mm, x86: add support for PUD-sized transparent hugepages

The current transparent hugepage code only supports PMDs.  This patch
adds support for transparent use of PUDs with DAX.  It does not include
support for anonymous pages.  x86 support code also added.

Most of this patch simply parallels the work that was done for huge
PMDs.  The only major difference is how the new ->pud_entry method in
mm_walk works.  The ->pmd_entry method replaces the ->pte_entry method,
whereas the ->pud_entry method works along with either ->pmd_entry or
->pte_entry.  The pagewalk code takes care of locking the PUD before
calling ->pud_walk, so handlers do not need to worry whether the PUD is
stable.

[dave.jiang@intel.com: fix SMP x86 32bit build for native_pud_clear()]
  Link: http://lkml.kernel.org/r/148719066814.31111.3239231168815337012.stgit@djiang5-desk3.ch.intel.com
[dave.jiang@intel.com: native_pud_clear missing on i386 build]
  Link: http://lkml.kernel.org/r/148640375195.69754.3315433724330910314.stgit@djiang5-desk3.ch.intel.com
Link: http://lkml.kernel.org/r/148545059381.17912.8602162635537598445.stgit@djiang5-desk3.ch.intel.com
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Tested-by: Alexander Kapshuk <alexander.kapshuk@gmail.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Jan Kara <jack@suse.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Nilesh Choudhury <nilesh.choudhury@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 29 insertions, 1 deletions

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 035a688e5472..d8b75d7d6a9e 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -424,6 +424,10 @@ static inline int pmd_devmap(pmd_t pmd)
 {
         return 0;
 }
+static inline int pud_devmap(pud_t pud)
+{
+        return 0;
+}
 #endif
 
 /*
@@ -1199,6 +1203,10 @@ void unmap_vmas(struct mmu_gather *tlb, struct vm_area_struct *start_vma,
 
 /**
  * mm_walk - callbacks for walk_page_range
+ * @pud_entry: if set, called for each non-empty PUD (2nd-level) entry
+ *             this handler should only handle pud_trans_huge() puds.
+ *             the pmd_entry or pte_entry callbacks will be used for
+ *             regular PUDs.
  * @pmd_entry: if set, called for each non-empty PMD (3rd-level) entry
  *             this handler is required to be able to handle
  *             pmd_trans_huge() pmds.  They may simply choose to
@@ -1218,6 +1226,8 @@ void unmap_vmas(struct mmu_gather *tlb, struct vm_area_struct *start_vma,
  * (see the comment on walk_page_range() for more details)
  */
 struct mm_walk {
+        int (*pud_entry)(pud_t *pud, unsigned long addr,
+                         unsigned long next, struct mm_walk *walk);
         int (*pmd_entry)(pmd_t *pmd, unsigned long addr,
                          unsigned long next, struct mm_walk *walk);
         int (*pte_entry)(pte_t *pte, unsigned long addr,
@@ -1801,8 +1811,26 @@ static inline spinlock_t *pmd_lock(struct mm_struct *mm, pmd_t *pmd)
         return ptl;
 }
 
-extern void __init pagecache_init(void);
+/*
+ * No scalability reason to split PUD locks yet, but follow the same pattern
+ * as the PMD locks to make it easier if we decide to.  The VM should not be
+ * considered ready to switch to split PUD locks yet; there may be places
+ * which need to be converted from page_table_lock.
+ */
+static inline spinlock_t *pud_lockptr(struct mm_struct *mm, pud_t *pud)
+{
+        return &mm->page_table_lock;
+}
+
+static inline spinlock_t *pud_lock(struct mm_struct *mm, pud_t *pud)
+{
+        spinlock_t *ptl = pud_lockptr(mm, pud);
+
+        spin_lock(ptl);
+        return ptl;
+}
 
+extern void __init pagecache_init(void);
 extern void free_area_init(unsigned long * zones_size);
 extern void free_area_init_node(int nid, unsigned long * zones_size,
                 unsigned long zone_start_pfn, unsigned long *zholes_size);