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Message-Id: <20221118011135.2179157-1-peterx@redhat.com>
Date: Thu, 17 Nov 2022 20:11:35 -0500
From: Peter Xu <peterx@...hat.com>
To: linux-kernel@...r.kernel.org, linux-mm@...ck.org
Cc: Mike Kravetz <mike.kravetz@...cle.com>,
Muchun Song <songmuchun@...edance.com>, peterx@...hat.com,
Nadav Amit <nadav.amit@...il.com>,
Miaohe Lin <linmiaohe@...wei.com>,
James Houghton <jthoughton@...gle.com>,
David Hildenbrand <david@...hat.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Rik van Riel <riel@...riel.com>,
Andrea Arcangeli <aarcange@...hat.com>
Subject: [PATCH RFC v2 12/12] mm/hugetlb: Introduce hugetlb_walk()
huge_pte_offset() is the main walker function for hugetlb pgtables. The
name is not really representing what it does, though.
Instead of renaming it, introduce a wrapper function called hugetlb_walk()
which will use huge_pte_offset() inside. Assert on the locks so when
walking the pgtable.
Note, the vma lock assertion will be a no-op for private mappings.
Signed-off-by: Peter Xu <peterx@...hat.com>
---
fs/hugetlbfs/inode.c | 4 +---
fs/userfaultfd.c | 6 ++----
include/linux/hugetlb.h | 13 +++++++++++++
mm/hugetlb.c | 28 ++++++++++++++--------------
mm/page_vma_mapped.c | 2 +-
mm/pagewalk.c | 4 +---
6 files changed, 32 insertions(+), 25 deletions(-)
diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index 265508981ba1..ed7934015290 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -390,9 +390,7 @@ static bool hugetlb_vma_maps_page(struct vm_area_struct *vma,
bool result = false;
hugetlb_walker_lock();
- ptep = huge_pte_offset(vma->vm_mm, addr,
- huge_page_size(hstate_vma(vma)));
-
+ ptep = hugetlb_walk(vma, addr, huge_page_size(hstate_vma(vma)));
if (!ptep)
goto out;
diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index a602f008dde5..f31fe1a9f4c5 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -237,14 +237,12 @@ static inline bool userfaultfd_huge_must_wait(struct userfaultfd_ctx *ctx,
unsigned long flags,
unsigned long reason)
{
- struct mm_struct *mm = ctx->mm;
pte_t *ptep, pte;
bool ret = true;
- mmap_assert_locked(mm);
-
- ptep = huge_pte_offset(mm, address, vma_mmu_pagesize(vma));
+ mmap_assert_locked(ctx->mm);
+ ptep = hugetlb_walk(vma, address, vma_mmu_pagesize(vma));
if (!ptep)
goto out;
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 8f85ad0d5bdb..e75b1ffb93a5 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -1296,4 +1296,17 @@ bool want_pmd_share(struct vm_area_struct *vma, unsigned long addr);
#define flush_hugetlb_tlb_range(vma, addr, end) flush_tlb_range(vma, addr, end)
#endif
+/*
+ * Safe version of huge_pte_offset() to check the locks. See comments
+ * above huge_pte_offset().
+ */
+static inline pte_t *
+hugetlb_walk(struct vm_area_struct *vma, unsigned long addr, unsigned long sz)
+{
+ if (!hugetlb_walker_locked())
+ hugetlb_vma_assert_locked(vma);
+
+ return huge_pte_offset(vma->vm_mm, addr, sz);
+}
+
#endif /* _LINUX_HUGETLB_H */
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index e81af6a46c59..6c77ae7a3d94 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -4814,7 +4814,7 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
} else {
/*
* For shared mappings the vma lock must be held before
- * calling huge_pte_offset in the src vma. Otherwise, the
+ * calling hugetlb_walk() in the src vma. Otherwise, the
* returned ptep could go away if part of a shared pmd and
* another thread calls huge_pmd_unshare.
