mm: fix false-positive WARN_ON() in truncate/invalidate for hugetlb

Hugetlb pages have ->index in size of the huge pages (PMD_SIZE or
PUD_SIZE), not in PAGE_SIZE as other types of pages.  This means we
cannot user page_to_pgoff() to check whether we've got the right page
for the radix-tree index.

Let's introduce page_to_index() which would return radix-tree index for
given page.

We will be able to get rid of this once hugetlb will be switched to
multi-order entries.

Fixes: fc127da085c2 ("truncate: handle file thp")
Link: http://lkml.kernel.org/r/20161123093053.mjbnvn5zwxw5e6lk@black.fi.intel.com
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reported-by: Doug Nelson <doug.nelson@intel.com>
Tested-by: Doug Nelson <doug.nelson@intel.com>
Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: <stable@vger.kernel.org>	[4.8+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 4 deletions

diff --git a/mm/truncate.c b/mm/truncate.c
index a01cce450a26..8d8c62d89e6d 100644
--- a/mm/truncate.c
+++ b/mm/truncate.c
@@ -283,7 +283,7 @@ void truncate_inode_pages_range(struct address_space *mapping,
 
                         if (!trylock_page(page))
                                 continue;
-                        WARN_ON(page_to_pgoff(page) != index);
+                        WARN_ON(page_to_index(page) != index);
                         if (PageWriteback(page)) {
                                 unlock_page(page);
                                 continue;
@@ -371,7 +371,7 @@ void truncate_inode_pages_range(struct address_space *mapping,
                         }
 
                         lock_page(page);
-                        WARN_ON(page_to_pgoff(page) != index);
+                        WARN_ON(page_to_index(page) != index);
                         wait_on_page_writeback(page);
                         truncate_inode_page(mapping, page);
                         unlock_page(page);
@@ -492,7 +492,7 @@ unsigned long invalidate_mapping_pages(struct address_space *mapping,
                         if (!trylock_page(page))
                                 continue;
 
-                        WARN_ON(page_to_pgoff(page) != index);
+                        WARN_ON(page_to_index(page) != index);
 
                         /* Middle of THP: skip */
                         if (PageTransTail(page)) {
@@ -612,7 +612,7 @@ int invalidate_inode_pages2_range(struct address_space *mapping,
                         }
 
                         lock_page(page);
-                        WARN_ON(page_to_pgoff(page) != index);
+                        WARN_ON(page_to_index(page) != index);
                         if (page->mapping != mapping) {
                                 unlock_page(page);
                                 continue;