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[PATCH v2 05/11] mm: add follow_pte_pmd()

From Ross Zwisler <ross.zwisler@linux.intel.com>
Newsgroups linux.kernel
Subject [PATCH v2 05/11] mm: add follow_pte_pmd()
Date 2015-11-14 01:20 +0100
Message-ID <quwJs-4ZF-5@gated-at.bofh.it> (permalink)
References <quwzM-4US-1@gated-at.bofh.it>
Organization linux.* mail to news gateway

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Similar to follow_pte(), follow_pte_pmd() allows either a PTE leaf or a
huge page PMD leaf to be found and returned.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Suggested-by: Dave Hansen <dave.hansen@linux.intel.com>
---
 include/linux/mm.h |  2 ++
 mm/memory.c        | 38 ++++++++++++++++++++++++++++++--------
 2 files changed, 32 insertions(+), 8 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 80001de..393441c 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1166,6 +1166,8 @@ int copy_page_range(struct mm_struct *dst, struct mm_struct *src,
 			struct vm_area_struct *vma);
 void unmap_mapping_range(struct address_space *mapping,
 		loff_t const holebegin, loff_t const holelen, int even_cows);
+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,
diff --git a/mm/memory.c b/mm/memory.c
index deb679c..7f4090e 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3512,8 +3512,8 @@ 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;
@@ -3529,12 +3529,20 @@ static int __follow_pte(struct mm_struct *mm, unsigned long address,
 		goto out;
 
 	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);
@@ -3557,9 +3565,23 @@ static inline int follow_pte(struct mm_struct *mm, unsigned long address,
 
 	/* (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
-- 
2.1.0

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Thread

[PATCH v2 00/11] DAX fsynx/msync support Ross Zwisler <ross.zwisler@linux.intel.com> - 2015-11-14 01:10 +0100
  [PATCH v2 09/11] ext2: add support for DAX fsync/msync Ross Zwisler <ross.zwisler@linux.intel.com> - 2015-11-14 01:10 +0100
  [PATCH v2 07/11] mm: add find_get_entries_tag() Ross Zwisler <ross.zwisler@linux.intel.com> - 2015-11-14 01:10 +0100
  [PATCH v2 10/11] ext4: add support for DAX fsync/msync Ross Zwisler <ross.zwisler@linux.intel.com> - 2015-11-14 01:10 +0100
  [PATCH v2 11/11] xfs: add support for DAX fsync/msync Ross Zwisler <ross.zwisler@linux.intel.com> - 2015-11-14 01:10 +0100
  [PATCH v2 05/11] mm: add follow_pte_pmd() Ross Zwisler <ross.zwisler@linux.intel.com> - 2015-11-14 01:20 +0100
  [PATCH v2 01/11] pmem: add wb_cache_pmem() to the PMEM API Ross Zwisler <ross.zwisler@linux.intel.com> - 2015-11-14 01:20 +0100
  [PATCH v2 08/11] dax: add support for fsync/sync Ross Zwisler <ross.zwisler@linux.intel.com> - 2015-11-14 01:20 +0100
  [PATCH v2 03/11] pmem: enable REQ_FUA/REQ_FLUSH handling Ross Zwisler <ross.zwisler@linux.intel.com> - 2015-11-14 01:20 +0100
    Re: [PATCH v2 03/11] pmem: enable REQ_FUA/REQ_FLUSH handling Dan Williams <dan.j.williams@intel.com> - 2015-11-14 01:30 +0100
      Re: [PATCH v2 03/11] pmem: enable REQ_FUA/REQ_FLUSH handling Andreas Dilger <adilger@dilger.ca> - 2015-11-14 01:50 +0100
        Re: [PATCH v2 03/11] pmem: enable REQ_FUA/REQ_FLUSH handling Dan Williams <dan.j.williams@intel.com> - 2015-11-14 03:40 +0100
  [PATCH v2 06/11] mm: add pgoff_mkclean() Ross Zwisler <ross.zwisler@linux.intel.com> - 2015-11-14 01:20 +0100
  [PATCH v2 02/11] mm: add pmd_mkclean() Ross Zwisler <ross.zwisler@linux.intel.com> - 2015-11-14 01:20 +0100
    Re: [PATCH v2 02/11] mm: add pmd_mkclean() Dave Hansen <dave.hansen@intel.com> - 2015-11-14 02:10 +0100
  [PATCH v2 04/11] dax: support dirty DAX entries in radix tree Ross Zwisler <ross.zwisler@linux.intel.com> - 2015-11-14 01:20 +0100

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