linux-kernel - [PATCH 09/11] mm: page_vma_mapped_walk(): get vma_address

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Message-ID: <4542b34d-862f-7cb4-bb22-e0df6ce830a2@google.com>
Date:   Wed, 9 Jun 2021 23:50:23 -0700 (PDT)
From:   Hugh Dickins <hughd@...gle.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
cc:     Hugh Dickins <hughd@...gle.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Yang Shi <shy828301@...il.com>,
        Wang Yugui <wangyugui@...-tech.com>,
        Matthew Wilcox <willy@...radead.org>,
        Alistair Popple <apopple@...dia.com>,
        Ralph Campbell <rcampbell@...dia.com>, Zi Yan <ziy@...dia.com>,
        Peter Xu <peterx@...hat.com>, Will Deacon <will@...nel.org>,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: [PATCH 09/11] mm: page_vma_mapped_walk(): get vma_address_end()
 earlier

page_vma_mapped_walk() cleanup: get THP's vma_address_end() at the start,
rather than later at next_pte.  It's a little unnecessary overhead on the
first call, but makes for a simpler loop in the following commit.

Signed-off-by: Hugh Dickins <hughd@...gle.com>
Cc: <stable@...r.kernel.org>
---
 mm/page_vma_mapped.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c
index 006f4814abbc..f6839f536645 100644
--- a/mm/page_vma_mapped.c
+++ b/mm/page_vma_mapped.c
@@ -171,6 +171,15 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
 		return true;
 	}
 
+	/*
+	 * Seek to next pte only makes sense for THP.
+	 * But more important than that optimization, is to filter out
+	 * any PageKsm page: whose page->index misleads vma_address()
+	 * and vma_address_end() to disaster.
+	 */
+	end = PageTransCompound(page) ?
+		vma_address_end(page, pvmw->vma) :
+		pvmw->address + PAGE_SIZE;
 	if (pvmw->pte)
 		goto next_pte;
 restart:
@@ -239,10 +248,6 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
 		if (check_pte(pvmw))
 			return true;
 next_pte:
-		/* Seek to next pte only makes sense for THP */
-		if (!PageTransHuge(page))
-			return not_found(pvmw);
-		end = vma_address_end(page, pvmw->vma);
 		do {
 			pvmw->address += PAGE_SIZE;
 			if (pvmw->address >= end)
-- 
2.26.2