org, linux-mm@kvack.org
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>,
Mike Kravetz <mike.kravetz@oracle.com>,
peterx@redhat.com, Jerome Glisse <jglisse@redhat.com>,
"Kirill A . Shutemov" <kirill@shutemov.name>,
Hugh Dickins <hughd@google.com>,
Axel Rasmussen <axelrasmussen@google.com>,
Matthew Wilcox <willy@infradead.org>,
Andrew Morton <akpm@linux-foundation.org>,
Andrea Arcangeli <aarcange@redhat.com>,
Nadav Amit <nadav.amit@gmail.com>
Subject: [PATCH RFC 11/30] mm: Introduce ZAP_FLAG_SKIP_SWAP
Date: Fri, 15 Jan 2021 12:08:48 -0500 [thread overview]
Message-ID: <20210115170907.24498-12-peterx@redhat.com> (raw)
In-Reply-To: <20210115170907.24498-1-peterx@redhat.com>
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 <kirill@shutemov.name>
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 2380e1df6a49..0b1d04404275 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1632,6 +1632,8 @@ extern void user_shm_unlock(size_t, struct user_struct *);
/* 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.
@@ -1654,6 +1656,16 @@ zap_check_mapping_skip(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 43d8641dbe18..873b2515e187 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1268,8 +1268,7 @@ 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))
@@ -3168,7 +3167,10 @@ 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;
--
2.26.2
next prev parent reply other threads:[~2021-01-15 17:11 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-15 17:08 [PATCH RFC 00/30] userfaultfd-wp: Support shmem and hugetlbfs Peter Xu
2021-01-15 17:08 ` [PATCH RFC 01/30] mm/thp: Simplify copying of huge zero page pmd when fork Peter Xu
2021-01-15 17:08 ` [PATCH RFC 02/30] mm/userfaultfd: Fix uffd-wp special cases for fork() Peter Xu
2021-01-15 17:08 ` [PATCH RFC 03/30] mm/userfaultfd: Fix a few thp pmd missing uffd-wp bit Peter Xu
2021-01-15 17:08 ` [PATCH RFC 04/30] shmem/userfaultfd: Take care of UFFDIO_COPY_MODE_WP Peter Xu
2021-01-15 17:08 ` [PATCH RFC 05/30] mm: Clear vmf->pte after pte_unmap_same() returns Peter Xu
2021-01-15 17:08 ` [PATCH RFC 06/30] mm/userfaultfd: Introduce special pte for unmapped file-backed mem Peter Xu
2021-01-15 17:08 ` [PATCH RFC 07/30] mm/swap: Introduce the idea of special swap ptes Peter Xu
2021-01-18 19:40 ` Jason Gunthorpe
2021-01-19 14:24 ` Peter Xu
2021-01-15 17:08 ` [PATCH RFC 08/30] shmem/userfaultfd: Handle uffd-wp special pte in page fault handler Peter Xu
2021-01-15 17:08 ` [PATCH RFC 09/30] mm: Drop first_index/last_index in zap_details Peter Xu
2021-01-15 17:08 ` [PATCH RFC 10/30] mm: Introduce zap_details.zap_flags Peter Xu
2021-01-15 17:08 ` Peter Xu [this message]
2021-01-15 17:08 ` [PATCH RFC 12/30] mm: Pass zap_flags into unmap_mapping_pages() Peter Xu
2021-01-15 17:08 ` [PATCH RFC 13/30] shmem/userfaultfd: Persist uffd-wp bit across zapping for file-backed Peter Xu
2021-01-15 17:08 ` [PATCH RFC 14/30] shmem/userfaultfd: Allow wr-protect none pte for file-backed mem Peter Xu
2021-01-15 17:08 ` [PATCH RFC 15/30] shmem/userfaultfd: Allows file-back mem to be uffd wr-protected on thps Peter Xu
2021-01-15 17:08 ` [PATCH RFC 16/30] shmem/userfaultfd: Handle the left-overed special swap ptes Peter Xu
2021-01-15 17:08 ` [PATCH RFC 17/30] shmem/userfaultfd: Pass over uffd-wp special swap pte when fork() Peter Xu
2021-01-15 17:08 ` [PATCH RFC 18/30] hugetlb/userfaultfd: Hook page faults for uffd write protection Peter Xu
2021-01-15 17:08 ` [PATCH RFC 19/30] hugetlb/userfaultfd: Take care of UFFDIO_COPY_MODE_WP Peter Xu
2021-01-15 17:08 ` [PATCH RFC 20/30] hugetlb/userfaultfd: Handle UFFDIO_WRITEPROTECT Peter Xu
2021-01-15 17:08 ` [PATCH RFC 21/30] hugetlb: Pass vma into huge_pte_alloc() Peter Xu
2021-01-28 22:59 ` Axel Rasmussen
2021-01-29 22:31 ` Peter Xu
2021-01-30 8:08 ` Axel Rasmussen
2021-01-15 17:08 ` [PATCH RFC 22/30] hugetlb/userfaultfd: Forbid huge pmd sharing when uffd enabled Peter Xu
2021-01-15 17:09 ` [PATCH RFC 23/30] mm/hugetlb: Introduce huge version of special swap pte helpers Peter Xu
2021-01-15 17:09 ` [PATCH RFC 24/30] mm/hugetlb: Move flush_hugetlb_tlb_range() into hugetlb.h Peter Xu
2021-01-15 17:09 ` [PATCH RFC 25/30] hugetlb/userfaultfd: Unshare all pmds for hugetlbfs when register wp Peter Xu
2021-01-15 17:09 ` [PATCH RFC 26/30] hugetlb/userfaultfd: Handle uffd-wp special pte in hugetlb pf handler Peter Xu
2021-01-15 17:09 ` [PATCH RFC 27/30] hugetlb/userfaultfd: Allow wr-protect none ptes Peter Xu
2021-01-15 17:09 ` [PATCH RFC 28/30] hugetlb/userfaultfd: Only drop uffd-wp special pte if required Peter Xu
2021-01-15 17:09 ` [PATCH RFC 29/30] userfaultfd: Enable write protection for shmem & hugetlbfs Peter Xu
2021-01-15 17:12 ` [PATCH RFC 30/30] userfaultfd/selftests: Enable uffd-wp for shmem/hugetlbfs Peter Xu
2021-01-29 22:49 ` [PATCH RFC 00/30] userfaultfd-wp: Support shmem and hugetlbfs Peter Xu
2021-02-05 21:53 ` Mike Kravetz
2021-02-06 2:36 ` Peter Xu
2021-02-09 19:29 ` Mike Kravetz
2021-02-09 22:00 ` Peter Xu
2021-02-05 22:21 ` Hugh Dickins
2021-02-06 2:47 ` Peter Xu
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