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Commit 09796395 authored by Ross Zwisler's avatar Ross Zwisler Committed by Linus Torvalds
Browse files

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: default avatarRoss Zwisler <ross.zwisler@linux.intel.com>
Suggested-by: default avatarDave 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent d670ffd8

include/linux/mm.h

+2 −0
Original line number Diff line number Diff line
@@ -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,

mm/memory.c

+30 −7
Original line number Diff line number Diff line
@@ -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)))



	if (pmd_huge(*pmd)) {

		if (!pmdpp)

			goto out;



	/* We cannot handle huge page PFN maps. Luckily they don't exist. */

	if (pmd_huge(*pmd))

		*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);
@@ -3817,9 +3826,23 @@ 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