*/
@@ -4824,7 +4824,7 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
last_addr_mask = hugetlb_mask_last_page(h);
for (addr = src_vma->vm_start; addr < src_vma->vm_end; addr += sz) {
spinlock_t *src_ptl, *dst_ptl;
- src_pte = huge_pte_offset(src, addr, sz);
+ src_pte = hugetlb_walk(src_vma, addr, sz);
if (!src_pte) {
addr |= last_addr_mask;
continue;
@@ -5028,7 +5028,7 @@ int move_hugetlb_page_tables(struct vm_area_struct *vma,
hugetlb_vma_lock_write(vma);
i_mmap_lock_write(mapping);
for (; old_addr < old_end; old_addr += sz, new_addr += sz) {
- src_pte = huge_pte_offset(mm, old_addr, sz);
+ src_pte = hugetlb_walk(vma, old_addr, sz);
if (!src_pte) {
old_addr |= last_addr_mask;
new_addr |= last_addr_mask;
@@ -5091,7 +5091,7 @@ static void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct
last_addr_mask = hugetlb_mask_last_page(h);
address = start;
for (; address < end; address += sz) {
- ptep = huge_pte_offset(mm, address, sz);
+ ptep = hugetlb_walk(vma, address, sz);
if (!ptep) {
address |= last_addr_mask;
continue;
@@ -5404,7 +5404,7 @@ static vm_fault_t hugetlb_wp(struct mm_struct *mm, struct vm_area_struct *vma,
mutex_lock(&hugetlb_fault_mutex_table[hash]);
hugetlb_vma_lock_read(vma);
spin_lock(ptl);
- ptep = huge_pte_offset(mm, haddr, huge_page_size(h));
+ ptep = hugetlb_walk(vma, haddr, huge_page_size(h));
if (likely(ptep &&
pte_same(huge_ptep_get(ptep), pte)))
goto retry_avoidcopy;
@@ -5442,7 +5442,7 @@ static vm_fault_t hugetlb_wp(struct mm_struct *mm, struct vm_area_struct *vma,
* before the page tables are altered
*/
spin_lock(ptl);
- ptep = huge_pte_offset(mm, haddr, huge_page_size(h));
+ ptep = hugetlb_walk(vma, haddr, huge_page_size(h));
if (likely(ptep && pte_same(huge_ptep_get(ptep), pte))) {
/* Break COW or unshare */
huge_ptep_clear_flush(vma, haddr, ptep);
@@ -5839,7 +5839,7 @@ vm_fault_t hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
* until finished with ptep. This prevents huge_pmd_unshare from
* being called elsewhere and making the ptep no longer valid.
*
- * ptep could have already be assigned via huge_pte_offset. That
+ * ptep could have already be assigned via hugetlb_walk(). That
* is OK, as huge_pte_alloc will return the same value unless
* something has changed.
*/
@@ -6223,7 +6223,7 @@ struct page *hugetlb_follow_page_mask(struct vm_area_struct *vma,
return NULL;
hugetlb_walker_lock();
- pte = huge_pte_offset(mm, haddr, huge_page_size(h));
+ pte = hugetlb_walk(vma, haddr, huge_page_size(h));
if (!pte)
goto out_unlock;
@@ -6288,8 +6288,8 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
*
* Note that page table lock is not held when pte is null.
*/
- pte = huge_pte_offset(mm, vaddr & huge_page_mask(h),
- huge_page_size(h));
+ pte = hugetlb_walk(vma, vaddr & huge_page_mask(h),
+ huge_page_size(h));
if (pte)
ptl = huge_pte_lock(h, mm, pte);
absent = !pte || huge_pte_none(huge_ptep_get(pte));
@@ -6481,7 +6481,7 @@ unsigned long hugetlb_change_protection(struct vm_area_struct *vma,
last_addr_mask = hugetlb_mask_last_page(h);
for (; address < end; address += psize) {
spinlock_t *ptl;
- ptep = huge_pte_offset(mm, address, psize);
+ ptep = hugetlb_walk(vma, address, psize);
if (!ptep) {
address |= last_addr_mask;
continue;
@@ -7037,8 +7037,8 @@ pte_t *huge_pmd_share(struct mm_struct *mm, struct vm_area_struct *vma,
saddr = page_table_shareable(svma, vma, addr, idx);
if (saddr) {
- spte = huge_pte_offset(svma->vm_mm, saddr,
- vma_mmu_pagesize(svma));
+ spte = hugetlb_walk(svma, saddr,
+ vma_mmu_pagesize(svma));
/*
* When page ref==0, it means it's probably being
* freed; continue with the next one.
@@ -7400,7 +7400,7 @@ void hugetlb_unshare_all_pmds(struct vm_area_struct *vma)
hugetlb_vma_lock_write(vma);
i_mmap_lock_write(vma->vm_file->f_mapping);
for (address = start; address < end; address += PUD_SIZE) {
- ptep = huge_pte_offset(mm, address, sz);
+ ptep = hugetlb_walk(vma, address, sz);
if (!ptep)
continue;
ptl = huge_pte_lock(h, mm, ptep);
diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c
index 5ac8a89130f6..72d72cd73c8f 100644
--- a/mm/page_vma_mapped.c
+++ b/mm/page_vma_mapped.c
@@ -171,7 +171,7 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
hugetlb_walker_lock();
/* when pud is not present, pte will be NULL */
- pvmw->pte = huge_pte_offset(mm, pvmw->address, size);
+ pvmw->pte = hugetlb_walk(vma, pvmw->address, size);
if (!pvmw->pte) {
hugetlb_walker_unlock();
return false;
diff --git a/mm/pagewalk.c b/mm/pagewalk.c
index abf310011ab1..469e60b1b096 100644
--- a/mm/pagewalk.c
+++ b/mm/pagewalk.c
@@ -305,13 +305,11 @@ static int walk_hugetlb_range(unsigned long addr, unsigned long end,
hugetlb_walker_lock();
do {
next = hugetlb_entry_end(h, addr, end);
- pte = huge_pte_offset(walk->mm, addr & hmask, sz);
-
+ pte = hugetlb_walk(vma, addr & hmask, sz);
if (pte)
err = ops->hugetlb_entry(pte, hmask, addr, next, walk);
else if (ops->pte_hole)
err = ops->pte_hole(addr, next, -1, walk);
-
if (err)
break;
} while (addr = next, addr != end);
--
2.37.3
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