Re: [PATCH v3 09/12] mm/debug_vm_pgtable: Use struct pgtable_debug_args in PUD modifying tests

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Hi Anshuman,

On 7/22/21 3:39 PM, Anshuman Khandual wrote:
On 7/19/21 6:36 PM, Gavin Shan wrote:
This uses struct pgtable_debug_args in PUD modifying tests. The allocated
huge page is used when set_pud_at() is used. The corresponding tests
are skipped if the huge page doesn't exist. Besides, the following unused
variables in debug_vm_pgtable() are dropped: @prot, @paddr, @pud_aligned.

Please dont drop @prot, @paddr, @pud_aligned just yet.


Otherwise it will cause build warning ("unused variable") as
explain in previous reply.


Signed-off-by: Gavin Shan <gshan@xxxxxxxxxx>
---
  mm/debug_vm_pgtable.c | 130 ++++++++++++++++--------------------------
  1 file changed, 50 insertions(+), 80 deletions(-)

diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
index cec3cbf99a6b..57b7ead0708b 100644
--- a/mm/debug_vm_pgtable.c
+++ b/mm/debug_vm_pgtable.c
@@ -338,55 +338,55 @@ static void __init pud_basic_tests(struct pgtable_debug_args *args, int idx)
  	WARN_ON(!pud_bad(pud_mkhuge(pud)));
  }
-static void __init pud_advanced_tests(struct mm_struct *mm,
-				      struct vm_area_struct *vma, pud_t *pudp,
-				      unsigned long pfn, unsigned long vaddr,
-				      pgprot_t prot)
+static void __init pud_advanced_tests(struct pgtable_debug_args *args)
  {
+	unsigned long vaddr = (args->vaddr & HPAGE_PUD_MASK);
  	pud_t pud;
if (!has_transparent_hugepage())
  		return;
pr_debug("Validating PUD advanced\n");
-	/* Align the address wrt HPAGE_PUD_SIZE */
-	vaddr &= HPAGE_PUD_MASK;

Please just leave these unchanged. If has_transparent_hugepage() evaluates
negative, it skips the masking operation. As mentioned earlier please avoid
changing the test in any manner during these transition patches.


Ok.

+	if (args->pud_pfn == ULONG_MAX) {
+		pr_debug("%s: Skipped\n", __func__);

Just return. Please dont call out "Skipped". Applicable for all transition
patches here.


Ok.

+		return;
+	}
- pud = pfn_pud(pfn, prot);
-	set_pud_at(mm, vaddr, pudp, pud);
-	pudp_set_wrprotect(mm, vaddr, pudp);
-	pud = READ_ONCE(*pudp);
+	pud = pfn_pud(args->pud_pfn, args->page_prot);
+	set_pud_at(args->mm, vaddr, args->pudp, pud);
+	pudp_set_wrprotect(args->mm, vaddr, args->pudp);
+	pud = READ_ONCE(*(args->pudp));

Seems like an extra braces while de-referencing arg->pudp. Could these be
dropped. Just READ_ONCE(*args->pudp).


Ok. Will be dropped in v4.

