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mm/hmm: add missing call to hmm_pte_need_fault in HMM_PFN_SPECIAL handling 

Currently if a special PTE is encountered hmm_range_fault() immediately
returns EFAULT and sets the HMM_PFN_SPECIAL error output (which nothing
uses).

EFAULT should only be returned after testing with hmm_pte_need_fault().

Also pte_devmap() and pte_special() are exclusive, and there is no need to
check IS_ENABLED, pte_special() is stubbed out to return false on
unsupported architectures.

Fixes: 992de9a8b7 ("mm/hmm: allow to mirror vma of a file on a DAX backed filesystem")
Reviewed-by: Ralph Campbell <rcampbell@nvidia.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
This commit is contained in:
Jason Gunthorpe 2020-03-05 14:27:20 -04:00
parent 2288a9a681
commit 4055062749
1 changed files with 12 additions and 7 deletions
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19
mm/hmm.c
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@ -339,16 +339,21 @@ static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr,
pte_unmap(ptep);
return -EBUSY;
}
} else if (IS_ENABLED(CONFIG_ARCH_HAS_PTE_SPECIAL) && pte_special(pte)) {
if (!is_zero_pfn(pte_pfn(pte))) {
}
/*
* Since each architecture defines a struct page for the zero page, just
* fall through and treat it like a normal page.
*/
if (pte_special(pte) && !is_zero_pfn(pte_pfn(pte))) {
hmm_pte_need_fault(hmm_vma_walk, orig_pfn, 0, &fault,
&write_fault);
if (fault || write_fault) {
pte_unmap(ptep);
*pfn = range->values[HMM_PFN_SPECIAL];
return -EFAULT;
}
/*
* Since each architecture defines a struct page for the zero
* page, just fall through and treat it like a normal page.
*/
*pfn = range->values[HMM_PFN_SPECIAL];
return 0;
}
*pfn = hmm_device_entry_from_pfn(range, pte_pfn(pte)) | cpu_flags;