linux-kernel - [PATCH 2/2] mm/page_vma_mapped: page table boundary is already guaranteed

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Message-Id: <20191128010321.21730-2-richardw.yang@linux.intel.com>
Date:   Thu, 28 Nov 2019 09:03:21 +0800
From:   Wei Yang <richardw.yang@...ux.intel.com>
To:     akpm@...ux-foundation.org
Cc:     kirill.shutemov@...ux.intel.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        Wei Yang <richardw.yang@...ux.intel.com>
Subject: [PATCH 2/2] mm/page_vma_mapped: page table boundary is already guaranteed

The check here is to guarantee pvmw->address iteration is limited in one
page table boundary. To be specific, here the address range should be in
one PMD_SIZE.

If my understanding is correct, this check is already done in the above
check:

    address >= __vma_address(page, vma) + PMD_SIZE

The boundary check here seems not necessary.

Signed-off-by: Wei Yang <richardw.yang@...ux.intel.com>

---
Test:
   more than 48 hours kernel build test shows this code is not touched.
---
 mm/page_vma_mapped.c | 13 +------------
 1 file changed, 1 insertion(+), 12 deletions(-)

diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c
index 76e03650a3ab..25aada8a1271 100644
--- a/mm/page_vma_mapped.c
+++ b/mm/page_vma_mapped.c
@@ -163,7 +163,6 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
 			return not_found(pvmw);
 		return true;
 	}
-restart:
 	pgd = pgd_offset(mm, pvmw->address);
 	if (!pgd_present(*pgd))
 		return false;
@@ -225,17 +224,7 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
 					__vma_address(pvmw->page, pvmw->vma) +
 					PMD_SIZE)
 				return not_found(pvmw);
-			/* Did we cross page table boundary? */
-			if (pvmw->address % PMD_SIZE == 0) {
-				pte_unmap(pvmw->pte);
-				if (pvmw->ptl) {
-					spin_unlock(pvmw->ptl);
-					pvmw->ptl = NULL;
-				}
-				goto restart;
-			} else {
-				pvmw->pte++;
-			}
+			pvmw->pte++;
 		} while (pte_none(*pvmw->pte));
 
 		if (!pvmw->ptl) {
-- 
2.17.1