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Revert "ANDROID: mm: prevent reads of unstable pmd during speculation"

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This reverts commit f87e6b8d45.

Change-Id: I3a896b78e77f9db5a52bcf261a35c3ec4afefb9c
Signed-off-by: Alexander Winkowski <dereference23@outlook.com>
This commit is contained in:
Alexander Winkowski 2024-01-12 04:59:50 +00:00
commit 9c47c0190b
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GPG key ID: 72762A66704CDE44
1 changed files with 12 additions and 13 deletions
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25
mm/memory.c
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@ -3467,10 +3467,6 @@ static vm_fault_t __do_fault(struct vm_fault *vmf)
struct vm_area_struct *vma = vmf->vma;
vm_fault_t ret;
/* Do not check unstable pmd, if it's changed will retry later */
if (vmf->flags & FAULT_FLAG_SPECULATIVE)
goto skip_pmd_checks;
/*
* Preallocate pte before we take page_lock because this might lead to
* deadlocks for memcg reclaim which waits for pages under writeback:
@ -3493,7 +3489,6 @@ static vm_fault_t __do_fault(struct vm_fault *vmf)
smp_wmb(); /* See comment in __pte_alloc() */
}
skip_pmd_checks:
ret = vma->vm_ops->fault(vmf);
if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY |
VM_FAULT_DONE_COW)))
@ -3867,8 +3862,7 @@ static vm_fault_t do_fault_around(struct vm_fault *vmf)
end_pgoff = min3(end_pgoff, vma_data_pages(vmf->vma) + vmf->vma->vm_pgoff - 1,
start_pgoff + nr_pages - 1);
if (!(vmf->flags & FAULT_FLAG_SPECULATIVE) &&
pmd_none(*vmf->pmd)) {
if (pmd_none(*vmf->pmd)) {
vmf->prealloc_pte = pte_alloc_one(vmf->vma->vm_mm);
if (!vmf->prealloc_pte)
goto out;
@ -4237,11 +4231,16 @@ static vm_fault_t handle_pte_fault(struct vm_fault *vmf)
pte_t entry;
vm_fault_t ret = 0;
/* Do not check unstable pmd, if it's changed will retry later */
if (vmf->flags & FAULT_FLAG_SPECULATIVE)
goto skip_pmd_checks;
if (unlikely(pmd_none(*vmf->pmd))) {
/*
* In the case of the speculative page fault handler we abort
* the speculative path immediately as the pmd is probably
* in the way to be converted in a huge one. We will try
* again holding the mmap_sem (which implies that the collapse
* operation is done).
*/
if (vmf->flags & FAULT_FLAG_SPECULATIVE)
return VM_FAULT_RETRY;
/*
* Leave __pte_alloc() until later: because vm_ops->fault may
* want to allocate huge page, and if we expose page table
@ -4249,7 +4248,8 @@ static vm_fault_t handle_pte_fault(struct vm_fault *vmf)
* concurrent faults and from rmap lookups.
*/
vmf->pte = NULL;
} else {
} else if (!(vmf->flags & FAULT_FLAG_SPECULATIVE)) {
/* See comment in pte_alloc_one_map() */
if (pmd_devmap_trans_unstable(vmf->pmd))
return 0;
/*
@ -4279,7 +4279,6 @@ static vm_fault_t handle_pte_fault(struct vm_fault *vmf)
}
}
skip_pmd_checks:
if (!vmf->pte) {
if (vma_is_anonymous(vmf->vma))
return do_anonymous_page(vmf);