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mm/hmm: do not unconditionally set pfns when returning EBUSY 

In hmm_vma_handle_pte() and hmm_vma_walk_hugetlb_entry() if fault happens
then -EBUSY will be returned and the pfns input flags will have been
destroyed.

For hmm_vma_handle_pte() set HMM_PFN_NONE only on the success returns that
don't otherwise store to pfns.

For hmm_vma_walk_hugetlb_entry() all exit paths already set pfns, so
remove the redundant store.

Fixes: 2aee09d8c1 ("mm/hmm: change hmm_vma_fault() to allow write fault on page basis")
Link: https://lore.kernel.org/r/20200327200021.29372-8-jgg@ziepe.ca
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
This commit is contained in:
Jason Gunthorpe 2020-03-27 17:00:19 -03:00
parent f66c9a33ae
commit 846babe85e
1 changed files with 4 additions and 3 deletions
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7
mm/hmm.c
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@ -250,11 +250,11 @@ static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr,
pte_t pte = *ptep;
uint64_t orig_pfn = *pfn;
*pfn = range->values[HMM_PFN_NONE];
if (pte_none(pte)) {
required_fault = hmm_pte_need_fault(hmm_vma_walk, orig_pfn, 0);
if (required_fault)
goto fault;
*pfn = range->values[HMM_PFN_NONE];
return 0;
}
@ -275,8 +275,10 @@ static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr,
}
required_fault = hmm_pte_need_fault(hmm_vma_walk, orig_pfn, 0);
if (!required_fault)
if (!required_fault) {
*pfn = range->values[HMM_PFN_NONE];
return 0;
}
if (!non_swap_entry(entry))
goto fault;
@ -494,7 +496,6 @@ static int hmm_vma_walk_hugetlb_entry(pte_t *pte, unsigned long hmask,
i = (start - range->start) >> PAGE_SHIFT;
orig_pfn = range->pfns[i];
range->pfns[i] = range->values[HMM_PFN_NONE];
cpu_flags = pte_to_hmm_pfn_flags(range, entry);
required_fault = hmm_pte_need_fault(hmm_vma_walk, orig_pfn, cpu_flags);
if (required_fault) {