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, 31 insertions, 0 deletions

diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c
index 3feec5af4e67..6cbdff26bb96 100644
--- a/arch/x86/mm/pgtable.c
+++ b/arch/x86/mm/pgtable.c
@@ -445,6 +445,26 @@ int pmdp_set_access_flags(struct vm_area_struct *vma,
 
         return changed;
 }
+
+int pudp_set_access_flags(struct vm_area_struct *vma, unsigned long address,
+                          pud_t *pudp, pud_t entry, int dirty)
+{
+        int changed = !pud_same(*pudp, entry);
+
+        VM_BUG_ON(address & ~HPAGE_PUD_MASK);
+
+        if (changed && dirty) {
+                *pudp = entry;
+                /*
+                 * We had a write-protection fault here and changed the pud
+                 * to to more permissive. No need to flush the TLB for that,
+                 * #PF is architecturally guaranteed to do that and in the
+                 * worst-case we'll generate a spurious fault.
+                 */
+        }
+
+        return changed;
+}
 #endif
 
 int ptep_test_and_clear_young(struct vm_area_struct *vma,
@@ -474,6 +494,17 @@ int pmdp_test_and_clear_young(struct vm_area_struct *vma,
 
         return ret;
 }
+int pudp_test_and_clear_young(struct vm_area_struct *vma,
+                              unsigned long addr, pud_t *pudp)
+{
+        int ret = 0;
+
+        if (pud_young(*pudp))
+                ret = test_and_clear_bit(_PAGE_BIT_ACCESSED,
+                                         (unsigned long *)pudp);
+
+        return ret;
+}
 #endif
 
 int ptep_clear_flush_young(struct vm_area_struct *vma,