[PATCH v8 11/20] mm: pagewalk: Add p4d_entry() and pgd_entry()

Steven Price
2019-04-03T14:17:58Z

pgd_entry() and pud_entry() were removed by commit 0b1fbfe50006c410
("mm/pagewalk: remove pgd_entry() and pud_entry()") because there were
no users. We're about to add users so reintroduce them, along with
p4d_entry() as we now have 5 levels of tables.

Note that commit a00cc7d9dd93d66a ("mm, x86: add support for
PUD-sized transparent hugepages") already re-added pud_entry() but with
different semantics to the other callbacks. Since there have never
been upstream users of this, revert the semantics back to match the
other callbacks. This means pud_entry() is called for all entries, not
just transparent huge pages.

Signed-off-by: Steven Price <steven.price@arm.com>
---
include/linux/mm.h | 15 +++++++++------
mm/pagewalk.c | 27 ++++++++++++++++-----------
2 files changed, 25 insertions(+), 17 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 76769749b5a5..f6de08c116e6 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1367,15 +1367,14 @@ 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
+ * @pgd_entry: if set, called for each non-empty PGD (top-level) entry
+ * @p4d_entry: if set, called for each non-empty P4D entry
+ * @pud_entry: if set, called for each non-empty PUD entry
+ * @pmd_entry: if set, called for each non-empty PMD entry
* this handler is required to be able to handle
* pmd_trans_huge() pmds. They may simply choose to
* split_huge_page() instead of handling it explicitly.
- * @pte_entry: if set, called for each non-empty PTE (4th-level) entry
+ * @pte_entry: if set, called for each non-empty PTE (lowest-level) entry
* @pte_hole: if set, called for each hole at all levels
* @hugetlb_entry: if set, called for each hugetlb entry
* @test_walk: caller specific callback function to determine whether
@@ -1390,6 +1389,10 @@ 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 (*pgd_entry)(pgd_t *pgd, unsigned long addr,
+ unsigned long next, struct mm_walk *walk);
+ int (*p4d_entry)(p4d_t *p4d, unsigned long addr,
+ unsigned long next, struct mm_walk *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,
diff --git a/mm/pagewalk.c b/mm/pagewalk.c
index c3084ff2569d..98373a9f88b8 100644
--- a/mm/pagewalk.c
+++ b/mm/pagewalk.c
@@ -90,15 +90,9 @@ static int walk_pud_range(p4d_t *p4d, unsigned long addr, unsigned long end,
}

if (walk->pud_entry) {
- spinlock_t *ptl = pud_trans_huge_lock(pud, walk->vma);
-
- if (ptl) {
- err = walk->pud_entry(pud, addr, next, walk);
- spin_unlock(ptl);
- if (err)
- break;
- continue;
- }
+ err = walk->pud_entry(pud, addr, next, walk);
+ if (err)
+ break;
}

split_huge_pud(walk->vma, pud, addr);
@@ -131,7 +125,12 @@ static int walk_p4d_range(pgd_t *pgd, unsigned long addr, unsigned long end,
break;
continue;
}
- if (walk->pmd_entry || walk->pte_entry)
+ if (walk->p4d_entry) {
+ err = walk->p4d_entry(p4d, addr, next, walk);
+ if (err)
+ break;
+ }
+ if (walk->pud_entry || walk->pmd_entry || walk->pte_entry)
err = walk_pud_range(p4d, addr, next, walk);
if (err)
break;
@@ -157,7 +156,13 @@ static int walk_pgd_range(unsigned long addr, unsigned long end,
break;
continue;
}
- if (walk->pmd_entry || walk->pte_entry)
+ if (walk->pgd_entry) {
+ err = walk->pgd_entry(pgd, addr, next, walk);
+ if (err)
+ break;
+ }
+ if (walk->p4d_entry || walk->pud_entry || walk->pmd_entry ||
+ walk->pte_entry)
err = walk_p4d_range(pgd, addr, next, walk);
if (err)
break;
--
2.20.1