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mm/memory: handle_pte_fault() use pte_offset_map_nolock()

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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>
This commit is contained in:
Hugh Dickins 2023-06-08 18:45:05 -07:00 committed by Andrew Morton
parent 3db82b9374
commit c7ad08804f
2 changed files with 17 additions and 27 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

6
mm/khugepaged.c
View file

@ -1003,6 +1003,7 @@ static int __collapse_huge_page_swapin(struct mm_struct *mm,
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(struct mm_struct *mm,
};
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(struct mm_struct *mm,
}
}
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;

38
mm/memory.c
View file

@ -2786,10 +2786,9 @@ static inline int pte_unmap_same(struct vm_fault *vmf)
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_fault *vmf)
* 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_fault *vmf)
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;
@ -4898,27 +4898,16 @@ static vm_fault_t handle_pte_fault(struct vm_fault *vmf)
vmf->pte = NULL;
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(struct vm_fault *vmf)
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))) {