[patch 08/24] mm: page_vma_mapped_walk(): get vma_address_end() earlier

From: Hugh Dickins <hughd@google.com>
Subject: 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.

Link: https://lkml.kernel.org/r/4542b34d-862f-7cb4-bb22-e0df6ce830a2@google.com
Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: Kirill A. Shutemov <redacted>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Peter Xu <peterx@redhat.com>
Cc: Ralph Campbell <redacted>
Cc: Wang Yugui <redacted>
Cc: Will Deacon <will@kernel.org>
Cc: Yang Shi <redacted>
Cc: Zi Yan <ziy@nvidia.com>
Cc: <redacted>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/page_vma_mapped.c |   13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

--- a/mm/page_vma_mapped.c~mm-page_vma_mapped_walk-get-vma_address_end-earlier
+++ a/mm/page_vma_mapped.c

@@ -171,6 +171,15 @@ bool page_vma_mapped_walk(struct page_vm
 		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:

@@ -238,10 +247,6 @@ this_pte:
 		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)

_