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Date: Fri, 15 Jan 2021 12:09:05 -0500
From: Peter Xu <peterx@...hat.com>
To: linux-kernel@...r.kernel.org, linux-mm@...ck.org
Cc: Mike Rapoport <rppt@...ux.vnet.ibm.com>,
Mike Kravetz <mike.kravetz@...cle.com>, peterx@...hat.com,
Jerome Glisse <jglisse@...hat.com>,
"Kirill A . Shutemov" <kirill@...temov.name>,
Hugh Dickins <hughd@...gle.com>,
Axel Rasmussen <axelrasmussen@...gle.com>,
Matthew Wilcox <willy@...radead.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Andrea Arcangeli <aarcange@...hat.com>,
Nadav Amit <nadav.amit@...il.com>
Subject: [PATCH RFC 28/30] hugetlb/userfaultfd: Only drop uffd-wp special pte if required
Just like what we've done with shmem uffd-wp special ptes, we shouldn't drop
uffd-wp special swap pte for hugetlb too, only if we're going to unmap the
whole vma, or we're punching a hole with safe locks held.
For example, remove_inode_hugepages() is safe to drop uffd-wp ptes, because it
has taken hugetlb fault mutex so that no concurrent page fault would trigger.
While the call to hugetlb_vmdelete_list() in hugetlbfs_punch_hole() is not
safe. That's why the previous call will be with ZAP_FLAG_DROP_FILE_UFFD_WP,
while the latter one won't be able to.
Signed-off-by: Peter Xu <peterx@...hat.com>
---
fs/hugetlbfs/inode.c | 15 +++++++++------
include/linux/hugetlb.h | 13 ++++++++-----
mm/hugetlb.c | 27 +++++++++++++++++++++------
mm/memory.c | 5 ++++-
4 files changed, 42 insertions(+), 18 deletions(-)
diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index b5c109703daa..f9ff2ba5e47b 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -399,7 +399,8 @@ static void remove_huge_page(struct page *page)
}
static void
-hugetlb_vmdelete_list(struct rb_root_cached *root, pgoff_t start, pgoff_t end)
+hugetlb_vmdelete_list(struct rb_root_cached *root, pgoff_t start, pgoff_t end,
+ unsigned long zap_flags)
{
struct vm_area_struct *vma;
@@ -432,7 +433,7 @@ hugetlb_vmdelete_list(struct rb_root_cached *root, pgoff_t start, pgoff_t end)
}
unmap_hugepage_range(vma, vma->vm_start + v_offset, v_end,
- NULL);
+ NULL, zap_flags);
}
}
@@ -513,7 +514,8 @@ static void remove_inode_hugepages(struct inode *inode, loff_t lstart,
mutex_lock(&hugetlb_fault_mutex_table[hash]);
hugetlb_vmdelete_list(&mapping->i_mmap,
index * pages_per_huge_page(h),
- (index + 1) * pages_per_huge_page(h));
+ (index + 1) * pages_per_huge_page(h),
+ ZAP_FLAG_DROP_FILE_UFFD_WP);
i_mmap_unlock_write(mapping);
}
@@ -579,7 +581,8 @@ static int hugetlb_vmtruncate(struct inode *inode, loff_t offset)
i_mmap_lock_write(mapping);
i_size_write(inode, offset);
if (!RB_EMPTY_ROOT(&mapping->i_mmap.rb_root))
- hugetlb_vmdelete_list(&mapping->i_mmap, pgoff, 0);
+ hugetlb_vmdelete_list(&mapping->i_mmap, pgoff, 0,
+ ZAP_FLAG_DROP_FILE_UFFD_WP);
i_mmap_unlock_write(mapping);
remove_inode_hugepages(inode, offset, LLONG_MAX);
return 0;
@@ -613,8 +616,8 @@ static long hugetlbfs_punch_hole(struct inode *inode, loff_t offset, loff_t len)
i_mmap_lock_write(mapping);
if (!RB_EMPTY_ROOT(&mapping->i_mmap.rb_root))
hugetlb_vmdelete_list(&mapping->i_mmap,
- hole_start >> PAGE_SHIFT,
- hole_end >> PAGE_SHIFT);
+ hole_start >> PAGE_SHIFT,
+ hole_end >> PAGE_SHIFT, 0);
i_mmap_unlock_write(mapping);
remove_inode_hugepages(inode, hole_start, hole_end);
inode_unlock(inode);
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 8841d118f45b..93f3c46439b2 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -121,14 +121,15 @@ long follow_hugetlb_page(struct mm_struct *, struct vm_area_struct *,
unsigned long *, unsigned long *, long, unsigned int,
int *);
void unmap_hugepage_range(struct vm_area_struct *,
- unsigned long, unsigned long, struct page *);
+ unsigned long, unsigned long, struct page *,
+ unsigned long);
void __unmap_hugepage_range_final(struct mmu_gather *tlb,
struct vm_area_struct *vma,
unsigned long start, unsigned long end,
- struct page *ref_page);
+ struct page *ref_page, unsigned long zap_flags);
