* [merged mm-stable] mm-memory-handle_pte_fault-use-pte_offset_map_nolock.patch removed from -mm tree
@ 2023-06-19 23:22 Andrew Morton
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From: Andrew Morton @ 2023-06-19 23:22 UTC (permalink / raw)
To: mm-commits, zhengqi.arch, zackr, yuzhao, ying.huang, willy, will,
thomas.hellstrom, surenb, steven.price, song, sj, shy828301,
ryan.roberts, rppt, rcampbell, peterz, peterx, pasha.tatashin,
naoya.horiguchi, minchan, mike.kravetz, mgorman, lstoakes,
linmiaohe, kirill.shutemov, jgg, ira.weiny, hch, david,
christophe.leroy, axelrasmussen, apopple, anshuman.khandual,
hughd, akpm
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The quilt patch titled
Subject: mm/memory: handle_pte_fault() use pte_offset_map_nolock()
has been removed from the -mm tree. Its filename was
mm-memory-handle_pte_fault-use-pte_offset_map_nolock.patch
This patch was dropped because it was merged into the mm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
------------------------------------------------------
From: Hugh Dickins <hughd@google.com>
Subject: mm/memory: handle_pte_fault() use pte_offset_map_nolock()
Date: Thu, 8 Jun 2023 18:45:05 -0700 (PDT)
handle_pte_fault() use pte_offset_map_nolock() to get the vmf.ptl which
corresponds to vmf.pte, instead of pte_lockptr() being used later, when
there's a chance that the pmd entry might have changed, perhaps to none,
or to a huge pmd, with no split ptlock in its struct page.
Remove its pmd_devmap_trans_unstable() call: pte_offset_map_nolock() will
handle that case by failing. Update the "morph" comment above, looking
forward to when shmem or file collapse to THP may not take mmap_lock for
write (or not at all).
do_numa_page() use the vmf->ptl from handle_pte_fault() at first, but
refresh it when refreshing vmf->pte.
do_swap_page()'s pte_unmap_same() (the thing that takes ptl to verify a
two-part PAE orig_pte) use the vmf->ptl from handle_pte_fault() too; but
do_swap_page() is also used by anon THP's __collapse_huge_page_swapin(),
so adjust that to set vmf->ptl by pte_offset_map_nolock().
Link: https://lkml.kernel.org/r/c1107654-3929-60ac-223e-6877cbb86065@google.com
Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport (IBM) <rppt@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Qi Zheng <zhengqi.arch@bytedance.com>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: SeongJae Park <sj@kernel.org>
Cc: Song Liu <song@kernel.org>
Cc: Steven Price <steven.price@arm.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Will Deacon <will@kernel.org>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Zack Rusin <zackr@vmware.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
mm/khugepaged.c | 6 ++++--
mm/memory.c | 38 +++++++++++++-------------------------
2 files changed, 17 insertions(+), 27 deletions(-)
--- a/mm/khugepaged.c~mm-memory-handle_pte_fault-use-pte_offset_map_nolock
+++ a/mm/khugepaged.c
@@ -1003,6 +1003,7 @@ static int __collapse_huge_page_swapin(s
unsigned long address, end = haddr + (HPAGE_PMD_NR * PAGE_SIZE);
int result;
pte_t *pte = NULL;
+ spinlock_t *ptl;
for (address = haddr; address < end; address += PAGE_SIZE) {
struct vm_fault vmf = {
@@ -1014,7 +1015,7 @@ static int __collapse_huge_page_swapin(s
};
if (!pte++) {
- pte = pte_offset_map(pmd, address);
+ pte = pte_offset_map_nolock(mm, pmd, address, &ptl);
if (!pte) {
mmap_read_unlock(mm);
result = SCAN_PMD_NULL;
@@ -1022,11 +1023,12 @@ static int __collapse_huge_page_swapin(s
}
}
- vmf.orig_pte = *pte;
+ vmf.orig_pte = ptep_get_lockless(pte);
if (!is_swap_pte(vmf.orig_pte))
continue;
vmf.pte = pte;
+ vmf.ptl = ptl;
ret = do_swap_page(&vmf);
/* Which unmaps pte (after perhaps re-checking the entry) */
pte = NULL;
--- a/mm/memory.c~mm-memory-handle_pte_fault-use-pte_offset_map_nolock
+++ a/mm/memory.c
@@ -2786,10 +2786,9 @@ static inline int pte_unmap_same(struct
int same = 1;
#if defined(CONFIG_SMP) || defined(CONFIG_PREEMPTION)
if (sizeof(pte_t) > sizeof(unsigned long)) {
- spinlock_t *ptl = pte_lockptr(vmf->vma->vm_mm, vmf->pmd);
- spin_lock(ptl);
+ spin_lock(vmf->ptl);
same = pte_same(*vmf->pte, vmf->orig_pte);
- spin_unlock(ptl);
+ spin_unlock(vmf->ptl);
}
#endif
pte_unmap(vmf->pte);
@@ -4697,7 +4696,6 @@ static vm_fault_t do_numa_page(struct vm
* validation through pte_unmap_same(). It's of NUMA type but
* the pfn may be screwed if the read is non atomic.
