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 <kirill.shutemov@linux.intel.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Peter Xu <peterx@redhat.com>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: Wang Yugui <wangyugui@e16-tech.com>
Cc: Will Deacon <will@kernel.org>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c
index 6b9320340f1b40730bf367b7cba44e9f6a93b8dd..df89ea3df4f42b28c87d80d21c96c2fd97e9aec8 100644 (file)
--- 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:
@@ -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)