  	WARN_ON(pud_write(pud));
#ifndef __PAGETABLE_PMD_FOLDED
-	pudp_huge_get_and_clear(mm, vaddr, pudp);
-	pud = READ_ONCE(*pudp);
+	pudp_huge_get_and_clear(args->mm, vaddr, args->pudp);
+	pud = READ_ONCE(*(args->pudp));
  	WARN_ON(!pud_none(pud));
  #endif /* __PAGETABLE_PMD_FOLDED */
-	pud = pfn_pud(pfn, prot);
+	pud = pfn_pud(args->pud_pfn, args->page_prot);
  	pud = pud_wrprotect(pud);
  	pud = pud_mkclean(pud);
-	set_pud_at(mm, vaddr, pudp, pud);
+	set_pud_at(args->mm, vaddr, args->pudp, pud);
  	pud = pud_mkwrite(pud);
  	pud = pud_mkdirty(pud);
-	pudp_set_access_flags(vma, vaddr, pudp, pud, 1);
-	pud = READ_ONCE(*pudp);
+	pudp_set_access_flags(args->vma, vaddr, args->pudp, pud, 1);
+	pud = READ_ONCE(*(args->pudp));
  	WARN_ON(!(pud_write(pud) && pud_dirty(pud)));
#ifndef __PAGETABLE_PMD_FOLDED
-	pudp_huge_get_and_clear_full(mm, vaddr, pudp, 1);
-	pud = READ_ONCE(*pudp);
+	pudp_huge_get_and_clear_full(args->mm, vaddr, args->pudp, 1);
+	pud = READ_ONCE(*(args->pudp));
  	WARN_ON(!pud_none(pud));
  #endif /* __PAGETABLE_PMD_FOLDED */
- pud = pfn_pud(pfn, prot);
+	pud = pfn_pud(args->pud_pfn, args->page_prot);
  	pud = pud_mkyoung(pud);
-	set_pud_at(mm, vaddr, pudp, pud);
-	pudp_test_and_clear_young(vma, vaddr, pudp);
-	pud = READ_ONCE(*pudp);
+	set_pud_at(args->mm, vaddr, args->pudp, pud);
+	pudp_test_and_clear_young(args->vma, vaddr, args->pudp);
+	pud = READ_ONCE(*(args->pudp));
  	WARN_ON(pud_young(pud));
- pudp_huge_get_and_clear(mm, vaddr, pudp);
+	pudp_huge_get_and_clear(args->mm, vaddr, args->pudp);
  }
static void __init pud_leaf_tests(struct pgtable_debug_args *args)
@@ -406,24 +406,14 @@ static void __init pud_leaf_tests(struct pgtable_debug_args *args)
  }
  #else  /* !CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
  static void __init pud_basic_tests(struct pgtable_debug_args *args, int idx) { }
-static void __init pud_advanced_tests(struct mm_struct *mm,
-				      struct vm_area_struct *vma, pud_t *pudp,
-				      unsigned long pfn, unsigned long vaddr,
-				      pgprot_t prot)
-{
-}
+static void __init pud_advanced_tests(struct pgtable_debug_args *args) { }
  static void __init pud_leaf_tests(struct pgtable_debug_args *args) { }
  #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
  #else  /* !CONFIG_TRANSPARENT_HUGEPAGE */
  static void __init pmd_basic_tests(struct pgtable_debug_args *args, int idx) { }
  static void __init pud_basic_tests(struct pgtable_debug_args *args, int idx) { }
  static void __init pmd_advanced_tests(struct pgtable_debug_args *args) { }
-static void __init pud_advanced_tests(struct mm_struct *mm,
-				      struct vm_area_struct *vma, pud_t *pudp,
-				      unsigned long pfn, unsigned long vaddr,
-				      pgprot_t prot)
-{
-}
+static void __init pud_advanced_tests(struct pgtable_debug_args *args) { }
  static void __init pmd_leaf_tests(struct pgtable_debug_args *args) { }
  static void __init pud_leaf_tests(struct pgtable_debug_args *args) { }
  static void __init pmd_savedwrite_tests(struct pgtable_debug_args *args) { }
@@ -450,11 +440,11 @@ static void __init pmd_huge_tests(struct pgtable_debug_args *args)
  	WARN_ON(!pmd_none(pmd));
  }
-static void __init pud_huge_tests(pud_t *pudp, unsigned long pfn, pgprot_t prot)
+static void __init pud_huge_tests(struct pgtable_debug_args *args)
  {
  	pud_t pud;
- if (!arch_vmap_pud_supported(prot))
+	if (!arch_vmap_pud_supported(args->page_prot))
  		return;
pr_debug("Validating PUD huge\n");
@@ -462,15 +452,16 @@ static void __init pud_huge_tests(pud_t *pudp, unsigned long pfn, pgprot_t prot)
  	 * X86 defined pud_set_huge() verifies that the given
  	 * PUD is not a populated non-leaf entry.
  	 */
-	WRITE_ONCE(*pudp, __pud(0));
-	WARN_ON(!pud_set_huge(pudp, __pfn_to_phys(pfn), prot));
-	WARN_ON(!pud_clear_huge(pudp));
-	pud = READ_ONCE(*pudp);
+	WRITE_ONCE(*(args->pudp), __pud(0));
+	WARN_ON(!pud_set_huge(args->pudp, __pfn_to_phys(args->fixed_pud_pfn),
+			      args->page_prot));

Please dont break the line, we could go upto 100 width. Please do
the same for the entire series. Improves the readability.