*/
- vmf->ptl = pte_lockptr(vma->vm_mm, vmf->pmd);
spin_lock(vmf->ptl);
if (unlikely(!pte_same(*vmf->pte, vmf->orig_pte))) {
pte_unmap_unlock(vmf->pte, vmf->ptl);
@@ -4768,8 +4766,10 @@ static vm_fault_t do_numa_page(struct vm
flags |= TNF_MIGRATED;
} else {
flags |= TNF_MIGRATE_FAIL;
- vmf->pte = pte_offset_map(vmf->pmd, vmf->address);
- spin_lock(vmf->ptl);
+ vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd,
+ vmf->address, &vmf->ptl);
+ if (unlikely(!vmf->pte))
+ goto out;
if (unlikely(!pte_same(*vmf->pte, vmf->orig_pte))) {
pte_unmap_unlock(vmf->pte, vmf->ptl);
goto out;
@@ -4899,26 +4899,15 @@ static vm_fault_t handle_pte_fault(struc
vmf->flags &= ~FAULT_FLAG_ORIG_PTE_VALID;
} else {
/*
- * If a huge pmd materialized under us just retry later. Use
- * pmd_trans_unstable() via pmd_devmap_trans_unstable() instead
- * of pmd_trans_huge() to ensure the pmd didn't become
- * pmd_trans_huge under us and then back to pmd_none, as a
- * result of MADV_DONTNEED running immediately after a huge pmd
- * fault in a different thread of this mm, in turn leading to a
- * misleading pmd_trans_huge() retval. All we have to ensure is
- * that it is a regular pmd that we can walk with
- * pte_offset_map() and we can do that through an atomic read
- * in C, which is what pmd_trans_unstable() provides.
- */
- if (pmd_devmap_trans_unstable(vmf->pmd))
- return 0;
- /*
* A regular pmd is established and it can't morph into a huge
- * pmd from under us anymore at this point because we hold the
- * mmap_lock read mode and khugepaged takes it in write mode.
- * So now it's safe to run pte_offset_map().
+ * pmd by anon khugepaged, since that takes mmap_lock in write
+ * mode; but shmem or file collapse to THP could still morph
+ * it into a huge pmd: just retry later if so.
*/
- vmf->pte = pte_offset_map(vmf->pmd, vmf->address);
+ vmf->pte = pte_offset_map_nolock(vmf->vma->vm_mm, vmf->pmd,
+ vmf->address, &vmf->ptl);
+ if (unlikely(!vmf->pte))
+ return 0;
vmf->orig_pte = ptep_get_lockless(vmf->pte);
vmf->flags |= FAULT_FLAG_ORIG_PTE_VALID;
@@ -4937,7 +4926,6 @@ static vm_fault_t handle_pte_fault(struc
if (pte_protnone(vmf->orig_pte) && vma_is_accessible(vmf->vma))
return do_numa_page(vmf);
- vmf->ptl = pte_lockptr(vmf->vma->vm_mm, vmf->pmd);
spin_lock(vmf->ptl);
entry = vmf->orig_pte;
if (unlikely(!pte_same(*vmf->pte, entry))) {
_
Patches currently in -mm which might be from hughd@google.com are
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2023-06-19 23:22 [merged mm-stable] mm-memory-handle_pte_fault-use-pte_offset_map_nolock.patch removed from -mm tree Andrew Morton
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