void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct *vma,
unsigned long start, unsigned long end,
- struct page *ref_page);
+ struct page *ref_page, unsigned long zap_flags);
void hugetlb_report_meminfo(struct seq_file *);
int hugetlb_report_node_meminfo(char *buf, int len, int nid);
void hugetlb_show_meminfo(void);
@@ -353,14 +354,16 @@ static inline unsigned long hugetlb_change_protection(
static inline void __unmap_hugepage_range_final(struct mmu_gather *tlb,
struct vm_area_struct *vma, unsigned long start,
- unsigned long end, struct page *ref_page)
+ unsigned long end, struct page *ref_page,
+ unsigned long zap_flags)
{
BUG();
}
static inline void __unmap_hugepage_range(struct mmu_gather *tlb,
struct vm_area_struct *vma, unsigned long start,
- unsigned long end, struct page *ref_page)
+ unsigned long end, struct page *ref_page,
+ unsigned long zap_flags)
{
BUG();
}
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 7959fb4b1633..731a26617673 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -3864,7 +3864,7 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct *vma,
unsigned long start, unsigned long end,
- struct page *ref_page)
+ struct page *ref_page, unsigned long zap_flags)
{
struct mm_struct *mm = vma->vm_mm;
unsigned long address;
@@ -3916,6 +3916,19 @@ void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct *vma,
continue;
}
+ if (unlikely(is_swap_special_pte(pte))) {
+ WARN_ON_ONCE(!pte_swp_uffd_wp_special(pte));
+ /*
+ * Only drop the special swap uffd-wp pte if
+ * e.g. unmapping a vma or punching a hole (with proper
+ * lock held so that concurrent page fault won't happen).
+ */
+ if (zap_flags & ZAP_FLAG_DROP_FILE_UFFD_WP)
+ huge_pte_clear(mm, address, ptep, sz);
+ spin_unlock(ptl);
+ continue;
+ }
+
/*
* Migrating hugepage or HWPoisoned hugepage is already
* unmapped and its refcount is dropped, so just clear pte here.
@@ -3967,9 +3980,10 @@ void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct *vma,
void __unmap_hugepage_range_final(struct mmu_gather *tlb,
struct vm_area_struct *vma, unsigned long start,
- unsigned long end, struct page *ref_page)
+ unsigned long end, struct page *ref_page,
+ unsigned long zap_flags)
{
- __unmap_hugepage_range(tlb, vma, start, end, ref_page);
+ __unmap_hugepage_range(tlb, vma, start, end, ref_page, zap_flags);
/*
* Clear this flag so that x86's huge_pmd_share page_table_shareable
@@ -3985,7 +3999,8 @@ void __unmap_hugepage_range_final(struct mmu_gather *tlb,
}
void unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
- unsigned long end, struct page *ref_page)
+ unsigned long end, struct page *ref_page,
+ unsigned long zap_flags)
{
struct mm_struct *mm;
struct mmu_gather tlb;
@@ -4004,7 +4019,7 @@ void unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
mm = vma->vm_mm;
tlb_gather_mmu(&tlb, mm, tlb_start, tlb_end);
- __unmap_hugepage_range(&tlb, vma, start, end, ref_page);
+ __unmap_hugepage_range(&tlb, vma, start, end, ref_page, zap_flags);
tlb_finish_mmu(&tlb, tlb_start, tlb_end);
}
@@ -4059,7 +4074,7 @@ static void unmap_ref_private(struct mm_struct *mm, struct vm_area_struct *vma,
*/
if (!is_vma_resv_set(iter_vma, HPAGE_RESV_OWNER))
unmap_hugepage_range(iter_vma, address,
- address + huge_page_size(h), page);
+ address + huge_page_size(h), page, 0);
}
i_mmap_unlock_write(mapping);
}
diff --git a/mm/memory.c b/mm/memory.c
index 59d56f57ba2c..993ec7a7961a 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1499,8 +1499,11 @@ static void unmap_single_vma(struct mmu_gather *tlb,
* safe to do nothing in this case.
*/
if (vma->vm_file) {
+ unsigned long zap_flags = details ?
+ details->zap_flags : 0;
i_mmap_lock_write(vma->vm_file->f_mapping);
- __unmap_hugepage_range_final(tlb, vma, start, end, NULL);
+ __unmap_hugepage_range_final(tlb, vma, start, end,
+ NULL, zap_flags);
i_mmap_unlock_write(vma->vm_file->f_mapping);
}
} else
--
2.26.2
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