+	WARN_ON(!pud_clear_huge(args->pudp));
+	pud = READ_ONCE(*(args->pudp));
  	WARN_ON(!pud_none(pud));
  }
  #else /* !CONFIG_HAVE_ARCH_HUGE_VMAP */
  static void __init pmd_huge_tests(struct pgtable_debug_args *args) { }
-static void __init pud_huge_tests(pud_t *pudp, unsigned long pfn, pgprot_t prot) { }
+static void __init pud_huge_tests(struct pgtable_debug_args *args) { }
  #endif /* CONFIG_HAVE_ARCH_HUGE_VMAP */
static void __init p4d_basic_tests(void)
@@ -492,27 +483,26 @@ static void __init pgd_basic_tests(void)
  }
#ifndef __PAGETABLE_PUD_FOLDED
-static void __init pud_clear_tests(struct mm_struct *mm, pud_t *pudp)
+static void __init pud_clear_tests(struct pgtable_debug_args *args)
  {
-	pud_t pud = READ_ONCE(*pudp);
+	pud_t pud = READ_ONCE(*(args->pudp));
- if (mm_pmd_folded(mm))
+	if (mm_pmd_folded(args->mm))
  		return;
pr_debug("Validating PUD clear\n");
  	pud = __pud(pud_val(pud) | RANDOM_ORVALUE);
-	WRITE_ONCE(*pudp, pud);
-	pud_clear(pudp);
-	pud = READ_ONCE(*pudp);
+	WRITE_ONCE(*(args->pudp), pud);
+	pud_clear(args->pudp);
+	pud = READ_ONCE(*(args->pudp));
  	WARN_ON(!pud_none(pud));
  }
-static void __init pud_populate_tests(struct mm_struct *mm, pud_t *pudp,
-				      pmd_t *pmdp)
+static void __init pud_populate_tests(struct pgtable_debug_args *args)
  {
  	pud_t pud;
- if (mm_pmd_folded(mm))
+	if (mm_pmd_folded(args->mm))
  		return;
pr_debug("Validating PUD populate\n");
@@ -520,16 +510,13 @@ static void __init pud_populate_tests(struct mm_struct *mm, pud_t *pudp,
  	 * This entry points to next level page table page.
  	 * Hence this must not qualify as pud_bad().
  	 */
-	pud_populate(mm, pudp, pmdp);
-	pud = READ_ONCE(*pudp);
+	pud_populate(args->mm, args->pudp, args->start_pmdp);
+	pud = READ_ONCE(*(args->pudp));
  	WARN_ON(pud_bad(pud));
  }
  #else  /* !__PAGETABLE_PUD_FOLDED */
-static void __init pud_clear_tests(struct mm_struct *mm, pud_t *pudp) { }
-static void __init pud_populate_tests(struct mm_struct *mm, pud_t *pudp,
-				      pmd_t *pmdp)
-{
-}
+static void __init pud_clear_tests(struct pgtable_debug_args *args) { }
+static void __init pud_populate_tests(struct pgtable_debug_args *args) { }
  #endif /* PAGETABLE_PUD_FOLDED */
#ifndef __PAGETABLE_P4D_FOLDED
@@ -1152,10 +1139,7 @@ static int __init debug_vm_pgtable(void)
  	pud_t *pudp, *saved_pudp;
  	pmd_t *pmdp, *saved_pmdp, pmd;
  	pgtable_t saved_ptep;
-	pgprot_t prot;
-	phys_addr_t paddr;
  	unsigned long vaddr;
-	unsigned long pud_aligned;
  	spinlock_t *ptl = NULL;
  	int idx, ret;
@@ -1164,7 +1148,6 @@ static int __init debug_vm_pgtable(void)
  	if (ret)
  		return ret;
- prot = vm_get_page_prot(VMFLAGS);

Please dont drop these just yet and wait until [PATCH 11/12].

  	vaddr = get_random_vaddr();
  	mm = mm_alloc();
  	if (!mm) {
@@ -1178,19 +1161,6 @@ static int __init debug_vm_pgtable(void)
  		return 1;
  	}
- /*
-	 * PFN for mapping at PTE level is determined from a standard kernel
-	 * text symbol. But pfns for higher page table levels are derived by
-	 * masking lower bits of this real pfn. These derived pfns might not
-	 * exist on the platform but that does not really matter as pfn_pxx()
-	 * helpers will still create appropriate entries for the test. This
-	 * helps avoid large memory block allocations to be used for mapping
-	 * at higher page table levels.
-	 */

Please move this comment as is to the right place inside init_args()
in the first patch itself. If possible all comments should be moved
during the first patch and just the code remains till [PATCH 11/12].


I will include all comments in PATCH[01/12]. In that case, we won't
introduce more changes to unrelated function (init_args()).

-	paddr = __pa_symbol(&start_kernel);
-
-	pud_aligned = (paddr & PUD_MASK) >> PAGE_SHIFT;
-

Please dont drop these just yet and wait until [PATCH 11/12].


Otherwise, it will cause build warning.

  	pgdp = pgd_offset(mm, vaddr);
  	p4dp = p4d_alloc(mm, pgdp, vaddr);
  	pudp = pud_alloc(mm, p4dp, vaddr);
@@ -1282,11 +1252,11 @@ static int __init debug_vm_pgtable(void)
  	pmd_populate_tests(&args);
  	spin_unlock(ptl);
- ptl = pud_lock(mm, pudp);
-	pud_clear_tests(mm, pudp);
-	pud_advanced_tests(mm, vma, pudp, pud_aligned, vaddr, prot);
-	pud_huge_tests(pudp, pud_aligned, prot);
-	pud_populate_tests(mm, pudp, saved_pmdp);
+	ptl = pud_lock(args.mm, args.pudp);
+	pud_clear_tests(&args);
+	pud_advanced_tests(&args);
+	pud_huge_tests(&args);
+	pud_populate_tests(&args);
  	spin_unlock(ptl);
spin_lock(&mm->page_table_lock);



Thanks,
Gavin





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