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mm: add follow_pte_pmd()
Patch series "Write protect DAX PMDs in *sync path". Currently dax_mapping_entry_mkclean() fails to clean and write protect the pmd_t of a DAX PMD entry during an *sync operation. This can result in data loss, as detailed in patch 2. This series is based on Dan's "libnvdimm-pending" branch, which is the current home for Jan's "dax: Page invalidation fixes" series. You can find a working tree here: https://git.kernel.org/cgit/linux/kernel/git/zwisler/linux.git/log/?h=dax_pmd_clean This patch (of 2): Similar to follow_pte(), follow_pte_pmd() allows either a PTE leaf or a huge page PMD leaf to be found and returned. Link: http://lkml.kernel.org/r/1482272586-21177-2-git-send-email-ross.zwisler@linux.intel.com Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com> Suggested-by: Dave Hansen <dave.hansen@intel.com> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Christoph Hellwig <hch@lst.de> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Dave Chinner <david@fromorbit.com> Cc: Jan Kara <jack@suse.cz> Cc: Matthew Wilcox <mawilcox@microsoft.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -1212,6 +1212,8 @@ void unmap_mapping_range(struct address_space *mapping,
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loff_t const holebegin, loff_t const holelen, int even_cows);
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int follow_pte(struct mm_struct *mm, unsigned long address, pte_t **ptepp,
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spinlock_t **ptlp);
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int follow_pte_pmd(struct mm_struct *mm, unsigned long address,
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pte_t **ptepp, pmd_t **pmdpp, spinlock_t **ptlp);
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int follow_pfn(struct vm_area_struct *vma, unsigned long address,
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unsigned long *pfn);
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int follow_phys(struct vm_area_struct *vma, unsigned long address,
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37
mm/memory.c
37
mm/memory.c
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@ -3772,8 +3772,8 @@ int __pmd_alloc(struct mm_struct *mm, pud_t *pud, unsigned long address)
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}
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#endif /* __PAGETABLE_PMD_FOLDED */
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static int __follow_pte(struct mm_struct *mm, unsigned long address,
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pte_t **ptepp, spinlock_t **ptlp)
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static int __follow_pte_pmd(struct mm_struct *mm, unsigned long address,
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pte_t **ptepp, pmd_t **pmdpp, spinlock_t **ptlp)
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{
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pgd_t *pgd;
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pud_t *pud;
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@ -3790,11 +3790,20 @@ static int __follow_pte(struct mm_struct *mm, unsigned long address,
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pmd = pmd_offset(pud, address);
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VM_BUG_ON(pmd_trans_huge(*pmd));
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if (pmd_none(*pmd) || unlikely(pmd_bad(*pmd)))
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goto out;
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/* We cannot handle huge page PFN maps. Luckily they don't exist. */
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if (pmd_huge(*pmd))
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if (pmd_huge(*pmd)) {
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if (!pmdpp)
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goto out;
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*ptlp = pmd_lock(mm, pmd);
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if (pmd_huge(*pmd)) {
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*pmdpp = pmd;
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return 0;
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}
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spin_unlock(*ptlp);
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}
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if (pmd_none(*pmd) || unlikely(pmd_bad(*pmd)))
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goto out;
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ptep = pte_offset_map_lock(mm, pmd, address, ptlp);
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@ -3817,10 +3826,24 @@ int follow_pte(struct mm_struct *mm, unsigned long address, pte_t **ptepp,
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/* (void) is needed to make gcc happy */
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(void) __cond_lock(*ptlp,
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!(res = __follow_pte(mm, address, ptepp, ptlp)));
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!(res = __follow_pte_pmd(mm, address, ptepp, NULL,
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ptlp)));
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return res;
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}
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int follow_pte_pmd(struct mm_struct *mm, unsigned long address,
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pte_t **ptepp, pmd_t **pmdpp, spinlock_t **ptlp)
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{
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int res;
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/* (void) is needed to make gcc happy */
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(void) __cond_lock(*ptlp,
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!(res = __follow_pte_pmd(mm, address, ptepp, pmdpp,
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ptlp)));
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return res;
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}
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EXPORT_SYMBOL(follow_pte_pmd);
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/**
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* follow_pfn - look up PFN at a user virtual address
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* @vma: memory mapping
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