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mm: add follow_pte_pmd()

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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>
This commit is contained in:
Ross Zwisler 2017-01-10 16:57:21 -08:00 committed by Linus Torvalds
parent d670ffd875
commit 0979639595
2 changed files with 32 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
include/linux/mm.h
View File

@ -1212,6 +1212,8 @@ void unmap_mapping_range(struct address_space *mapping,
loff_t const holebegin, loff_t const holelen, int even_cows);
int follow_pte(struct mm_struct *mm, unsigned long address, pte_t **ptepp,
spinlock_t **ptlp);
int follow_pte_pmd(struct mm_struct *mm, unsigned long address,
pte_t **ptepp, pmd_t **pmdpp, spinlock_t **ptlp);
int follow_pfn(struct vm_area_struct *vma, unsigned long address,
unsigned long *pfn);
int follow_phys(struct vm_area_struct *vma, unsigned long address,

37
mm/memory.c
View File

@ -3772,8 +3772,8 @@ int __pmd_alloc(struct mm_struct *mm, pud_t *pud, unsigned long address)
}
#endif /* __PAGETABLE_PMD_FOLDED */
static int __follow_pte(struct mm_struct *mm, unsigned long address,
pte_t **ptepp, spinlock_t **ptlp)
static int __follow_pte_pmd(struct mm_struct *mm, unsigned long address,
pte_t **ptepp, pmd_t **pmdpp, spinlock_t **ptlp)
{
pgd_t *pgd;
pud_t *pud;
@ -3790,11 +3790,20 @@ static int __follow_pte(struct mm_struct *mm, unsigned long address,
pmd = pmd_offset(pud, address);
VM_BUG_ON(pmd_trans_huge(*pmd));
if (pmd_none(*pmd) || unlikely(pmd_bad(*pmd)))
goto out;
/* We cannot handle huge page PFN maps. Luckily they don't exist. */
if (pmd_huge(*pmd))
if (pmd_huge(*pmd)) {
if (!pmdpp)
goto out;
*ptlp = pmd_lock(mm, pmd);
if (pmd_huge(*pmd)) {
*pmdpp = pmd;
return 0;
}
spin_unlock(*ptlp);
}
if (pmd_none(*pmd) || unlikely(pmd_bad(*pmd)))
goto out;
ptep = pte_offset_map_lock(mm, pmd, address, ptlp);
@ -3817,10 +3826,24 @@ int follow_pte(struct mm_struct *mm, unsigned long address, pte_t **ptepp,
/* (void) is needed to make gcc happy */
(void) __cond_lock(*ptlp,
!(res = __follow_pte(mm, address, ptepp, ptlp)));
!(res = __follow_pte_pmd(mm, address, ptepp, NULL,
ptlp)));
return res;
}
int follow_pte_pmd(struct mm_struct *mm, unsigned long address,
pte_t **ptepp, pmd_t **pmdpp, spinlock_t **ptlp)
{
int res;
/* (void) is needed to make gcc happy */
(void) __cond_lock(*ptlp,
!(res = __follow_pte_pmd(mm, address, ptepp, pmdpp,
ptlp)));
return res;
}
EXPORT_SYMBOL(follow_pte_pmd);
/**
* follow_pfn - look up PFN at a user virtual address
* @vma: memory mapping