mm/mremap: convert huge PUD move to separate helper

With TRANSPARENT_HUGEPAGE_PUD enabled the kernel can find huge PUD
entries.  Add a helper to move huge PUD entries on mremap().

This will be used by a later patch to optimize mremap of PUD_SIZE aligned
level 4 PTE mapped address

This also make sure we support mremap on huge PUD entries even with
CONFIG_HAVE_MOVE_PUD disabled.

[aneesh.kumar@linux.ibm.com: fix build failure with clang-10]
Link: https://lore.kernel.org/lkml/YMuOSnJsL9qkxweY@archlinux-ax161
Link: https://lkml.kernel.org/r/20210619134310.89098-1-aneesh.kumar@linux.ibm.com
Link: https://lkml.kernel.org/r/20210616045239.370802-4-aneesh.kumar@linux.ibm.com
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Hugh Dickins <hughd@google.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Kalesh Singh <kaleshsingh@google.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/mremap.c b/mm/mremap.c
index a369a6100698b077a8e1274836f1478784b3ed25..4bcaf17424c884d40b2b83be73d445c739792a94 100644 (file)
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -324,10 +324,61 @@ static inline bool move_normal_pud(struct vm_area_struct *vma,
 }
 #endif
 
+#ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
+static bool move_huge_pud(struct vm_area_struct *vma, unsigned long old_addr,
+                         unsigned long new_addr, pud_t *old_pud, pud_t *new_pud)
+{
+       spinlock_t *old_ptl, *new_ptl;
+       struct mm_struct *mm = vma->vm_mm;
+       pud_t pud;
+
+       /*
+        * The destination pud shouldn't be established, free_pgtables()
+        * should have released it.
+        */
+       if (WARN_ON_ONCE(!pud_none(*new_pud)))
+               return false;
+
+       /*
+        * We don't have to worry about the ordering of src and dst
+        * ptlocks because exclusive mmap_lock prevents deadlock.
+        */
+       old_ptl = pud_lock(vma->vm_mm, old_pud);
+       new_ptl = pud_lockptr(mm, new_pud);
+       if (new_ptl != old_ptl)
+               spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
+
+       /* Clear the pud */
+       pud = *old_pud;
+       pud_clear(old_pud);
+
+       VM_BUG_ON(!pud_none(*new_pud));
+
+       /* Set the new pud */
+       /* mark soft_ditry when we add pud level soft dirty support */
+       set_pud_at(mm, new_addr, new_pud, pud);
+       flush_pud_tlb_range(vma, old_addr, old_addr + HPAGE_PUD_SIZE);
+       if (new_ptl != old_ptl)
+               spin_unlock(new_ptl);
+       spin_unlock(old_ptl);
+
+       return true;
+}
+#else
+static bool move_huge_pud(struct vm_area_struct *vma, unsigned long old_addr,
+                         unsigned long new_addr, pud_t *old_pud, pud_t *new_pud)
+{
+       WARN_ON_ONCE(1);
+       return false;
+
+}
+#endif
+
 enum pgt_entry {
        NORMAL_PMD,
        HPAGE_PMD,
        NORMAL_PUD,
+       HPAGE_PUD,
 };
 
 /*
@@ -347,6 +398,7 @@ static __always_inline unsigned long get_extent(enum pgt_entry entry,
                mask = PMD_MASK;
                size = PMD_SIZE;
                break;
+       case HPAGE_PUD:
        case NORMAL_PUD:
                mask = PUD_MASK;
                size = PUD_SIZE;
@@ -395,6 +447,12 @@ static bool move_pgt_entry(enum pgt_entry entry, struct vm_area_struct *vma,
                        move_huge_pmd(vma, old_addr, new_addr, old_entry,
                                      new_entry);
                break;
+       case HPAGE_PUD:
+               moved = IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
+                       move_huge_pud(vma, old_addr, new_addr, old_entry,
+                                     new_entry);
+               break;
+
        default:
                WARN_ON_ONCE(1);
                break;
@@ -414,6 +472,7 @@ unsigned long move_page_tables(struct vm_area_struct *vma,
        unsigned long extent, old_end;
        struct mmu_notifier_range range;
        pmd_t *old_pmd, *new_pmd;
+       pud_t *old_pud, *new_pud;
 
        old_end = old_addr + len;
        flush_cache_range(vma, old_addr, old_end);
@@ -429,15 +488,22 @@ unsigned long move_page_tables(struct vm_area_struct *vma,
                 * PUD level if possible.
                 */
                extent = get_extent(NORMAL_PUD, old_addr, old_end, new_addr);
-               if (IS_ENABLED(CONFIG_HAVE_MOVE_PUD) && extent == PUD_SIZE) {
-                       pud_t *old_pud, *new_pud;
 
-                       old_pud = get_old_pud(vma->vm_mm, old_addr);
-                       if (!old_pud)
+               old_pud = get_old_pud(vma->vm_mm, old_addr);
+               if (!old_pud)
+                       continue;
+               new_pud = alloc_new_pud(vma->vm_mm, vma, new_addr);
+               if (!new_pud)
+                       break;
+               if (pud_trans_huge(*old_pud) || pud_devmap(*old_pud)) {
+                       if (extent == HPAGE_PUD_SIZE) {
+                               move_pgt_entry(HPAGE_PUD, vma, old_addr, new_addr,
+                                              old_pud, new_pud, need_rmap_locks);
+                               /* We ignore and continue on error? */
                                continue;
-                       new_pud = alloc_new_pud(vma->vm_mm, vma, new_addr);
-                       if (!new_pud)
-                               break;
+                       }
+               } else if (IS_ENABLED(CONFIG_HAVE_MOVE_PUD) && extent == PUD_SIZE) {
+
                        if (move_pgt_entry(NORMAL_PUD, vma, old_addr, new_addr,
                                           old_pud, new_pud, need_rmap_locks))
                                continue;