[RFC 04/20] mm/mapping_dirty_helpers: use mmu_gather

Nadav Amit
2021-01-31T00:17:09Z

From: Nadav Amit <namit@vmware.com>

Avoid open-coding mmu_gather for no reason. There is no apparent reason
not to use the existing mmu_gather interfaces.

Use the newly introduced pte_may_need_flush() to check whether a flush
is needed to avoid unnecassary flushes.

Signed-off-by: Nadav Amit <namit@vmware.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will@kernel.org>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Nick Piggin <npiggin@gmail.com>
Cc: x86@kernel.org
---
mm/mapping_dirty_helpers.c | 37 +++++++++++--------------------------
1 file changed, 11 insertions(+), 26 deletions(-)

diff --git a/mm/mapping_dirty_helpers.c b/mm/mapping_dirty_helpers.c
index b59054ef2e10..2ce6cf431026 100644
--- a/mm/mapping_dirty_helpers.c
+++ b/mm/mapping_dirty_helpers.c
@@ -4,7 +4,7 @@
#include <linux/bitops.h>
#include <linux/mmu_notifier.h>
#include <asm/cacheflush.h>
-#include <asm/tlbflush.h>
+#include <asm/tlb.h>

/**
* struct wp_walk - Private struct for pagetable walk callbacks
@@ -15,8 +15,7 @@
*/
struct wp_walk {
struct mmu_notifier_range range;
- unsigned long tlbflush_start;
- unsigned long tlbflush_end;
+ struct mmu_gather tlb;
unsigned long total;
};

@@ -42,9 +41,9 @@ static int wp_pte(pte_t *pte, unsigned long addr, unsigned long end,
ptent = pte_wrprotect(old_pte);
ptep_modify_prot_commit(walk->vma, addr, pte, old_pte, ptent);
wpwalk->total++;
- wpwalk->tlbflush_start = min(wpwalk->tlbflush_start, addr);
- wpwalk->tlbflush_end = max(wpwalk->tlbflush_end,
- addr + PAGE_SIZE);
+
+ if (pte_may_need_flush(old_pte, ptent))
+ tlb_flush_pte_range(&wpwalk->tlb, addr, PAGE_SIZE);
}

return 0;
@@ -101,9 +100,7 @@ static int clean_record_pte(pte_t *pte, unsigned long addr,
ptep_modify_prot_commit(walk->vma, addr, pte, old_pte, ptent);

wpwalk->total++;
- wpwalk->tlbflush_start = min(wpwalk->tlbflush_start, addr);
- wpwalk->tlbflush_end = max(wpwalk->tlbflush_end,
- addr + PAGE_SIZE);
+ tlb_flush_pte_range(&wpwalk->tlb, addr, PAGE_SIZE);

__set_bit(pgoff, cwalk->bitmap);
cwalk->start = min(cwalk->start, pgoff);
@@ -184,20 +181,13 @@ static int wp_clean_pre_vma(unsigned long start, unsigned long end,
{
struct wp_walk *wpwalk = walk->private;

- wpwalk->tlbflush_start = end;
- wpwalk->tlbflush_end = start;
-
mmu_notifier_range_init(&wpwalk->range, MMU_NOTIFY_PROTECTION_PAGE, 0,
walk->vma, walk->mm, start, end);
mmu_notifier_invalidate_range_start(&wpwalk->range);
flush_cache_range(walk->vma, start, end);

- /*
- * We're not using tlb_gather_mmu() since typically
- * only a small subrange of PTEs are affected, whereas
- * tlb_gather_mmu() records the full range.
- */
- inc_tlb_flush_pending(walk->mm);
+ tlb_gather_mmu(&wpwalk->tlb, walk->mm);
+ tlb_start_vma(&wpwalk->tlb, walk->vma);

return 0;
}
@@ -212,15 +202,10 @@ static void wp_clean_post_vma(struct mm_walk *walk)
{
struct wp_walk *wpwalk = walk->private;

- if (mm_tlb_flush_nested(walk->mm))
- flush_tlb_range(walk->vma, wpwalk->range.start,
- wpwalk->range.end);
- else if (wpwalk->tlbflush_end > wpwalk->tlbflush_start)
- flush_tlb_range(walk->vma, wpwalk->tlbflush_start,
- wpwalk->tlbflush_end);
-
mmu_notifier_invalidate_range_end(&wpwalk->range);
- dec_tlb_flush_pending(walk->mm);
+
+ tlb_end_vma(&wpwalk->tlb, walk->vma);
+ tlb_finish_mmu(&wpwalk->tlb);
}

/*
--
2.25.1